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Edmund P. Green and Frederick T. Short

a group of about sixty

species of underwater marine flowering plants, grow in

the shallow marine and estuary environments of all the

world’s continents except Antarctica. The primary food

of animals such as manatees, dugongs, and green sea

turtles, and critical habitat for thousands of other ani-

mal and plant species, seagrasses are also considered

one of the most important shallow-marine ecosystems

for humans, since they play an important role in fishery

production. Though they are highly valuable ecologically

and economically, many seagrass habitats around the

world have been completely destroyed or are now in

rapid decline. The World Atlas of Seagrasses is the first

authoritative and comprehensive global synthesis of the

distribution and status of this critical marine habitat.

Illustrated throughout with color maps, photographs,

tables, and more, and written by an international team

of collaborators, this unique volume covers seagrass

ecology, scientific studies to date, current status,

changing distributions, threatened areas, and conserva-

tion and management efforts for twenty-four regions of

the world. As human populations expand and continue

to live disproportionately in coastal areas, bringing new

threats to seagrass habitat, a comprehensive overview

Digitized by the Internet Archive
in 2010 with funding from
UNEP-WCMC, Cambridge

http://www.archive.org/details/worldatlasofseagO3gree

World Atlas of Seagrasses

Published in association with
UNEP-WCMC by the University of
California Press

University of California Press
Berkeley and Los Angeles, California
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No part of this book may be reproduced by any means
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The contents of this volume do not necessarily reflect
the views or policies of UNEP-WCMC, contributory
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employed and the presentations do not imply the
expression of any opinion whatsoever on the part of
UNEP-WCMC or contributory organizations, editors or
publishers concerning the legal status of any country,
territory, city or area or its authority, or concerning the
delimitation of its frontiers or boundaries or the
designation of its name or allegiances.

Cloth edition ISBN
0-520-24047-2

Cataloging-in-publication data is on file with the Library
of Congress

Citation Green EP. and Short F.T. (2003) World Atlas of
Seagrasses. Prepared by the UNEP World Conservation
Monitoring Centre. University of California Press,
Berkeley, USA.

World Atlas of Seagrasses
Edmund P. Green & Frederick T. Short

UNIVERSITY OF CALIFORNIA PRESS

BERKELEY LoS ANGELES LONDON

WORLD ATLAS OF SEAGRASSES

World Atlas of Seagrasses

Prepared by

UNEP World Conservation
Monitoring Centre

219 Huntingdon Road
Cambridge CB3 ODL, UK

Tel: +44 (0) 1223 277 314

Fax: +44 (0) 1223 277 136
E-mail: infofaunep-wcmc.org
Website: www.unep-wcmc.org

Director
Mark Collins

Scientific editors
Edmund P. Green
Frederick T. Short

Assistant scientific editor
Michelle Taylor

Cartographer
Corinna Ravilious

Technical editor
Catherine Short

Layout
Yves Messer

A Banson production
27 Devonshire Road
Cambridge CB1 2BH, UK

Color separations
Swaingrove

Printed in China

Jackson Estuarine Laboratory contribution number
396.

——

UNEP WCMC

The UNEP World Conservation Monitoring Centre is the
biodiversity assessment and policy implementation arm
of the United Nations Environment Programme (UNEP),
the world’s foremost intergovernmental environmental
organization. UNEP-WCMC aims to help decision-
makers recognize the value of biodiversity to people
everywhere, and to apply this knowledge to all that they
do. The Centre's challenge is to transform complex data
into policy-relevant information, to build tools and
systems for analysis and integration, and to support the
needs of nations and the international community as they
engage in joint programs of action.

UNEP-WCMC provides objective, scientifically rigorous
products and services that include ecosystem assess-
ments, support for implementation of environmental
agreements, regional and global biodiversity in-
formation, research on threats and impacts, and
development of future scenarios for the living world.

lllustrations in Appendix 3 and at foot of pages:

Mark Fonseca: Zostera marina

Phillips RC, Menez EG [1988]. Seagrasses. Smithsonian
Contributions to the Marine Sciences 34. Smithsonian

Institution Press, Washington DC: Zostera asiatica

QDPI Northern Fisheries Centre, Cairns: Halophila australis,
Halophila capricorn

Ron Phillips: All remaining illustrations

Supporting institutions

Department for
International
Development

The David and Lucile
Packard Foundation

(Yoru of NEW HAMPSHIRE

International Coral Reef Action Network

Intemational Council for Science

Scientific Committee on Oceanic Research

The United Nations Environment Programme is the principal United Nations body in the field of the
environment. Its role is to be the leading global environmental authority that sets the global
environmental agenda, promotes the coherent implementation of the environmental dimension of
sustainable development within the United Nations system and serves as an authoritative advocate for
the global environment. http://www.unep.org

The UK Department for Environment, Food and Rural Affairs is working for sustainable development:
a better quality of life for everyone, now and for generations to come. This includes a better environ-
ment at home and internationally, and sustainable use of natural resources; economic prosperity
through sustainable farming, fishing, food, water and other industries that meet consumers’
requirements; thriving economies and communities in rural areas and a countryside for all to enjoy.

The Department for International Development is the UK Government department working to
promote sustainable development and eliminate world poverty. This publication is an output from a
research program funded by DFID for the benefit of developing countries. The views expressed are not
necessarily those of DFID. http://www.dfid.gov.uk/

The David and Lucile Packard Foundation, started in 1964, provides international and national support
to non-profit organizations in conservation, science and many other areas. The foundation currently
provides funding to SeagrassNet, a global seagrass monitoring program based at the University of
New Hampshire. http://www.packard. org/, http://www.seagrassnet.org/

The University of New Hampshire is a land-grant, sea-grant and space-grant public institution with
10 000 undergraduate and 2 000 graduate students, and a well-established marine program. The
Jackson Estuarine Laboratory is the primary marine research organization at UNH and has a strong
seagrass research component. http://www.unh.edu/, http://marine.unh.edu/jel/home.html

The World Seagrass Association is committed to the science, protection and management of the
seagrass ecosystem worldwide. The members come from many countries and include leading
scientists in marine and seagrass biology. The association supports training and information
exchange and raises global awareness of seagrass science and environmental management issues.
http://www.worldseagrass.org/

The Convention on Wetlands, signed in Ramsar, Iran, in 1971, is an intergovernmental treaty which
provides the framework for local, regional and national actions for the conservation and wise use of
wetlands and their resources. There are presently 135 Contracting Parties to the Convention, with
1 230 wetland sites, totaling 105.9 million hectares, designated for inclusion in the Ramsar List of
Wetlands of International Importance. http://ramsar.org/

The International Coral Reef Action Network is an innovative and dynamic global partnership of many
of the world's leading coral reef science and conservation organizations. Established in 1999 to halt
and reverse the decline of the health of the world's coral reefs the partnership draws on its partners’
investments in reef monitoring and management to create strategically linked actions at local,
national and global scales. http://icran.org/

The Scientific Committee on Oceanic Research (SCOR) was the first interdisciplinary body formed by
the International Council for Science. SCOR activities focus on promoting international cooperation in
planning and conducting oceanographic research. http://www.jhu.edu/~scor

The Estuarine Research Federation (ERF) is a private, non-profit organization. The federation was
created in 1971 to address broad estuarine and coastal issues; it holds biannual international
meetings and supports the scientific publication Estuaries. http://www.erf.org/

WORLD ATLAS OF SEAGRASSES

Acknowledgments

a special mention and deserve extra thanks. First and foremost amongst these are the 58 authors who have given

freely and extensively of their time and experience in writing the 25 chapters that constitute this World Atlas.
Without their attention to detail and efforts in sourcing data outside the mainstream scientific literature this book
would not have been possible. The contributions of the assistant scientific editor, Michelle Taylor, the cartographer,
Corinna Ravilious, and technical editor, Catherine Short, have been equally invaluable in the synthesis of information
from many hundreds of disparate sources and for ensuring consistency throughout every section. The editors have a
particular debt of gratitude to all these people.

The origins of the World Atlas of Seagrasses go back to late 1997 when the need for a global compendium of
information on seagrasses was first acknowledged. Hans de Jong, Eddie Hegerl, Paul Holthus, Richard Luxmore and
the participants at the third International Seagrass Biology Workshop, 19-26 April 1998, Manila and Bolinao,
Philippines, were particularly helpful in pulling these ideas together. Nicholas Davidson, Salif Diop, Will Rogowski,
Ed Urban, Genevieve Verbrugge and Marjo Vierros provided great support during the fundraising, support which was
instrumental in making the necessary resources available. We are, of course, notably grateful to our sponsors, listed
at the beginning of the World Atlas, for investing funds in this work. Special mention is due here to the David and
Lucile Packard Foundation and University of New Hampshire for supporting Fred Short’s time.

A long period of data collection followed soon after work began and involved much detailed correspondence with
very many people. Our thanks go out to everyone who answered our ‘phone calls and e-mails, but even more so to
those who provided us with seagrass distribution data or maps, especially William Allison, Alex Arrivillaga, Susanne
Baden, Seth Barker, David Blackburn, Simon Blyth, Christoffer Bostrom, Nikki Bramwell, Marnie Campbell, Jacoby
Carter, Rob Coles, Helen Cottrell, Lucy Conway, Charlie Costello, Jeffrey Dahlin, Dick de Jong, Karen Eckert, Caroline
Erftemeijer, Randolph Ferguson, Mark Finkbeiner, Terence Fong, Mark Fonseca, Sarah Gage, Martin Gullstrom, Rob
Hughes, Herman Hummel, Hitoshi lizumi, Chung It Choi, Emma Jackson, Pauline Kamermans, Hilary Kennedy, Ryo
Mabuchi, lan May, Pete McLain, Thomas Meyer, Mark Monaco, Kenji Morita, lvan Nagelkerken, Brian Pawlak, Karin
Pettersson, Ron Phillips, Martin Plus, Chris Pickerell, Jean Pascal Quod, Thorsten Reusch, Ron Rozsa, Jan Steffen,
Marieke van Katwijk, Mikael von Numers, Rob Williams, Lisa Wood, Masumi Yamamuro and members of the Wider
Caribbean Sea Turtle Conservation Network [WIDECAST): Timothy Austin, Andy Caballero, Didiher Chacon, Juan
Manuel Diaz and Alan Mills. Clearly a number of data sharing agreements were necessary as these data were
identified and we thank Mary Cordiner for sorting out these institutional complexities.

The coordinators of the Global Seagrass Workshop, Mark Spalding and Michelle Taylor, and all 23 delegates
(page 283] are gratefully acknowledged for the time and effort they made to review, amend and correct the seagrass
distribution data. The workshop itself would not however have been possible without considerable logistic and
organizational support from Janet Barnes, Joy Bartholomew, Jean Finlayson, Anne Giblin, Pam Price, Ed Urban and
Susan White, also all the staff at the Tradewinds Hotel, St Petersburg Beach, Florida.

Jamie Adams, Mary Edwards and Sergio Martins have provided additional geographical information systems
support at various stages during the preparation of the maps for the World Atlas and Elizabeth Allen, Janet Chow,
Mary Cordiner and Michael Stone have spent very many long hours formatting and organizing the reference sections
for the chapters and on-line bibliography (http://www.unep-wemc.org/marine/seagrassatlas/references).

Readers will quickly note the wonderful photographs which have been kindly donated. Credit is given next to
individual photographs but thanks are also due here to Nancy Diersing, Florence Jean, Karine Magalhaes, Kate
Moran and John Ogden all of whom helped us track down owners of pictures which we wanted to use. Most of the
drawings of seagrasses in Appendix 3 and illustrated at the foot of the pages were donated by Ron Phillips, whom
we especially thank for this contribution. Rob Coles, Mark Fonseca and Mike Fortes provided additional drawings for
Appendix 3 and the page corners, and we thank them as well.

When reviewing correspondence and notes spanning the last five years it is all too easy to overlook or forget
someone. Sincere apologies to anyone whom we have neglected to mention here. Please be assured that this was
simply an oversight brought about by the effort of completing the book and nothing else!

T: World Atlas of Seagrasses is a product of global collaboration between many different people but a few merit

Ed Green and Fred Short

Preface

Centre. The World Summit on Sustainable Development adopted, in the area of biodiversity, a

commitment to reverse the trend of losses by 2010. To achieve this we need hard facts on which to
base decisions. The World Atlas of Seagrasses meets that need for a vital marine ecosystem whose
importance has largely been overlooked until now.

| t is with great pleasure that | introduce this new book from the UNEP World Conservation Monitoring

This book would not have been possible without a remarkable collaboration between the 58 authors from
25 countries. The World Atlas of Seagrasses has played a role in fostering international collaboration by
gathering information from many different sources all over the world. On behalf of UNEP | would like to
express my gratitude to all the authors who have contributed their knowledge.

| would also like to thank the sponsors of the World Atlas of Seagrasses including the UK Department for
Environment, Food and Rural Affairs, the UK Department for International Development, the Secretariat
of the Ramsar Convention on Wetlands, the David and Lucile Packard Foundation, the University of New
Hampshire, the World Seagrass Association, the Scientific Committee on Oceanic Research, the
Estuarine Research Federation and the International Coral Reef Action Network.

| am confident that this book will help not only UNEP but all interested parties to focus on the

implementation of sustainable development in the marine environment worldwide.

Klaus Toepfer
Executive Director, United Nations Environment Programme (UNEP)

vii

viii

WORLD ATLAS OF SEAGRASSES

Foreword

maestros that take center stage. It is true that rain forests, coral reefs, whales, tigers and the like

carry an important representational role as they fill our television screens and become a priority in our
conservation programs. But we should not forget the many other ecological players that make up
nature’s orchestra. The living world is an interactive and integrated continuum that we partition into
ecosystems for our own scientific convenience. The less well-known ecosystems often play a distinct and
very important part in the overall harmony that we need to maintain, but only poorly understand. One
such ecosystem is the beds of seagrass that are found on coastlines around the world.

Seagrass beds are unusual in that they are very widespread, occurring on shallow coastlines in all
but the coldest waters of the world. A small group of flowering plants, just 60 among the 270 000 species
of fish, plants and other organisms that have colonized the sea, they owe their success to this ability to
tolerate a wide range of conditions. So why have they been selected for this global report?

First of all, seagrass beds are an important but under-rated resource for coastal people. Physically
they protect coastlines from the erosive impact of waves and tides, chemically they play a key role in
nutrient cycles for fisheries and biologically they provide habitat for fish, shellfish and priority ecotourism
icons like the dugong, manatee and green turtle. And yet, despite these important attributes, they have
been overlooked by conservationists and coastal development planners throughout their range.

This World Atlas of Seagrasses is literally putting seagrass beds onto the map, for the first time. It is
a groundbreaking synthesis that provides people everywhere with the first world view of where seagrasses
occur and what has been happening to them. It is a worrying story. Seagrass beds have been needlessly
destroyed for short-term gain without real analysis of the values that the intact ecosystems bring to
coastal society. There is no proper strategy for their protection. Their significance is not well appreciated
and awareness is very low. This World Atlas will go a long way towards reversing these trends.

As ever in the production of an analysis of this kind, our scientists at the UNEP World Conservation
Monitoring Centre have been able to achieve their results only by standing on the shoulders of giants. We
acknowledge and applaud the dedicated band of seagrass ecologists and taxonomists who have laid the
groundwork for this World Atlas and prepared much of the text. | hope it will bring well-deserved
recognition for them and for their seagrasses, and establish a baseline from which to build a more
sustainable future for coastal peoples and the home of the gentle dugong.

| n describing the complex relationships that exist in the living world we all too often focus on the

Mark Collins
Director, UNEP-WCMC

Contents

Acknowledgments

Preface

Foreword

Introduction to the World Atlas of Seagrasses
Key to maps and mapping methods

GLOBAL OVERVIEW

The distribution and status of seagrasses
MAPS

] World seagrass distribution

2 Global seagrass biodiversity

FIGURES

1 Relative size-frequency distribution of

538 seagrass polygons in latitudinal
swathe 20-30°S
2 Growth of marine protected areas which

include seagrass ecosystems, shown both
as the number of sites [line] and the total

area protected (shaded area]

TABLES

1 A list of seagrass species by family

2 Major taxonomic groups found In
seagrass ecosystems, with brief notes

3 Threatened species regularly recorded
from seagrass communities worldwide

4 Estimates of seagrass coverage for
selected areas described in this
World Atlas

5 Functions and values of seagrass from

the wider ecosystem perspective
6 Summary of the goods and services
provided by seagrass ecosystems

Uf Summary of marine protected areas that

contain seagrass ecosystems, from the

UNEP-WCMC Protected Areas Database

REGIONAL CHAPTERS
1 THE SEAGRASSES OF Scandinavia and the Baltic
Sea
Map
1.1. Scandinavia
FIGURES
1.1 Average (+1 SE) above-ground biomass
values for eelgrass (Zostera marina]
along the Baltic Sea coastline

1.2 Aerial photographs of two typical exposed

eelgrass (Zostera marina] sites at the
Hanko Peninsula, southwest Finland

21
22

Contents

3 Norwegian eelgrass coverage

-4_ Map of eelgrass area distribution in
Danish coastal waters

.5 Maximum colonization depth of
eelgrass patches in Danish estuaries
and along open coasts in 1900 and
1996-97

.6 Secchi depths and maximum
colonization depths of eelgrass patches
in Danish estuaries and open coasts in
1900 and 1992

1.7. Long-term changes in the distribution

of eelgrass (Zostera marina} in the

southeastern Baltic Sea [Puck Lagoon,

Poland)

2 THE SEAGRASSES OF Western Europe

MAPS

2.1. Western Europe (north)
2.2 Western Europe [south]
Case STUDIES

2.1. The Wadden Sea

2.2. Glénan Archipelago

THE SEAGRASSES OF The western Mediterranean
MaP

3.1 The western Mediterranean
CASE STUDIES

3.1 Italy

3.2. France

3.3 Spain

TABLES

3.1 Examples of general features of
Mediterranean seagrass meadows

3.2 Distribution of seagrasses throughout
the western Mediterranean (Italy, France
and Spain]

THE SEAGRASSES OF The Black, Azov, Caspian
and Aral Seas

MAP

4.1 The Black, Azov, Caspian and Aral Seas

THE SEAGRASSES OF The eastern Mediterranean
and the Red Sea

Maps

5.1. The eastern Mediterranean

5.2 The Red Sea

CASE STUDY

5.1 Israeli coast of the Gulf of Elat

x WORLD ATLAS OF SEAGRASSES

6 THE SEAGRASSES OF The Arabian Gulf and Arabian 9.2 Occurrence of seagrasses in coastal
region 74 states of India 104
Map 9.3 Associated biota of seagrass beds of
6.1. The Arabian Gulf and Arabian region 75 India 105
CASE STUDIES
6.1. The Bahrain Conservancy 76 10 THE SEAGRASSES OF Western Australia 109
6.2 Rapid assessment technique 77 Map
6.3 Marine turtles and dugongs in the 10.1 Western Australia 111
Arabian seagrass pastures 79 Case STUDY
TABLE 10.1 Shark Bay, Western Australia: How
6.1 Seagrass species in the Arabian region 75 seagrass shaped an ecosystem 116
TABLES
7 THE SEAGRASSES OF Kenya and Tanzania 82 10.1 Western Australian endemic seagrass
MAP species 110
7.1. Kenya and Tanzania 83 10.2. Summary of major human-induced
CASE STUDIES declines of seagrass in Western
7.1 Gazi Bay, Kenya: Links between Australia 113
seagrasses and adjacent ecosystems 84
7.2 Seagrass beach cast at Mombasa 11 THE SEAGRASSES OF Eastern Australia 119
Marine Park, Kenya: A nuisance or a MAP
vital link? 88 11.1 Eastern Australia 121
CASE STUDIES
8 THE SEAGRASSES OF Mozambique and 11.1. Mapping deepwater (15-60 m)
southeastern Africa 93 seagrasses and epibenthos in the
MAPS Great Barrier Reef lagoon 124
8.1 Mozambique and southeastern Africa 94 FIGURE: Probability of the occurrence
8.2 The Seychelles 94 of deepwater seagrasses in the Great
8.3 Mauritius 94 Barrier Reef Lagoon
Case STUDY FIGURE: Frequency of the probability of
8.1. Inhaca Island and Maputo Bay area, occurrence of seagrasses within each
southern Mozambique 96 depth stratum
FIGURE 11.2 Westernport Bay 126
8.1 Digging of Zostera capensis meadows FIGURE: Distribution of estuarine
at Vila dos Pescadores, near Maputo city 99 habitats in Westernport Bay, Australia
TABLES 11.3. Expansion of Green Island seagrass
8.1 Area cover and location for the meadows 128
seagrass Zostera capensis in South FIGURE: Seagrass distribution at Green
Africa 94 Island in 1994, 1972, 1959 and 1936
8.2 Seagrass cover and area lost in
Mozambique 99 12 THE SEAGRASSES OF New Zealand 134
Map
9 THE SEAGRASSES OF India 101 12.1 New Zealand 135
MAPS CASE STUDY
9.1 India 103 12.1 A seagrass specialist 140
9.2 Andaman and Nicobar Islands 103 FIGURE
CASE STUDY 12.1 An example of changes in the historical
9.1 Kadmat Island 106 distribution of seagrasses in New
TABLE: Characterization of a seagrass Zealand 139
meadow at Kadmat Island, TABLES
Lakshadweep 12.1 Area of seagrass in New Zealand
TABLE: Benthic macrofauna in the estuaries where benthic habitats have
seagrass bed at Kadmat Island, been mapped 135
Lakshadweep 12.2 List of locations where seagrasses have
FIGURE been recorded in New Zealand 136
9.1 Abundance of seagrass species at
various depths in the Gulf of Mannar 13 THE SEAGRASSES OF Thailand 144
{southeast coast) 105 Map
TABLES 13.1 Thailand 145
9.1 Quantitative data for major seagrass CASE STUDY

beds in Indian waters 102 13.1 The dugong - a flagship species 147

TABLE
13.1 Occurrence of seagrass species in
Thailand

14 THE SEAGRASSES OF Malaysia

MAPS

14.1 Peninsular Malaysia

14.2 Sabah

CASE STUDIES

14.1 The seagrass macroalgae community
of Teluk Kemang

14.2 The subtidal shoal seagrass community
of Tanjung Adang Laut

14.3 Coastal lagoon seagrass community at
Pengkalan Nangka, Kelantan

TABLE

14.1. Estimate of known seagrass areas in
Peninsular Malaysia

15 THE SEAGRASSES OF The western Pacific islands

MAPS

15.1 Western Pacific islands (west)

15.2 Western Pacific islands [east]

CASE STUDIES

15.1 Kosrae
Maps: Lelu Harbour ca 1900 and 1975;
Okat Harbour and Reef 1978 and 1988

15.2 SeagrassNet - a western Pacific pilot
study

16 THE SEAGRASSES OF Indonesia

Map

16.1. Indonesia

CASE STUDIES

16.1 Banten Bay, West Java

16.2 Kuta and Gerupuk Bays, Lombok

16.3 Kotania Bay
TABLE: Distribution of seagrass

TABLES

16.1 Average biomass of seagrasses at
various locations throughout
Indonesia

16.2 Average density of seagrasses at
various locations throughout the
Indonesian Archipelago

16.3 Average shoot density of seagrass
species in mixed and monospecific
seagrass meadows in the Flores Sea

16.4 Average growth rates of seagrass
leaves using leaf-marking techniques

16.5 Indonesian seagrass-associated flora
and fauna: number of species

16.6 Present coverage of seagrasses in
Indonesia

The Philippines and Viet Nam

17 THE SEAGRASSES OF Japan

MAP
17.1. Japan

146

152

157

161

163
163

164

168
17)
173
176

177
178

172

Contents

ea EEN EE EEE

CASE STUDIES

17.1. Akkeshi, eastern Hokkaido

17.2 Rias coast in Iwate Prefecture,
northeastern Honshu

TABLES

17.1 Seagrasses recorded in Japan

17.2 Traditional uses of seagrasses in Japan

17.3 Estimates of total areas of algal and
seagrass beds in Japan in 1978 and
1991, and the percent area lost

18 THE SEAGRASSES OF The Republic of Korea

MAP

18.1 Republic of Korea

CASE STUDY

18.1 Recent research on seagrasses

TABLES

18.1 Physical characteristics of seagrass
beds on the west, south and east coasts
of the Republic of Korea

18.2 Seagrass species distributed on the
coasts of the Republic of Korea

18.3 Habitat characteristics of seagrass
species in the Republic of Korea

18.4 Morphological characteristics of
seagrasses distributed in the Republic
of Korea

18.5 The estimated areas of seagrasses
distributed on the coasts of the Republic
of Korea

19 THE SEAGRASSES OF The Pacific coast of North

America

Map

19.1. The Pacific coast of North America

Case STUDIES

19.1. The link between seagrass and
migrating black brant along the Pacific
Flyway

19.2 The link between the seagrass Zostera
marina (ts ‘ats ‘ayem] and the
Kwakwaka wakw Nation, Vancouver
Island, Canada

19.3. The link between seagrasses and
humans in Picnic Cove, Shaw Island,
Washington, United States

TABLE

19.1 Zostera marina and Zostera japonica
basal area cover in the Northeast Pacific

20 THE SEAGRASSES OF The western North Atlantic

Map

20.1 The western North Atlantic

CASE STUDIES

20.1 Portsmouth Harbor, New Hampshire
and Maine
FiGuRE: Eelgrass distribution by depth

in Portsmouth Harbor, Great Bay Estuary,

on the border of New Hampshire and
Maine, United States

189

190

186
188

188

193

195

196

194

195

197

199

201

200

202

203

204

207

209

208

xii

WORLD ATLAS OF SEAGRASSES

20.2 Ninigret Pond, Rhode Island 211
FIGURE: Eelgrass distribution in Ninigret
Pond, Rhode Island (United States]
plotted by depth for 1974 and 1992
FIGURE: Change in eelgrass area in
Ninigret Pond, Rhode Island (United
States] plotted against increasing number
of houses in the watershed

20.3 Maquoit Bay, Maine 213

TABLE

20.1 The area of eelgrass, Zostera marina,
in the western North Atlantic 212

THE SEAGRASSES OF The mid-Atlantic coast of
the United States 216
Map
21.1. The mid-Atlantic coast of the United
States 217
Case STUDIES
21.1 Seagrasses in Chincoteague Bay: a
delicate balance between disease,
nutrient loading and fishing gear impacts 220
FIGURE: Recovery and recent decline of
seagrass (Zostera marina and Ruppia
maritima} distribution in Chincoteague Bay
FIGURE: Aerial photograph taken in 1998 of
a portion of Chincoteague Bay, Virginia,
seagrass bed showing damage to the bed
from a modified oyster dredge
FIGURES
21.1 Seagrass distribution (mainly Zostera
marina and Ruppia maritima) in
Chesapeake Bay 218
21.2 Changes in seagrass (Zostera marina
and Halodule wrightii) distribution in
the Cape Lookout area [southern Core
Sound, North Carolina) between 1985
and 1988 218

22 THE SEAGRASSES OF The Gulf of Mexico 224
Map
22.1 The Gulf of Mexico 225
CASE STUDIES
22.1 Tampa Bay 226
22.2 Laguna Madre 228
FIGURE: Seagrass cover in the Laguna
Madre of Texas
22.3 Laguna de Términos 231

23 THE SEAGRASSES OF The Caribbean 234
Map
23.1 The Caribbean 235

CASE STUDIES

23.1 Florida's east coast 236
23.2 Parque Natural Tayrona, Bahia de

Chengue, Colombia 239
23.3 Puerto Morelos Reef National Park 240

24 THE SEAGRASSES OF South America: Brazil,

Argentina and Chile 243
Map
24.1 South America 245
CASE STUDIES
24.1 |Itamaraca Island, northeast Brazil 244
24.2 Abrolhos Bank, Bahia State, northeast

Brazil 247
24.3 Ruppia maritima in the Patos Lagoon

system 248
FIGURE

24.1 Cumulative number of companion
species to the Brazilian seagrasses

reported since 1960 245
APPENDICES
1 Seagrass species, by country or
territory 251

2 Marine protected areas known to
include seagrass beds, by country or

territory 256

3 Species range maps 262
The Global Seagrass Workshop 287
INDEX 288

REGIONAL MAPS

Europe Plate |, facing p 38
Africa, West and South Asia Plate III, facing p 102
Australasia Plate V, facing p 118
The Pacific Plate VII, facing p 166
Asia Plate IX, facing p 182
North America Plate XI, facing p 214
The Caribbean Plate XIII, facing p 230
South America Plate XIV, facing p 231

COLOR PLATES

The beauty of seagrasses Plate Il, facing p 39
Impacts to seagrass ecosystems Plate IV, facing p 103
Seagrass ecosystems Plate VI, facing p 119
Seagrasses and people Plate VIII, facing p 167
The sex life of seagrasses Plate X, facing p 183
Diversity of seagrass habitats Plate XII, facing p 215

Introduction to

Introduction

THE WORLD ATLAS OF SEAGRASSES

providing important ecological and economic

components of coastal ecosystems worldwide.
Although there are extensive seagrass beds on all the
world’s continents except Antarctica, seagrasses have
declined or been totally destroyed in many locations. As
the world’s human population expands and continues
to live disproportionately in coastal areas, a comp-
rehensive overview of coastal resources and critical
habitats is more important than ever. The World Atlas
of Seagrasses documents the current global distri-
bution and status of seagrass habitat.

Seagrasses are a functional group of about
60 species of underwater marine flowering plants.
Thousands more associated marine plant and animal
Species utilize seagrass habitat. Seagrasses range
from the strap-like blades of eelgrass (Zostera
caulescens) in the Sea of Japan, at more than 4 m long,
to the tiny, 2-3 cm, rounded leaves of sea vine [e.g.
Halophila decipiens) in the deep tropical waters of
Brazil. Vast underwater meadows of seagrass skirt the
coasts of Australia, Alaska, southern Europe, India,
east Africa, the islands of the Caribbean and other
places around the globe. They provide habitat for fish
and shellfish and nursery areas to the larger ocean,
and performing important physical functions of filtering
coastal waters, dissipating wave energy and anchoring
sediments. Seagrasses often occur in proximity to, and
are ecologically linked with, coral reefs, mangroves,
salt marshes, bivalve reefs and other marine habitats.
Seagrasses are the primary food of manatees, dugongs
and green sea turtles, all threatened and charismatic
species of great public interest.

Seagrasses are subject to many threats, both
anthropogenic and natural. Runoff of nutrients and
sediments from human activities on land has major
impacts in the coastal regions where seagrasses thrive;
these indirect human impacts, while difficult to
measure, are probably the greatest threat to seagrasses

Greve are valuable and overlooked habitats,

worldwide. Both nutrient and sediment loading affect
water clarity; seagrasses’ relatively high light require-
ments make them vulnerable to decreases in light
penetration of coastal waters. Direct harm to seagrass
beds occurs from boating, land reclamation and other
construction in the coastal zone, dredge-and-fill
activities and destructive fisheries practices. Human-
induced global climate change may well impact
seagrass distribution as sea level rises and severe
storms occur more frequently. The World Atlas of
Seagrasses makes it clear that seagrasses receive little
protection despite the myriad threats to this habitat.
Most of our understanding of seagrass ecosystems
is based on site-specific studies, usually in developed
nations. Very little is known about the importance of
seagrasses in maintaining regional or global
biodiversity, productivity and resources, partly because
seagrasses are under-appreciated and their distribution
is so poorly documented. As a result, seagrasses are
rarely incorporated specifically into coastal management
plans and are vulnerable to degradation. Seagrass
ecosystems in the Caribbean, Indian Ocean, Southeast
Asia and Pacific are especially poorly researched, yet it is
in these regions that the direct economic and cultural
dependence of coastal communities upon marine
resources, including seagrasses, tends to be highest.
The purpose of the World Atlas of Seagrasses is to
present a global synthesis of the distribution and status
of seagrasses. Such syntheses are available for other
coastal ecosystems and have been instrumental in
creating awareness, driving clearer conservation and
management efforts and focusing priorities at the
international level. For example, over the last ten years,
opinion on the status of coral reefs has changed from a
predominant view that the majority of coral reefs were
unaffected by human activities, to the present view in
which the global decline of coral reefs, and the increas-
ing threats to them, are widely acknowledged. A similar
understanding of seagrass ecosystems is needed in

Photo: M. Kochzius

WORLD ATLAS OF SEAGRASSES

A patch reef in the Philippines surrounded by a luxuriant mixed
bed of Thalassia hemprichii and Syringodium isoetifolium.

order to achieve the visibility and recognition necessary
to protect this valuable global resource. Public percep-
tion translates into political interest. Perceptions of
seagrass ecosystems must achieve comparable status
with those of coral reef and mangrove ecosystems,
through the creation of global maps, global estimates of
loss, knowledge of human impacts to the ecosystem,
regular monitoring of ecosystem status and a global plan
of action to reverse seagrass ecosystem decline. It is our
hope that the World Atlas of Seagrasses will contribute
to the more widespread recognition, understanding, and
protection of seagrass ecosystems worldwide.

ORGANIZATION OF THIS WORLD ATLAS

The World Atlas of Seagrasses is presented in two
sections. The first section comprises a Global Overview
of the state of our knowledge of seagrasses. It presents
detailed ecosystem distribution and species diversity
maps and the most accurate possible estimate of
global seagrass area. Appendices supply seagrass
species lists for almost 180 countries and territories, a
list of marine protected areas known to include
seagrasses and a collection of species range maps. The
Global Overview was based on a compilation of
seagrass literature and a workshop held in Florida with
seagrass scientists from around the world contributing
their regional knowledge and expertise. The Global
Seagrass Workshop, sponsored by UNEP-WCMC, with
considerable assistance from the World Seagrass
Association, was held in St Petersburg, Florida in
November 2001 specifically to begin assembling
information on global seagrass distribution for the
World Atlas (see page 287}. Twenty-three delegates
from 15 countries participated, and all are represented
here as chapter authors. The workshop was a forum for
discussion on the organization of an atlas, regional

seagrass distribution, and seagrass functions and
threats at a global level. Later, additional chapter
authors were asked to contribute to represent regions
of the world not yet well covered; also, chapter authors
invited co-authors to join their effort. The geographical
coverage of the World Atlas reflects this process.

The second section of the World Atlas of
Seagrasses consists of 24 regional and national
chapters. In each chapter, the authors have synthesized
knowledge of seagrasses, the plants’ biogeography,
ecology and associated species, historical perspectives
and threats to the ecosystem as well as management
policies pertaining to seagrasses. Wherever possible,
the authors have estimated the area of seagrass in
their region and summarized its status. Case studies
throughout the chapters highlight particularly interest-
ing seagrass habitats and areas where human or
natural impacts to seagrasses are of concern.

Dugong feeding on Halophila ovalis, Vanuatu, western Pacific
islands.

Of course, any comprehensive atlas builds on
the work of many scientists beyond the chapter
authors. Seagrass science owes much to den Hartog’s
Seagrasses of the World and the many subsequent
publications and books that are referenced throughout
the World Atlas. All of the references used to compile
the World Seagrass Distribution Map (reproduced on
page 21], as well as the individual chapter references,
appear in an online bibliography at http://www.
unep-wcmc.org/marine/seagrassatlas/references.

Photo: L. Murray

Photo: S.0. Bandeira

Additionally, the sources of information that contribute
to the World Seagrass Distribution Map may be queried
online through a GIS database at http://www-stort.
unep-wemc.org/imaps/marine/seagrass. Inevitably, in
a complex collaboration of this type, some sources of
data are overlooked. Indeed, we have become aware of
additional sources of information on the distribution of
seagrasses since our printing deadline. Readers with
information on seagrass distribution that they would
like to add to the database may contact us directly.

The seagrass distributions mapped in this World
Atlas were derived from scientific journals, books, other
publications and reports, reliable websites and personal
communications. Where these sources provided maps of
actual seagrass beds, that mapped extent of seagrass
(polygon) was entered directly onto the World Seagrass
Distribution Map. More frequently, publications and
other sources simply mention the occurrence of

=e 52 =
Women harvesting shellfish, Pinna muricata, from an intertidal
seagrass flat at low tide, Matibane, Mozambique.

seagrass at a particular location (e.g. a bay, beach, town
or known latitude/longitude). In these cases, the
seagrass occurrence is shown on the distribution map as
a dot, designating the mentioned location. The World
Seagrass Distribution Map at the beginning of the World
Atlas gives the compilation of all the available
information on seagrass distribution, as both actual beds
and as locations indicated by dots, of all seagrass
species combined. Species range maps (in Appendix 3)
depict the area where a certain seagrass species may be

Introduction

Eutrophication reduces water clarity and stimulates growth of
epiphytic algae, as on this Zostera marina in southern Norway.

expected to occur, based on individual species reports
collected for the World Seagrass Distribution Map. Using
an overlay of all the species range maps, a global map of
seagrass species diversity was created (reproduced on
page 22). Additionally, regional maps show the same
information as the World Seagrass Distribution Map, but
at a finer scale and with the locations of the case studies
in the region. Finally, each of the chapters has its own
map, showing seagrass distribution and important
locations discussed in the chapter.

THREATS TO SEAGRASSES

The synthesis represented by the World Atlas of
Seagrasses confirms that seagrasses are one of the
most widespread marine ecosystems, quite possibly
the most widespread shallow marine ecosystem, in the
world. They cover an area that can only be crudely
estimated at present; the area we are able to document
in the World Atlas is certainly a gross underestimate.
The threats to seagrasses worldwide are similar and
widespread. Seagrasses everywhere are vulnerable to
eutrophication from nutrient over-enrichment of the
environment and to turbid conditions caused by upland
clearing and disturbance, both leading to reduced light
availability. Seagrasses are also subject to total
destruction through coastal construction and other
direct human impacts. Direct use of seagrass plants by
humans is limited, but seagrass beds support impor-
tant coastal fisheries worldwide, and because they
occur in easily accessible, shallow, sheltered areas
these are often subsistence fisheries. Seagrasses are
an important coastal ecosystem in need of more study,
awareness and protection.

Ed Green
Fred Short

Photo: C. Bostrom

WORLD ATLAS OF SEAGRASSES

Essential information

LEGEND TO MAPS

Seagrass (location only, extent unknown)

Seagrass area

Number of species (map page 22)
1-2

3-6

7-9

10-11

12-15

MAPPING METHODS

The seagrass features mapped throughout this World Atlas were derived
from very many different sources. Selection criteria were used when
reviewing thousands of records from hundreds of sources to determine
which features would be mapped.

The approach adopted was one that minimized subjectivity. For
example a statement such as "...in Gerupuk Bay, southern Lombok,
Halodule uninervis densities ranged from...” (page 173] would result in a
point at that location. At the scale of a global atlas a point in Gerupuk Bay
is sufficiently accurate. Statements such as “extensive terracing of these
expanses of the intertidal zone [of the Kimberley Coast, Western
Australia] often results in seagrass, particularly Enhalus acoroides, high
in the intertidal just below the mangroves” (page 110] have not been
recorded on the maps because no exact locations or extent of seagrass
were available. At the scale of a global atlas an assumption that seagrass
occurs along large sections of the Kimberley coast would have been too
inaccurate without independent reference. Some islands or coastal areas
have comprehensive coverage on the maps. These are derived from
studies where an entire area has been mapped in great detail, often using
aerial photography or satellite remote sensing. Corsica is one example”
and the data were available for inclusion in the World Atlas maps. The
decision to construct the maps only on referenced sources [e.g. Corsica)

ABBREVIATIONS USED

m meter mg milligram
km kilometer g gram

ha hectare kg kilogram
cm/s centimeters per second kcal calorie

Bathymetry
0-200 m
200-2000 m
a >2000 m

Species range maps (Appendix 3)
Zosteraceae

Hydrocharitaceae

Posidoniaceae

Cymodoceaceae

and not extrapolation from rather inexact statements le.g. the Kimberley
Coast] does create some apparent discrepancies but in all cases these
are due to this decision. As such the collected total of seagrass features
mapped in the World Atlas should be regarded as a minimal
representation of actual coverage.

Two further rules were applied to the making of the seagrass
maps. Firstly, in some cases only crude maps were available, often
covering very large areas with swathes simply indicative of the presence
of seagrass [e.g. the global National Geographic 2000 Coral World map).
They were cut to match shallow bathymetry data to avoid
misrepresenting the depths at which seagrasses are found. Secondly,
when no specific location was available beyond the name of a very small
island a point was placed in the center of that island. Yap, Micronesia, is
one example. Seagrass is recorded as occurring all around Yap with no
more precise locators so this is recorded as a point centered on the
island. Yap is small enough so that, at the scale at which these maps are
most useful, a visible point covers the island entirely.

1 Pasqualini V, Pergent-Martini C, Pergent G [1999]. Environmental
impact identification along the Corsican coast (Mediterranean sea]
using image processing. Aquatic Botany 65: 311-320.

psu practical salinity units {almost
equal to parts per thousand]

UV ultraviolet

°C degrees Centigrade

Bold type is used to indicate the corresponding author and contact details at the end of each chapter.

Global overview

The distribution and status of seagrasses

THE DISTRIBUTION AND STATUS

OF SEAGRASSES

which grow submerged in shallow marine and

estuarine environments worldwide. In many
places they cover extensive areas, often referred to as
seagrass beds or seagrass meadows. Although there
are relatively few species of seagrass, the complex
physical structure and high productivity of these eco-
systems enable them to support a considerable bio-
mass and diversity of associated species. Seagrasses
themselves are a critically important food source for
dugong, manatee, sea turtles and waterfowl. Many
other species of fish and invertebrates, including sea
horses, shrimps and scallops, utilize seagrass for part
of their life cycles, often for breeding or as juveniles.
Seagrasses are considered to be one of the most
important shallow marine ecosystems to humans,
playing a significant role in fisheries production as well
as binding sediments and providing some protection
from coastal erosion.

The overview summarizes the distribution, impor-
tance and status of seagrasses worldwide. Firstly we
consider the definition of seagrasses, both as species
and as habitats, and look at their geographic distribution
patterns. Much of this work is the presentation of
entirely new datasets that have been developed for this
atlas, including a detailed distribution database and digi-
tal maps compiled from numerous sources, often gener-
ously contributed. Next we consider the importance of
seagrasses to humans. Finally we look at human
impacts on these ecosystems, including both threats and
management measures for the protection of seagrass
beds. Much of this chapter has benefited from the spec-
ialist input of seagrass experts worldwide, and especially
those who are also contributors to this World Atlas.

Gites are a mixed group of flowering plants

Definitions
Seagrasses are flowering plants which grow fully
submerged and rooted in estuarine and marine

M. Spalding
M. Taylor
C. Ravilious
F. Short

E. Green

environments. They are not true grasses. Although they

are all monocotyledons, they do not have a single

evolutionary origin, but are a polyphyletic group,
defined by the particular ecological niche they inhabit.

Five particular adaptations to enable survival in this

niche have been identified":

) an ability to grow whilst completely submerged,
which presents problems, notably of lowered gas
concentrations and rates of diffusion;

fo) an adaptation to survive in high, and often varying,
salinity;

) an anchoring system to withstand water
movements;

a submarine pollination mechanism;
an ability to compete with other species in the
marine environment.

The adaptations have led to a number of
morphological characteristics which are widespread
amongst seagrasses, notably: flattened leaves [with the
exception of Syringodium and some Phyllospadix spp.);
elongated or strap-like leaves [with the exception of
species in the genus Halophila\); and an extensive
system of roots and rhizomes".

Considerable arguments remain over the
nomenclature and taxonomic relations of the sea-
grasses, and it is likely that there will be considerable
changes to the accepted classification in coming
years“ and hence to the number of species con-
sidered to be seagrasses. In the present work we have
adopted a conservative approach, and consider 59
species, based on species lists used in Hemminga and
Duarte”! and in Short and Coles", with further advice
from the authors of this World Atlas. These species
are listed in Table 1. It is important to bear in mind,
however, that “the actual number of seagrass species
is a matter of debate, depending in part on their
proximity to the marine environment and on the level

WORLD ATLAS OF SEAGRASSES

of discrimination in
genetics”.

Many species of the genus Ruppia are accepted
as seagrasses, commonly occurring in the marine
environment and often intermingled with other
seagrass species”. Species in the genera Potamogeton

physical taxonomy and

Overview Table 1

A list of seagrass species by family
Genus Species Author
Hydrocharitaceae
Enhalus
Halophila
Halophila
Halophila
Halophila
Halophila
Halophila
Halophila
Halophila johnsonii’
Halophila minor’
Halophila ovalis
Halophila ovata’
Halophila spinulosa
Halophila stipulacea
Halophila tricostata
Thalassia hemprichii
testudinum

(L.f.) Royle

Doty & Stone
Ascherson

Ascherson

Larkum

Ostenfeld

Ascherson

Doty & Stone
Eiseman

(Zollinger) den Hartog
(R. Brown] Hooker f.
Gaudichaud

(R. Brown) Ascherson
(Forsskal) Ascherson
Greenway
(Ehrenberg) Ascherson
Banks ex Konig

acoroides
australis
baillonii
beccarii
capricorni
decipiens
engelmanni
hawaiiana’

Thalassia

Cymodoceaceae
Amphibolis
Amphibolis
Cymodocea
Cymodocea
Cymodocea

{Labill.) Sonder et Ascherson
(Black] den Hartog
Ostenfeld

(Ucria] Ascherson
Ehrenberg & Hemprich ex
Ascherson

serrulata (R. Brown] Ascherson
beaudette* (den Hartog) den Hartog
bermudensis* den Hartog

emarginata* den Hartog

pinifolia* (Miki) den Hartog
uninervis (Forsskal} Ascherson
wrightii Ascherson

Syringodium filiforme Kutzing

Syringodium isoetifolium {Ascherson) Dandy
Thalassodendron _ ciliatum (Forsskal) den

Hartog

den Hartog

antarctica
griffithii
angustata
nodosa
rotundata

Cymodocea
Halodule
Halodule
Halodule
Halodule
Halodule
Halodule

Thalassodendron — pachyrhizum

and Lepilaena are occasionally important members of
seagrass ecosystems, but are often regarded as
seagrass associates or facultative members of the
seagrass community. We have included Ruppia spp.
when they occur in marine and estuarine environ-
ments, but these species are less well covered in the

Genus Species Author
Posidoniaceae

Posidonia angustifolia Cambridge & Kuo
Posidonia Hooker f.
Posidonia Cambridge & Kuo
[including the conspecific Posidonia robertsoniae™"
Posidonia denhartogii* Kuo & Cambridge
Posidonia kirkmani* Kuo & Cambridge
(L.] Delile

den Hartog

Cambridge & Kuo

australis
coriacea*

oceanica
ostenfeldii*
sinuosa

Posidonia
Posidonia
Posidonia

Zosteraceae
Zostera
Zostera
Zostera

asiatica Miki

caespitosa = Miki

capensis Setchell

Zostera capricorni — Ascherson

including the conspecific Zostera mucronata, Zostera muelleri and
Zostera novazelandica™”)

caulescens Miki

Japonica Aschers. & Graebner

Zostera marina Linnaeus

Zostera noltii Hornemann

Zostera tasmanica _ (Martens ex Aschers.] den Hartog
(formerly Heterozostera)
Phyllospadix iwatensis
Phyllospadix
Phyllospadix
Phyllospadix serrulatus
Phyllospadix torreyi

Zostera
Zostera

Makino
Makino
Hooker

Japonicus
scouleri
Ruprecht ex Aschers.
S. Watson

Ruppiaceae

Ruppia cirrhosa (Petagna] Grande
(formerly spiralis)

Ruppia maritima Linnaeus

Ruppia megacarpa Mason

Ruppia tuberosa Davis & Tomlinson

Note:

* Species designations that are a matter of debate and currently
under genetic and morphometric investigation.

t Species proposed as conspecific with Halophila ovalis®’.

literature than many other species and have not been
universally accepted as seagrasses

Typically, seagrasses grow in areas dominated by
soft substrates such as sand or mud, but some species
can be found growing on more rocky substrates [e.g
Phyllospadix]. Seagrasses require high levels of light,
more than other marine plants, because of their
complex below-ground structures which include
considerable amounts of non-photosynthetic tissues.
Thus, although they have been recorded to 70 m in clear
waters", they are more generally restricted to shallow
waters due to the rapid attenuation of light with depth.

Seagrasses can form extensive monospecific
stands or areas of mixed species. Such areas are
known as seagrass beds or meadows, and make up a
unique marine ecosystem or biotope. Seagrasses can
also grow in isolated patches, or as part of a habitat
mosaic with other habitats such as corals, mangroves,
bivalve reefs, rocky benthos or bare sediments
Generally it is the larger seagrass beds and meadows
which have been the subject of intensive study and
mapping worldwide. Although typically permanent over
periods of decades, seagrass systems can be highly
dynamic, moving into new areas and disappearing from
others over relatively short timeframes.

DEVELOPING SEAGRASS DISTRIBUTION
INFORMATION AND MAPS

In order to develop a clearer picture of the distribution of
seagrasses worldwide, a new dataset was developed at
UNEP-WCMC, based on literature review and outreach
to expert knowledge. An output from this dataset is
presented here in the World Seagrass Distribution Map
(Map 1, which appears on page 21).

Initial efforts focused on the acquisition of point-
source information which was compiled into a
spreadsheet with details on species as well as
information on location in both descriptive terms and,
wherever possible, geographic coordinates. This work
continued throughout a second data-gathering phase,
during which maps on the distribution of seagrasses
were developed on a geographical information system
(GIS). The two datasets remained closely linked: the
point locations from the first phase were linked to the
GIS, and the GIS layer also allowed for the
incorporation of boundary information delimiting
particular seagrass areas [polygons]. A third phase
involved the presentation of the initial maps prepared
by UNEP-WCMC to the Global Seagrass Workshop in
Florida, 2001, where they were thoroughly checked by
regional and national seagrass experts. As a result,
new data points were added, new datasets and
references were provided, and incorrectly located or
Spurious data points were removed.

At the conclusion of this effort, over 520 major

The distribution and status of seagrasses

Quadrat sampling in an intertidal Zostera marina bed, Maine, USA

sources had been used in developing seagrass
distribution data [see the online bibliography at
http://www.unep-wemc.org/marine/seagrassatlas/
references}. These sources provide information on
seagrasses in more than 120 countries and territories
worldwide, and the majority include information on
specific species. All data sources were documented
and can be queried online through the GIS (go to
http://stort.unep-wcemc.org/imaps/marine/seagrass).

Despite the broad range of sources, the
geographic information can be seen largely to fall into
three categories, as discussed below.

Direct habitat maps

Direct habitat maps are high-resolution maps, typically
prepared from remotely sensed data but in some cases
mapped entirely from field observations; they
represent the polygons showing the true spatial extent
of seagrass distribution. They provide the most
accurate data available for habitat distribution, but are
available for only a very limited area worldwide. In
some cases they do not provide species-specific
distribution information. Sources included some
broader maps showing seagrasses over several
kilometers or tens of kilometers of coastline, but also
many maps prepared and presented for individual study
sites in expert publications.

Expert interpolations

In some cases, maps have been based on the
interpolation of ground-based knowledge and
observation - seagrasses may be known from a series

WAT

WORLD ATLAS OF SEAGRASSES

of point locations, and with an accurate benthic chart it
is possible to interpolate between these points to
generate an outline of assumed seagrass area. Clearly
the accuracy of such maps is highly variable, but can be
relatively reliable with sufficient background infor-
mation and cautious interpretation. These maps were
utilized with caution and included in the GIS only if
better data were unavailable and the source was
considered to be reliable.

Point-based samples

For wide areas of the globe, maps of any sort were
unavailable; however, it was possible to gather accurate
point locations of seagrass beds from a large number of
site-based seagrass publications, herbarium records
and national species inventories. Clearly, as points,
these give no indication of actual seagrass area, but they
are very useful in a broader mapping context where no
further information is available.

Developing the distribution map

The source maps used for producing the World
Seagrass Distribution Map were created using many
mapping techniques, and with various goals. There are
also differences in resolution, which will clearly influ-
ence the area of seagrass portrayed on a map. With
remote sensing, accuracy is limited by the resolution
and bandwidths utilized by the sensor, the degree of
ground-truthing and sensitivity of the interpretation, as
well as by the depth of the water column, the clarity of
the water and other attributes of the benthos. Some
remotely sensed images will pick up only shallow
(<10 m) seagrass beds with a high shoot density, while
large pixel size will fail to capture small or highly
patchy seagrass areas. Error also plays a part, and
some mapping systems may incorporate non-seagrass
species, notably macroalgae. Although typically more
accurate, direct sampling can have many similar
problems, particularly associated with water depth
and clarity.

Combining data from multiple sources, as
undertaken here, exacerbates these problems, as
there are always differences in both quality and
definition between studies. Seagrass shoot density
varies considerably and, while some studies will
consider only seagrass ecosystems where seagrass
shoots are continuous at high densities [such a
definition may in fact be forced by the mapping
techniques], others may include all areas of even very
sparse seagrass growth. Differences in scale between
studies introduce further variance: lower resolution
maps may tend to ignore minor breaks in seagrass
beds, while finer resolution maps will pick up even
small breaks which, it could be argued, are still a part
of the seagrass habitat. Further problems may be

associated with time. Seagrass systems are highly
variable through time, with some showing seasonal
variations and others showing dramatic interannual
variation. Finally, it is important on a composite map,
such as that presented here, to be aware that gaps
where there are no data cannot be distinguished from
gaps where seagrasses do not occur.

The results of this data gathering have been used
to show the distribution of individual species, and to
show the overall distribution of seagrass habitat. The
World Seagrass Distribution Map includes all the
species-specific information as well as additional
points and areas where species were not specified.

Interpolation of the species distributions was
used to generate species range maps (see Appendix 3).
The known occurrences of each species were used to
set the limits to a generalized outline of the range of
that species. Like the raw datasets, preliminary range
maps were reviewed at the Global Seagrass Workshop
in Florida. It should be noted that they do not indicate
definite occurrence of a seagrass species, but rather
show where a species might be expected to occur
should environmental conditions be suitable. Such
maps are useful in biogeographic studies and
comparisons between species, and also for predicting
possible species occurrence in areas which have not
been previously investigated.

The data that constitute the World Seagrass
Distribution Map were also used to make a preliminary
calculation of seagrass area at global and regional
levels. Such work has been done in more detail for
other nearshore marine habitats'””'; however the
weaknesses and gaps in the seagrass dataset mean
that initial area calculations, presented below, are only
broadly indicative.

SPECIES DISTRIBUTION

From the world seagrass distribution datasets
described above, we assembled species records for
more than 120 countries and territories. The datasets
include some records for countries where point
locations were unavailable [i.e. only species lists were
available), and hence these are not shown on the maps.
All the datasets were used to generate species lists by
country, presented in Appendix 1. The species lists show
that the countries with greatest seagrass diversity are
countries which extend into both tropical and temperate
climates, including Australia (29 species), the United
States (23 species including all overseas territories) and
Japan (16 species]. The greatest seagrass species
diversity in single-climate countries occurs in the
tropics. Tropical countries with the highest seagrass
species diversity include India and the Philippines (both
with 14 species) and Papua New Guinea (12 species).
The Philippines and Papua New Guinea, together with

Indonesia (12 species], are considered to be the center
of global seagrass biodiversity.

The geographic data from the same seagrass
distribution datasets were used to generate the
species range maps presented in Appendix 3. (Range
maps were not prepared for Ruppia species as the
existing data were deemed insufficient.] The species
range maps update earlier work by den Hartog” and
by Phillips and Menez". They show areas where the
species may be expected to occur, but they may leave
out some areas where seagrass information is not
available.

By amalgamating the species range maps, a
global map of seagrass biodiversity was created (Map 2,
page 22). The biodiversity map indicates the number of
seagrass species in various parts of the globe; a
previous effort is provided in Hemminga and Duarte™|.
Map 2 is modeled on similar maps compiled for corals!”

and for mangroves'"’.

Biogeographic patterns
Map 2 shows the three clear centers of high diversity,
all of which occur in the eastern hemisphere. The first
and largest of these lies over insular Southeast Asia.
The other two centers are adjacent to this region but
remain distinctive, being Japan/Republic of Korea
and southwestern Australia. Other areas of
significant diversity include southern India and
eastern Africa. Looking at diversity patterns in more
detail, and also at the individual species ranges that
underpin them, it is possible to distinguish general
regions of seagrass occurrence, each with distinctive
floral characteristics” '”. The following list of
seagrass regions is largely based on Short et al.'”.

1 Tropical Indo-Pacific (IX in Short et al.'”)).
Mirroring the biodiversity found in coral reefs and
mangrove forests, this is a region dominated by
tropical seagrass species, with a great focus of
diversity in insular Southeast Asia and northern
Australia, continued high diversity across the
Indian Ocean and up the Red Sea, but relatively
rapid attenuation of biodiversity across the Pacific
islands. Key genera include Cymodocea, Enhalus,
Halodule, Halophila, Syringodium, Thalassia and
Thalassodendron.

2. Southern Australia (X). A highly diverse region,
dominated by temperate species. The particular
center of diversity occurs in southwestern
Australia (with species in the genera of
Amphibolis, Halophila, Posidonia and Zostera).

3 Northwestern Pacific [I]. The third-highest
diversity region which, although connected to
insular Southeast Asia, is dominated by
temperate species (notably species of Zostera
and Phyllospadix). The genus Phyllospadix is

The distribution and status of seagrasses

Halophila capricorni female flower, Lizard Island, Queensland,
Australia

unique to the North Pacific, occurring in both the
east and the west.

4 Northeastern Pacific (I): A lower-diversity temp-
erate area, dominated by Zostera and Phyllospadix
species. This region is closely linked to the more
diverse western North Pacific but also includes
three endemic species, Phyllospadix scouleri,
Phyllospadix serrulatus and Phyllospadix torreyi.

5 North Atlantic [Ill]. A low-diversity temperate
area, dominated by Zostera and Ruppia species,
with Halodule reaching its northern limit at 35°N
in North Carolina, USA. Europe is distinguished by
having a second species of the Zostera genera,
Zostera noltii. Zostera marina is the main species
of the region.

6 Wider Caribbean (IV). A tropical area with
moderate seagrass diversity, including species of
Halodule, Halophila, Syringodium and Thalassia.
Although the tropical communities of Brazil are
geographically isolated they are not sufficiently
distinct to merit consideration as a separate flora
(limited to species of Halodule, Halophila and
Ruppia).

7 Mediterranean [VI]. An area of relatively diverse
temperate and tropical seagrass flora, which
includes seagrass communities just outside the
Mediterranean in northwest Africa as well as
communities in the Black Sea Basin and the
Caspian and Aral Seas. Species of Cymodocea,
Posidonia and Zostera are common; Ruppia also
plays an important role in the region, particularly
in the Black, Caspian and Aral Seas.

Photo: W. Lee Long, DPI

WORLD ATLAS OF SEAGRASSES

8 South Africa [VIII]. The region has both temperate
and tropical species from the genera Halodule,
Halophila, Ruppia, Syringodium, Thalassodendron
and Zostera.

In addition to these floristically distinct regions
there are three other geographically distinct seagrass
areas which are of biogeographic interest, but which
are poorly known and lack a distinctive floral
characteristic, being largely depauperate.

9 Chile [II]. One species, Zostera tasmanica
(formerly Heterozostera), has been found along
this coast.

10 Southwest Atlantic [V]. Along the coast of
Argentina and southern Chile there are extensive
communities of Ruppia.

11. West Africa [VII]. Only one species, Halodule
wrightii, has been recorded; the distribution is
poorly known.

Considerable further work is required in order to
understand fully the distribution patterns of sea-
grasses; to determine the patterns of evolution and
migration of species; and to uncover the inter-
connections between these regions. Some of the
patterns observed in the tropical floras mirror the
patterns observed in corals and mangroves. The South-
east Asian center of diversity is a particular feature of
several marine biodiversity maps produced to date,
including mangroves’ and several major groups of
coral reef taxa’. It is important to distinguish this
Southeast Asian region from the separate centers of
diversity seen in southwestern Australia and Japan, as
these two areas have larger ranges of climate from
temperate to tropical (Map 2).

Theories for the development of the Southeast
Asian center of diversity have been advanced for a
number of species groups. It has been variously
suggested that this region may have been a center for
species accumulation linked to favorable ocean
currents (“the vortex model of coral reef bio-
geography"; a location where high diversity was
maintained thanks to benign climatic conditions during
recent ice ages'”'; or a center for species evolution with
the combination of benign conditions and changing sea
levels ("eustatic diversity pump model").

The high diversity of temperate species in Japan
and southwestern Australia is also of considerable
evolutionary interest, but its cause remains a matter of
speculation. There is evidence that the southwestern
Australian flora may contain important relict
elements'” but more recent events associated with the
dramatic changes during and following the last ice age
must also be considered.

It is important to consider the evolutionary origin

of seagrasses. The relatively low number of seagrass
species could lead to the inference of a recent
evolutionary history; however den Hartog” reports
evidence for the existence of marine angiosperms as
long ago as 100 million years, and there are clear
examples of seagrass fossils from the Cretaceous.
Further studies have failed to produce evidence of any
massive diversification or of major extinction events,
and so it may be that seagrasses have simply followed
a relatively conservative evolutionary pathway. More
work is required in this field".

ASSOCIATED SPECIES AND HABITATS

Seagrasses do not grow in isolation but form an
integral and often defining part of highly complex
ecosystems. The seagrasses themselves are an
important standing stock of organic matter, which is
relatively stable in the tropics and has broad intra-
annual variation in temperate regions. The productivity
of these ecosystems is usually enhanced by other
primary producers, including macroalgae and epiphytic
algae. The abundant plant material of seagrass beds
forms an integral part of many food chains.
Additionally, the complex three-dimensional structure
of the seagrass bed is important, providing shelter and
cover, binding sediments and, at fine scales, even
altering the patterns and strength of currents in the
water. The complex, modified seagrass environment
provides a great variety of niche spaces on and within
the sediments, on the plant surfaces and within the
water column.

Thus, despite the relatively small number of
seagrass species, a vast array of other species can be
found within seagrass ecosystems. Many are obligate
members of the seagrass ecosystem, found nowhere
else. Others may be restricted to seagrass areas for
shorter periods of their life histories, using them as
breeding or nursery areas, or settling there for their
adult lives. Many more are found across a broad range
of marine habitats, but regularly inhabit seagrass
areas. Table 2 provides a list of some of the major
taxonomic groups typically associated with seagrass
ecosytems.

Seagrass ecosystems often play an important
role in the functioning of a wider suite of coastal and
marine ecosystems, including coral reefs and man-
groves in the tropics, but also soft muddy bottoms,
intertidal flats, salt marshes, oyster reefs and even
pelagic ecosystems.

Levels of species diversity in seagrass eco-
systems can be very high indeed. Humm'” listed 113
species of algal epiphytes from Thalassia testudinum
beds in Florida. Using this, combined with lists from
26 other publications worldwide, Harlin” produced a
list of some 450 algal species that are epiphytic

The distribution and status of seagrasses

Overview Table 2
Major taxonomic groups found in seagrass ecosystems, with brief notes
Taxonomic group Notes

Bacteria

Fungi Including Plasmodiophora
Diatoms (Bacillariophyta]
Blue-green algae (Cyanophyta]
Red algae (Rhodophyta)

Brown algae (Phyaeophyta]
Green algae (Chlorophyta)

Including calcareous species
Including Padina
Notably Ulva, Halimeda and Caulerpa

Protozoa
Sponges
Cnidarians

Polychaetes
Ribbon worms
Sipunculid worms
Flatworms
Crustaceans

Bivalve mollusks
Gastropod mollusks
Cephalopod mollusks
Bryozoans
Echinoderms

Tunicates
Fish

Reptiles
Birds

Includes the slime molds Labyrinthula spp., and Foraminifera

Includes epiphytic and free-standing species

Includes epiphytic hydrozoans, sea anemones, solitary corals and Scleractinia such as Pavona,
Psammacora, Porites, Pocillopora, Siderastrea

Including rag-worms (nereids)

Includes amphipods, and many decapod crustaceans including crabs, stomatopods and commercially
important shrimp and lobster

Some oysters and scallops, also many boring species

A broad range including Conus, Cypraea and commercially important species of Strombus

Squid and cuttlefish often found over seagrass areas

Epiphytic on seagrass and rocks

A range of commercially important holothurian species, ophiroids are widespread, but also asteroids and
echinoids

Ascideans

All groups, but including the commercially important Haemulidae (grunts), Siganidae (rabbitfish),
Lethrinidae {emperors}, Lutjanidae [snappers], Bothidae (left-eye flounders), Syngnathidae (pipefishes and
sea horses]; many of the latter, which are used in the aquarium trade and Chinese medicine trade, are

considered threatened
Notably the green turtle Chelonia mydas
Notably brant (geese) and other migrating waterfowl and wading birds

Mammals
senegalensis

Source: Key references for this table include various chapters in Phillips and McRoy

Atlas.

on seagrasses, still probably an underestimate.
Hutchings" listed some 248 arthropods, 197 mollusks,
171 polychaetes and 15 echinoderm species from
Jervis Bay in New South Wales, Australia. In Florida,
Roblee et al.” noted 100 species of fish and 30 species
of crustaceans in seagrass beds.

A number of studies have compared diversity in
seagrass beds with that observed in adjacent eco-
systems. Seagrasses consistently have higher levels of
diversity than adjacent non-vegetated surfaces; how-
ever, if other vegetated surfaces, or coral reefs, are
compared these often have similar to significantly

higher levels of diversity”.

Notably the sirenian species dugong Dugong dugon and manatee Trichechus manatus, Trichechus

('8| and review comments by the contributors to this World

Despite this high diversity and the importance of
associated species, there is no detailed database of
species associated with seagrass beds. Many of the
species that have been recorded are also found in other
ecosystems, although some appear to be restricted to
seagrass ecosystems or dependent on them for at least
a part of their life cycles. Such seagrass-dependent
species range from particular epiphytic algae” to the
large seagrass-grazing manatee and dugong. Most of
the comprehensive faunal assessments have been
undertaken in temperate waters, or the relatively low-
diversity waters of the Caribbean, and it seems likely
that further work in the Indo-Pacific in particular will

WORLD ATLAS OF SEAGRASSES

lead to large increases in the recorded numbers of
seagrass associates.

Threatened and restricted range species

Within the wider conservation arena, species with
restricted distributions, together with threatened
species, are often singled out for attention. Apart from
concerns over these individual species, they are often
used as “flagship species” to draw attention to partic-
ular areas and issues. Amongst the seagrasses,
however, the problems of taxonomic uncertainty under-
mine the determination of both threat and restricted
range.

Two species of seagrass have been listed as
threatened by IUCN-The World Conservation Union'*”
{see Table 3): Halophila johnsonii and Phyllospadix
serrulatus. A number of countries harbor the sole
populations of a seagrass species (national endemics},
most notable of which is Australia, with 13 species
found nowhere else in the world. Such national
endemism has no inherent ecological significance,
although it can be used as a basis to support

Overview Table 3

conservation actions. Using the species range maps, it
is possible to calculate the total area of each species
range. For such calculations it was necessary to modify
the broad range maps and not to include areas outside
the continental shelf in the calculations. These range-
area Statistics are provided next to the species range
maps in Appendix 3. From this work we can see that only
a small number of species have truly restricted ranges,
notably: Halodule bermudensis (1000 km’), Halophila
hawaiiana (7000 km’), Halophila johnsonii (12000 km’),
Posidonia ostenfeldii (66000 km’), Posidonia kirkmanii
(66000 km’) and Halodule beaudettei (74000 km’).
However, all these six species are in the process
of taxonomic review and their individual species
designations are presently in question.

Given the problems of taxonomy, and the low
threat to the existence of individual seagrass species,
measures of restricted range, endemism or threat of
extinction are probably of little value in seagrass
conservation efforts. Similar arguments are not true for
seagrass-associated animals, although here lack of
knowledge hampers a true assessment of the full

Threatened species regularly recorded from seagrass communities worldwide

Common name Status
Johnson's seagrass

Surf grass

Horseshoe crab
Horseshoe crab
Big-bellied sea horse
Sea horse

Short-headed sea horse
Lined sea horse

Sea pony

Spiny or thorny sea horse
Sea horse

Species

Halophila johnsonii
Phyllospadix serrulatus
Carcinoscorpius rotundicauda
Tachypleus tridentatus
Hippocampus abdominalis
Hippocampus borboniensis
Hippocampus breviceps
Hippocampus erectus
Hippocampus fuscus
Hippocampus histrix
Hippocampus jayakari

Notes:
* Juveniles regularly observed in seagrass beds.

Common name Status
Spotted or yellow sea horse Vu
Slender sea horse Vu
White's sea horse Vu
Dwarf sea horse Vu
Nassau grouper En
Venezuelan grouper Vu
Gag grouper Vu
Green turtle En
Dugong Vu
West Indian manatee Vu
West African manatee Vu

Species

Hippocampus kuda
Hippocampus reidi
Hippocampus whitei
Hippocampus zosterae
Epinephelus striatus*
Mycteroperca cidi*
Mycteroperca microlepis*
Chelonia mydas

Dugong dugon
Trichechus manatus
Trichechus senegalensis

This list includes only species which are partially or wholly dependent on seagrasses and may be incomplete.
DD - Data Deficient: A taxon is Data Deficient when there is inadequate information to make a direct, or indirect, assessment of its risk of
extinction based on its distribution and/or population status. A taxon in this category may be well studied, and its biology well known, but

appropriate data on abundance and/or distribution is lacking.

R - Rare: Taxa with small world populations that are not at present Endangered or Vulnerable but are at risk. These taxa are usually localized
within restricted geographic areas or habitats or are thinly scattered over a more extensive range
Vu - Vulnerable: A taxon is Vulnerable when it is not Critically Endangered or Endangered but is facing a high risk of extinction in the wild in the

medium-term future.

En - Endangered: A taxon is Endangered when it is not Critically Endangered but facing a very high risk of extinction in the wild in the near future.
Critically Endangered: A taxon is Critically Endangered when it is facing an extremely high risk of extinction in the wild in the immediate future.

Source: Walter and Gillett'2!. |UCN!4,

threats facing many species. Table 3 provides a list of
some of the known seagrass species and seagrass
associates listed as threatened by IUCN". The clear
focus of this list towards a few groups is probably
indicative of the general lack of knowledge of the status
of many seagrass associates. This problem has also
been more widely recognized by IUCN! which
acknowledges that “there has been no systematic
assessment” apart from some limited groups. Of the
species which have been listed, most remain poorly
known or are ranked at a relatively low level of threat
such as “Vulnerable”.

DISTRIBUTION OF SEAGRASS HABITAT

The known locations of seagrass ecosystems, based
on the mapping efforts described above, are presented
in the World Seagrass Distribution Map {Map 1) and in
the maps which appear in Chapters 1-24. In some
parts of the world, notably the western North Atlantic,
the Gulf of Mexico, Queensland [Australia], Western
Australia and some parts of the Mediterranean, the
maps are based on fairly comprehensive information
on seagrass distribution. Elsewhere, available
information is more sporadic, restricted to individual
sites, bays or national coverages for smaller countries,
though there may be some documentation of broader
distribution patterns. Typically this is the case for
areas such as the western Pacific, the Indian Ocean
and the Caribbean. Over a few large stretches of the
world’s coasts, there exists almost no information on
whether or not seagrasses occur, let alone their
density, extent or species composition. This is notably
the case for West Africa, South America, Greenland,
northern China and the Siberian coast, and parts of
Southeast Asia and the Pacific islands.

The World Seagrass Distribution Map shows the
broad distribution of seagrasses in most of the world’s
oceans and seas, including the Black, Caspian and Aral
Seas, and further shows the considerable latitudinal
range of seagrasses. The most northerly locations for
seagrasses are for Zostera marina which is recorded at
Veranger fjord in Norway at 70°30'N, Chéshskaya Guba
in Russia (67°30'N) and in Alaska [at 66°33’N). The
most southerly locations are for Zostera capricorni in
New Zealand, with the southernmost record being at
46°55'S on Stewart Island, and Ruppia maritima in the
Straits of Magellan (54°S).

A limitation of these distribution maps is that
they provide no information on the extent of coast-
lines surveyed without finding seagrass and hence do
not distinguish between “no seagrass” and “no
information". Gaps in the distribution maps may
result from the lack of available data for certain parts
of the world, but in other areas they reflect knowledge
that no seagrass exists. Thus the western coastlines

The distribution and status of seagrasses

A sea horse, Hippocampus kuda, among Enhalus acoroides,

southern Peninsular Malaysia

of South America and of much of West Africa may
indeed have more seagrass communities than are
reflected here.

CALCULATING GLOBAL SEAGRASS AREA

The calculation of a global seagrass habitat area is very
important and useful for an assessment of the role of
seagrasses in global processes, particularly in global
carbon budgets, and also in assessing historical and
future loss of seagrass and in priority setting and
management of natural resources for activities such as
fisheries and conservation.

To date the only global area estimate for
seagrasses has been one of some 600000 km?”
reportedly derived from Charpy-Roubaud and
Sournia””. The latter paper, however, does not provide
an area estimate directly, and it would appear that the
figure of 600000 km’ is derived from a global estimate
of seagrass productivity’ *” and typical seagrass
productivity figures taken from an unspecified source.
This estimate’ seems too large, as the original source
of global productivity was itself based on an area
estimate of only 350000 km’ for seagrasses, salt
marshes and mangrove communities combined.

The calculation of global and regional habitat
areas for the marine environment can be done using
two broad approaches. The first is to estimate or model
probable habitat area utilizing known and mapped
parameters, such as bathymetry, coastal features or
existing biogeographic knowledge. The second involves

WORLD ATLAS OF SEAGRASSES

Overview Table 4
Estimates of seagrass coverage for selected areas
described in this World Atlas

Location Area (km?}
Scandinavia 1850
Western Europe 338
Western Mediterranean 4152
Euro-Asian Seas 2600
Saudi Arabia

Mozambique

India

Western Australia

Eastern Australia

New Zealand

Thailand

Peninsular Malaysia

Kosrae, Federated

States of Micronesia

Indonesia

Philippines

Viet Nam

Japan

Korea, Republic of

Pacific coast of North America 1000
Western North 374
Atlantic coast of USA

Mid-Atlantic coast 292
of USA

Gulf of Mexico 19349
East coast of Florida 2 800
Mexico 500
Belize 1500
Curacao

Bonaire

Tobago

Martinique

Guadeloupe

Grand Cayman

Brazil

Chile

Argentina

Chapter

Note: Almost certainly an underestimate in most cases.

the use of mapped data to develop a more direct
calculation. In many studies, elements of both
approaches have been combined.

Using a simple modeling approach, the total area
of continental shelf (coastal waters to a depth of 200 m)
worldwide has been estimated at almost 25 million
km?" Assuming a constant slope, this estimate would
imply an area of approximately 5 million km? of benthos

Average area

0.61
0.03

tS
one

=
g
7

N Hectares

Overview Figure 1
Relative size-frequency distribution of 538 seagrass polygons in
latitudinal swathe 20-30°S

Notes: The number of polygons is plotted on the primary y-axis [bars]
against a logarithmic scale of area. The percentage frequency of each size
class is plotted on the secondary y-axis [dots] and the mean area of all
polygons in each size category is stated at the top of the columns. In this
swathe there are 180 seagrass polygons of 1-10 ha in area. In other words
33 percent of the polygons in this swathe have an average area of 4.84 ha
In the area calculation it was therefore assumed that a third of all points at
these latitudes were each representative of a seagrass area 4.84 ha in size,
that 37 percent of points were representative of areas 35.7 ha in size, etc.

within the depth range of most seagrasses, although
for large parts of the globe turbidity, substrate
characteristics and other factors reduce this area of
potential seagrass. In reality, seagrasses occupy only a
fraction of the world’s nearshore waters. If the total
area of seagrasses is less than 10 percent of the
shallow water area of the world’s continental shelves,
then the maximum area would be 500000 km’. This
upper limit incorporates many assumptions and is
likely to be an overestimate.

Many of the authors of the subregional and
national chapters of this World Atlas of Seagrasses
have either summarized the existing seagrass maps for
their area or consulted expert opinion to produce
estimates of seagrass coverage. Further details are
provided in the relevant chapters but these totals are
summarized in Table 4.

These chapters document some 164000 km’? of
seagrass but as these cover a limited geographic area
and a subset of known locations they cannot be used to
generate a global area.

The World Seagrass Distribution Map, developed

ona GIS, is now the most comprehensive map of global
seagrass occurrence in existence. Using this we have
begun to explore the direct calculation of global
seagrass area.

The World Seagrass Distribution Map dataset
includes more than 37000 polygons and some 8800
points. A total area of 124000 km‘ is clearly defined by
the polygons but these provide only partial geographic
coverage from a few areas which tend to be well known.
Point data represent seagrass areas where habitat
maps are not available. Though more poorly known

The distribution and status of seagrasses

large and important seagrass meadows and should be
factored into any calculation of area. We have
experimented with methods of using the polygon data
to estimate the seagrass area of these points by
calculating logarithmic size-frequency distributions of
polygon data in 10-degree latitudinal swathes.
The distribution was then applied to the points within
the swathe, generating an estimate for total seagrass
area (Figure 1}. Very small polygons, from data derived
from remote sensing (these small polygons tend to be
single or clusters of few pixels), and very large

than mapped areas, these locations are likely to have polygons, derived from sketch maps covering

Overview Table 5
Functions and values of seagrass from the wider ecosystem perspective

Function Ecosystem values

Primary production - including Seagrasses are highly productive, and play a critical role as food for many herbivores (manatee, dugong,

benthic and epibenthic production turtles, fish, waterfowl, etc.]. This productivity lies at the base of the food chain and is also exported to
adjacent ecosytems.

Canopy structure The growing structures of seagrasses provide a complex three-dimensional environment, used as a

habitat, refuge and nursery for numerous species, including commercially important fish and shellfish.

Epiphyte and epifaunal substratum The large surface area of seagrass above-ground biomass provides additional space for epiphytes and
epifauna,-supporting high secondary productivity.

Nutrient and contaminant filtration Seagrasses help to both settle and remove contaminants from the water column and sediments, improving
water quality in the immediate environment and adjacent habitats.

Sediment filtration and trapping — The canopy of seagrasses helps to encourage settlement of sediments and prevent resuspension, while
the root systems help to bind sediments over the longer term, improving water quality and in some places
helping to counter sea-level rise.

Creating below-ground structure The complex and often deep structures of the seagrass roots and rhizomes support overall productivity
and play a critical role in binding sediments.

Oxygen production The oxygen released from photosynthesis helps improve water quality and support faunal communities in

seagrasses and adjacent habitats.

Many seagrass ecosystems are net exporters of organic materials, supporting estuarine and offshore

productivity.

Seagrasses hold nutrients in a relatively stable environment, and nutrient recycling can be relatively

Organic production and export

Nutrient regeneration and
recycling efficient, supporting overall ecosystem productivity.

Organic matter accumulation Along with sediments the organic matter of roots, rhizomes and even leaves can remain bound within the
sediment matrix, or accumulate on adjacent coastlines or other habitats, building up the level of the
benthos and supporting other food webs.

By holding and binding sediments, and by preventing the scouring action of waves directly on

the benthos, seagrasses dampen the effects of wave and current energy, reduce processes of erosion,
reduce turbidity and increase sedimentation.

Seagrasses are capable of both self-maintenance and spreading to new areas via sexual and asexual
reproduction. Recovery following storms, disease or human-induced damage can be relatively rapid.

The complex community of the seagrass ecosystem supports important biodiversity and provides trophic
interactions with other important ecosystems such as coral reefs, mangroves, salt marshes and shellfish

Wave and current energy
dampening

Seed production/vegetative
expansion
Self-sustaining ecosystem

reefs.
As perennial structures, seagrasses are one of the few marine ecosystems which store carbon for
relatively long periods. In a few places such carbon may be bound into sediments or transported into the

Carbon sequestration

deeper oceans and thus play an important role in long-term carbon sequestration.

Source: Derived from Short et al'*"’ and Global Seagrass Workshop recommendations.

WORLD ATLAS OF SEAGRASSES

Overview Table 6

Summary of the goods and services provided by seagrass
ecosystems

Commercial and artisanal fisheries’

Finfish (snappers, emperors, rabbitfish, surgeonfish,
flounder}

Mollusks (conch, oysters, mussels, scallops, clams)’
Crustacea (shrimp, lobster, crab]

Mammals and reptiles (dugongs, manatee, green turtle} ””

Nursery habitat for offshore fisheries” ™

Food
Seeds of Zostera marina used to make flour by Seri Indians”
Rhizomes of Enhalus used as food in Lamu, Kenya”

Fodder or bedding for animals" “”

Fiber

Used in mat weaving, Lamu, Kenya”

Basket making, thatch, stuffing mattresses, upholstery“
Insulation’

Packing material”

Fertilizer and mulch“

Building dikes“

Coastal protection from erosion” *”

Water purification

Reducing eutrophication and phytoplankton blooms”
Removing toxic organic compounds from water column and
sediment

Interaction with adjacent ecosystems”

Nutrient export

Source of food or shelter, as a nursery, resting ground or
feeding ground”

Water column filtration™

Maintenance of biodiversity and threatened species”
Dugongs, manatee, green turtle”

Carbon dioxide sink’

Cultural, esthetic and intrinsic values“
Places of natural beauty

Recreational value

Educational value

Stabilizing sediments

Binding function of roots

Role of shoots in reducing surface flow and encouraging
settlement”

Source: Various sources - see references by entries

enormous areas [e.g. the global National Geographic
“Coral World” map], were excluded from this analysis
to avoid serious under- and overestimates respectively.

When combined with polygon data this method
generates an estimate for the global coverage of
seagrass of 177000 km’ (using median polygon areas
reduced the estimate by 4 percent). It is based on the
most comprehensive dataset on seagrass distribution
to date. However it is necessarily and unavoidably
based upon a number of crude assumptions and is
intended to be no more than indicative of the global
extent of seagrass. In any event, even the 177000 km’
is an underestimate of the actual global seagrass area,
since for many areas seagrasses have not been
documented. Until our knowledge of seagrasses in
large areas such as insular Southeast Asia, the east
coast of South America and the west coast of Africa
improves, it is unlikely that a better estimate can
be generated.

THE VALUE OF SEAGRASSES

Seagrasses are a critical ecosystem: their role in
fisheries production, and in sediment accumulation
and stabilization, is well documented, but there are
many other important roles, both in terms of their place
in the ecosystem and their value to humanity. Table 5
lists a number of the functions of seagrasses from a
wider ecosystem perspective.

Seagrasses have a relatively low biomass
compared with terrestrial ecosystems, but have a very
high biomass in relation to planktonic-based marine
communities. Figures for average biomass vary
considerably between seagrass species and between
studies; communities of Amphibolis, Phyllospadix and
Posidonia in particular are noted for their high
biomass, the last’s enhanced by extensive stem and
root systems. In contrast, species of Halophila, with
their small petiolate leaves and high turnover rates,
rarely achieve high biomass.

Duarte and Chiscano’, in a literature review,
calculated from nearly 400 samples an average
biomass for different seagrass species, and by
averaging these values derived an average biomass for
seagrass of 460 g dry weight/m’ {above- and below-
ground biomass combined]. As an estimate of global
seagrass biomass, such estimates are biased towards
large seagrass species. Taking these factors into
account, the median biomass statistic of 205 g dry
weight/m’, also from data in Duarte and Chiscano, may
be a more accurate reflection of the typical biomass for
seagrass communities worldwide.

In terms of productivity, Duarte and Chiscano
estimated an average net primary production of about
1012 g dry weight/m’/year. Even allowing for
overestimation, such figures are very high for marine

(26)

communities, with the same source citing productivity
figures for macroalgal communities of 1 g dry
weight/m’/day and of phytoplankton of 0.35 g dry
weight/m‘/day.

The high productivity and biomass of seagrasses
are an integral part of many of their uses and values
from a human perspective. A broad sample of the
goods and services provided by seagrasses is shown in
Table 6, while further information on a number of these
is given in the text, both here and in many of the
regional and national chapters.

Fisheries

Seagrass ecosystems are highly productive and also
have a relatively complex physical structure, thus
providing a combination of food and shelter that enables
a high biomass and productivity of commercially
important fish species to be maintained” °”. Seagrasses
also provide an important nursery area for many
species utilized in offshore fisheries and in adjacent
habitats such as coral reefs and mangrove forests. In
most cases, the association between commercially
important species and seagrasses Is not obligatory; the
same species are found in other shallow marine
habitats. There are, however, a number of studies which
clearly show the higher biomass of such species
associated with seagrasses as compared with adjacent

unvegetated areas”.

Sediment stabilization and coastal protection

Seagrasses are the only submerged marine photo-
trophs with an underground root and rhizome system.
This below-ground biomass is often equal to that of the
above-ground biomass, and can be considerably more
e.g. Posidonia’. The role of these roots and rhizomes in
binding sediments is highly important, as has been
illustrated in a number of studies that have compared
erosion on vegetated versus non-vegetated areas
during storm events. The role of seagrass shoots in this
process is also important, as these provide a stable
surface layer above the benthos, baffling currents and
therefore encouraging the settlement of sediments and

inhibiting their resuspension”.

Water purification and nutrient cycling

By enhancing processes of sedimentation, and through
the relatively rapid uptake of nutrients both by
seagrasses and their epiphytes, seagrass ecosystems
remove nutrients from the water column. Once
removed these nutrients can be released only slowly
through a process of decomposition and consumption,
quite different from the rapid turnover observed in
phytoplankton-dominated systems. In this way
seagrasses can reduce problems of eutrophication and

bind organic pollutants”.

The distribution and status of seagrasses

Mitigating climate change

The role of the world’s oceans in removing carbon
dioxide from the atmosphere is still being investigated
and remains poorly understood. It appears that
biological processes in the surface layers of the world’s
oceans are one of the few mechanisms actively
removing carbon dioxide from the global carbon
cycle. Within these processes, seagrasses clearly
have a minor role to play, although their high
productivity gives them a disproportionate influence on
primary productivity in the global oceans on a unit area
basis, and they typically produce considerably more
organic carbon than the seagrass ecosystem
requires’. Any removal of carbon either through
binding of organic material into the sediments or
export into the deep waters off the continental shelf
represents effective removal of carbon dioxide from the
ocean-atmosphere system which could play some role
in the amelioration of climate change impacts.

Maintaining biodiversity and threatened species

The concept of seagrasses as high-diversity marine
ecosystems has often been overlooked, but this role
has already been briefly outlined above. Seagrasses
also play a role in safeguarding a number of threatened
species, including those such as sirenians, turtles and
sea horses, which are widely perceived to have very
high cultural, esthetic or intrinsic values by particular
groups. The wider functions of biodiversity include the
maintenance of genetic variability, with potential
biochemical utility, and a possible, though poorly
understood, role in supporting ecosystem function and
resilience.

Economic valuation

There have been very few studies of the direct
economic value of seagrasses. In Monroe County,
Florida, the value of commercial fisheries for five
species which depend on seagrasses was estimated at
US$48.7 million per year, whilst recreational fisheries,
as well as the diving and snorkeling industry in that
county, contribute large sums to the economy and are
also indirectly dependent on seagrasses”.

Costanza et al.’ calculated a global value of
annual ecosystem services for “seagrass/algae beds”
of US$19004 per hectare per year. With their estim-
ated total area for these combined ecosystems of
2000000 km’ they calculated a global annual value of
US$3 801000000000 [i.e. US$3.8 trillion], based
almost entirely on their role in “nutrient cycling”,
which is only one of many values of the ecosystem. The
same source gives no value to seagrass/algae beds for
food production.

Further information is needed to demonstrate the
full economic value of seagrass ecosystems worldwide.

WORLD ATLAS OF SEAGRASSES

Damage to seagrass beds caused by yachts in Jersey, Channel
Islands, UK

It will be important not only to measure direct value
from activities such as fisheries but also indirect values
associated with various functions {Table 5] including
maintenance of water quality and protecting coastlines.
In many ways dollar values provide only a part of the
true picture of the value of an ecosystem, and it Is
important to consider other possible means to quantify
value, including employment, protein supply or even
quality of life as alternative measures which address
value from a human perspective. It should be noted that
even when dollar values are estimated they do not
represent the entire worth of the ecosystem and in no
way constitute a purchase value.

THREATS TO SEAGRASSES

The global threats to seagrasses have received
considerable attention from a number of authors [e.g.
Short et al”, Phillips and Durako'”, Short and Wyllie-
Echeverria’, Hemminga and Duarte’) and their
efforts are only summarized here. In many cases it
seems likely that declines in seagrass areas have been
the result not of individual threats but a combination of
impacts. Typical combined impacts may include in-
creased turbidity, increased nutrient loads and direct
mechanical damage. Seagrasses exist at the land-sea
margin and are highly vulnerable to the world’s human

populations which live disproportionately along the
coasts. Such conditions threaten seagrass ecosystems
and have resulted in substantial loss of many seagrass
areas in the more populated parts of the world, as well
as degradation of much wider areas over the last
100 years.

A number of natural threats to seagrasses have
been recorded. Geological impacts may include
coastal uplift or subsidence, raising or lowering beds
to less than ideal growing conditions. Meteorological
impacts can also affect seagrasses: major storm
events in particular may remove surface biomass and
even uproot and erode wide areas of shallow water.
Finally there are biological impacts. Typically these
are part of the ongoing processes in seagrass
ecosystems, such as grazing by fish, sea urchins,
sirenians, geese or turtles; they also include
disruption to the sediments by burrowing animals or
foraging species such as rays. It is rare that such
activities should disrupt seagrass beds over large
areas. Diseases, however, represent an important
biological impact which can have very widespread
effects. The eelgrass wasting disease recorded from
the North Atlantic in the 1930s" *” was caused by the
slime mold Labyrinthula zosterae”*”. This wasting
disease continues to occur and remains a threat to
eelgrass in the North Atlantic!” Similarly in Florida
Bay, disease caused by Labyrinthula sp. has been
implicated in an extensive seagrass die-off'".

Human threats to seagrasses are now
widespread. Many result in direct destruction of these
habitats. Dredging to develop or widen shipping lanes
and open new ports and harbors, and certain types of
fishery such as benthic trawling, have led to losses of
wide areas of seagrass. Boating activities frequently
lead to propeller damage, groundings or anchor
damage, often increasing sediment resuspension or
creating holes and initiating “blow-out" areas in
seagrass beds. Construction activities within coastal
waters have sometimes led to losses: land reclamation
is aclear example, as is the construction of aquaculture
ponds in some areas. Even the construction of docks
and piers can lead to some direct losses, and to further
losses arising from shading or fragmentation of
seagrass beds. The alteration of the hydrological
regime as a result of coastal development and the
building of sea defenses can also impact seagrasses.
There are examples of direct and deliberate removal of
seagrasses, for example to “clean” tourist beaches or
to maintain navigation channels.

In addition, many seagrass beds have been
affected by the indirect impacts of human activities.
Land-based threats include increases of sediment
loads: higher turbidity reduces light levels, while very
high sedimentation smothers entire seagrass beds.

Similarly, while seagrasses can assimilate certain
levels of nutrient and toxic pollutants, high levels of
increased nutrients from sewage disposal, overland
runoff and enriched groundwater discharge can reduce
seagrass photosynthesis by excess epiphytic over-
growth, planktonic blooms or competition from
macroalgae. Toxins can poison and kill seagrasses
rapidly. Another indirect threat comes from the
introduction of alien or exotic species. The alga

Overview Table 7
Summary of marine protected areas [MPAs] that contain seagrass ecosystems, from the UNEP-WCMC Protected Areas Database

Country or territory Number of sites
Anguilla

Antigua and Barbuda
Australia

Bahamas

Bahrain

Belize

Brazil

British Indian Ocean Territory
Cambodia

Canada

Cayman Islands
China

Colombia

Costa Rica

Croatia

Cuba

Cyprus

Dominica
Dominican Republic
France

French Polynesia
Germany
Guadeloupe

Guam

Guatemala
Honduras

India

Indonesia

Israel

Italy

Jamaica

Kenya

Korea, Republic of
Madagascar
Malaysia
Martinique
Mauritania
Mauritius

Mexico

The distribution and status of seagrasses

Caulerpa taxifolia, released into the Mediterranean in
the 1980s, has smothered and killed wide areas of
seagrass beds. In 1999, the same species was first
observed off the coast of California and could have the
same impact there”.

Climate change represents a relatively new threat,
the impacts of which on seagrasses are largely
undetermined“. Potential threats from climate change
may come from rising sea levels, changing tidal

Country or territory Number of sites
Monaco i
Mozambique

Netherlands Antilles
Nicaragua

Palau

Panama

Papua New Guinea
Philippines

Puerto Rico

Reunion

Russian Federation

Saint Lucia

Saint Vincent and the Grenadines
Saudi Arabia

Seychelles

Singapore

Slovenia

South Africa

Spain

Tanzania

Thailand

Tonga

Trinidad and Tobago

Tunisia

Turks and Caicos Islands
Ukraine

United Kingdom

United States

United States minor outlying island
Venezuela

Viet Nam

Virgin Islands (British)

Virgin Islands (US)

OF SS Sw nM — WwW Oe DY OW — — — LY OC

Note: Few of these sites are managed directly to support seagrass
protection, and in many cases they do not protect the most
important areas of seagrass In a region.

WORLD ATLAS OF SEAGRASSES

regimes, localized decreases in salinity, damage from
ultraviolet radiation, and unpredictable impacts from
changes in the distribution and intensity of extreme
events. In contrast there could be increases in
productivity resulting from higher carbon dioxide
concentrations”.

Various studies have attempted to quantify the
decline of seagrasses, although it must be accepted
that seagrasses have been degraded or lost over vast
areas without any knowledge of their existence. Short
and Wyllie-Echeverria’””” provide an analysis of
seagrass losses from reports worldwide. They found
that a loss of 2900 km’ of seagrass was documented
between the mid-1980s and the mid-1990s, and they
extrapolated likely seagrass losses over that time
period alone of up to 12000 km’ worldwide.

PROTECTING SEAGRASSES

The dramatic and accelerating declines in seagrass
areas worldwide are mirrored in other coastal
ecosystems such as mangroves and coral reefs”.
Concerns about these declines have prompted some
increase in efforts to protect these ecosystems.
Perhaps the most valuable protection measure is the
wholesale reduction of the full suite of anthropogenic
impacts via legislation and enforcement at local and

—— Number of sites

200 (left-hand scale)

~~ il Total area protected,
thousand km
(right-hand scale]

150

1900 10 20 30 40 50 60 70 80 90 2002

Overview Figure 2

Growth of marine protected areas which include seagrass
ecosystems, shown both as the number of sites (line] and the total
area protected (shaded area]

Notes: The total area statistics are for the entire MPAs; there is no
information on the area of seagrass within these sites but it Is likely to be
only a small fraction of the total area. Figure 2 covers only those sites for
which a date of designation has been recorded. In addition to the 205 sites
shown here there are a further 42 with a total area of some 3 500 km?
whose year of designation is not known

regional scales. Unfortunately the cost is high and rates
of improvement are low.

More practical protection, although only localized
in effect, is the establishment of marine protected
areas [MPAs], legally gazetted sites where certain (but
by no means all) human activities are controlled or
prohibited in order to provide some protection of
marine resources or to promote sustainable fisheries.
Whether out of direct interest or as an indirect
beneficiary, seagrass habitat is present in an
increasing number of sites in the expanding MPA
network. The total number of MPAs has increased
dramatically in recent years, from less than 500 MPAs
worldwide in 1960 to more than 4000 by 2001 (UNEP-
WCMC data, but note that this figure includes intertidal
as well as subtidal sites}. No MPAs have been
designated solely for the protection of seagrasses;
however seagrasses are often one of a list of key
habitats singled out when sites are recommended for
protection [e.g. the Great Barrier Reef Marine Park in
Australia]. Many other sites include seagrasses even
when the key natural resource behind their protection
may be something else, such as a coral reef. In the
majority of MPAs, seagrasses are not acknowledged or
directly protected. With increased awareness, MPA
boundaries and protection could be expanded to
incorporate adjacent seagrass habitats (e.g. Florida
Bay adjacent to the Everglades).

UNEP-WCMC maintains a global database on
MPAs on behalf of the IUCN World Commission on
Protected Areas. Linked to the current work, a list of
the areas which are known to contain seagrass habitat
has been prepared and is presented in Appendix 2. A
summary of this information is provided in Table 7.

Worldwide there are some 247 MPAs known to
include seagrasses. These are located in 72 countries
and territories. These numbers are likely to be
conservative: seagrasses may well occur at a site but
not be recorded, or not be listed in literature which
has been used to develop this database. Even so, it
seems likely that this list is far smaller than the
equivalent network for coral reefs {more than 660")
and mangrove forests {over 1800, unpublished data
2000) and clearly does not present any form of global
network. Added to this must be the recognition that
the vast majority of these sites do not provide any
clear protection for seagrasses - their inclusion
within MPAs is largely fortuitous.

Figure 2 shows the increase in seagrass MPAs
over the past century. It should be noted that the area
figures (shaded area) are a measure of the total area
covered by these MPAs. At the present time it is
impossible to determine the area of seagrasses within
these sites, although it is likely to be only a very small
fraction of the total area. It should further be noted that

The distribution and status of seagrasses

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WORLD ATLAS OF SEAGRASSES

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designation as “protected” covers a broad range of
types of protection, both in terms of legal status and
practical application of that status. Some sites, such as
the National Estuarine Research Reserves in the
United States, do not provide any direct habitat
protection under their supporting legislation. In many
other cases, even where the legislation may provide a
formal safeguard, management may be inadequate.
The world’s largest MPA, Australia’s Great Barrier Reef
Marine Park, has made some efforts to prevent
trawling in seagrass areas, but this entire park, like
most others worldwide, is still subject to influences
from beyond the park boundaries.

In a recent analysis by regional experts, manage-
ment effectiveness was considered for some 342 MPAs
in Southeast Asia and was rated as “good” for only 46
sites (14 percent)’. Finally, many of the threats facing
seagrasses come from remote sources, notably terres-
trial runoff. Few protected areas currently manage
entire watersheds and the legal framework is typically
powerless to control nutrient and toxic pollution and
sedimentation arising outside an MPA.

In addition to the designation of MPAs, other legal
measures have proved beneficial to seagrasses in some
places, although seagrasses themselves are rarely
singled out as the object of protection. Such legislation
includes restrictions on particular activities such as
trawling, dredging or the release of land-based sources
of degradation such as sediments and pollutants. For
example, in Queensland waters (Australia) all sea-
grasses and other marine plants are specifically
protected under the Fisheries Act of 1994, for the
protection of commercial and recreational fishing
activities. In South Australia seagrass is protected
under the Native Vegetation Act 1992. In the United
States, seagrass habitats are protected under Section
404(c) of the Clean Water Act from direct dredge and fill
activities without a permit’. Although clearly
important, such legislation is rare, and still insignificant
at the global level.

In addition to legal protection, public education
can play an important role in safeguarding seagrasses,
notably via the protection of charismatic seagrass
associates such as turtles and dugongs, but also in the
directing of activities which could impact seagrasses.
Coles and Fortes’ provide a valuable review of
methods for direct and indirect protection of
seagrasses.

Seagrass restoration may include both the
improvement of overall conditions for seagrass growth
in an area, such as an improvement in water clarity
resulting from decreased runoff or nutrient inputs, as
wellas direct transplanting or seeding of seagrasses”.
Sometimes transplanting is mandated as mitigation for
unavoidable damage to seagrasses incurred in coastal

The distribution and status of seagrasses

The shallow seagrass beds of Montepuez Bay, Mozambique, at low
tide

development. Transplanting cannot be successful
unless the conditions for seagrass to thrive pre-exist’””.
Although widely undertaken in some areas, many
transplantation efforts have had low success rates and
transplanting can be quite labor intensive and ex-
pensive”. Technologies for more uniformly successful
and less expensive seagrass transplanting are evolving,
and include developing models for site selection”,
advanced methods for transplanting” and seeding”,
and scientific success criteria’. Restoration of
seagrasses is now at the stage where technologies are
available, but overcoming insufficient water quality
conditions remains the greatest obstacle to seagrass

restoration worldwide.

CONCLUSIONS

We know a substantial amount about seagrasses in
many parts of the world, but there remain considerable
gaps in our knowledge. As the taxonomies of various
species are revised, even our understanding of how
many species of seagrass there are will be subject to
debate and change.

The range of individual seagrass species is
presented in a new series of maps. By combining these
range maps we are also able to look at biodiversity
patterns in seagrasses as a whole. The primary
centers of seagrass biodiversity are identified here as
insular Southeast Asia, Japan and southwest
Australia, with additional areas in southern India and

Photo: F. Gell

WORLD ATLAS OF SEAGRASSES

eastern Africa. While there are some important
parallels between seagrasses and the two other major
tropical coastal ecosystems of coral reefs and
mangroves, there are also important divergences,
notably with the seagrass centers of diversity in Japan
and in southwestern Australia but also with the
occurrence of seagrasses in high latitudes as well as
the tropics.

It is clear that, despite the relative paucity of
seagrass species, as a habitat these communities are
in fact highly diverse. There are many thousands of
species recorded living in association with seagrass
communities, although only a small proportion of these
are strictly confined to seagrass ecosystems. There is
an urgent need to develop a more comprehensive
understanding of the full range and diversity of life in
seagrasses.

The work presented here includes a detailed map
of the known locations of seagrass habitats around the
world. Once again we are made aware of considerable
gaps in our knowledge. There is an urgent need for
clearer documentation of the existence and location of
seagrass ecosystems in western South America and in
West Africa, for example. Even within areas of high
seagrass biodiversity, in many cases little is known
about the actual distribution of seagrasses. Much of
our data for the World Seagrass Distribution Map is
based on individual points of occurrence and not on
area of coverage. The importance of the high levels of
primary productivity in seagrasses is well known, and
these are clearly disproportionate to the total area
covered by these habitats. It would be invaluable to
develop an accurate estimate of the total area of
seagrasses worldwide in order to better analyze the
role that these may play in global and regional
fisheries, and in climatic and oceanic carbon cycles. In
the absence of any better data we have undertaken an
analysis of seagrass area and suggest a conservative
estimate of 177000 km’.

There can be no doubt of the value of seagrasses,
although such values are often overlooked. For fish,
many species are not obligatory users of seagrass
ecosystems, but appear to benefit from their presence.
Many others use seagrass ecosystems for a short (but
often critical) part of their life histories, and seagrasses
are rarely considered in assessing these fisheries.
Economic evaluations are often constrained by
analytical procedures and many fail to calculate the
total economic value of an ecosystem. The critical role
of seagrasses in stabilizing sediments, reducing
erosion and even cleaning coastal waters is rarely
accounted for in such analyses. In addition, other

measures, which include social welfare, health and
well-being, are difficult to measure.

The threats to seagrasses have been widely
considered by other authors and include natural and
anthropogenic causes. The latter appear to have
increased dramatically in recent years, and include
direct physical destruction and a range of indirect
threats, the most critical being decreases in water
clarity resulting from nutrient and sediment inputs but
also including climate change. In many cases,
seagrass declines have been linked to multiple
stresses, acting together. In only a few places around
the world are measures being taken to address these
threats. In the present work we have assembled an
assessment of marine protected areas with
seagrasses worldwide. Some 247 sites are known to
include seagrass ecosystems. This is a far lower figure
than for other shallow marine ecosystems, while
further concern must be expressed about the
effectiveness of these sites in protecting seagrasses,
both from direct impacts and from the indirect impacts
such as pollution and sedimentation which may be
carried into the seagrass areas from beyond the
reserve boundaries.

The chapters which make up the bulk of this
work provide a more detailed examination of seagrass
distribution and of the various themes considered here.
They provide detailed examples of seagrass com-
munities around the world, and illustrate issues
relating to distribution, status and management of
these beautiful and critically important ecosystems.

ACKNOWLEDGMENTS

This chapter would not have been possible without the help and input
from all the participants at the Global Seagrass Workshop which was held
at the Estuarine Research Federation meeting in St Petersburg, Florida
in October 2001. The chapter's authors have also drawn heavily on all the
chapters written by the regional authors (see Table of Contents]. The
assistance provided by Sergio Martins and Mary Edwards is gratefully
acknowledged. Jackson Estuarine Laboratory contribution number 397.

AUTHORS

M. Spalding, UNEP World Conservation Monitoring Centre, 219
Huntingdon Road, Cambridge, CB3 ODL, UK. Contact address: 17 The
Green, Ashley, Newmarket, Suffolk, CB8 9EB, UK. Tel: +44 (0)1638
730760. E-mail: mark{dmdspalding.co.uk

M. Taylor, C. Ravilious, E. Green, UNEP World Conservation Monitoring
Centre, 219 Huntingdon Road, Cambridge, CB3 ODL, UK.

F. Short, University of New Hampshire, Jackson Estuarine Laboratory, 85
Adams Point Road, Durham, NH 03824, USA.

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(at

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1 The seagrasses of

Scandinavia and the Baltic Sea

SCANDINAVIA AND THE BALTIC SEA

global seagrass resource; however, the first

reports on the importance of seagrass meadows
for coastal ecosystems derive from this area, from
Denmark''“|. This chapter summarizes the distribution
and importance of eelgrass, Zostera marina, in
Scandinavian and Baltic coastal waters. Although most
of the quantitative information is based on research
carried out in non-tidal areas of Denmark, Sweden and
Finland, the approach is holistic, and includes
distribution maps and anecdotal information on
eelgrass from Iceland, Norway and the coastal areas of
the Baltic Sea, including Germany, Poland, Lithuania,
Latvia and Estonia [see Map 1.1).

Gases supports only a small fraction of the

DISTRIBUTION PATTERNS

Norway

In the north Atlantic, eelgrass is found around Iceland,
where about 30 sites have been identified since the
1950s". Eelgrass forms isolated populations on
shallow exposed and sheltered sandy bottoms along
the entire Norwegian coast” and extends into the White
Sea. The only Norwegian seagrass paper reports
eelgrass densities between 50 and 160 shoots/m* and
canopy heights generally between 15 and 60 cm,
although in extreme cases the length of an individual
plant may exceed 180 cm". Areas of low density have
the highest canopies. The average biomass [April-
November}-at the two sites studied was 20 and 40 g dry
weight/m?, respectively (range: 12-60 g dry weight/m’,
Figure 1.1] The associated fauna is rich (265 taxa,
including mobile macrofauna and epiphytes] and
ranges between 5 000 and 10 000 individuals/m’. The
crustacean species assemblage is dominated by six or
seven families of amphipods, while the epiphytic
community is characterized by hydroids, bryozoans and
crustose and upright algae’. Consequently, these
shallow, vegetated sites are of great importance for
young year classes of fish in the Skagerrak area’””.

C. Bostrom
S.P. Baden
D. Krause-Jensen

The Swedish west coast and Denmark
On the Swedish west coast, as well as in Danish waters,
eelgrass is the most widely distributed seagrass, and
dominates sandy and muddy sediments in coastal
areas of low to moderate wave exposure. In Denmark,
very exposed areas facing the North Sea are devoid
of eelgrass. Along moderately exposed Danish and
Swedish coasts eelgrass forms extended belts
interrupted by sandbars, while protected eelgrass
populations generally form more coherent patches.
Due to its wide salinity tolerance (5-35 psu)'”, eelgrass
grows in the inner parts of brackish estuaries and
sheltered bays and in fully marine waters. In areas of
low salinity, Ruppia spp. and Zostera noltii can co-occur
at the inner edges (0.5-1.5 m depth) of eelgrass.
Eelgrass occurs from shallow (0.5-1 m) water
down to maximum colonization depths that often match
the Secchi depth. In the inner parts of estuaries, the
maximum colonization depth is about 3 m, in outer
parts 4 m and along open coasts about 5 m'""". In rare
cases of very clear waters, eelgrass penetrates to 10m
mean sea level (tidal range +0.1 to 0.4 mJ. Eelgrass
displays a bell-shaped distribution pattern along the
depth gradient, with maximum abundance at
intermediate depths and lower abundances in shallow
and deep water’ '. The biomass of Danish and
Swedish eelgrass populations peaks in late summer at
levels reaching above 250 g dry weight/m*. Maximum
shoot densities range between 1000 and 2500
shoots/m?'*'*". Exposure, desiccation and ice scour
may reduce seagrass abundance in shallow water,
while reductions in seagrass abundance towards the
lower depth limit correlate with light attenuation along
the depth gradient'® *7".

In southernmost Sweden, eelgrass meadows
flourish on stony and sandy bottoms at 2-4 m depth,
and may reach densities and standing crops
corresponding to 3600 shoots/m* and 470 g dry
weight/m’, respectively {site 11 in Figure 1.1)". The

)
i a

WORLD ATLAS OF SEAGRASSES

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So

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Figure 1.1

Average [+1 SE] above-ground biomass values (g dry weight/m’)
for eelgrass (Zostera marina] along the Baltic Sea coastline

(>1 500 km)

Source: Various sources”

Oresund area between Denmark and Sweden (sites 8-
10 in Figure 1.1) also supports well-developed eelgrass
meadows at 1.5-6 m depth'”. In September 2000, four
eelgrass sites along this 100-km coastline showed the
following features: coverage: 20-80 percent; density:
293-1 573 shoots/m’; above-ground biomass: 69-193 g
dry weight/m’; shoot length: 25-125 cm; and shoot
width: 0.2-0.5 cm”.

There are qualitative and quantitative data on the
leaf fauna (defined as the sessile and motile fauna
living on the leaves], mobile epifauna [intermediate
predator invertebrates and fish) and piscivore fish
(secondary predators) from the Swedish west
coast'”*"!, Data on infauna are more scarce” *. Due to
the high organic content of most western Swedish
seagrass beds (2-24 percent ash-free dry weight}, the
infauna (40-130 000 individuals/m’) is dominated by
polychaetes and nematodes. The leaf fauna is
dominated by tube-building amphipods, mainly
detritivores and suspension feeders (80-250 000
individuals/m’*), whereas the abundance of herbivores
is low. Shrimps and crabs make up 90 percent of the
mobile epifauna, and fishes constitute only about 10
percent of the intermediate predator abundance (30-
160 individuals/m’, with maximum abundances in late
summer]. The piscivore fishes (eelpout, cod and
salmon] are few during daytime’. Faunal communities
of Danish eelgrass beds are similarly rich, but have
received little attention since the 1960s! and 1970s”,

Western Baltic Sea and Germany

The western Baltic Sea, composed of the Kiel and the
Mecklenburger Bights, is a transition zone between
marine [North Sea] and brackish (Baltic proper) water
and shows fluctuations in salinity (generally 10-18 psu
but occasionally 8-28 psu” *”}. In this region eelgrass
is found both along exposed sandy shores and in long,
inner bays ("Forden") and shallow lagoons ("Bodden",
“Haffs") with reduced water exchange and muddy
substrate’ *". Along exposed shores, the upper limit
of distribution is set by wave-induced disturbance.
Typically, continuous beds are found from 2.5 m depth
and deeper. Additionally, patchy beds are found
between the sand reefs and the shore at depths of 1-
2m. In sandy areas, eelgrass grows down to a depth
of 8 m, and there is an almost continuous belt of
eelgrass all along the shoreline, although on gravel-
and stone-dominated substrates plants are rare.
Extended populations are found in Orth Bay, in Kiel
Fjord [(Falkenstein) between Travemiinde and
Klutzhoved, in the Wismar Bay and north of Zingst
Peninsula’. Zostera noltii has been reported from
Schleimunde, Heiligenhafen, Wismar Bay and
Greifswald Lagoon".

In the Kiel area (Belt Sea) the eelgrass growing
period is approximately 210 days, and growth is initiated
in June, peaks in August-September and stops in
March. Shoot lengths range between 20 and 140 cm'*:*!.
In Kiel Fjord (Friedrichsort and Moeltenort), eelgrass
density is 600-1 600 shoots/m?'”. The biomass range in
Kiel Bight is 450-600 and 200-800 g dry weight/m* on
mud and sand, respectively, and the daily production is
1.5-2.2 g carbon/m’'*". In the 1970s, the mean annual
eelgrass standing stock for two sites in Schleswig-
Holstein (Kiel Bight) was 42.5 metric tons/ha””.

A typical feature of shallow (depths of 1-3 m)
eelgrass beds is their co-occurrence with blue mussels
(Mytilus edulis), which represents a facultative
mutualism™”. Isopods (/dotea spp.) and snails
(Hydrobia spp., Littorina spp.) are abundant grazers,
and remove eelgrass biomass and_ epiphytes,
respectively, highlighting the importance of biological
interactions, which may locally override the negative
symptoms of eutrophication’. In shallow lagoons
(e.g. Schlei Estuary], eelgrass is also consumed by
birds, especially mute swans (Cygnus olor).

The Swedish east coast

Eelgrass penetrates into the brackish (0-12 psu) Baltic
Sea, and is common in most coastal areas. The northern
and eastern distribution limits of eelgrass correlate with
the 5 psu halocline. The usual depth of eelgrass in the
Baltic Sea is 2-4 m [range 1-10 m). Zostera noltii extends
to southern Sweden, and to Lithuania in the eastern
Baltic’. At present, the northern limit of Zostera noltiiin

NORTH
SEA

NORWAY

SWEDEN

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Hallands Vadero ¢ !

DENMARK ‘<a
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-

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3 4 t Fredshog
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« Kiel Bight Zinyst Peninsula
© Oh Rigen
Heiligenhaten! Bag Greifswald
Ye freer f Lagoon
Mecklenburger Bight’ __GERMANY
Map 1.1
Scandinavia

the Baltic Sea is unknown. Due to lack of tides, all
seagrass beds in the Baltic Sea are permanently
submerged, and often mixed with limnic angiosperms
(e.g. Potamogeton spp. and Myriphyllum spp.).

On the brackish (6-8 psu) east coast of Sweden, the
most extensive eelgrass meadows are probably found in
the sandy Kalmarsund-Oland. Along the southeastern
coast of Sweden (Sandhammaren to Vastervik], eelgrass
is common on sandy bottoms with good water exchange.
The demographic information from this area is based on
anecdotal evidence, diving observations made during
coastal monitoring (University of Kalmar], and

Oland

Curonian Spit

POLAND

Scandinavia and the Baltic Sea

WHITE
SEA

Bothnian

Sea eco

Archipelago

“<* Gulf of

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of tvarminne F inland
.

Po Hanko Peninsula

ESTONIA
BALTIC

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Gotland ee
.

Palanga
LITHUANIA

Puck Lagoon

unpublished data by S. Tobiasson. Dense shallow stands
have short (20 cm], narrow (2-3 mm] leaves and usually
grow in mixed stands with Potamogeton pectinatus,
Ruppia maritima, Zannichellia palustris and
bladderwrack Fucus vesiculosus, while the deepest
stands are sparse, monospecific and have longer (>80
cm] and broader (5 mm) leaves.

The coverage pattern is usually patchy (patch area
10-50 m? with a mean coverage of 50-75 percent, range
5-100 percent). At the main distribution depth, the mean
shoot density is 500-600 shoots/m’, but ranges between
100 and 1040 shoots/m’, depending on depth. The

\) \ y

Photos: J. Lindholm

WORLD ATLAS OF SEAGRASSES

Figure 1.2
Aerial photographs of two typical exposed eelgrass (Zostera

marina) sites at the Hanko Peninsula, southwest Finland, northern
Baltic Sea (adjacent to site 16 in Figure 1.1]

a. Kolaviken (59°49'N, 22°59'E): the high-energy regime at this site
is reflected in a complex, patchy bed structure.

b. Ryssholm (59°60'N, 23°05'E): the continuous eelgrass bed is
interrupted by sandbars, while circular to highly irregular,
elongated patches are found at the outer edge of the bed.

Notes: The areas covered by eelgrass in [a] and (b] are 23 and 6 hectares,
respectively. The depth range covered by eelgrass is approximately 2-6 m.

above-ground biomass may exceed 100 g dry weight/m’
(site 13 in Figure 1.1). The steep, exposed coastal areas
of southern Sweden (Skane] and the east coast of the
Oland Island lack eelgrass". The semi-exposed sandy
shores of Gotland Island support extensive eelgrass
meadows. The northern limit of distribution is in the
northern Archipelago of Stockholm”! Few studies of the
associated fauna have been carried out’ *”, but these
meadows support more than 20 infaunal species and a
rich leaf fauna with over 30 species!”

Finland and Aland Islands

In Finland, eelgrass grows exclusively on exposed or
moderately exposed bottoms with sandy sediments.
The spatial patterns of eelgrass beds in shallow water

TR ae

are mainly controlled by physical factors (Figure 1.2). In
the Archipelago Sea, eelgrass beds are found towards
the leeside of islands, while more sheltered, inner bays
on the mainland do not support eelgrass beds.
Eelgrass sites in Finland vary in terms of patch size [(1-
75 m‘}, shoot density (50-500 shoots/m’), shoot length
(20-100 cm), biomass (10-32.1 g ash-free dry
weight/m’“”' and sediment properties (organic content
0.5-1.5 percent, grain size 0.125-0.5 mm). The low
shoot densities result in low areal production rates
(138-523 mg dry weight/ m’*/day'"']. The associated
fauna of Finnish seagrass beds is well described”. A
rich sedimentary fauna (25 000-50 000 individuals/m’,
50 species“ and a distinct leaf fauna!)
contributes significantly to coastal biodiversity in
Finland. Northern Baltic seagrass communities lack
crabs and echinoderms, and the nursery role for
economically important fish species is limited, but
seagrass beds serve as feeding grounds for fish.

HUMAN USE OF SEAGRASSES

The direct use and manufacture of eelgrass-based
materials has been local and intermittent. In Denmark
and other countries dried eelgrass leaves have been
used as fuel, packing and upholstery material, insulation
and roof material, feeding and bedding for domestic
livestock, fertilizer and as a resource to obtain salt": “*“"!.
In Sweden, dried eelgrass leaves have mainly been used
for insulation of houses. Historically, the abundant
eelgrass resources of the sheltered lagoons in the
western Baltic Sea [Germany] have been utilized for
upholstery and insulation. The last eelgrass collector at
Maasholm, Germany, retired in the 1960s. In the
southeastern Baltic Sea, human communities on the
Curonian Spit (Lithuania) used eelgrass as upholstery
material before the Second World War, indicating
abundant eelgrass meadows in the area before the
1940s". The current appreciation of seagrasses
primarily concerns the services that seagrasses provide
to the overall functioning of coastal ecosystems in terms
of enhancing biodiversity, providing nursery and foraging
areas for commercially important species, improving
water quality by reducing particle loads and absorbing
dissolved nutrients, stabilizing sediments and
influencing global carbon and nutrient cycling'”.

HISTORICAL AND PRESENT DISTRIBUTION

Norway

Along the southeastern coast of Norway (between the
Norwegian-Swedish border and Kristiansand], almost
100 sites have been monitored since the 1930s in
connection with beach seine surveys each autumn
{September-October) by the Institute of Marine
Research”. The presence of vegetation has been
estimated by aquascope, and seagrass cover has been

divided into the following categories: 1 = no vegetation, 2
= few plants, 3 = some plants, 4 = many plants, 5 =
bottom totally covered. Unfortunately, only a small
fraction of this dataset has been compiled and most is
unpublished. The general impression, however, is that
the coverage of eelgrass increased during the 1930s, and
since then it has varied irregularly (Figure 1.3 a, b). Some
areas showed signs of reduction in the late 1960s, and
apparently there was a reduction probably indirectly
related to the great bloom of Chrysochromulina in 1988.
Now the coverage seems generally to be good’.

The western and eastern coasts of Sweden
During the 1980s inventories of the shallow coastal
areas including eelgrass were carried out along the
Swedish west coast as a basis for coastal zone
management. In 2000, a revisit and inventory of 20 km’ of
eelgrass meadows in five coastal regions along 200 km
of the Skagerrak coast was carried out using the same
methods (aquascope] as during the 1980s, but mapping
accuracy was improved by using the global positioning
system (GPS]. This study showed that areal cover had
decreased 58 percent (with regional variations) in 10-15
years. In the 1980s, eelgrass covered about 20 km’ of
bottom along this 200-km section of the west coast,
while only about 8.4 km’ was present in 2000". Since
1994, one eelgrass site in southwest Sweden near
Trelleborg (site 11 in Figure 1.1) has been included in the
local coastal monitoring program. Shoot density and
biomass of eelgrass at this site has increased
significantly since 1994 (linear regression for biomass:
p<0.001, r = 0.81), and this positive trend seems to be
true for many of the eelgrass monitoring sites in the
Oresund region (sites 8-11 in Figure 1.1'") probably due
to greater exposure and/or invertebrate grazing’"'. No
estimates of the total area covered by eelgrass along the
whole Swedish west coast (>400 km] exist. An estimation
of the total eelgrass coverage along the southeastern
Swedish coast [including the Oland Island) yields
minimum and maximum numbers between 60 and 130
km’, respectively”. Between this region and the
northern distribution limit in the Stockholm Archipelago
eelgrass is still common, but far less abundant due to
lack of suitable substrate®”.

Denmark

In Denmark, records of eelgrass distribution date back to
around 1900, and provide a unique opportunity to
describe long-term changes. In 1900, eelgrass was
widely distributed in Danish coastal waters, and covered
approximately 6 726 km’ or one seventh of all Danish
marine waters (Figure 1.4'**]. The standing crop ranged
between 270 and 960 g dry weight/m’, in sparse and
dense stands, respectively, and total annual eelgrass
production was estimated at 8 million metric tons dry

Scandinavia and the Baltic Sea

Figure 1.3
Norwegian eelgrass coverage

%
s
=
o
&
&
s
2
3
N
s
=
w
2
7)
‘So
as

80 90 2000

. Long-term trends in the presence of eelgrass (Zostera marina)
at shallow, soft-bottom sites assessed by aquascope in
southeastern Norway (Kristiansand to the Norwegian-Swedish
border] during the period 1933-2000.

Monotypic Zostera marina

Mixed Zostera marina

Coverage

b. Coverage at sites where eelgrass occurs in single stands (green
line) and mixed with benthic algae (black line).

Notes: 1 = no coverage, 5 = bottom totally covered. Number of sites
sampled each year (38-134, mean 93] vary due to variation in water
turbidity. No data obtained during 1940-44.

Source: Norwegian Institute of Marine Research

weight”. In the 1930s, wasting disease led to substantial
declines in eelgrass populations, especially in northwest
Denmark where salinity is highest (Figure 1.4°]. In 1941,
eelgrass covered only 7 percent of the formerly
vegetated areas, and occurred only in the southern, most
brackish waters and in the low-saline inner parts of
Danish estuaries (Figure 1.4% *'). No national
monitoring took place between 1941 and 1990, but
analyses of aerial photos during the period from 1945 to
the 1990s show an initial lag after the wasting disease
followed by marked recolonization in the 1960s" °”)
Today eelgrass again occurs along most Danish
coasts but has not reached the former areal
extension’ *”. Based on comparisons of eelgrass area
distribution in two large regions, Oresund and
Limfjorden, in 1900 and in the 1990s, we estimate that
the present distribution area of eelgrass in Danish

WORLD ATLAS OF SEAGRASSES

Figure 1.4

Map of eelgrass area distribution in Danish coastal waters in 1901, 1933, 1941 and 1994

North Sea

Kattegat

Baltic Sea

North Sea y 1933
B
Sweden
g

Kattegat

Baltic Sea

\ y
§Za\ Germany J
237° eat

Baltic Sea

North Sea 7) 1994

q Sweden

Kattegat

Notes: Dark green areas indicate healthy eelgrass while black areas (on the 1933 map] indicate where eelgrass was affected by the wasting disease but

still present in 1933. The arrow shows the location of Limfjorden.

Source: Various sources: 1901 [redrawn”), 1933 (redrawn), 1941 (redrawn'®*!) and 1994 (coarse map based on visual examination of aerial photos and
data from the national Danish monitoring program, produced by Jens Sund Laursen)

coastal waters constitutes approximately 20-25 percent
of that in 1900 (Figure 1.4). The area distribution of
eelgrass in Limfjorden was thus estimated at 345 km’?
in 1900"! and at only 84 km? in 1994 (based on aerial
photography data from the Limfjord counties]. In
Oresund, eelgrass covered about 705 km? in 1900"! and
only about 146 km? in 1996-2000". Differences in
methodology influence these comparisons since the
distribution maps of eelgrass from the beginning of the
last century were based on extrapolation between sites

visited in field surveys, while maps from the 1990s were
based on image analysis of aerial photography. This
large areal reduction is partly attributed to the loss of
deep eelgrass populations as a consequence of
impoverished light conditions due to eutrophication. In
1900, maximum colonization depths averaged 5-6 m in
estuaries and 7-8 m in open waters (Figures 1.5 and
1.6]. In the 1990s, colonization depths were reduced by
about 50 percent to 2-3 m in estuaries and 4-5 m in
open waters.

Colonization depth
in estuaries

Colonization depth
along open coasts
40 1900

30
20

S
oS
>
rs)
Cc
oO
=
>
oO
re
[re

fej eaye (0
Bo 0 2) 0) 2
Colonization depth (m)

Figure 1.5
Maximum colonization depth of eelgrass patches in Danish
estuaries and along open coasts in 1900 and 1996-97

Source: Based on data from 12 sites in estuaries and 18 sites along open
coasts investigated by Ostenfeld'“’ in 1900 and by the national Danish
monitoring program in 1996-97

Germany, Poland and Lithuania

In Germany (Kiel Bight), eelgrass competes with
increasing amounts of filamentous algae, and in some
areas the depth distribution of eelgrass decreased from
6 m in the 1960s to less than 2 m at the end of the
1980s'"'. In the Greifswald Lagoon [island of Rigen),
the distribution of eelgrass has remained fairly stable,
despite the almost total disappearance of red algal
belts during the period 1930 to 1988". Nevertheless,
eelgrass is by far the most abundant macrophyte on
sandy to muddy shores in this area’”’.

In Poland (Gulf of Gdansk, Puck Lagoon], abundant
eelgrass meadows grew down to a depth of 10 m in the
1950s, but were almost totally replaced by filamentous
brown algae and Zannichellia palustris during the period
1957-87"! (Figure 1.7). The change from dense sea-
grass beds to algal-dominated assemblages has caused
a shift in the commercially important fish communities.
Hence, eel (Anguilla anguilla) and pike (Esox lucius) have
decreased in abundance and have been partly replaced
by roach (Rutilus rutilus)'**”. In addition, eelgrass
suffers from heavy metal contamination’.
Transplantation of eelgrass has been tested in the Puck
Lagoon’. Recently natural recolonization has taken
place in some areas of this lagoon”.

Along Lithuanian coasts in the southeastern
Baltic Sea, eelgrass had virtually disappeared before
any scientific evaluation was made. Eelgrass most
likely occurred along the 90-km-long sea side of the
Curonian Spit, covering thousands of hectares”. In

Scandinavia and the Baltic Sea

»1900 @ 1992

[=
f=
a
a
3
c
i)
o
oat
=
a)
i)
(=)

Secchi depth (m}

Figure 1.6
Secchi depths and maximum colonization depths of eelgrass
patches in Danish estuaries and open coasts in 1900 and 1992

Source: Measured by Ostenfeld'“’ in 1900 and by the national Danish
monitoring program in 1992

1998, filamentous green algae (Cladophora glomerata)
dominated along the coast, and eelgrass was
considered rare and endangered; no eelgrass was
found during underwater surveys during 1993-97°".

Figure 1.7
Long-term changes in the distribution of eelgrass (Zostera marina)
in the southeastern Baltic Sea (Puck Lagoon, Poland)

Notes: Scale bar in lower right corner corresponds to approximately
5 km. Green areas indicate eelgrass cover.

Source: Modified after Kruk-Dowgiallo®”

WORLD ATLAS OF SEAGRASSES

One northern site (Palanga) supported eelgrass,
indicating that eelgrass was probably present formerly
along the whole Lithuanian coast’’ *!. The seagrass
literature from Latvia and Estonia is scarce, but
eelgrass has been reported to occur sparsely among
algal-dominated assemblages in the Gulf of Riga’””.

Finland

The only long-term analysis of an eelgrass site in
southwest Finland recorded no change in density and
standing stock between 1968 and 1993’. In 1993,
eelgrass biomass was about 85 g dry weight/m’ and
corresponded well with the yearly means for 1968-70 in
terms of ash-free dry weight (20 g/m’). By contrast, the
associated eelgrass fauna showed marked signs of
eutrophication. Total abundance of infauna had
increased almost fivefold, and the total animal biomass
had more than doubled over 25 years. The number of
taxa showed minor changes over time. These faunal
changes indicate increased food availability, due to
eutrophication. Unfortunately, no long-term data from
other Finnish eelgrass sites exist to verify this result.
Genetic analysis of Finnish eelgrass meadows suggests
an age of these plant ecosystems between 800 and 1 600
years'” ”!, indicating that eelgrass colonization must
have taken place at present salinities. Those eelgrass
populations near their limit of distribution in terms of
salinity were not affected by the wasting disease in the
1930s” and have also persisted through severe
anthropogenic stress and long-term physical stress in
terms of landlift, wind disturbance, sedimentation and
fluctuations in temperature and ice cover. Based on very
crude areal estimates, and extrapolations from the
number of known eelgrass sites verified by diving (totally
about 50 sites), our guess is that the total coverage of
eelgrass in Finland is probably less than 10 km’.

THREATS

Kattegat and Skagerrak

Since the lower depth limit of eelgrass is determined by
water transparency, eutrophication is a main threat to
especially deep eelgrass populations. Maximum Secchi
depths and colonization depths approached 12m in
open Danish waters in 1900 but rarely exceeded 6m
in the 1990s (Figure 1.6). The maximum colonization
depth is also correlated to the concentration of water
column nitrogen, which is the main determinant of
phytoplankton biomass in Danish coastal waters”.
Eutrophication-gained filamentous algae (mainly
ephemeral] may shade seagrasses, hamper water
exchange and cause a decline in associated faunal
communities, e.g. shrimps and crabs!" 1?” In
shallow stagnant waters with limited oxygen pools, as
well as in deeper stratified waters, the oxygen-
consuming decomposition of ephemeral algae and

detritus may lead to anoxia. High water temperature
also stimulates microbial decomposition rates and
thereby further increases the risk of anoxia. Oxygen
deficiency in the meristematic region of eelgrass is a
likely key factor explaining events of mass mortality in
eelgrass beds", possibly in combination with sulfide
exposure”. Shallow eelgrass populations often show
large and rapid fluctuations, suggesting that stochastic
interactions between water temperature, light,
nutrients and physical disturbance like strong wave
action and ice scouring play important regulating roles,
and that recolonization may also happen relatively fast
in deeper water if conditions improve’ *”.

Other threats include siltation and mechanical
damage. For example, the construction in 1995-2000 of
the Oresund bridge between Denmark and Sweden,
almost 8 km long and one of the most massive marine
constructions in Scandinavia, was likely to affect the
large eelgrass populations in Oresund. However, strict
regulations on dredged quantities and spillage during
the construction works prevented detectable negative
impacts on eelgrass” 77!

In some Danish estuaries where eelgrass and
blue mussel occur in mixed populations, mussel
fishery may constitute a threat to eelgrass
populations”. In Sweden the increasing leisure boat
harbors with uncontrolled anchoring, dredging and
water currents from propellers are the main physical
threats to seagrass meadows.

The Baltic Sea

As in Denmark and Sweden, the drifting and sessile
forms of fast-growing, filamentous algae constitute a
serious threat to seagrasses in other areas of the
Baltic®’”"*", which will probably have negative effects on
the whole eelgrass community”. During the past ten
years, increasing amounts of ephemeral, filamentous
algal mats have been observed at shallow localities in
the northern Baltic Sea“, with profound negative
effects on the benthic communities". In 1968-71
filamentous algal mats were already common at
eelgrass sites, but their biomass was less than 5 g ash-
free dry weight/m?“". Today, the biomass of drifting
algae in Finland commonly exceeds 1000 g dry
weight/m?'”'* and subsequent periodic anoxia is also
common in shallow areas. It is clear that these algae are
a major threat to the Baltic Sea seagrass ecosystems. In
the heavy traffic coastal areas of the Baltic Sea, oil spill
accidents could be detrimental to seagrass vegetation.
Other threats include sand suction and construction.

NATIONAL AND SCANDINAVIAN POLICY

Several political initiatives affect Scandinavian seagrass
populations. In 1987, the Danish Government passed an
Action Plan on the Aquatic Environment including

measures on wastewater treatment, the storage of
animal manure and reductions of agricultural nitrogen
and phosphorus. The aim was to reduce annual total
nitrogen discharge by 50 percent, and that of phosphorus
by 80 percent, within five years. A second action plan
containing further measures was passed in 1998 to
ensure that the planned reductions of nitrogen and
phosphorus discharges will be in effect before 2003. In
addition there are several directives concerning point
sources and _ protection of groundwater. An
announcement on mussel fishery in Denmark prohibits
fishery at water depths shallower than 3 m in order to
protect eelgrass beds. A nationwide Danish monitoring
program was established in 1988 to demonstrate the
effects of the Action Plan (for latest adjustments, see
Environmental Protection Agency). Large construction
works typically have associated monitoring programs, as
was the case for the fixed link across Oresund.

As in Denmark, a series of action plans aiming to
reduce nutrient discharge have been agreed in Sweden
since the late 1980s, but not fulfilled. The latest action
plan against coastal nutrient pollution is part of
Swedish national environmental goals {Governmental
Proposition 2000), and specifically says that total
nitrogen discharge with anthropogenic origin from land
should be reduced by 30 percent from 1995 not later
than 2010, whereas phosphorous should decrease
continuously from 1995 to 2010 with no specific aim.
However, not only nutrient pollution but also
overfishing might be part of the decreasing extension of
seagrass through a possible, but still unverified, top-
down control mechanism”. In the Baltic, as well as in
the Kattegat and Skagerrak, most fish stocks are
overfished to levels below biological safe limits. This is
a much-debated topic, but has so far not been the
subject of serious action plans.

Finland is not committed to monitor seagrass
meadows. However, Finland follows political agree-
ments, which are carried out by national (e.g. Water
Protection Targets for 2005, Renewed Nature
Conservation Act [1996], Renewed Water Act and EIA
(Environment Impact Assessment) procedures) and
international (Habitat Directive and Natura 2000)
environmental programs. Thus, seagrasses in Finland
are only indirectly protected through limitations on
nutrient discharges. A new governmental program
initiated in June 2001 aims at reducing nutrient
discharges to the Baltic Sea and protecting and
monitoring marine coastal biodiversity.

At the international level, seagrasses are listed in
the Rio Declaration (1992/93:13] as diverse habitats in
need of protection and monitoring (Chapter 17 part D
17.86 d). Further, the European Water Framework
Directive, the Habitat Directive, the Helsinki Convention
(HELCOM}, the Oslo-Paris Convention (OSPAR) and the

Scandinavia and the Baltic Sea

Convention on Biodiversity also place demands for
monitoring seagrasses in Scandinavia“. More details
on political initiatives on nutrient reductions and
monitoring are summarized in Laane et al." (Chapter
6.2). On the initiative of the Helsinki Commission, a Red
List of marine biotopes in the Baltic Sea” serves as an
instrument in conservation, management and policy-
making. In the Red List “sublittoral sandy bottoms
dominated by macrophytes” and “sand banks of the
sublittoral photic zone with or without macrophyte
vegetation” are classified as “heavily endangered” and
“endangered”, respectively’. Accordingly, during the
implementation of the European Union Water Frame-
work Directive, eelgrass should be included as an indi-
cator species. In future years, the coverage, depth
range and biodiversity of eelgrass beds may potentially
be used for ecological classification of Baltic coastal
waters. Guidelines for monitoring eelgrass and other
key macrophytes are included in the HELCOM
COMBINE program”.

However, classification of Baltic Sea seagrass
meadows as threatened is only a first step obligating
regular quantitative estimates of the distribution
patterns, dynamics and diversity of seagrass meadows.
Consequently, these parameters should be obtained
and evaluated within standardized, national monitoring
programs. Presently, only a fraction of the Baltic Sea
seagrass resources undergo regular monitoring. In
future, such measures are crucial in order to
understand and sustain these important ecosystems.

ACKNOWLEDGMENTS

The authors would like to thank the following persons for data, comments
or logistical support during the preparation of the manuscript: Penina
Blankett, Hartvig Christie, Jan Ekebom, Stein Fredriksen, Jakob
Gjoseter, Frida Hellblom, Agnar Ingolfsson, Hans Kautsky, Jonne Kotta,
Hordur Kristinsson, Jouni Leinikki, Mikael von Numers, Serge} Olenin,
Panu Oulasvirta, Lars-Eric Persson, Eeva-Liisa Poutanen, Thorsten
Reusch, Aadne Sollie, Stefan Tobiasson and Jan Marcin Weslawski.
Susanne P. Baden gained financial support from WWF (World Wildlife
Fund) and the County of Vastra Gotaland, and Dorte Krause-Jensen from
the European Union (#EVK3-CT-2001-00065 "CHARM" and EVK3-CT-
2000-00044 "M&MS"}.

AUTHORS

Christoffer Bostrém, Abo Akademi University, Department of Biology,
Environmental and Marine Biology, Akademigatan 1, FIN-20500 Abo,
Finland. Tel: +358 (0)2 2154052, 4631045. Fax: +358 (0)2 2153428. E-mail:
christoffer.bostrom(dabo.fi

Susanne P. Baden, Goteborg University, Department of Marine Ecology,
Kristineberg Marine Research Station, S-45034 Fiskebackskil, Sweden.

Dorte Krause-Jensen, National Environmental Research Institute,
Department of Marine Ecology, Vejlsovej 25, 8600 Silkeborg, Denmark.

W \ JY
ra a

WORLD ATLAS OF SEAGRASSES

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Lappalainen A, Hallfors Kangas GP [1977]. Littoral benthos of the
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Roos C [2000]. A Seasonal Study of the Production of Eelgrass (Zostera
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Bostrom C [2001]. Ecology of Seagrass Meadows in the Baltic Sea. PhD
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Bostrom C, Bonsdorff E [1997]. Community structure and spatial variation
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Bostrém C, Bonsdorff E [2000]. Zoobenthic community establishment
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Bostrom C, Mattila J [1999]. The relative importance of food and shelter for

seagrass-associated invertebrates: A latitudinal comparison of habitat
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Lehmann MCG [1814]. Der endeckte Nutzen des Seegrases zum Fillen
der Kissen und Polster. Kobenhagen bey Schubothe

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Thayer GW, Wolfe DA, Williams RB [1975]. The impact of man on
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Brondegaard VJ [1987]. Folk og Flora: Dansk etnobotanik. Bind 1. 2nd
edn. Rosenkilde og Bagger, Kabenhavn.

Olenin S. Personal communication.

Hemminga MA, Duarte CM [2000]. Seagrass Ecology. Cambridge
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Gjoseeter J, Sollie A. Personal communication.

Tobiasson S. Personal communication.

Blegvad H [1935]. En epidemisk sygdom i beendeltangen (Zostera marina
L.J.. In: Blegvad H [ed] Beretning til Ministreriet for Sofart og Fiskeri fra
Den Danske Biologiske Station 1934. CA Reitzels Forlag, Kobenhavn.
XXXIX pp 1-8.

Lund S [1941]. Tangforekomsterne i de danske farvande og
mulighederne for deres udnyttelse. Dansk Tidssk Farm 15(6): 158-174.
Frederiksen M, Krause-Jensen D, Laursen JS [Submitted manuscript,
a]. Long-term changes in area distribution of eelgrass [Zostera marina]
in Danish coastal waters.

Frederiksen M, Krause-Jensen D, Holmer M [Submitted manuscript b].
Long-term changes in eelgrass (Zostera marina] landscapes: Influence
of physical setting on spatial distribution.

Olesen B [1993]. Population Dynamics of Eelgrass. PhD thesis,
Department of Plant Ecology, University of Aarhus.

Kaas H, Mahlenberg F, Josefson A, Rasmussen B, Krause-Jensen D,
Jensen HS, Svendsen LM, Windolf J, Middelboe AL, Sand-Jensen K,
Pedersen MF [1996]. Marine Areas. Danish Inlets - State of the
Environment, Trends and Causal Relations. The Monitoring Programme
under the Action Plan for the Aquatic Environment 1995. Ministry of
Environment and Energy. National Environmental Research Institute
Technical Report No. 179. 205 pp.
http://www.dmu.dk/1_viden/2_Publikationer/3_fagrapporter/rapporter/
FR179.pdf (accessed July 2002].

Krause-Jensen D, Middelboe AL, Christensen PB, Rasmussen MB,
Hollebeek P [2001]. Benthic Vegetation Zostera marina, Ruppia spp..,
and Laminaria saccharina. The Authorities Control and Monitoring
Programme for the fixed link across Oresund. Benthic vegetation.
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Environmental Authorities. 115 pp.

Schramm W [1996]. The Baltic Sea and its transitions zones. In: Schramm,

W, Nienhuis, PH [eds] Marine Benthic Vegetation - Recent Changes and
the Effects of Eutrophication. Springer-Verlag, Berlin. pp 131-163.
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distribution of macrophytobenthic communities in the Greifswalder
Bodden. Acta Ichthyologica et Piscatoria 22: 135-143.

Kruk-Dowgiallo L [1991]. Long-term changes in the underwater
meadows of the Puck Lagoon. Acta Ichthyologica et Piscatoria 22: 77-84.
Kruk-Dowgiallo L [1994]. Distribution and biomass of phytobenthos of
the inner Puck Bay in the summer of 1987. In: The Puck Bay -
Possibilities of Restoration. 10S, Warszawa. pp 109-122 {in Polish with
English abstract).

Kruk-Dowgiallo L [1996]. The role of filamentous brown algae in the
degradation of the underwater meadows in the Gulf of Gdansk.
Oceanological Studies 1-2: 125-135.

Ciszewski P, Kruk-Dowgiallo L, Zmudzinski L [1992]. Deterioration of
the Puck Bay and biotechnical approaches to its reclamation. In:
Bjornestad E, Hagerman L, Jensen K (eds) Proceedings of the 12th
Baltic Marine Biologists Symposium. Olsen & Olsen, Fredensborg. pp
43-46.

Ciszewski P, Ciszewska L, Kruk-Dowgiallo L, Osowiecki A, Rybicka D,
Wiktor J, Wolska-Pys M, Zmudzinsky L, Trokowicz, D [1992]. Trends of

Scandinavia and the Baltic Sea

long-term alterations of the Puck Bay ecosystem. Studia i materialy
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Kruk-Dowgiallo L, Pempkowiak J [1997]. Macrophytes as indicators of
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Weslawski JM, Personal communication.

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Proceedings Estonian Academy of Sciences Biology Ecology 49:253-269.
Bostrom C, Bonsdorff E, Kangas P, Norkko A [2002]. Long term changes
ina brackish water Zostera marina community indicate effects of
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Reusch TBH, Bostrom C, Stam WT, Olsen JL [1999]. An ancient eelgrass
clone in the Baltic. Marine Ecology Progress Series 183: 301-304.
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Borum J [1985]. Development of epiphytic communities on eelgrass
(Zostera marina} along a nutrient gradient in a Danish estuary. Marine
Biology 87: 211-218.

Isaksson I, Pihl L [1992]. Structual changes in benthic macrovegetation
and associated epibenthic faunal communities. Netherlands Journal of
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Greve T, Borum J, Pedersen 0 [in press, 2003]. Meristematic oxygen
dynamics in eelgrass (Zostera marina}. Limnology and Oceanography 48.
Holmer M, Bondgaard EJ [2001]. Photosynthetic and growth response of
eelgrass to low oxygen and high sulfide concentrations during hypoxic
events. Aquatic Botany 70: 29-38.

Danish Ministry of the Environment and Energy, Danish Ministry of
Transport, Swedish Control and Steering Group for the Oresund Fixed
Link [2001]. Final Report on the Environment and the Oresund Fixed
Link's Coast-to-coast Installation. 11th semi-annual report. 22 pp.
Feedback Monitoring Centre [2001]. Annual Compliance Test of
Eelgrass Variables in 2000. 42 pp + appendices.
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omrader lukket for muslingefiskeri i perioden 1988-1995.
Limfjordsovervagningen ved Ringkobing Amtskommune, Viborg Amt og
Nordjyllands Amt.

Norkko J, Bonsdorff E, Norkko A [2000]. Drifting algal mats as an
alternative habitat for benthic invertebrates: Species specific responses
to a transient resource. Journal of Experimental Marine Biology and
Ecology 248: 79-104.

Norkko A, Bonsdorff E [1996]. Population responses of coastal
zoobenthos to stress induced by drifting algae. Marine Ecology
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Programbeskrivelse for det nationale program for overvagning af
vandmiljoet 1998-2003. Redegorelse fra Miljastyrelsen no. 1, Ministry of
Environment and Energy. 397 pp.

Heck Jr KL, Pennock JR, Valentine JF, Coen LD, Sklenar SA [2000].
Effects of nutrient enrichment and large predator removal on seagrass
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Oceanography 45: 1041-1057.

Laane A, Pitkanen H, Arheimer B, Behrendt H, Jarosinski W, Lucane S,
Pachel K, Raike A, Shekhovtsov A, Svendsen L, Valatka S [2002].
Evaluation of the Implementation of the 1988 Ministerial Declaration
regarding Nutrient Load Reductions in the Baltic Sea Catchment Area.
Finnish Environment Institute, Helsinki.

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Animal Communities in the Baltic Sea. Annex for HELCOM COMBINE
programme. 12 pp.

Institute of Marine Research, Flodevigen Marine Research Station.
Unpublished data.

WORLD ATLAS OF SEAGRASSES

2 The seagrasses of

WESTERN EUROPE

estern Europe is considered here as the coasts
W the North Sea, the Channel and Irish Sea as
well as the Atlantic coasts of the British Isles,

France, Spain and Portugal. Two seagrass species are
found in coastal and estuarine areas: Zostera marina
and Zostera noltii. A third species, Cymodocea nodosa,
occurs less abundantly in the southern part of the area
(Portugal). The widgeon grasses, Ruppia maritima and
Ruppia cirrhosa, sometimes considered to be
seagrasses, occur in brackish water sites', such as
low-salinity ponds and mesohaline to polyhaline
coastal lagoons; occurrence under marine conditions is
very rare in western Europe and generally ephemeral.
The seagrasses are found on soft sediments to a
maximum depth of about 10 m. They occupy a large
variety of marine and estuarine habitats. They often
grow in dense beds and extensive meadows creating a
productive and diverse habitat used as shelter, nursery,
spawning or food area by a large variety of animal
species. Among these, several are of commercial
interest or cultural value. Therefore, seagrass beds are
recognized as an important reservoir of coastal
biodiversity; they shelter in the same _ habitat
endofaunal and epifaunal species in the sediment, and
creeping and walking species on the leaves, as well as
swimming species” ”. Seagrasses are consequently of
considerable economic and conservation importance.
The dense root network of the seagrasses is able to
stabilize the underlying sediment and to increase the
sedimentation fluxes by reducing the hydrodynamic
forces. Their essential ecological role in terms of
primary production at the scale of the coastal
ecosystem is mainly recognized in the areas where
hard bottom surfaces with macroalgae cover are
scarce. The importance of the beds was higher at the
beginning of the 20th century, before the “wasting
disease” struck. The proliferation of the pathogenic
slime mold (Labyrinthula zosterae) in the leaves of
Zostera marina, considered to be the consequence of

C. Hily
M.M. van Katwijk
C. den Hartog

weakening of the plants under continuous unfavorable
environmental conditions, resulted in the 1930s in the
loss of almost 90 percent of the Zostera marina
populations of western Europe” *. After this period,
many beds progressively recovered but the area
covered remained low in most areas compared with
previous distribution. Zostera marina lives mainly in the
infralittoral (or sublittoral]) zone but can develop
occasionally in the lower and middle part of the
mediolittoral (or eulittoral) zone. There the species
develops a morphological variety with narrow and short
leaves previously considered as a separate species,
named Zostera angustifolia, and which in many areas
behaves as an annual. It is noteworthy that in the
United Kingdom a specific distinction between Zostera
angustifolia and Zostera marina is still made“. Zostera
nolti lives higher on the shore and occurs in the middle
and upper parts of the mediolittoral belt. The species
can also live under permanent subtidal conditions in
small brackish streams and coastal lagoons with
euhaline conditions.

In the United Kingdom, Zostera marina is the
more common species; it is widely, but patchily,
distributed around the coasts of England, Scotland and
Wales; the main concentrations occur along the west
coast of Scotland including the Hebrides and in
southwest England including Devon and Cornwall, as
well as the Scilly Isles and Channel Islands. The
intertidal form of Zostera marina is also widely
distributed, but less abundant; sites with major
concentrations occur in the Exe Estuary, in Hampshire,
the Thames Estuary, and the Moray and Cromarty
Firths in Scotland. Zostera noltii has a predominantly
eastern distribution in the United Kingdom, more or
less coinciding with the distribution of the intertidal
Zostera marina form”.

In Ireland, Whelan carried out an extensive sur-
vey of Zostera spp.; Zostera marina is frequently found
along the coasts under subtidal conditions (Ventry Bay,

Regional map: Europe

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il WORLD ATLAS OF SEAGRASSES

THE BEAUTY OF SEAGRASSES

oto: F.T. Short

Fish sheltering in a cluster of sea urchins in an Enhalus acoroides bed,

Komodo National Park, Indonesia

E.P. Green

Photo

e [ares ‘
ic invertebrates in a bed of Tha Clownfish and anemone in Enhalus acoroides and Thalassia
hemprichii meadow in Kavieng, Papua New Guinea

N OW
\ 0 100 200 300 Kilometers
= aa

oy
¢

Cromarty Firth

. .
sae, Moray Firth

Ringkobing Fjord

NORTH
SEA
Galway » . eS ina)
; Firth Frisian Is.
Wadden
Sea

Strangford *

@IRELAND Tire :

. a .

.
a7 Ueyn Peninsula aoe
% a 2 NETHERLANDS
‘ “ as Samau Thames g.Grevelingen
Ventry Bay we Estuary .
GERMAN
we > Solent BELGIUM 50°
Isle of Wight

Exe Estuary
- s
Scilly Isles, Se irs

Plymouth Sound
Ile de Batz—_ Channel Is.
Moléne oes
Bay of Brest—

~Cotentin Peninsula FRANCE

\ *S Mont St. Michel Bay
Brehat Archipelago

Glénan Isles He Gulf of Morbihan

Map 2.1
Western Europe (north)

Galway sites, West Cork sites). Wasting disease
symptoms were observed in this country in the 1930s”.

The sandy, surf-exposed North Sea coasts of
Denmark, Germany, the Netherlands, Belgium and
France are devoid of seagrass. Seagrasses are
restricted to the Wadden Sea area, which is protected
from the full hydrodynamic forces of the ocean by the
Frisian Islands. Along the Danish west coast, Zostera
marina occurs in the enclosed Ringkobing Fjord. In the
southern part of the Netherlands some intertidal popu-
lations of the two Zostera species occur in the
estuarine branches of the mouths of the rivers Rhine
and Meuse. Some of these branches were diked in the
second part of the 20th century, but still contain some
submerged beds of Zostera marina (Lake Grevelingen,
Lake Veere).

In France, the two Zostera seagrass species are
widely distributed. The brackish water species Ruppia
maritima and Ruppia cirrhosa are uncommon and
mostly encountered in brackish ponds along the
Channel coast, and the Guérande north of the Loire
Estuary; their distribution is insufficiently known. Many
small Zostera marina beds occur along the Channel
coasts from the west of Normandy to the west of
Brittany, mainly on the sandy bottom under both
intertidal and subtidal marine conditions'”. From the
west of Brittany to the south of the Bay of Biscay, the
sites are either subtidal around islands (Moléne and
Glénan Archipelagos) or in very sheltered bays [Bay of
Brest, Gulf of Morbihan, Arcachon Basin) in which they
can occupy large areas.

Western Europe

Bay of Brest
ATLANTIC OCEAN

Glénan Isles~*

Gulf of Morbihan

Loire Estuary

Marennes-Oléron Basin

Bay of Biscay

{reachon Basin

PORTUGAL

Ria Formosa
.

Alfacs Bay

A
pork

Gibraltar "@ MEDITERRANEAN SEA

Map 2.2
Western Europe (south]

In Spain and Portugal, seagrass beds are
localized in drowned river mouths (rias] and protected
bays (e.g. Vigo Bay), with a zoned occurrence of
the two species of Zostera. Zostera noltii occurs on
the large muddy mediolittoral flats and Zostera
marina (accompanied sometimes by Cymodocea
nodosa (e.g. Ria Formosa)) in the upper part of the
infralittoral. Many of these beds are concentrated in
the numerous Galician rias in northwestern Spain'”’.
In Europe, Zostera marina reaches the southern limit
of its Atlantic distribution in southern Spain near

Gibraltar.

BIOGEOGRAPHY

Zostera marina occurs under a large range of

environmental conditions which can be identified as the

following three main biotopes:

) Sheltered habitats in enclosed and semi-
enclosed bays, estuaries and rias, with turbid
low-salinity waters and muddy sediments.
Eelgrass beds are limited to a narrow depth range
{<2 m) and because of the high turbidity do not
extend much below mean sea level. These beds
often appear as long narrow [<30 m wide} ribbons
along the small subtidal channels which groove
the muddy intertidal flats (many North Sea sites,
Galicia, Arcachon Basin). In some sites (United
Kingdom, Brittany) the intertidal Zostera marina

WORLD ATLAS OF SEAGRASSES

form ("Zostera angustifolia") can extend across
large muddy areas in the mediolittoral belt,
mainly on poorly drained sediments with a thin
water layer remaining at the sediment surface
during the low-tide period.

) Semi-open habitats under marine conditions
(salinity of 32-36 psu). These beds occur on sandy
and locally even on coarse sediments from a
depth of +2 m mean sea level to -3 m. Their
spatial extension depends on the rocky platforms,
small islands and hard substrate structures
which protect the beds from the most extreme
hydrodynamic forces {strong currents, swell and
waves]. This type is common along the western
coasts of the Channel.

) Open habitats under fully marine and subtidal
conditions [-2 to -10 m mean sea level) mainly
around islands in very clear waters. Swell is
probably the main factor limiting the extension of
these beds to the intertidal zone. Zostera marina
can occasionally be observed in artificial lagoons,
brackish pools and abandoned salt production
areas on the French Atlantic coast!” with a
morphology close to its intertidal morph.

Zostera noltii is very often found in estuarine and
sheltered environments as described above but
occupies higher levels on the shore. The species mainly
occurs in muddy and sandy sediments and can form
extensive beds on tidal flat areas [Wadden Sea, United
Kingdom, Ireland, Gulf of Morbihan and Arcachon
Basin). The species is never found below the low-tide
mark.

PRODUCTIVITY, BIOMASS AND ROLE IN NUTRIENT
CYCLES
The primary production of Zostera marina meadows is
the highest of the coastal sedimentary environments of
the region. The associated organisms supported by
eelgrass production are numerous and diverse. The
beds are used as refuge and nursery areas by many
species, including commercial fish and invertebrates.
At this latitude, growth of the perennial morph is
continuous throughout the year, although limited in
winter, so there is a permanent flux of seagrass tissues
inducing a detritus-based food chain. The detritus often
becomes accumulated by waves and tidal currents
outside the beds which thus spatially extend their
functional role in the marine ecosystem". It has been
calculated that 1 g (dry weight) of seagrass detritus
supports on average 9 mg of bacteria and protists”’.
The living leaves are used as a Substrate by diatoms,
bacteria and heterotrophic protists and many macro-
epiphytes (algae and invertebrates).

The total surface area available for the superficial

biofilm and epiphytes, calculated by adding the surface
area of all the leaves of the shoots, can reach 6 to 8 m’
in 1m? of sediment [leaf area index]. Whelan and
Cullinane’ identified 60 algal species in Ventry Bay
(Ireland) and Connan and Hily'“’ found 82 epiphytic
algal species in Brittany beds including 60 species in
only one bed in the Bay of Brest. Some of these species
are found only on Zostera leaves, or have their most
luxuriant development on these, such as the small
Phaeophytes Ascocyclus magnusii, Myriotrichia
clavaeformis, Cladosiphon zosterae and Punctaria
tenuissima, and the Rhodophytes Fosliella lejolisii,
Erythrotrichia bertholdii, Erythrotrichia boryana and
Rhodophysema georgii. This epiphytic community,
described as Fosliello-Myriotrichietum clavaeformis,
occurs only along the oceanic coasts and is very
sensitive to pollution.

In western Europe, many commercial fish and
shellfish species use eelgrass meadows as a habitat.
Some fish predators occupy the beds during tidal and
nocturnal migrations (Labridae, Morone labrax and
flatfish]. Others use the beds as spawning sites and
nursery areas (Mullus surmuletus). The juveniles of the
crab Maja squinado, an important commercial species
in France, hibernate in the sediments of the subtidal
beds'’. The beds are actively exploited by handnet
fishermen for the shrimp Leander serratus. Many
commercial bivalves such the clams Venerupis
pullastra, Venus verrucosa, razor shells, Lutraria
lutraria, and pectinids, Chlamys opercularis and
Pecten maximus, are especially abundant in the
Zostera marina beds and are heavily exploited for
recreational fishing.

Some rare and endangered species like the sea
horse (Hippocampus sp.) still occur in Zostera marina
beds in the area. A few invertebrates directly consume
the eelgrass leaves, e.g. the sea urchin Sphaerechinus
granularis and the sea rabbit Aplysia punctata. Brent
geese (Branta bernicla) used to be strongly dependent
on the eelgrass meadows (Zostera noltii and Zostera
marina) which are generally found in their main
migration sites. At present they have found alternative
food sources following the loss of eelgrass. Other birds
such as teal, widgeon, pintail, mallard, shoveler,
pochard, mute swan and coot are also consumers of
eelgrass.

HISTORICAL PERSPECTIVES

Before the outbreak of the wasting disease in the 1930s,
eelgrass beds were very common along the European
coasts. The beds were locally harvested for different
uses (soil improvement (Galicia, Spain), embankment or
dikes around fields on small islands (Brittany, France],
sea walls [the Netherlands), filling of mattresses and
cushions (Normandy, France, the Netherlands],

packaging, roofing and insulation material); therefore
eelgrass was historically of economic importance. As an
example, about 150 km’ were covered by eelgrass in the
western Wadden Sea'””!. Despite this abundance, already
by the 18th century, Martinet'”’’ was urging development
of a method to multiply eelgrass, because “one cannot
have too much of it””"”. Though little documentation is
available, it seems that Zostera marina was more
abundant than Zostera noltii. Most of the subtidal
Zostera marina beds did not recover from the wasting

Case Study 2.1
THE WADDEN SEA

The Wadden Sea is one of the world’s largest
international marine wetland reserves. Before the
1930s it contained large beds of subtidal and low-
intertidal Zostera marina, whereas many mid-
intertidal flats were covered with a mixed bed of
Zostera marina and Zostera noltii. After the wasting
disease in the 1930s, seagrasses survived only in the
mid-intertidal zone (a narrow zone around 0 m mean
sea level}. Here, new losses occurred from the 1970s
onwards. Increased turbidity, increased shell-
fisheries, increased construction activities and in-
creased nutrient loads are the main factors that have

caused the losses and lack of recovery, although the
causes of the wasting disease losses during the
1930s are still open to dispute

Currently, Dutch seagrass beds cover 2 km’,
German seagrass beds 170 km* and Danish
seagrass beds some 30 km’. In the Netherlands, an

{20, 37)

intensive monitoring program has revealed large
fluctuations in cover of Zostera marina particularly:
for example a sixfold increase in area was observed
within two years [followed by some decrease],
whereas at another area an 80 percent decrease was
observed between two different years (followed by
some increase]. The Zostera noltii bed cover
fluctuates less than twofold, which may be ascribed
to some habitat characteristics, including firm clay
banks, and the plants’ perennial reproductive
strategy. The Zostera marina beds in the Wadden
Sea are mainly {but not totally) annual. These
fluctuations in cover make the populations
vulnerable to local and temporal disturbances,
caused by human actions or by ice scour or gales,
particularly when the area becomes small, and the
habitat offers no local refugia.

Since 1987, the University of Nijmegen,
assigned by and in cooperation with the Dutch
Government, has investigated the possibilities for
restoration of Zostera marina in the western Wadden

Western Europe

disease. From the 1960s onwards the eulittoral beds of
Zostera marina and Zostera noltii declined, probably as
a consequence of increased turbidity’. In one site the
increased turbidity was found to be more related to
increased sediment particles, dredging and filling
activities than to increased phytoplankton.

AN ESTIMATE OF HISTORICAL LOSSES
Without doubt, the losses of areas occupied by eelgrass
have been very great since the beginning of the 20th

Sea. Water clarity of the Dutch Wadden Sea has
improved and shellfisheries have been locally
prohibited. Experiments in the field, in outdoor
mesocosms and in the laboratory, as well as
literature, long-term environmental data and global
information system [GIS] studies, all provided
knowledge of suitable donor populations, habitat
requirements and potential habitats®” *** |n 2002,
transplanting began in the western Wadden Sea.
Risks will be spread in space and time, the
transplants will be protected in the field during the
first years (to prevent seed-bearing shoots drifting to
open sea} and protective mussel ridges will be
constructed to provide refugia for the transplants.

Photo: M. van Katwijk

WORLD ATLAS OF SEAGRASSES

century in western Europe. After the wasting disease in
the 1930s which destroyed most of the Zostera marina
beds, the recovery was very slow and at many sites
eelgrass did not recover at all. From the 150 km’ in the
western Wadden Sea estimated to be covered by
seagrass in 1919 by van Goor'™”, the area estimate in
1971 was reduced to 5 km? only in intertidal areas!”
and the beds were estimated to cover approximately
2 km? in 1994, mainly consisting of Zostera noltii*".
Giesen" considered that in 1990 Zostera marina had
declined to the point of virtual disappearance in the
Dutch Wadden Sea; at present only two locations of this
species are still known in the area.

In a few cases, anthropogenic shoreline

modifications have facilitated the growth of eelgrass
beds. In the second part of the 20th century several

Aerial photograph showing the impact of shellfisheries on an
intertidal Zostera noltii bed

large constructions along the coast of the Netherlands
modified the sites colonized by eelgrass. The
construction of a dam in 1964, 25 km upstream of the
Grevelingen Estuary, isolated the ecosystem from the
freshwater influence; at that period the eelgrass beds
covered about 12 km‘? in the intertidal belt. Then, in
1971, a second dam at the mouth of the estuary isolated
the system from the sea’s influence. The Grevelingen
Estuary was transformed into a stagnant salt water
lake. The new conditions favored the extension of the
Zostera marina beds, which became permanently
submerged, and occupied about 34 km’ in the period
1971-85". Zostera noltii, which was the most common

seagrass before this human intervention, declined to
almost complete disappearance; in the early 1990s a
small, completely submerged stand of a few square
meters was found in very shallow water. The extension
of the Zostera marina beds soon came to a halt. A
large-scale die-off started around 1986-87, and has so
far not been explained in a convincing way” *".

Most of the recent observations underline,
however, the gradual regression of the eelgrass bed
areas under anthropogenic influence. Human impact
may be exercised directly by dredging, filling and mar-
ina development, aquaculture of mollusks (Ostreidae,
Mytilidae, Veneridae) and fish farms, anchoring and
other boat activities, and directly and indirectly by the
effects of eutrophication, such as increasing turbidity,
development of invasive macroalgae and floating
blankets of macroalgae which may suffocate the
seagrasses, and development of high biomass of
epiphytic microalgae and macroalgae on the leaves. In
the geographic area considered, the intensity of these
perturbations varies from one region to the other.

Along the Channel coasts the natural harbors are
used as semi-permanent anchoring sites for pleasure
boats as here the optimal conditions for this activity,
including tidal level considerations, protection from
swell and currents, and distance from the shore are
met. Unfortunately, these are exactly the sites where
Zostera marina has its ecological optimum. This
activity is an important cause of the erosion of eelgrass
beds and it is increasing very rapidly everywhere. In the
same way, recreational fishing is increasing; the
digging of mollusks during low tide at spring tides by
very destructive tools induces a rapid regression of the
intertidal parts of Zostera marina beds. Numerous
eelgrass sites of Zostera noltii and Zostera marina are
progressively disappearing with the rapid extension of
aquaculture, in France and Spain, on intertidal sites. In
Cornwall and Devon (southern England) many losses
were pointed out by Giesen”’ by comparing the results
given by Covey and Hocking’, and Holme and Turk”;
no explanations were found for these losses. The less-
threatened beds are probably the deeper subtidal
Zostera marina meadows under semi-exposed
conditions particularly around small islands, but the
continuously increasing turbidity of the coastal waters
in western Europe, generally recognized but not really
quantified, is probably a factor in the variations of the
lower limits observed in many beds. As an example,
the lower limit of Zostera marina in Ventry Bay [Ireland]
was 13 m in 1977-78, 10 m in 1980 and continued to fall
after 1980".

The loss of eelgrass has not been quantified for
the whole region, but probably more than 50 percent of
the beds are subject to one or other of the types of
perturbations mentioned, and are threatened by total

or partial destruction over the next ten years. A review
of the abundant literature concerning eelgrass in
western Europe suggests that the general trend of
recovery after the almost complete disappearance of
the sublittoral beds in the 1930s is largely being
reversed by the diverse, and generally adverse, local
and regional anthropogenic impacts.

AN ESTIMATE OF PRESENT COVERAGE

In France, along the Channel and Atlantic coasts, most
of the eelgrass sites are known. Along the western
coast of the Cotentin Peninsula, beds of Zostera marina
occur near Granville, and the most eastern beds of
Zostera noltii are in Baie des Veys near Isigny on the
eastern side of the peninsula’. Eelgrass beds in
Brittany were located and mapped in 1999 by Hily et
al." although the exact area of each bed has not been
determined. This study identified more than 70 sites
from the Mont St Michel Bay in the north to the Loire
Estuary in the south of Brittany. Most of them are small
beds between 1 and 5 ha, but there are at least ten
large beds covering 10 to more than 100 ha (including
the Gulf of Morbihan, Glénan Archipelago, lle de Batz,
Bay of Brest, Brehat Archipelago, Abers Estuaries and
Etel Ria). To the south, the Marennes-Oléron Basin is a
large site of Zostera noltii. Further to the south the
Arcachon Basin is the largest site of Zostera noltii (70
km? in 1984] in Europe, and also a large site of Zostera
marina (4 km? in 1984)”.

In the United Kingdom, most of the beds are
mapped and consist of about 140 sites of Zostera
marina [including the intertidal sites) and about 70
sites of Zostera noltii'”. Some of them extend over a
considerable area, such as the Zostera marina bed in
the Cromarty Firth, Scotland, which covers 12 km’!
and is considered the largest bed in the United
Kingdom. In the cross-border sites of Scotland and
England, the Solway Firth and the northern
Northumberland coasts have coverage respectively of
2 and 9 km’: * Along the coast of England, the
seagrass coverage of some large sites has been
documented: Essex estuaries (8.44 km’], North Thames
Estuary (3.25 km’J, Solent and Isle of Wight (4.40 km’),
Plymouth Sound and estuaries (6.50 km‘). Some
smaller beds occur in Devon and Cornwall. In Wales,
the main sites are in the Lleyn Peninsula and the
Sarnau, while in Northern Ireland the beds in the
Strangford Lough cover 6.30 km’"!. Zostera marina
beds are also common on the semi-sheltered
sediments of the Channel Islands.

Along the southeastern coasts of the North Sea,
seagrass beds are restricted to the sheltered Wadden
Sea and southwest Netherlands and cover a total of
200 km’.

In Spain, the actual seagrass coverage is not

known, but many beds are recorded from the numerous
rias of the Galicia region (Zostera noltii covers
approximately 20 km* between the French and
Portuguese coasts'"). In Portugal, the Ria Formosa is
recorded as a site for intertidal Zostera nolti/ beds and
subtidal beds of Zostera marina and Cymodocea
nodosa.

It is at present not possible to measure the
potential seagrass habitat in the whole region.
However, it can be estimated that it would be more than
three times the actual coverage both for Zostera
marina and Zostera noltii. An estimate for Brittany is
planned in 2003 with a long-term survey of the coastal
benthic communities (REBENT network survey)
including Zostera beds. In the United Kingdom the
Habitat Action Plan for seagrass beds developed by the
UK Biodiversity Steering Group may result in quite an
accurate estimate of the potential habitat in this area.

PRESENT THREATS

Direct destruction of beds

As a result of the rapid development of pleasure fishing
and sailing over the last 20 years, filling and dredging
for extension or creation of harbors have destroyed
many eelgrass beds. As a consequence of economic
and environmental arguments such developments are
becoming less harmful nowadays, but the damage has
been done.

Oyster and mussel aquaculture on littoral
sediments has been the cause of the destruction of
many eelgrass beds because the optimal conditions for
the culture of these animals correspond with the
optimal conditions for the beds. This activity is still
expanding, and will probably be one of the main threats
to the beds in the future.

Anchoring and mooring outside harbors is
damaging. Anchoring causes the formation of deep
holes which in their turn may become points of impact
for the eroding forces, while the chains dragging across
the bottom destroy the surrounding biocenoses
including the seagrass communities.

Hand fishing for clams using rakes, forks and
hoes to catch the endofaunal bivalves at low tide, as
well as within the seagrass beds, results in whole
plants with their rhizomes being pulled out of the
sediment. This causes considerable damage to the
seagrass beds, because it is generally followed by
erosion. Collecting clams in this way is becoming very
popular, so this type of perturbation is increasing in
western Europe. The same kind of perturbation is
caused in the eulittoral seagrass beds by digging for
polychaetes such as Arenicola and Nereis to be used
as bait.

Professional fishermen on boats dredge on the
limits of the beds to catch bivalves. The natural

Western Europe 43

4
i)

44 WORLD ATLAS OF SEAGRASSES

acclimation of the Japanese clam Venerupis
philippinarum in the south of the area [from south
Brittany to Spain) increases the direct impact of this
activity on the seagrass beds because this species
develops dense populations in and around the eelgrass
beds of the sheltered bays and estuaries'. In the
Netherlands, much damage has been done to the few
still existing eelgrass beds by professional cockle
fisheries with their modern, effective, but environ-
mentally unfriendly equipment.

Indirect destruction of beds

Eutrophication is the main cause of indirect destruction
of seagrass beds. The increase of organic matter and
nutrients from terrestrial effluents favors phyto-
plankton, causing blooms which in their turn decrease
light availability. Moreover, plankton production
increases not only in terms of instantaneous biomass
but the period of production also becomes longer and
longer, and can be observed all year in some areas with
numerous successive small blooms”. As a cons-
equence of these plankton blooms, the water trans-
parency decreases, limiting the light available for the
growth of Zostera.

Apart from this shading effect by plankton, a
further reduction of light is brought about by increased
epiphyte cover on Zostera leaves in which both diatoms
and macroalgae participate. The specific community of
small epiphytes mentioned above is, however, the first
element to disappear from the seagrass bed in the case
of eutrophication. Eutrophication also increases the
production of green macroalgae (Enteromorpha, Ulva);
particularly in semi-enclosed, sheltered bays the green
algae can form thick blankets which float around and
can be deposited on the Zostera beds of the sandy and
muddy intertidal flats during periods of very calm
weather. Under such conditions the seagrass beds
become smothered and suffocated, leading to complete
die-off within a very short time“. When these blankets
are deposited on the bare surface of the intertidal flats,
the spatial competition favors the green algae which
prevent the extension of the seagrass beds, and reduce
the growth of shoots by shading and suffocation effects
in the areas where they border the seagrass beds. In
these conditions the beds decrease progressively, and
may completely disappear in a few years.

The increase of turbidity is not only associated
with eutrophication, but can also result from an
increasing input of terrigenous particles by river
effluents as a consequence of large-scale changes in
agricultural practices; modern practices encourage the
leaching of soil in winter. Extraction of calcareous
sediments and calcareous macroalgae (Lithophyllum
sp.) from sublittoral beds induces high turbidity; the
high levels of sediment in suspension in the water

reduce light and cover the leaves of seagrass during
resedimentation. Dredging for harbor and channel
maintenance and releasing the dredged sediments on
the seafloor also increases turbidity and lowered light
levels.

Spatial competition with invasive species may
also limit the extension of seagrass beds in western
Europe. The brown algae Sargassum muticum is able
to develop in the eelgrass beds where the sediment
floor is coarse or includes gravel, stones and/or shells.
In these beds Sargassum gradually takes over and
prevents the rejuvenation of eelgrass”.

Most of these threats concern the eelgrass
Zostera marina. The intertidal species Zostera noltii
has been assumed to be threatened by a combination of
various factors including turbidity, eutrophication and
associated epiphyte cover, the decrease of mud snail
populations (Hydrobia ulvae) which graze on the
epiphytes, and also as a result of bioturbation by the
lugworm Arenicola marina. These processes have been
well studied in the Dutch Wadden Sea by Philippart'””.

Finally, a very important potential threat is
shipping. The Channel and the southern North Sea are
among the world’s busiest shipping routes and the
chance that accidents will occur cannot be excluded
{adverse weather conditions; human error). Notorious
disasters were those with the tankers Torrey Canyon
and Amoco Cadiz in the western Channel and recently
Erika in North Biscay. The impact of these oil spills on
the whole coastal ecosystem has been disastrous.

POLICY RESPONSES
The European Union (EU) elaborated a Habitats
Directive for both terrestrial and marine habitats which
identifies the main natural habitats and their cultural
value for further consideration in terms of protection
and conservation. In this context eelgrass beds are
identified as particular ecological units of several
marine habitats: sandy shore, mud flats and coastal
subtidal sandy sediments. These initiatives have led to
eelgrass habitats being specifically targeted for
conservation and restoration™’. But although they are
considered as biotopes of special interest, they are not
considered as “endangered” and so not considered for
immediate and strong protection. In France Zostera
marina is listed in the Red Book of threatened species
but is not in the list of protected species. Zostera noltii
is not considered. Additionally, very locally and in few
localities, some Zostera beds are protected by
municipal authorities. In March 2002, Zostera marina
and Zostera noltii were both incorporated in the Dutch
Red List of threatened plants.

In the United Kingdom, the eelgrass beds have
been considered for many years as targets for
conservation and a habitat action plan for seagrass

Case Study 2.2
GLENAN ARCHIPELAGO

In the northern part of the Bay of Biscay, the Glénan
Isles are located 9 miles off the continental coast of
south Brittany, France. The area is characterized by
ten small islands and numerous rocky islets
surrounding an enclosed, shallow [<5m deep),
sandy area well protected from the oceanic swell.
Aerial photographs are available from the year 1932
and allowed estimates of the long-term develop-
ment of the areas covered by eelgrass”.

This is an interesting experimental site be-
cause the continental influence (eutrophication and
associated consequences) is minimized which
allows the observation of the natural dynamics of the
beds under climatic factors, but also because
human activities (anchoring, fishing) induce local
perturbations in the eelgrass beds. So it is possible
to separate the role of each of the factors that
control the dynamics.

Based on the cover in 1932, it can be
considered that a surface of 10 km‘ is suitable for
eelgrass beds, but in 1990 only 25 percent of this
area was colonized by eelgrass. In 2000, this percen-
tage increased to around 40 percent as a result of
positive climatic conditions since 1995; this tendency
is also observed in many beds of the Brittany
coasts! However this evolution is moderated by the
negative impacts of numerous human activities”:
fo) dredging for clams by professional fishing

boats prevents recolonization in the opened

central subtidal part of the area;

anchoring by numerous pleasure boats

Anchoring on a Zostera marina bed in Glénan Archipelago.

Western Europe

throughout the year induces fragmentation of
the beds in five main sheltered subtidal sites;
recreational fishing for clams induces
fragmentation of the intertidal beds;
extraction of calcareous sediments {maerl
beds) 1.5 miles off the archipelago induces
heavy turbidity in the northern waters of the
archipelago which may limit the extension of
the beds in depth la decrease of the deeper
limits of the laminarians close to the beds was
recently demonstrated"").

This example underlines the complexity of the
dynamics of the eelgrass beds which are under the
influence of factors working at various spatial and
temporal scales: here the positive climatic factors
working at the global scale compensate for the
negative impacts of the perturbations induced by
human activities at the local scale.

This example also underlines the difficulties of
seagrass conservation: it is hard to explain to the
authorities and users alike that human activities
must be moderated in the beds because of their
impacts while the spatial cover is actually
increasing. It is necessary to explain that under
adverse climatic conditions [which are expected in
the future) the cumulative effect, with human
impacts, would induce dramatic and rapid loss of
the beds, and consequently preventive action should
be planned.

Fortunately, the management authorities at
this site are working with the scientific teams on a
sustainable development plan to preserve the image
of high environmental quality in this tourist area.

Photo: C. Hily

WORLD ATLAS OF SEAGRASSES

Zostera marina on a maerl bed in the Bay of Brest

beds was prepared by the UK Biodiversity Steering
Group. In a complementary way, the South West
Regional Biodiversity Habitat Action Plan has also been
developed. These initiatives are integrated in the EU
Habitats Directive which requires the identification of
European marine sites in a network called “Natura
2000": sites which should be managed in order to
maintain or restore the favorable conservation status of
their habitats and species. Each state of the EU has the
statutory responsibility, via the conservation agencies,
for developing conservation objectives in each site,
defined as a statement of the nature conservation
aspirations fora site. In the United Kingdom these sites
are called SACs (special areas of conservation), in

REFERENCES

1 den Hartog C [1981]. Aquatic plant communities of poikilosaline
waters. Hydrobiologia 81: 15-22.

2 den Hartog C [1983]. Structural uniformity and diversity in Zostera-
dominated communities in western Europe. Marine Technology
Society Journal 17: 105-117.

3 Hily C, Bouteille M [1999]. Modifications of the specific diversity and
feeding guilds in an intertidal sediment colonized by an eelgrass
meadow (Zostera marina] (Brittany, France). Comptes Rendus de
UAcadémie des Sciences Serie Ill, Sciences de la Vie/Life Sciences
322: 1121-1131.

4 den Hartog C [1987]. "Wasting disease” and other dynamic
phenomena in Zostera beds. Aquatic Botany 27: 3-13.

5 Giesen W [1990]. "Wasting Disease” and Present Eelgrass
Condition. Report to Dutch Ministry of Transport and Waterways.
University of Nijmegen, Netherlands. 138 pp.

France they are called “sites Natura 2000". The
regulations suggest that relevant authorities from the
various sites should work together within a
management group. In most countries, the presence of
Zostera beds has been a criterion (but not the only one]
to retain a site as a SAC. When a bed is included ina
SAC, specific management is required for the bed. This
procedure is to be applied independently by each
country, and has not yet been achieved. Some sites
derive their conservation status from a combination of
several different directives, and this can reinforce the
conservation of Zostera beds. For example, some sites
are also RAMSAR sites and/or sites of the EU Birds
Directive, which reinforces the international recognition
of the site's importance and requires the government to
strongly protect the site. However, the sites indicated
according to these directives are far from covering all
the eelgrass beds in Europe. It therefore remains very
important to give global consideration to eelgrass
habitats on a wide scale and it remains necessary to
define specific conservation regulations at the level of
the species or genus and/or the habitat.

ACKNOWLEDGMENTS

Dr R.M. Asmus kindly provided Zostera marina cover percentages for the
German Wadden Sea. Thanks to Ingrid Peuziat who provided data on the
Glenan Archipelago.

AUTHORS

Christian Hily, Institut Universitaire Européen de la Mer (University of
western Brittany], Technopole Brest Iroise, 29280, Plouzane, France.
Tel: +33 (0)2 98 49 86 40. Fax: +33 (0)2 98 49 86 45. E-mail:
christian. hily(univ-brest.fr

Marieke M. van Katwijk, Department of Environmental Studies, University
of Nijmegen, P.O. Box 9010, 6500GL Nijmegen, Netherlands.

Cornelius den Hartog, Department of Aquatic Ecology and Environmental
Biology, University of Nijmegen, P.0. Box 9010, 6500GL Nijmegen,
Netherlands.

6 Davison DM, Hughes DJ [1998]. Zostera Biotopes: An Overview of
Dynamics and Sensitivity Characteristics for Conservation
Management of Marine SACs. Reports UK Marine SACs Project,
Task Manager, AMMW Wilson, SAMS. 95 pp.

7 Stewart A, Pearman DA, Preston CD [1994]. Scarce Plants in
Britain. JNCC, Peterborough.

8 Whelan PM [1986]. The Genus Zostera in Ireland. PhD thesis,
University College Cork, Ireland. 215 pp.

9 Whelan PM, Cullinane JP [1987]. The occurrence of “wasting

disease” of Zostera marina in Ireland in the 1930s. Aquatic Botany

27: 285-289.

Hily C, Raffin C, Connan C [1999]. Les herbiers de zostéres en

Bretagne: Inventaire des sites, faune et flore. Rapport Diren Region

Bretagne, Universite de Bretagne Occidentale, Brest. 57 pp.

Curras A, Sanchez-Mata A, Mora J [1993]. Estudio comparativo de

la macrofauna bentonica de un fondo de Zostera marina y un fondo

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arenoso libre de cubierta vegetal. Cahiers de Biologie Marine 35:
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Gruet Y [1976]. Répartition des herbiers de Zostera
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Atlantique et du Nord de la Vendée. Bulletin Société des Sciences
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Whelan PM, Cullinane JP [1985]. The algal flora of a subtidal
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41-51.

Hily C. Personal observations.

van Goor ACJ [1919]. Het zeegrass (Zostera marina] en zijn
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van Katwijk MM [2000]. Possibilities for Restoration of Z. marina
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Netherlands. 160 pp.

de Jonge VN, de Jong DJ [1992]. Role of tide, light and fisheries in
the decline of Zostera marina in the Dutch Wadden Sea.
Netherlands Institute for Sea Research Publications Series 20:
161-176.

den Hartog C, Polderman PJG [1975]. Changes in the seagrass
populations of the Dutch Waddenzee. Aquatic Botany 1: 141-147.
Philippart CJM [1994]. Eutrophication as a Possible Cause of
Decline in the Seagrass Zostera noltii of the Dutch Wadden Sea.
PhD thesis, University of Wageningen, Netherlands. 157 pp.
Dijkema KS, van Tienen G, van Beek JG [1989]. Habitats of the
Netherlands, German and Danish Wadden Sea 1:100,000. Research
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Nienhuis PH, de Bree BHH, Herman PMJ, Holland AMB,
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the distribution and biomass of eelgrass, Zostera marina, in
Grevelingen Lagoon, the Netherlands. Netherlands Journal of
Aquatic Ecology 30: 107-117.

Herman PMJ, Hemminga MA, Nienhuis PH, Verschuure JM, Wessel
EGJ [1996]. Wax and wane of eelgrass Zostera marina and water
column silicon levels. Marine Ecology Progress Series 144: 303-307.
Covey R, Hocking S [1987]. Helford River Survey. A report to the
Helford River Steering Group. 121 pp.

Holme NA, Turk SM [1986]. Studies on the marine life of the
Helford River: Fauna records up to 1910. Cornish Biological
Records No. 9. 26 pp.

Le Gall J, Larsonneur C [1972]. Sequences et environnements

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sédimentaires dans la Baie des Veys [Manche]. Revue de
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Auby | [1991]. Contribution a l'etude des herbiers de Zostera noltii
dans le bassin ‘Arcachon: Dynamique, production et dégradation,
macrofaune associée. These de doctorat, Universite de Bordeaux.
234 pp.

RSPB [1995] Annual Report of the Royal Society for the Protection
of Birds. RSPB, Sandy, Bedfordshire.

Hawker D [1993]. Eelgrass in the Solway Firth. Report for Scottish
Natural Heritage.

Percival SM, Sutherland WJ, Evans PR [1997]. Intertidal habitat loss
and wildfowl numbers: Application of a spatial depletion model.
Journal of Applied Ecology 35(1): 57-63.

Laborda AJ, Cimadevilla |, Capdevila L, Garcia JR [1997].
Distribucion de las praderras de Zostera noltii Hornem., 1832 en el
litoral del norde de Espana. Publ Espec Inst Esp Oceanogr 23: 273-
282.

den Hartog C, Hily C [1997]. Les herbiers de Zosteéres. In: Dauvin
JC (ed) Les Biocénoses marines et littorales francaises des cotes
Atlantiques Manche et Mer du Nord: Synthese, menaces et
perspectives. MNHN, Paris. pp 140-144.

Chauvaud L, Jean F, Ragueneau 0, Thouzeau G [2000]. Long-term
variation of the Bay of Brest ecosystem: Benthic-pelagic coupling
revisited. Marine Ecology Progress Series 200: 35-48.

den Hartog C [1994]. Suffocation of a littoral Zostera bed by
Enteromorpha radiata. Aquatic Botany 47: 21-38.

den Hartog C [1997]. ls Sargassum muticum a threat to eelgrass
beds? Aquatic Botany 58: 37-41.

Wynne DW, Avery M, Campbell L, Gubbay S, Hawkswell S, Juniper
T, King M, Newbery P, Smart J, Steel C, Stones T, Taylor J,
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van Katwiijk MM, Hermuus DCR, de Jong DJ, Asmus RM, de Jonge
VN [2000]. Habitat suitability of the Wadden Sea for restoration of
Zostera marina beds. Helgoland Marine Research 54: 117-128.
van Katwiijk MM, Schmitz GHW, Gasseling AP, Van Avesaath PH
[1999]. Effects of salinity and nutrient load and their interaction on
Zostera marina. Marine Ecology Progress Series 190: 155-165.
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Castric A. Personal communication.

WORLD ATLAS OF SEAGRASSES

3 The seagrasses of

THE WESTERN MEDITERRANEAN

date back to the beginning of the 19th century,

when the most widespread and well-known
species, Posidonia oceanica, was described for the first
time. Since then thousands of papers have detailed
different aspects of seagrass distribution, ecology,
physiology, faunal and algal assemblages and, recently,
genetics. Two international workshops in the early
1980s were dedicated to the endemic Posidonia
oceanica and led to joint research programs among
European countries to study the structure and
functioning of the Posidonia oceanica ecosystem. Less
information exists on the other Mediterranean
seagrass species, although some of them are quite
common and widespread in the basin. A significant
contribution to the synthesis of the work conducted on
Mediterranean seagrasses was offered by the
organization of the Fourth International Seagrass
Biology Workshop held in Corsica in 2000".

Give on seagrasses in the Mediterranean basin

SPECIES DISTRIBUTION

Six seagrass species are present in the Mediterranean
Sea, forming an almost continuous belt all along the
coasts: Posidonia oceanica; Cymodocea nodosa, also
present along the North Atlantic African coasts and
Portugal; Zostera marina and Zostera noltii, both with
a wide temperate distribution; Halophila stipulacea,
probably a recent introduction from the Red Sea; and
Ruppia spp., with a wide temperate distribution (Table
3.1). Extremely limited information is available on
Ruppia in the Mediterranean and it will not be
considered further.

Posidonia oceanica forms continuous meadows
from the surface to a maximum depth of some 45 m and
is common on different types of substrate, from rocks to
sand, with the exception of estuaries where the input of
freshwater and fine sediment is high. Posidonia oceanica
beds have classically been considered one of the climax

MPF

G. Procaccini

M.C. Buia

M.C. Gambi

M. Perez

G. Pergent

C. Pergent-Martini

J. Romero

communities of the Mediterranean coastal area’.
Meadows are very dense with over 1000 shoots/m?
although this varies from year to year“. The horizontal
and vertical growth of rhizomes, and the slow decay of
this material, causes Posidonia oceanica to form a
biogenic structure called “matte”, that arises from the
bottom up to a few meters and can be thousands of years
old". Posidonia oceanica is a monoecious species, with
male and female flowers in the same inflorescence.
Sexual reproduction is sporadic, especially in some
areas. Posidonia oceanica has low genetic variability and
meadows represent genetically distinct populations,
even at a scale of a few kilometers”. A clear genetic
distinction exists between northwestern, southwestern
and eastern populations. Meadows are composed of a
mosaic of large and ancient clones”.

Cymodocea nodosa most commonly occurs in
shallow water but exceptionally can reach a depth of
30-40 m. Shallow and deep stands are generally
discontinuous. Cymodocea nodosa is usually found on
sandy substrate and sheltered sites". In France, the
most important beds are known in coastal lagoons.
Shoot density reaches almost 2000 shoots/m’*". It has
classically been considered to be a pioneer species in
the succession leading to a Posidonia oceanica climax
system. However it also grows in areas previously
colonized by Posidonia oceanica and characterized by
dead matte. Cymodocea nodosa is a dioecious species.
Seeds remain for a long time in the sediment, attached
to the mother plant. The only existing analysis of
Mediterranean meadows showed high genetic diversity.
In fact, plants 5 m apart within a meadow were
genetically distinct individuals”.

Zostera marina is considered to be a relict
species in the Mediterranean, where it forms perennial
meadows distributed from the intertidal to a few
meters deep. It can grow on sandy and muddy
substrate and is also present in lagoons", though it is

Languedoc-
Roussillon

Medes Is.

- Catalan
Coast

Alfacs Bay

<> .

Balearic Islands

Marseille?

The western Mediterranean

, sa Gulf of Trieste.

share
« CROATIA

@Numana » *

FRANCE Uguria” ~ Venice Lagoon —
Pete game o*s
- Po River

- A5°N
Delta 5

°
Monaco
of LIGURIAN SEA

Tuscany

Corsica ITALY

Lazio
bs Apulla’ A DRIATIC
SEA

Campania

Sardin
se Ischia L*

TYRRHENIAN
SEA

MEDI TER RAN EAN [SE A

MOROCCO

v
0 100 200 300 Kilometers eb cene
Le 35° y

Map 3.1
The western Mediterranean

rare throughout the Mediterranean. Shoot density in
Zostera marina beds is almost 1000 shoots/m?""".
Zostera marina is a monoecious plant. Studies on the
genetic diversity of this species have never been
performed in the Mediterranean.

Zostera noltii grows from the intertidal to depths
of a few meters on sandy and muddy substrate”. It is
also present in enclosed and sheltered areas, where it
can form mixed beds with Cymodocea nodosa, at
densities up to almost 1300 shoots/m’. Zostera noltii is
a monoecious species and no information is available
about the genetic variability of its populations.

Table 3.1

Examples of general features of Mediterranean seagrass meadows

Posidonia
oceanica
deep

161
1.1-2.6
52-94

6 526 324
7-147 3-21.3
0.077-0.4 -

Posidonia

oceanica
shallow
700
6.16-29
175-670

925-
0.

Density (shoots/m’)

Leaf area index {m’/m*]
Leaf biomass (g dw/m’}
Below biomass (g dw/m’)
Epiphyte biomass (g dw/m’
Animal biomass (g dw/m?)
Number of algal species 36 50
Number of animal species 38-60 22-84
Animal density (individuals/m*) 380-1 100 210-680
Leaf production (g dw/m7/y] 162-722 71.3-232
Rhizome elongation (cm/y) 1.1-7.4
Leaf lifespan [months] 11

3.4
1.

23.6-

Cymodocea
nodosa

1925
2-3.5

17-159
300-750

-12.5
0-2.6
35
83
1 486
1 623

3.6-57.8

IONIAN
SEA

20°E

Halophila stipulacea was recently introduced to
the western Mediterranean Sea and was reported for
the first time in 1988. In the eastern Mediterranean
basin this species has been observed from the
beginning of the 19th century and Is believed to have
been transported from the Red Sea, through the Suez
Canal, an example of Lessepsian migration. In the
Mediterranean it is distributed from the intertidal zone
to 25 m'”!. It can grow on sandy and muddy substrate,
and is present in enclosed areas. Shoot density is
extremely high, up to almost 19000 shoots/m? in
shallow water”. Halophila stipulacea is a dioecious

Zostera
marina

Zostera
noltii

Halophila
stipulacea
shallow deep

19728 13000
5 5.9 0.2-0.4
157.8 - 13-79 45-775
- 31-62 21-161

- 0.7-3.2

Halophila
stipulacea

216-1093
1.7-6.7

269-1 246

109-2299
18-91
1-3

Source: Modified from Buia et al”. Values derived from key studies listed in Buia et al

WORLD ATLAS OF SEAGRASSES

Photo: Laboratory of Benthic Ecology (SZN)

Case Study 3.1
ITALY

LIGURIAN COAST

The Ligurian area is one of the best among the
Italian coasts for information on the distribution
and general status of seagrasses, in particular for
Posidonia oceanica. Almost 50 Posidonia oceanica
main meadows have been recorded and
mapped”. Their extension ranges from a few to
several hundred hectares, covering in total about
48 km’. In general all the prairies are in different
states of degradation due to coastal modifications
for harbor and town development. In addition
some Posidonia oceanica beds were impacted in
the early 1990s by a crude oil spill following the
wrecking of the oil tanker Haven, considered to be
one of the worst Mediterranean oil spills"

Posidonia oceanica banquette on the Cava dell'Isola beach,
Ischia Island, Italy.

TYRRHENIAN COAST (ISLAND OF ISCHIA)

At a smaller spatial scale, the best-known
Posidonia oceanica meadows are those
surrounding the Island of Ischia, in the northern

part of the Gulf of Naples. Posidonia oceanica
covers about 17 km’ of the seafloor, and its
meadows, forming a continuous belt around the
island, were mapped in detail in 1979! The
different exposure of the coasts of the island,
coupled with different environmental conditions
and bottom type, give rise to meadows extremely
diversified in terms of physiognomy [continuous
and patchy beds], depth range [from 0 down to
38 m in depth], shoot density {from a mean of 900
shoots/m? at 1 m to 80 shoots/m* at 30 m depth)
and biodiversity of associated communities (more
than 800 associated species], and with low
intrinsic genetic variability, coupled with a degree
of isolation between shallow and deep stands”

A recent monitoring of beds around the
island [in the year 2000) demonstrates a
substantial stability of distribution and the
presence of other settlements not previously
reported. However, long-term studies carried
out since 1979 in beds off Lacco Ameno have
detected a reduction in shoot density, as a result of
anchoring, the impact of the local fishery and a
nearby wastewater outfall.

NORTH ADRIATIC COAST (VENICE LAGOON)
Zostera marina |s present on the Italian coasts of
the north Adriatic Sea — it was first recorded here
in the 14th century. Posidonia oceanica has
experienced a strong decrease in this area, being
now limited to a few patches in the Gulf of
Trieste™. The worst decline of Posidonia
oceanica has occurred in the Venice lagoon. In
1990 Zostera marina covered an area of 36.5 km’,
forming pure and continuous beds of 2.4 km? and
beds mixed with Zostera noltii over the other 34
km?:4_ Zostera noltii was the most widespread
species (42.5 km’) and Cymodocea nodosa was
also present [15.6 km?]. Monitoring results four
years later from the southern part of the
lagoon” showed an increase of about 7.6
percent in the overall extent of seagrass beds,
but with more Zostera marina {an increase of
13.5 percent], a decrease of 10.1 percent in
Cymodocea nodosa and a large decline in
Zostera noltii (24.7 percent]. The monospecific
and discontinuous beds have increased while
mixed species beds have declined. A high survival
rate for Zostera marina, Cymodocea nodosa and
Zostera noltii has been achieved in transplanting
experiments using sods and rhizomes at various
sites in the lagoon”?

species. Male flowers are frequent in the
Mediterranean Sea but female flowers were only
observed for the first time in 1998, in Sicily'’!. Studies
on the genetic variability of two populations located
along the Sicilian coasts showed that each shoot
represents a genetically distinct individual. Genetic
relatedness was higher among individuals collected at
the same depth'”.

ASSOCIATED SPECIES

Seagrass ecosystems of the western Mediterranean
are extremely rich in a number of associated plant and
animal species. However, complete lists of associated
species have been compiled only in a few cases, such
as the Posidonia oceanica and Cymodocea nodosa
meadows of the island of Ischia, where more than 800
and 250 species have been listed, respectively’, or in
the Medes Islands'”’. Posidonia oceanica beds are the
exclusive habitat for many algal and animal species,
such as the coralline red algae Pneophyllum fragile
and Hydrolithon farinosum, the brown algae Castagnea
cilindrica, Giraudia sphacelarioides and Myrionema
orbiculare, the bryozoan Electra posidoniae, the
hydroids Aglaophenia harpago, Sertularia perpusilla,
Campanularia asymmetrica, Cordylophora pusilla and
Laomedea angulata’*”.

Posidonia oceanica meadows are nursery
grounds for the juveniles of many commercially
important species of fishes and invertebrates, such as
several species of the family Sparidae (e.g. Diplodus
sargus and Diplodus annularis), Serranidae (e.g.

Case Study 3.2
FRANCE

MARSEILLE-CORTIOU REGION

A long-term monitoring study of Posidonia
oceanica beds in the Marseille-Cortiou region has
recorded fluctuations over the 1883-1987 period,
and the impact of a sewage treatment plant. In the
period 1890 to 1898, when a sewage outlet was first
set up in Marseille, the seagrass bed had reached
a depth of 30 m and occupied an area of about
6.32 km*. A number of authors noted loss of
Posidonia oceanica between 1900 and 1970 as the
city of Marseille expanded", At the end of the
1970s the bed covered a smaller area, with a loss
of 5-6 percent per decade.

When the wastewater treatment plant was
set up in 1987, the lower limit of the seagrass bed
was just 10 m and it included vast stretches of
dead matte. Since then there have been further,
much greater, losses amounting to 40 percent of

The western Mediterranean

Serranus cabrilla), Labridae {e.g. Coris julis and
Crenilabrus maculatus) and Scorpaenidae (e.g.
Scorpaena scrofa and Scorpaena porcus), and the sea
urchin Paracentrotus lividus. Among the rare or
endangered associated species are the endemic sea
star Asterina pancerii, the sea horse Hippocampus
hippocampus and the bivalve Pinna nobilis: these
species are protected, in both Italy and France, or are
included among species requiring a specific legislation
for protection’.

EXTENT OF COVERAGE

Information on the distribution of seagrasses is
scattered and therefore an estimate of the total area
covered by seagrasses is difficult to make. However the
beds in some areas are well known.

The Italian coastline is 7500 km long, without
taking into account the numerous small islands
scattered all around the peninsula. It is almost entirely
surrounded by seagrass meadows that, considering the
three most abundant species [Posidonia oceanica,
Cymodocea nodosa and Zostera noltii), extend from 0.2
to 45 m. Clearly the potential area covered by seagrass
is enormous. Some 2 350 km’ of seagrass are known to
occur in Liguria, Lazio, Sardinia, Veneto and Friuli
(Table 3.2). France has approximately 1150 km? of
Posidonia oceanica beds, but estimates for other
species are not available. On the Mediterranean coasts
of Spain, some regions have mapped their seagrass
meadows in great detail allowing an estimate of more
than 1000 km’ to be made.

the 1970 area. This is most likely due to the high
levels of suspended matter, ammonium and
phosphate coming from the treatment plant. After
1994, a natural recolonization of Posidonia
oceanica was observed in certain areas, due to
increased water clarity.

CORSICA

Corsican coasts experience low human impact
with many marine protected areas; almost
71 percent of the Corsican coastline is still in its
natural state. Posidonia oceanica beds occupy a
total surface area of 624 km?"" mainly along the
eastern side of the island, where the continental
shelf is very wide. Their distribution is limited on
the steep and indented west coast. Upper limits
are generally between 1 and 10 m depth, while
the lower limit at several sites on the east coast
is situated below 40 m. The lower limit rises to
a depth of 15-20 m near large cities such
as Ajaccio.

WORLD ATLAS OF SEAGRASSES

The beds of Posidonia oceanica are among the
most important Mediterranean ecosystems, and their
conservation is a high national and international
priority (e.g. EU Habitats Directive 92/43/CEE, 21 May
1992}. Posidonia oceanica beds exert a multifunctional
role within coastal systems, comparable to that of other
seagrasses in temperate and tropical areas, offering
substrate for settlement, food availability and shelter,
as well as participating in key biogeochemical and
geological processes.

Table 3.2

Sites Po Cn Zm Zn Hs Area
(km?)
ITALY
Liguria* v v 48
Tuscany* v v v =
Lazio v v v 200
Campania* v v v v -
Calabria* v v v v -
Apulia v v v =
Central v -

Adriatic coasts

Veneto and v v v v 96
Friuli V.G.

Sicily* v v v v -
Sardinia v J 2 000
FRANCE

Provence Alpes ¥ v v v 3
Cote d'Azur

PRODUCTION AND BIOMASS

Both below-ground and above-ground biomass values
of Posidonia oceanica exceed those of other seagrasses,
including the Australian Posidonia species”. A striking
feature is the distinct partitioning of the biomass, mainly
directed into the lignified rhizomes, which can account
for up to 90 percent of total biomass'*" “and production
where leaves account for more than 90 percent”. In an
extensive study net primary production was estimated
to range from 130-1284 g dry weight/m’/year. However,

Distribution of seagrasses throughout the western Mediterranean (Italy, France and Spain)

Comments

On rocky and sandy bottom, from 0 to 35 m'”,

On rocky and sandy bottom, from 0 to 40 m
Large extensions of dead "matte". Meadows in regression at north of the

(o9**)

Tevere River due to sedimentation from construction works. Illegal trawling
within the depth of 40 m7"

Beds with different typology, extension and morphological features, due to
the highly variable environmental conditions and sea bottom
topography”.

Beds with different typology, extension and morphological features, due to
the highly variable environmental conditions and sea bottom topography.
Posidonia oceanica is frequent along the southern Adriatic and the lonian
coasts. Meadows grow on old “matte” remains, in the Gulf of Taranto, while
they grow on sand or rocks along the Adriatic side of Apulia. Posidonia
aceanica is also present at the Tremiti Islands”.

Posidonia oceanica is absent from the Po River delta to the northern Apulian
coasts. No information on other seagrasses except for Zostera marina
(Numana Harbor, south of Ancona).

Seagrasses are not abundant along the northern coasts of the Adriatic Sea,
which is influenced by the freshwater inflow and fine sediment coming from
the Po River. Posidonia oceanica is present only in a few patches in the Gulf
of Trieste and in the Venice lagoon, where Zostera marina is present in one
of the few spots of the Mediterranean Sea’ *°”"),

Posidonia oceanica is present all along the Sicilian coast. Dense prairies are
present along the southeast and northwest coasts of the island on
calcareous sediments. Illegal trawling within the 40-m zone has caused
significant loss of Posidonia oceanica meadows in recent years, together
with the damage caused by anchoring and recreational activities”,
Posidonia oceanica extends all along the Sardinian coast, from a few meters
to 30 m, and occasionally 40 m, depth. Prairies on the southern and northern
coasts of the island are more fragmented (author's unpublished data).

Posidonia oceanica is the most abundant species. Cymodocea nodosa:
dense monospecific meadow from 0 to 15 m depth and mixed beds with
Zostera noltii and Caulerpa prolifera. Zostera marina: dense meadows
present in the Gulf of Fos, while small beds occur in the Bay of Toulon.
Zostera noltii is present in small patches in the Berre lagoon!” *”).

this production is only minimally used for direct
consumption by herbivores’. The very high biodiversity
found in Posidonia oceanica beds is mostly due to the
primary role of this seagrass as a multidimensional
habitat for organisms directly participating in the
system's trophic dynamics‘.

The Posidonia oceanica matte not only represents
a net sink of carbon and other elements” “” but also,
when growing near the surface, can attenuate the wave
action. Under such conditions, it has been estimated that

Sites Po Cn Zm Zn Hs Area
(km’]
Languedoc- v v v 26
Roussillon*
Corsica v v v 624
SPAIN
Catalonia v v v v 40
Valencia v v v 270
Murcia v v v 95
Andalucia v v v v -
Balearic Is* v v v 750
Notes:

The western Mediterranean

the removal of 1 m* of matte can cause 20 m of coastal

regression”

ashore gives rise to a

. Moreover, the deposition of dead leaves
typical structure called

“banquette” which, mixed with sand, can in some areas

(49)

develop up to 2-3 m high
tant role in attenuation of waves and in the protection
beaches from erosion’. In addition, the banquette

. The banquette has an impor-

of
is

hosting a reduced, but highly specialized fauna [isopods,

amphipods and interstitial flatworms] that contribute
the decomposition of the seagrass material.

Comments

Posidonia oceanica is present only in small patches between 7 and 15 m
depth, with dead and living beds 1-4 km from the coast (extent not
available]. The region is characterized by the presence of many

coastal lagoons with monospecific Zostera marina beds [e.g. Salse lagoon)
or mixed beds with Zostera noltii (e.g. Thau lagoons}. In open sea Zostera
noltii occurs in small patches (e.g. Harbor of Banyuls}"°**”

Posidonia oceanica meadows on sandy bottom on the east coast and on
rocky bottom on the west coast. Dense Cymodocea nodosa meadows on
sand or muddy bottom in shallow bays and in lagoons. Zostera noltil is only
present in lagoons, often in association with Cymodocea nodosa**:*"".

Mostly on sandy bottom, but also on rocky bottom. From near the surface
to 25 m. Conspicuous regressions have been reported, but most meadows
seem to be stabilized nowadays‘.

This region has extensive meadows of Posidonia oceanica from near the
surface to 25 m, exceptionally 30 m, generally on sandy bottom. The deep
limit has suffered a significant regression due to illegal trawl fishing
(Sanchez-Lisaso, unpublished data}.

The main meadows are dominated by Posidonia oceanica, extending from
the surface to 25-30 m. Conspicuous regressions have been observed near
the deep limit due to illegal trawl fishing. Cymodocea nodosa and Zostera
noltii appear in shallow waters'””.

Posidonia oceanica is abundant in the eastern part of the area, with
extensive meadows on sandy and rocky substrata. The western limit of
Posidonia oceanica is near Malaga; from this point westwards (to the
Gibraltar strait), Zostera marina dominates'””.

Extensive and dense meadows occur all around these islands, reaching up
to 40 m depth, with some locally degraded sites, mainly due to tourism
(moorings, sewage, etc.]. One locality has been invaded by Caulerpa
taxifolia. In shallow bays, dense Cymodocea nodosa meadows are frequent.

Cymodocea nodosa is also found below 30 m'””.

Po Posidonia oceanica; Cn Cymodocea nodosa; Zm Zostera marina; Zn Zostera noltil, Hs Halophila stipulacea.

/ species present. - insufficient data.

* Interactions with Caulerpa taxifolia and Caulerpa racemosa. ** http://gis.cnuce.cnr.it/posid/html/posid.html

WORLD ATLAS OF SEAGRASSES

Case Study 3.3
SPAIN

CATALAN COAST

The main seagrass species on the Catalan coast is
Posidonia oceanica. In the sandy coasts of the
southern part of the country this species forms a
large and continuous green belt of meadows only
interrupted by rivers. This seagrass belt used to
extend from 10 to approximately 25 m depth,
although significant regressions have been detected
and in many areas the deep limit is now between 17
and 20 m. Along the northern rocky coast, the
meadows occur from near the surface to 20-25 m.
With the publication of an edict protecting
seagrasses in 1991, the autonomous government
(Generalitat de Catalunya) has taken several actions
for a proper management of these plants and, more
specifically, of the Posidonia oceanica meadows.
This includes a monitoring network, launched in
1998. This network consists of a total of 28
permanently marked sites [nearly one every 15 km]
from which basic data on the vitality of Posidonia
oceanica (e.g. shoot density, cover, etc.] are collected
every year™!. Underwater work is performed by

volunteers {more than 400 for the whole project),

trained and supervised by expert scientists. This
monitoring network, after the first four years, has
allowed a general diagnosis of both the status and
the recent trends of seagrasses on the Catalan
coast. The results obtained so far indicate that 42
percent of the studied meadows are in a normal or
healthy state, while the rest show light (36 percent]
or strong (22 percent) evidence of degradation.
During the four-year period of the survey there have
been no net changes in the Posidonia oceanica beds.
Only in 15 percent of the sites has a negative,
although slight, trend been detected from a decrease
in water transparency, illegal trawl fishing and
oversedimentation. Overall the Catalan seagrass
beds appear to have remained remarkably stable
over the period 1998-2001.

MEDES ISLANDS

The Medes Islands are a small and deserted
archipelago situated 1.6 km off Spain’s main coast, in
the northern part of Catalonia. A large Posidonia
oceanica meadow, extending from 5 to 15-20 m
depth, and covering about 9 ha, is found in the
sedimentary bottom of the southwest face of the
main islands. This meadow has been extensively
studied’ * jn the course of the monitoring program
of the marine reserve established there in 1990. The

dataset has one of the longest series for this species,
and the results show significant interannual
differences. From the first observations in 1984 and
1987, density and cover decreased sharply (e.g. at
the 5 m depth station, density decreased from 628
+19 shoots/m? in 1984 to 481 +14 shoots/m? in 1994,
while cover decreased from 76 percent in 1984 to 48
percent in 1994) probably due, at least in the shallow
station, to very high mooring activity on the seagrass
bed. However, after the establishment of the marine
reserve in 1990 anchoring was no longer allowed,
and a system of low-impact mooring was deployed
between 1992 and 1993. The density and cover values
subsequently recovered [e.g. at the 5 m depth
station, density reached 708 +24 shoots/m? and cover
73 percent in 2001). Moreover, it would also seem
that meteorological conditions [e.g. incoming
irradiance) in these later years have been optimal,
probably contributing to the observed increase.

ALFACS BAY (EBRO DELTA)

Although Posidonia oceanica is the most abundant
seagrass species on the Catalan coast, in some
specific habitats other marine angiosperms can
dominate. This is the case in the two bays at each side
of the Ebro Delta, the southern one of which (Alfacs
Bay] has been extensively studied and mapped. In this
bay, 50 km? in extent, dense meadows extend from
very near the surface to 2-3 m and, more rarely, 4 m
in depth. This narrow bathymetric range is due to high
water turbidity. Cymodocea nodosa, with the green
alga Caulerpa prolifera interspersed in some places,
dominates these meadows. Some patches of Zostera
noltii, as well as Ruppia cirrhosa, exist in shallow
areas. The presence of Zostera marina was detected
in the early 1980s, but it has never been seen again. A
detailed map was produced in 1986 revealing a total
surface of seagrass beds of 3.5 km’, including 1 km?
of patchy beds in the southern zone. In the last ten
years, the bay has undergone some remarkable
vegetation changes”. Cymodocea nodosa has greatly
expanded in the southern part of the bay, covering
now about 2.5 km? which represents, for this southern
area, an increase of approximately 15 percent a year.
This increase may be associated with work performed
to stabilize the sandbar, since sand instability was one
of the main processes controlling seagrass
abundance in this area®. In the northern parts of
Alfacs Bay, the most remarkable change is the
replacement of a mixed Zostera noltii and Ruppia
cirrhosa bed, described in 1982", by Cymodocea
nodosa with abundant drifting macroalgae, such as
Ulva spp. and Chaetomorpha linum, by 1997.

Mediterranean seagrass meadows host many
commercially important fish species. As well as
nurseries they provide essential feeding grounds for
cephalopods, crustaceans, shellfish and finfish’”.
Although specific fisheries legislation does not allow
destructive fishing (e.g. trawling) in seagrasses, such
restrictions are often violated. The only fishery allowed
in the Posidonia oceanica meadows are small fisheries
based on the use of standing nets and cages.

Posidonia oceanica detritus is used as fertilizer in
agriculture in Tunisia®” and the leaves have also been
used in small proportions in chicken feed’, with an in-
crease in egg production and weight. More recently,
different attempts to exploit the banquette were focused
on production of methane’, conversion of detritus into
fungal biomass'” and formation of dried pellet for prep-
aration of light bricks for buildings. Further anecdotal
uses of air-dried leaf detritus to protect glass objects in
transport, and to fill pillows and mattresses, have been
reported. Posidonia oceanica detritus is used in Corsica
as thermal insulation material on roofs’ and as sound-
proof material”. The ability of Posidonia oceanica leaves
to produce active substances, which accelerate the
growth of bacteria such as Staphylococcus aureus, has
been demonstrated. This seems to be related to the
Presence of chicoric acid, one of the most abundant

metabolites found in this seagrass’.

THREATS
Beds of Posidonia oceanica have suffered a progressive
regression throughout the Mediterranean due to
trawling, fisheries and sand extraction and development
of coastal infrastructure’’*", such as harbors and
artificial beaches, and associated enhanced turbidity
and sedimentation. The damming of rivers has caused
changes in sedimentation in the littoral zone, either
exposing or burying seagrass habitats. One dramatic
example occurred in Port-Man Bay [southeast Spain],
where a seagrass meadow was buried under a large
amount of highly toxic mining debris. Eutrophication,
which decreases water transparency and promotes
epiphyte overgrowth, is a serious regional threat.
Sometimes associated with fish cages, the most com-
mon causes are sewage and industrial waste discharge.
Caulerpa taxifolia is a tropical green seaweed
accidentally introduced in the Monaco area in 1984. After
its introduction, Caulerpa taxifolia spread through
France, to Italy and Spain (the Balearic Islands) by 1992,
and to Croatia in 1994". The area colonized has now
reached more than 60 km’ along the French and Italian
coasts. Caulerpa taxifolia grows throughout the entire
depth range of the Mediterranean seagrass species and,
in some places, is progressively overwhelming them.
Another strong competitor with seagrass beds is the
introduced congeneric species Caulerpa racemosa,

The western Mediterranean

: Sa a
Posidonia oceanica growing on rocks and forming matte, Porto
Conte, Sardinia

which has become widespread in the last ten years.
Experimental work on the interactions between intro-
duced Caulerpa species and local seagrasses show that
dense meadows of both Posidonia oceanica and
Cymodocea nodosa are likely to be less affected by
seaweed invasion. The competitive success of Caulerpa
racemosa with Posidonia oceanica meadows is a
function of seagrass density and edge-meadow
orientation. Competition between Caulerpa racemosa
and Cymodocea nodosa seems to favor the expansion of
Zostera noltii**“', The locations of interactions between
seagrasses and Caulerpa spp. are listed in Table 3.2.

Although Mediterranean seagrasses are now
being increasingly well monitored, reliable estimates,
made by direct observation, of the area of seagrass lost
or degraded by the various pressures are not available
for most of the western Mediterranean coastline. In fact
only in the last few years have maps of distribution
been produced. In the future the application of aerial
cartography techniques may supply important
information on seagrass status throughout the
Mediterranean").

In general, for Posidonia oceanica, the following
statement by the European Union for Coastal
Conservation is probably accurate: “The situation in the
Western Mediterranean is serious. Shoot density is
rapidly decreasing, up to 50 percent over a few decades.
Besides, increased turbidity and pollution have resulted
in a squeeze of the beds; in various places living beds
have withdrawn between 10 and 20 m depth. Dead beds
occur abundantly, even in waters which have already
been protected for 35 years. For the French mainland
coast habitat loss is estimated at 10-15 percent; but
taking into account the decrease of shoot density the
overall decline of the resource will be between 30 and
40 percent. This is probably a good estimate for most
Western Mediterranean coastlines, although the

Photo: Laboratory of Benthic Eco

WORLD ATLAS OF SEAGRASSES

situation around the islands and in the Eastern
Mediterranean Is better”.

In France a disappearance of Posidonia oceanica
beds between 0 and 20 m has been observed in the last
30 years for 13 percent of the seafloor in the Alpes
Maritime department, 6.6 percent in Var and 18.4
percent in Bouches du Rhéne””*". In Spain, a compari-
son of old marine charts with present distribution data
in Catalonia indicates that meadow area is now about
75 percent of that at the beginning of the 20th century.

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4 The seagrasses of

The Black, Azov, Caspian and Aral Seas

THE BLACK, AZOV, CASPIAN AND

ARAL SEAS

Asian seas is their total (Aral and Caspian) or

near-total [Azov and Black) isolation from open
ocean systems. These temperate seas have many
common environmental features especially with regard
to variable salinity and levels of pollutants.
Geographical proximity and isolation determine a
number of special features inherent in these seas: they
have a distinctly continental climate, no tides (but
considerable long-term fluctuations of sea level, and
both coastal upwelling and downwelling, have
occurred), minimal or zero water exchange with other
seas and seawater of unusual chemical composition”.
All four seas contain the estuaries of major rivers and
are consequently dependent on the influx of freshwater.
In nearly every case these rivers have been severely
disrupted from their natural state by the construction of
dams, and upriver pollution and water extraction, as
well as changes in rainfall across their watersheds.
Therefore long-term changes in seawater chemical
composition and concentration have occurred near the
river mouths. Distinguishing hydrological charac-
teristics of the coastal shelves, the main potential
habitat for seagrasses, are their shallow depth (about
20 m) and large area, marked seasonal and interannual
fluctuations in productivity, winter ice cover, pre-
dominant wind-induced seawater circulation, and fast
water exchange owing to the small capacity.

Highest productivity is found in the brackish areas
of the north Caspian Sea, the northwestern Black Sea,
and the Sea of Azov and Kerch Strait” “°. This high
productivity is due to massive freshwater influx from the
Rivers Volga, Danube and Don, and the correspondingly
high nutrient input, fast turnover of these nutrients,
intense summer warming, high dissolved oxygen
content of the brackish water and the longer summer
daily growth period at higher latitudes. However, at the
same time anthropogenic pollution substantially
reduces the biological diversity and productivity of the

Ts principal characteristic of the temperate Euro-

N.A. Milchakova

water bodies, and has been especially damaging to the
traditional fisheries of these four seas. In the Caspian
and Azov Seas, which are of the greatest significance for
commercial fishing in the region, the usable fish stock
has been reduced by more than half. The largest
sturgeon stock in the Caspian Sea has dramatically
decreased. In the last two years, the commercial stock
{approximately 250000 metric tons) of kilka,
Clupeonella cultriventris, has been reduced by 40
percent. Twenty thousand Caspian seals and about 10
million birds have died. High concentrations of heavy
metals and oil products were detected in the dead
animals".

Seagrasses play a key role in the coastal eco-
systems of the seas and occupy vast areas in the
shallow bays and gulfs of the Black, Azov, Caspian and
Aral Seas. The diversity of algae, invertebrates and
fishes in seagrass communities is astonishing. The
condition and distribution of seagrasses are strongly
influenced by freshwater influx, industrial, municipal
and agricultural sewage, shipping, sea-bottom
dredging, dumping, and oil and gas extraction on the
shelf. Fluctuations in the sea level of the Caspian and
Aral Seas also influence the coastal ecosystems.

BLACK SEA

There are four seagrasses, two seagrass associates
and about 300 macroalgae in the flora of the Black
Sea’. Communities of Zostera marina, Zostera noltii,
Potamogeton pectinatus and Ruppia cirrhosa occupy
vast areas in shallow bays and gulfs, especially in the
northwestern part of the sea”. The distribution and
ecology of Black Sea seagrass was first reported at the
beginning of the 20th century"" ™, with further details
of seagrass biology and community structure in the
Black Sea, and environmental impacts on the
seagrasses, being obtained in subsequent decades”
"18! During 1934-37 communities of Zostera marina
were seriously damaged due to a wasting disease

Photo: F.T. Short

RRS Aas

WORLD ATLAS OF SEAGRASSES

Early symptoms of wasting disease in Zostera marina - an
epidemic in the 1930s seriously damaged communities of this
seagrass in the Black Sea

epidemic similar to that registered along the North
Atlantic population of this species'’”. Fortunately,
Zostera noltii, also widely found in the shallow bays and
coves, was not affected’ ”.,

During the 1970s and 1980s, the stock of Zostera
spp. growing in the four largest bays of the Black Sea,
the Tendrovsky, Dzharilgatsky and Yagorlitsky Bays and
the Karkinitsky Gulf, was estimated at 633000 metric
tons’ 7! After 1982 the coasts of these bays
accumulated considerable cast-off of Zostera spp.,
estimated at 35000 metric tons dry weight’. However,
according to previously calculated data on the annual
leaf production of Zostera spp., the actual annual
estimate was about 4000 metric tons dry weight.

Many researchers have noted that Zostera spp.
usually grow in the coastal salt lakes and sometimes in
the deltas of the rivers'**. There is no information on
the distribution of Zostera spp. along the shores of
Georgia and Bulgaria. Zostera noltii is found in Sinop
Bay, on the Anatolian coast of Turkey.

Seagrasses in the Black Sea grow in single
species and mixed communities, located on silt and
sandy sediments, often with a portion of shell grit. The
depths at which they are found range from 0.5-17 m,
across a Salinity gradient of 0.3-19.5 psu. Some 115
algal species have been identified growing in Zostera
marina communities, and 62 in communities of Zostera
nolti!. The majority of the algae are epiphytes
encrusting the leaves and occasionally the rhizomes
and roots. Cladophora, Enteromorpha, Ceramium,
Polysiphonia and Kylinia spp. predominate. There are
more than 70 species of invertebrates, 34 fishes and 19
fish larvae in seagrass meadows, among which
shrimps, scad and perch predominate”.

The average biomass of Zostera marina in

Karkinitsky Gulf is 1109 g wet weight/m’ with a density
of 105 shoots/m?*'”". Lower biomass and higher density
occur in the Donuzlav Salt Lake (836 g wet weight/m*
and 218 shoots/m’}"". Near the mouth of the Chernaya
River, where the salinity is less than in other parts of the
Black Sea (11-17 psu], seagrass biomass reaches
2986 g wet weight/m* and density 1136 shoots/m? 7)
although the maximum biomass values recorded for the
Black Sea occur in Kamysh Burun Bay in the southern
part of the Kerch Strait (5056 g wet weight/m’)'"”. In the
Kerch Strait, which links the Black and Azov Seas,
Zostera marina biomass ranges from 2008 g wet
weight/m* at Cape Fonar” to 3958 g wet weight/m? in
Kerch Bay’, and plant density from 916 to 600
shoots/m’ respectively. The longest shoots of Zostera
marina, at more than 2 m, have also been found in the
Kerch Strait”, though in other areas of the Black Sea
their length more typically varies between 25 and 100
cm'*'"!. For Zostera noltii, biomass estimates vary from
0.5 to 2 kg wet weight/m’; the highest values were
registered at depths down to 1 m in summer 820.31.

The total sea-bottom area occupied by Zostera
spp. in the bays of the northwestern Black Sea is more
than 950 km’, or 40 percent of the total area of all the
bays”. Zostera spp. communities cover a similar por-
tion, about 50 percent, of the sea bottom in shallow bays
of Sevastopol region, the Kerch Bay and Kerch Strait.

Though most investigators have acknowledged
that the recent eutrophication of coastal ecosystems of
the Black Sea has led to degradation of key benthic and
plankton communities”, the dynamics of the long-
term changes observed in Zostera spp. communities
have revealed that there are many localities, including
dumping grounds, where recovery of the seagrass beds
is occurring. Estimates of Zostera marina biomass
have increased two- to threefold in Laspi, Kazachaya,
Kamyshovaya, Streletskaya, Severnaya, Holland and
Kerch Bays, and in the Kerch Strait, over a period from
1981-83 to 1994-99" '* *7 | The greatest increase in
biomass, from 1185 to 3958 g wet weight/m’, has
occurred in Kerch Bay, and the greatest increase in
shoot density, from 252 to 936 shoots/m’, in
Streletskaya Bay. This increase in the yield of Zostera
spp. biomass is probably due to several factors, the
most significant of which is likely to be reduced
industrial pollution and the natural resilience of
Zostera marina and Zostera noltii to environmental
changes. According to unpublished data obtained by the
Southern Research Institute for Fishery and
Oceanography in Kerch, the amount of Zostera spp. in
meadows in the Karkinitsky Gulf has also increased,
despite extensive annual excavation of sand.

My own observations indicate that self-
restoration and enlargement of Zostera beds Is
occurring in Sevastopol, Kerch and Yalta Bays, all of

30°E

UKRAINE
Sivash National
Nature Park
Chemomorsky \ Molochny
National Reserve \ Salt Lake
\ | /Belosaraisky
Yagorlitsky and \

Tendrowky Bags ~ Utlyuk \ W,
: \ sl ate \ 4 ~z, Berdyansky

~
SEA OF
{ZO} Fs

Karkiniishy Gl \ ry — Kerch Srrait

Danube Delta —* Gulf ‘
Biosphere Reserve «= Sevastopol Q4
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3 Lapsi Bay

Obitochny

ROMANIA

Arabaisky Bay

Donuclay Salt Lake
Yalta Bay

GEORGIA

BULGARIA BLACK SEA

3 Sinop Bay

TURKEY
Q 100 200 300 400 500 Kilometers
|

The Black, Azov, Caspian and Aral Seas

which have been subject to considerable disturbance
from recreational activities. Indeed not only seagrass
but all Black Sea benthic macrophytes are stabilizing
and recovering from recreational pressures over wide
areas. In contrast seagrass and algae communities are
most degraded in areas with heavy sedimentation
loads. This decline has occurred particularly along the
deepest boundary of macrophyte growth.

Black Sea Zostera spp. are traditionally used in
local agriculture as a forage additive and for winter
insulation for barns for livestock”. It has been proved
experimentally that the daily yield of milk of cows
whose fodder was mixed with Zostera marina
increased by 15-20 percent. Weight increases of 20-30
percent in sheep fed Zostera, and of 10-15 percent in
pigs’, have also been observed. Seagrass additives
appear to increase milk quality and fat in dairy cows
and provide better quality and quantity of sheep wool.
Zostera spp. are a valuable source of pectins, aquatic
solutions which produce firm gels. Being rich in
hemicellulose and pectin substances, seagrasses are
also used as a gluing component in mixed fodder
granulation and packaging.

In the Black Sea, seagrasses have been placed
under protection in ten nature reserves under the
national control of Ukraine and Romania®**. The
largest of them are the Danube Delta Biosphere
Reserve and the Chernornorsky National Reserve.

SEA OF AZOV
There are four species of seagrass, three seagrass
associates and 64 macroalgae in the flora of the sea”.
The Zostera spp. have a Mediterranean origin and are
believed to have appeared in the Sea of Azov in the
Paleocene”.

The meadows of Zostera noltii are the most

RUSSIAN
/ Leo FEDERATION

The Black, Azov, Caspian and Aral Seas

50° E 6QreE
Minor Bays and Sea———*,

Astrakhansky . gsecae

National Reserve KAZAKHSTAN

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extensive and dense compared with other seagrasses.
This species grows on silt-sandy sediments with shell
grit from 0.2 to 8 m'“* and across a salinity gradient of
2-26 psu. Zostera marina inhabits the same depths but
covers a considerably smaller area. Zostera spp. grow in
single-species beds and also in mixed communities with
other seagrasses, mostly Potamogeton pectinatus and
Ruppia cirrhosa, and with algae such as Ceramium,
Polysiphonia, Cladophora and Enteromorpha spp.
Zostera noltii and Zostera marina are found almost
everywhere along the shoreline of the sea’, and also in
the coastal salt lakes, river mouths and floodplains. This
is due to their tolerance to salinity fluctuations. Zostera
noltii in the Sea of Azov has shoots 15-70 cm long, while
those of Zostera marina measure 20-90 cm.

The vast meadows of Zostera noltii and Zostera
marina predominate in the northern part of the sea,
close to sandy spits, and in the coastal salt lakes.
Communities of Zostera noltii are also widely prevalent
in the eastern Sea of Azov, while Zostera marina is
found here only in patches”. In the western part of
the sea, Zostera spp. are rare, being usually found as
solitary sparse seagrass beds. Along the southern
coast Zostera spp. are dispersed. Zostera spp., washed
ashore after the leaf fall, abundantly cover the coast.
The annual commercial after-storm harvest amounts
to about 1200 metric tons dry weight.

Recent field measurements have recorded the
biomass of both Zostera species around the Sea of
Azov. Zostera noltii biomass in the bays {wet weights:
Arabatsky 1197 g/m’, Kasantyp 284 g/m’, Tamansky
374 g/m’, Belosaraisky 860 g/m’, Obitochny 1180 g/m?
and Berdyansky 400 g/m’) is generally comparable
with the salt lakes (wet weights: Sivash
1157-1 400 g/m’, Molochny 378 g/m? and Utlyuk 667
g/m’) but higher than the seaward coasts of the large

oe eee en

RAS Mae

WORLD ATLAS OF SEAGRASSES

sand spits which are such a feature of the Sea of
Azov (wet weights: Belosaraiskaya 28 g/m’, Fedotov 30
g/m?, Obitochnaya 45 g/m’ and Berdyanskaya
30 g/m?)!"® 2839314 The biomass of Zostera marina
was also measured at three of these locations: in
Sivash (2000 g wet weight/m’) and Molochny (592 g wet
weight/m’) salt lakes and Tamansky Bay (219 g wet
weight/m? at 1 m depth but more than ten times this
at 3.5 m).

Analysis of the long-term dynamics of the
structure of Zostera communities indicates that,
despite changes in the environment and increased
eutrophication, the recent 60 years have not been
marked with radical changes. For example, in the late
1930s, the biomass of Zostera marina in Utlyuk Salt
Lake was estimated to range from 213 to 2242 g wet
weight/m?"' and in the early 1970s from 333 to 1024 g
wet weight/m?'!. Furthermore, over the past 30 years,
the biomass of Zostera noltii in Utlyuk Salt Lake has
increased from 260 to 667 g wet weight/m? |’.

The local population traditionally uses Zostera
spp. cast-off to insulate housing, for livestock during
winter and as an efficient means of deterring rodents in
barns. The high silica content of this material reduces
its flammability and therefore its risk as a fire hazard. It
has been experimentally proved that dried Zostera
marina mixed with urea is a valuable forage additive for
livestock.

Seagrasses of the Sea of Azov have been placed
under the protection of many international conventions
and the state laws of Ukraine'!. They are the object of
protection in seven nature reserves, the largest of
which are Sivash National Nature Park and the coastal
Molochny Salt Lake.

CASPIAN SEA

Three species of seagrass, two seagrass associates
and 65 macroalgae make up the submerged flora of the
Caspian Sea". The earliest work on the composition
and distribution of Caspian Sea seagrasses was
produced in 1784” but it was not until the 1930s that
the most comprehensive reviews on the topic were
published“. This was the first time that the
hypothesis about Zostera noltii 's penetration into the
Caspian Sea from the Black and Azov Seas was
advanced. Presumably Zostera noltii was introduced
from the Mediterranean to the Caspian Sea in the
Paleocene, 36-65 million years ago. At that time the
Black Sea, the Sea of Azov and the Caspian Sea were
connected by the Kumo-Manych Strait.

Zostera noltii communities were then widely
distributed throughout the Caspian Sea’**“*“!, typically
at depths of 2.5-4.5 m along eastern shores, though
occasionally as shallow as 0.5 m and as deep as 18 m,
across a narrow range of salinity, 12-13 psu. Single

species and mixed communities of Zostera noltii were
found on sand sediments with shell grit but never on a
silt bottom. Highest productivity takes place in mixed
communities of Zostera noltii and Charophyceae,
Ruppia and Potamogeton spp. Species of Chara,
Ceramium, Polysiphonia, Laurencia, Enteromorpha
and Cladophora are common algae in seagrass beds.

The distribution of seagrasses and macrophytes
in the Caspian Sea changed markedly in the period
1934-61 to 1967-81. In the 1930s there were extensive
Zostera noltii beds along western coasts, principally
Baku and Kirova Bays in present-day Azerbaijan, with
records indicating the presence of this species at
Derbent, Izerbesh and Makhachkala, and_ in
Astrakhansky and Kizlarsky Bays in modern Russia.
Along the eastern coast Kaidak, Mangyshlaksky,
Kazakhsy and Turkmensky Bays, and the Mangyshlak
Peninsula, were the main locations of mixed Zostera,
Ruppia and Potamogeton beds. Estimates of the
biomass of Zostera noltii and Ruppia cirrhosa in the
Caspian Sea at this time were much higher than in the
present day. In Kaidak Bay, with the salinity of the
seawater ranging from 25 to 51 psu, the highest salinity
level ever documented for Zostera noltii, the biomass of
Zostera noltii was estimated to be 7000-8000 g wet
weight/m’ and that of Ruppia cirrhosa 10000-12000 g
wet weight/m? “*. The shoots of Zostera noltii from
Kaidak Bay were 75-100 cm long, while in the open sea
the length was 25-30 cm. In comparison with Kaidak
Bay, in the open sea the biomass of this species was
substantially less, varying from 100 to 1500 g wet
weight/m’. The total stock of Zostera nolti for the
Caspian Sea was estimated at approximately 700000
metric tons (wet weight), with about 500000 metric
tons for the eastern and 200000 metric tons for the
western coast. The area covered by the seagrass in just
the northeastern Caspian Sea was 1650 km’.

During the 1950s coastal configurations changed
and many shallow bays such as Kaidak Bay, in which
Zostera noltii and other macrophytes formerly
flourished, vanished and the area of others such as
Krasnovodsky Bay decreased substantially “““". Ever
since that time, Zostera noltii communities have been
degrading, having almost completely vanished along
the western coast and becoming seriously depleted in
the east. In 1935-38 the biomass of Zostera noltii along
the eastern coast ranged from 50 to 8000 g wet
weight/m?**!. By 1971-74 the range had decreased to
50-1 300 g wet weight/m?'*“”, and in the early 1980s it
was 127-1340 g wet weight/m’ ''. Despite the decline
in biomass the area of some beds in Krasnovodsky Bay
enlarged considerably, so much so that in the early
1970s different experts evaluated the stock of Zostera
noltii in Krasnovodsky Bay to be 200 000-440 000 metric
tons wet weight. Apparently, such an expansion may be

due to environmental changes and the drop in sea level
which brought about the extinction of competing algae
such as the Charophyceae.

At present, available data indicate that Zostera
noltii is only rarely found in the western Caspian Sea at
Makhachkala and in Kizlarsky Bay. Seagrasses have
completely disappeared from the southern Caspian
Sea“ *!. Single and mixed communities of Ruppia
spp. are found growing in Astrakhansky Bay in the west
and in Komsomolez, Kazakhsy, Krasnovodsky and
Turkmensky Bays in the east, on silt sediments at
depths from 0.5 to 3 m.

Though the areas of sea bottom covered with
seagrasses have substantially declined, they are still
important in the ecology of the Caspian Sea. Seagrasses
play an important role in the nutrition of invertebrates
on which the state of commercial fish stocks depends“
6.48) In the northern Caspian Sea, Zostera noltii growth is
of special significance, because this is where wild carp,
Caspian roach, bream and other valuable fish spawn
and feed’. Other seagrasses are the usual food item for
waterfowl. Ruppia spp. constitute up to 25 percent of the
intestinal content of swans and gray geese and 54-84
percent of that of ducks.

The seagrass communities have been placed
under protection in two national nature reserves
(Astrakhansky and Krasnovodsky National Reserves).

ARAL SEA

There are two seagrasses, Potamogeton pectinatus
and 16 macroalgae in the flora of the Aral Sea’.
Presumably Zostera noltii was introduced from the
Mediterranean to the Aral Sea, also through the Kumo-
Manych Strait. The most extensive knowledge about
seagrass distribution had been acquired prior to the
severe anthropogenic disruption of the Amudarya and
Syrdarya river systems in the mid-1950s'" that caused
catastrophic changes to the ecosystem of the Aral Sea
and adjacent water bodies.

Zostera noltii grew from 0.1 to 10 m deep, with
most growth being concentrated at 0.1-2 m depth in
the northern shallow bays’"’. In the mid-1950s, the
biomass of Zostera noltii was estimated to be 17 to
800 g wet weight/m?, with the largest values
registered near the mouth of the Syrdarya River. In
recent years, the environmental crisis which Is wiping
out a large part of the Aral Sea has manifested itself
in drastic increases in salinity which, in turn, have led
to changes in the biological components of all
ecosystems. However, the areas occupied by Zostera

REFERENCES

1 Kosarev AN, Yablonskaya EA [1994]. The Caspian Sea. Backhuys
Publishers, Hague.

2 Matishov GG, Denisov W [1999]. Ecosystems and bioresources of

The Black, Azov, Caspian and Aral Seas

noltii and estimates of its biomass have increased in
the northern bays, while in the more brackish area
near the Syrdarya’s mouth biomass has considerably
decreased. Records from the early 1990s show that
biomass is now apparently positively correlated with
salinity. In the Syrdarya Estuary at salinity of 7 psu
biomass was just 42 g wet weight/m’, whereas in
Tshe-Bas Bay Zostera noltii not only tolerates salinity
as high as 45 psu but thrives on silt-sandy and sandy
sediments supporting beds with biomass of 2258 g
wet weight/m’. Intermediate values were observed in
the Berg Strait (417 g wet weight/m? at 23 psu),
Butakov Bay (899 g wet weight/m* at 36 psu) and
Shevchenko Bay (1076 g wet weight/m* at 30 psu)".
As the Aral Sea continues to disintegrate, Zostera
noltii communities are expected to persist mostly in
bays of the Minor Sea, where the sea level has
remained constant for the past decade.

Total macrophytic stock in the sea is estimated at
1.34 million metric tons wet weight. The share
contributed by Zostera noltii is about 8.1 percent
(109000 metric tons wet weight}, while algae such as
Charophyceae and Vaucheria dichotoma contribute
77.6 and 13.4 percent, respectively'"’.

Compared to phytoplankton, macrophytes such
as Zostera noltii are of little importance in the food
chains of the Aral Sea. However they are ecologically
important. The meadows of Zostera noltii are the
spawning location of diverse invertebrates and fish.
Benthic invertebrates and fish predominantly feed on
diatoms (Navicula spp. and Merismopedia spp.) and are
found in abundance”' *’ However, during the past 50
years, the catches of commercial fish have collapsed to
the point where the Aral Sea has almost lost its
significance for fisheries.

There are no data regarding nature reserves
along the coastal zones of the Aral Sea.

ACKNOWLEDGMENTS

| am grateful to Prof. R.C. Phillips (Marine Research Florida Institute],
0.A. Akimova, G.F. Guseva, M.Yu. Safonov (IBSS), Dr 1.1. Serobaba
(YugNIRO], Or |.|. Maslov (Nikita Botanical Garden] and Ms Olga
Klimentova for their help in preparing this chapter.

AUTHOR

Nataliya A. Milchakova, Department of Biotechnologies and
Phytoresources, Institute of Biology of the Southern Seas, National
Academy of Sciences of Ukraine, 2 Nakhimov Ave., Sevastopol 99011,
Crimea, Ukraine. Tel: +38 (0]692 544110. Fax: +38 (0)692 557813. E-mail:
milcha(dibss.iuf.net

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Komsomolez (Dead Kultuk] and Kaidak. Botanical Journal 23(2):
122-144.

Kireyeva MS, Shchapova TF [1957a]. The material about taxonomic
composition and biomass of algae and high aquatic vegetation of
the Caspian Sea. Proceedings of the Institute of Oceanology 23:
125-137 lin Russian).

Kireyeva MS, Shchapova TF [1957b]. Bottom vegetation of
Krasnovodsk Bay. Proceedings of the Institute of Oceanology 23:
138-145.

Blinova El [1974]. Phytobenthos of the East Caspian Sea. Abstract.
In: All-Union Conference Marine Algology and Macrophytobenthos.
VNIRO Publishing House, Moscow. pp 12-14.

Petrov KM [1967]. Vertical distribution of aquatic vegetation in the
Black and Caspian seas. Oceanology 7(2): 314-320.

Salmanov MA [1987]. The Role of Microflora and Phytoplankton in
Production Processes in the Caspian Sea. Nauka Publishing, Moscow.
Zaberzhinskaya EB, Shakhbazi ChT [1974]. Bottom Vegetation of
Krasnovodsky Bay. Abstract. In: All-Union Conference Marine
Algology and Macrophytobenthos. VNIRO Publishing House,
Moscow. pp 51-53.

Dobrokhotova KV, Roldugin Il, Dobrokhotova OV [1982]. Aquatic
Plants. Kainar Publishing House, Alma-Ata.

Yablonskaya EA [1964]. About the role of phytoplankton and
benthos in food chains of organisms inhabiting the Aral Sea. In:
The Stock of Marine Plants and their Use. Nauka Publishing,
Moscow. pp 71-91.

Yablonskaya EA [1960]. The present state of benthos of the Aral
Sea. Proc VNIRO 43(1]: 115-149.

Orlova MI [1993]. Material contributing to total assessment of
production and destruction processes in coastal zone of the
northern Aral Sea.1. Results of the field studies and experiments,
1992. Proceedings of the Zoological Institute RAS ("Ecological
crisis in the Aral Sea”) 250: 21-37 lin Russian).

The eastern Mediterranean and the Red Sea

5 The seagrasses of

THE EASTERN MEDITERRANEAN

AND THE RED SEA

his chapter is divided into two sections and
[cose the seagrasses of the eastern
Mediterranean and the Red Sea. While the
eastern Mediterranean has a relatively restricted range

of species, the Red Sea is home to 11 species, all of
tropical origin.

EASTERN MEDITERRANEAN

Early contributions from the eastern Mediterranean
reported on the presence of Cymodocea nodosa [also
reported as Cymodocea aequorea or Cymodocea
major}, Posidonia oceanica [also as Zostera oceanica),
Zostera marina and Zostera noltii {also as Zostera
nana), in Greece, Syria and Egypt. Halophila stipulacea,
a migrant from the Red Sea, was first reported in the
Mediterranean from the island of Rodos late in the 19th
century". Lipkin’ summarized its distribution in the
Mediterranean through the early 1970s; during the last
three decades Halophila stipulacea has spread further,
mostly in the eastern basin [e.g. Methoni and Paxoi
Islands, lonian Sea’ *; Marmaris’; Korinthiakos
Kolpos”*!, but also at and near Sicily" '".

The most common seagrass in the eastern
Mediterranean is Cymodocea nodosa. It occurs on all
coasts of this basin on sandy and, less frequently,
muddy bottoms. The next most prevalent seems to be
Posidonia oceanica, a climax seagrass. In many regions
in the northern part of the basin the balance between
the two is inverted, with Posidonia oceanica becoming
the more common. The third in abundance appears to
be Zostera noltii and the least common Halophila
stipulacea. Zostera marina, a species common in the
western Mediterranean, seems to be rare in the
eastern part, if it still exists there at all. Collections of
the latter species reported by den Hartog' were from
the northern parts of the Aegean Sea, made in 1854,
1891 and 1910. Publications later than 1930, by Greek
and Turkish authors'"**”, reported Zostera marina from
the same area. Interestingly, more recent papers about

Y. Lipkin
S. Beer
D. Zakai

seagrasses on the Turkish and Greek northern Aegean
coasts" “ do not include Zostera marina among the
seagrasses of this area. The only report of this
seagrass from Egypt” - the latter reference being
based on the former - was probably a case of
misidentification; in later papers on Egyptian
Mediterranean seagrasses, Aleem did not mention
Zostera marina. However, Tackholm et al."" reported
that the filling of an ancient Egyptian mummy was
composed of Zostera marina, which indicates that the
plant must have occurred, or was even common, in
shallow Egyptian waters some 2000 years ago, and
seems to have gradually disappeared, first from the
warmer southeastern corner, then from wider and
wider areas in the eastern and central parts of the
eastern Mediterranean, and remained until rather
recently on its coldest, northernmost coasts. A similar
retreat from a former, wider range seems also to have
occurred with Zostera noltii, which is concentrated
mainly in the Aegean Sea with considerably less
representation in other parts of the northeastern
Mediterranean, and almost none in the south. It has
disappeared, or become very rare, even in the south
Aegean Sea’.

Ecosystem description

Cymodocea nodosa and Zostera noltii usually grow in
shallow water, from a few centimeters to a depth of 2.5-
3 m [it has been reported that Cymodocea nodosa
occupied a depth range of 5-10 m in the Bay of
Limassol, Cyprus®"]. Posidonia oceanica is found from
the shallows, where the tips of the leaves reach the
surface, down to 35-40 m. Halophila stipulacea, many
beds of which also occur in the shallows, e.g. at Rodos,
penetrates much deeper water. Bianchi et al.”
reported it as the deepest seagrass in the Bay of
Limassol, growing at 25-35 m (for Posidonia oceanica
they reported a range of 10-30 m). Fresh, seemingly in
situ, material was dredged from around 145 m off

66 WORLD ATLAS OF SEAGRASSES

SZN]

Photo: Laboratory of Benthic Ecol

growing on sand

Cyprus; however, below about 50 m it was rather
scarce”.

All four seagrasses grow in the eastern
Mediterranean on soft bottoms, quartz sand in shallow
waters and mud at greater depths. Cymodocea nodosa
frequently occurs in small sandy pockets that
accumulate in crevices or small depressions on rocky
flats, and Posidonia oceanica is often found on rough
substrates such as pebbles and gravel and even solid
rock. It is noteworthy that Halophila stipulacea,
growing in a wide range of environmental conditions in
the northern Red Sea, including all kinds of coastal
substrates'™“', has a much narrower ecological range in
the eastern Mediterranean, being restricted in this
basin to soft substrates only. The form with bullate
leaves, the so-called “bullata” ecophene, so common in
extreme conditions in the northern Red Sea, has not
been reported from the eastern Mediterranean. Several
ecotypes of Halophila stipulacea occur in the northern
Red Sea”. Probably only one of them has penetrated
and spread into the Mediterranean.

Seagrasses occupy extensive areas in Greek
waters”. Clusters of Cymodocea nodosa appear in very
shallow water only a few centimeters deep, mostly in
sheltered areas, and to a lesser extent on beaches
exposed to winds and waves. In sheltered areas,
Cymodocea nodosa tends to occupy deeper bottoms
and form larger beds. In the southern lonian Sea, such
beds appear from a depth of 60 cm down to 1.5-2 m. In
shallower water, the plant is found on sandy bottoms,
and a little deeper on muddy ones. Posidonia oceanica

occurs at greater depths, on sandy bottoms. Zostera
noltii (reported as Zostera nana) was represented by
scattered plants; no beds are recently reported.
Halophila stipulacea was rare in lonian Greece around
1990, occurring at two sites only, at about 2.5 m depth
at Methoni, together with the siphonous green alga
Caulerpa prolifera, and at Paxoi*”.

Most seagrass beds in the eastern Mediterranean
are composed of one seagrass species only. Beds of
Posidonia oceanica are usually very dense. Only when
they start to deteriorate, for example when affected by
pollution, do other marine plants, usually algae, invade.
In Cymodocea nodosa beds, the seagrass Is occasionally
accompanied by Caulerpa prolifera, which may reach 20
percent of the plant cover’. Mixed populations of
Posidonia oceanica and Cymodocea nodosa” or Zostera
noltii and Cymodocea nodosa” also occur.

Egypt

Reports on seagrass habitats and community
structure in the eastern Mediterranean are scanty,
compared with the information available on these
subjects in the western basin. The seagrass vegetation
of the bay at Marsa Matrih Harbor (western end of the
Mediterranean coast of Egypt) and its close vicinity was
described by Aleem in the early 1960s". He reported
healthy beds of Cymodocea nodosa, Halophila
stipulacea and Posidonia oceanica and provided a
distribution map. In 1957-60, Cymodocea nodosa beds
covered a continuous belt 10-40 m wide and about
750 m long in the inner part of the bay at a depth of
around 50 cm to 2 m, on the slope between the
watermark and the horizontal bottom that starts at 2
m. At the innermost part of the bay, the belt broke into
scattered patches. In extremely sheltered areas, the
seagrass was absent. Right below this belt, on the
lower parts of the slope at 2-8 m depth, a belt of
Halophila stipulacea of similar size occurred.
Posidonia oceanica formed a bed 70-120 m wide and
about 300 m long, outside the inner bay, in an area
more exposed to winds and waves.

At El Dab’a, about 160 km west of Al Iskandariya
(Alexandria), Posidonia oceanica covered a small area
along with a few small patches of Cymodocea nodosa.
Halophila stipulacea did not occur at this site. The
macrofauna and algal macroflora were also scarce,
both in numbers of species and in numbers of
individuals. For example, only 12 epiphytic algae were
found on the leaves and rhizomes of Posidonia
oceanica®”“”.

Aleem! described in detail the establishment,
development and stabilization of the seagrass beds at
Al Iskandariya. His description was later incorporated
by den Hartog'” into his account of the ecology of
Posidonia oceanica, and therefore will not be repeated

GREECE

The eastern Mediterranean and the Red Sea

Thermaikos®
Kolpos ~
1EGEAN
SEA

Paxoi ®

Korinthiakos
ee _~ lzmir Koérfezi

IONIAN SEA e

/Sikinos vy» Kos

7
Methoni ® at 16 =
Milos

Pholegandros

MEDITERRANEAN SE

Marsa MatrOh x

¢
El Dab'a

25° E

Map 5.1
The eastern Mediterranean

here. At that time (the 1950s), however, the Posidonia
oceanica beds, once established, persisted for long
periods of time. Later, as in some other Mediterranean
sites, they became affected by domestic and industrial
pollution and started to dwindle”.

The coast of Sinai and the southern part of the
Israeli coast are mostly covered with pure quartz sand,
with only a few rocky outcrops here and there. This part
of the eastern Mediterranean coast, lacking bays and
coves, Is highly exposed to wind and wave action. Wide
Cymodocea nodosa beds occur at depths of 2 m and
more, along the Sinai coast, below the littoral belt in
which the bottom sediment is intensively worked by the
breakers. A few small stands of Posidonia oceanica
were reported by Aleem" from the several rocky
habitats between Bir Said and El Arish; the status of
these sites has not been reported since 1955.

Sabkhet el Bardawil, the large lagoon on the
Mediterranean coast of Sinai, harbors a large bed of
Ruppia cirrhosa, which covers up to a third of the
lagoon’. The size of this bed fluctuates considerably
seasonally, and during severe winters it may disappear
completely.

Israel

Along the generally exposed Israeli coast, rich beds of
Cymodocea nodosa are found on sandy bottoms at
sheltered sites. The best developed is at Akko, at the
northern end of Haifa Bay. Small patches of the
seagrass also occur in sand-filled depressions on
submerged horizontal platforms just below mean sea

ry
Marmaris 320 400 Kilometers
a |

Al Iskandariya

e
Rodos Island

Ls Al Ladhiqiyah SYRIA

e CYPRUS

Tartods ® —_ Ras Ibn Hani
°

Al Arwad

Satda 6 LEBANON

Akko @

ISRAEL
Bur Sa'td

° Lara
Sabkhet el Bardawil El 'Arish JORDAN

Suez Canal
@ El Suweis
*®Al' Aqabah (Elat)

* Sinai
inal __ Gulf of Aqaba

SAUDI ARABIA

— Dahlak
«Archipelago
ERITREA « 4

0 100 200 300 Kilometers ETHIOPIA
aa

Map 5.2
The Red Sea

level. All Cymodocea nodosa populations are subject to
large seasonal and year-to-year fluctuations in size, on
occasion disappearing completely, eventually to renew
from the seed stocks in the sediment’. Area estimates
for Israel are very approximate since no exact mapping
has been carried out. We estimate the total Israeli

WORLD ATLAS OF SEAGRASSES

Mediterranean coast populations of Cymodocea nodosa
to be no more than a few hundred square meters.

Lebanon

From the Lebanese coast there is no information about
seagrass beds except that gathered by J.H. Powell on
the occurrence of a Cymodocea nodosa and Halophila
stipulacea bed some 800 m off Saida (Sidon), in which
the former comprised 70 percent of the seagrass
cover. To judge from the very few records of
seagrasses from the Lebanese coast, seagrass beds

are uncommon.

Syria

On the Syrian coast, too, seagrass beds are un-
common". Cymodocea nodosa and Zostera noltii beds
are found near the river mouths between TartoUs and
Banias, in the vicinity of Jable, in small, relatively calm
embayments north of Al Ladhigiyah (Latakia) and near
the harbors of TartoUs, Al Arwad and Al Ladhigiyah,
where they grow intermingled with Caulerpa scalpelli-
formis and/or Caulerpa prolifera’. Zostera noltii
appears also as an accompanying species in the plant
community dominated by Caulerpa scalpelliformis at
Tartods and Al Arwad.

These seagrasses grow on this coast on clayey
sand rich in organic matter. They seem to tolerate
considerable variations in salinity. Posidonia oceanica
is rare on the Syrian coast; Mayhoub'” found it in only
two localities: northwest of Al Arwad islet, and in a bay
near Ras Ibn Hani. In both cases, the beds were not well
developed; in his opinion they were in the process of
disappearing. He assumed that the rapid degradation
of the Posidonia oceanica beds northwest of Al Arwad
Island, a great part of which were already replaced by
Caulerpa, was the result of large sewage installations
that had been constructed a short while previously at
nearby Tartods“”.

Cyprus

Seagrass beds are widespread around the island of
Cyprus. Rich stands of Posidonia oceanica and
of Cymodocea nodosa are common at different
depths, Posidonia oceanica beds descending much
deeper than those of Cymodocea nodosa. Mixed
populations are found, but less often. Halophila
stipulacea beds are not as plentiful as those of the
other two; they also descend to considerable depths”.
The quickly expanding green alga Caulerpa racemosa
is considered a threat to the Posidonia oceanica beds.
Since first noticed in the island in 1991, it has spread,
unchecked, into a wide range of habitats from the
shallows to depths of at least 60 m, on sandy as
well as muddy bottoms, competing directly with
Posidonia oceanica\“*“*.

Turkey

Along the Turkish coasts, at the eastern part of the
Mediterranean coast, meadows of Posidonia oceanica
dominate the lower levels of the infralittoral zone, but
no further information about them is available, except
that Cymodocea nodosa and Zostera noltii have also
been found in the area‘. On the Aegean coast,
monospecific beds of Posidonia oceanica and of
Cymodocea nodosa were reported from Izmir Bay
(Izmir Korfezi], as were mixed beds of the two.
Cymodocea nodosa beds were 20-50 m in diameter,
whereas those of Posidonia oceanica were much larger
- 150 m and more in diameter”. Similar meadows are
probably common on the Aegean Turkish coast.

Greece

From Greek waters, Bianchi and Morri'” reported
dense monospecific stands of Cymodocea nodosa and
of Posidonia oceanica at the island of Kos, in the
eastern Aegean, the latter seagrass appearing to be
more common. In the western part, large seagrass
beds were reported from the islands of Sikinos, Milos
and Pholegandros. Vast beds of Cymodocea nodosa
were found on mud in shallow bays at the latter two
localities, at 0.3-4 m depth. Posidonia oceanica was
common on sandy deposits around the entire coast of
all three islands studied, not just in bays. In shallower
water they formed isolated tufts and in deeper water, 2-
8 m or more, they formed quite large beds".

RED SEA

Historical and present distribution

The Red Sea harbors 11 seagrass species, all of
tropical origin, which penetrated through its relatively
narrow mouth at Bab al Mandab. These are: Halodule
uninervis, _Cymodocea_ rotundata, Cymodocea
serrulata, Syringodium isoetifolium, Thalassodendron
ciliatum, Enhalus acoroides, Thalassia hemprichii,
Halophila ovalis, Halophila ovata, Halophila stipulacea
and Halophila decipiens'* “*. Only a single plant of
Halophila decipiens has hitherto been reported from
the Red Sea, grabbed from 30 m™’. For early records
and distribution see Lipkin".

Enhalus acoroides seems not to reach much
beyond the Tropic of Cancer, whereas the other ten
species continue to the northwestern part of the Red
Sea proper, but only seven [the above listed species
excluding Enhalus acoroides, Cymodocea serrulata,
Halophila ovata and Halophila decipiens) penetrate into
most of the Gulf of Elat {Gulf of Aqaba) and only five
(Halodule uninervis, Halophila stipulacea, Halophila
ovalis, Halophila decipiens and Thalassodendron
ciliatum) into much of the Gulf of Suez. Hulings and
Kirkman’ reported Cymodocea serrulata from “a
shallow lagoon on the west coast of the Gulf of Aqaba

The eastern Mediterranean and the Red Sea

40 km south of Eilat”, but this record should be
confirmed. Halophila stipulacea, Halodule uninervis
and Halophila ovalis appear at present to be the only
seagrasses that reach the tips of these gulfs?**°),
although old records also listed Thalassodendron
ciliatum and Syringodium isoetifolium from El Suweis
(Suez), at the tip of the Gulf of Suez, and from Al
Aqgabah at the tip of the Gulf of Elat, and in addition
listed Cymodocea rotundata and Cymodocea serrulata
from El Suweis’". Notably, Aleem'™“! did not find any
seagrass at Bur Taufiq, near El Suweis.

Halophila stipulacea, very common in the
northern part of the Red Sea, is rather scarce at its
central and southern parts’, as well as at the
tropical east African coast south of the Horn of Africa. It
becomes common again on the east African coast near
the Tropic of Capricorn’. Thus, Lipkin” concluded that
this species is of subtropical affinity rather than
tropical.

Some of the Red Sea seagrasses occur in the
intertidal zone and most species usually grow at the
shallow subtidal, not deeper than 5 m, but may be
found as deep as 10 m'*!. However, Halophila
stipulacea is widely found in the Gulf of Elat at depths
down to 50 and even 70 m and Thalassodendron
ciliatum down to 30 m'*°!. In the Gulf of Suez,
Halophila decipiens was found at 30 m, Halophila ovata
down to 20 m and one of the populations of Halophila
ovalis at 23 m'™”’. On the Jordanian coast of the Gulf of
Elat, two Halophila ovalis stands were found at 15 and
28 m, respectively”.

Most seagrasses in the Red Sea grow on mud, silt
or fine coralligenous sand, or mixtures of them. The
eurybiontic Halophila stipulacea and, to a lesser extent,
Halodule uninervis thrive on a wide variety of
substrates. Thalassodendron ciliatum and Thalassia
hemprichii, however, seem to prefer coarser substrata,
that is coarse sand admixed with coral and shell debris
or even rather large pieces of coral from the
surrounding fringing reefs or coral knolls at sites
exposed to considerable water movement”.

Almost all beds of Thalassodendron ciliatum and
Enhalus acoroides are monospecific, whereas
Syringodium isoetifolium, Thalassia hemprichii and
Halodule uninervis often occur in multispecific
seagrass communities. This tendency also changes
geographically, e.g. Syringodium isoetifolium forms
monospecific stands as well as occurring in
multispecific communities on the central Saudi Arabian
coast, whereas in the Gulf of Elat it was found only in
mixed populations.

Although seagrass beds are common in the Red
Sea, information about the seagrass habitats and plant
communities in this basin is very limited. A general
account of Red Sea seagrass beds was given by

The northern Red Sea taken from the Space Shuttle. The Red Sea
harbors 11 seagrass species - all of tropical origin.

Lipkin’, including information about the typical
accompanying fauna. Below is a summary of the few
available descriptions of the seagrass vegetation in
some Red Sea localities.

Eritrea

In the south, within the Dahlak Archipelago, on the
Eritrean coast, seagrasses are not common. A sparsely
vegetated Caulerpa racemosa-Thalassia hemprichii
community was reported from sandy patches at the
lowermost intertidal zone’. Small patches of
Halophila stipulacea and Halophila ovalis were also

found in the archipelago”.

Saudi Arabia

For the central part of the Saudi Arabian coast, in the
Jeddah area, Aleem'“” reported in the late 1970s that
Thalassodendron ciliatum, Syringodium isoetifolium,
Enhalus acoroides, Halophila ovalis and Halophila
stipulacea grew predominantly as pure stands, but
were sometimes mixed with other seagrasses. He
remarked that Thalassia hemprichii, Cymodocea
rotundata and Halodule uninervis tended to form mixed
communities. Thalassodendron ciliatum beds, to 20-
30 m’ in size, grew on coarse coralligenous sand with
shell debris and sometimes on dead corals that were
covered by a thin layer of sand. These stands of the
seagrass appeared at about 2 m or a little deeper’.
Beds of Thalassia hemprichii, to 100 m? in size, were

NASA archive number ST040-78-88, 1991

WORLD ATLAS OF SEAGRASSES

plentiful on the central coast of Saudi Arabia; they
appeared at 1-2 m depth as mixed vegetation in which
Thalassia hemprichii constituted 60-70 percent of the
plant cover, Cymodocea rotundata 20-30 percent and
Halodule uninervis 10-20 percent. Pure stands of
Halodule uninervis were common on this coast in
shallow water. In very shallow lagoons, a thin-leaved
form appears, whereas on open coasts, a little deeper,
the beds are composed of the wide-leaved form.
Cymodocea serrulata dominates in seagrass beds
between 0.5-2 m deep, making up 70 percent of the
plant cover. In the shallower beds [0.5-1 ml, it is
accompanied by Halodule uninervis and Halophila
ovalis and in the deeper beds (1-2 m] by Cymodocea
rotundata and Halodule uninervis. Small, 0.5-4 m? in
size, almost pure patches of Syringodium isoetifolium
occurred at one site along this coast at depths
of 0.5-1m. The green alga Caulerpa serrulata
accompanied the dominant seagrass in these patches.
In another site, Syringodium isoetifolium was mixed
with Thalassia hemprichii, Cymodocea rotundata and
Halodule uninervis. Beds of Enhalus acoroides were
unusual on the central Saudi Arabian Red Sea coast.
Pure patches, about 30 m’ in size, grew at 1-2 m on
coarse sand with shell debris on top and black mud
below, in one site on this coast. Halophila ovalis formed
small patches, 0.5-2 m in diameter, of sparse growth in
shallow water in most localities visited”.

Gulfs of Suez and Elat
At the Gulf of Suez and the Gulf of Elat, in the north,
thin-leaved Halodule uninervis formed sparse

Case Study 5.1
ISRAELI COAST OF THE GULF OF
ELAT

Along the Israeli coast of the Gulf of Elat, at the
northwestern end of the gulf, Halophila stipulacea
is the only seagrass found at all sites but one (the
middle of the site south of the Marine Laboratory,
where a small bed of Halodule uninervis is also
present}. In 2001 the distribution of Halophila
stipulacea was follows:

Along the northern shore of the Gulf of Elat.
An extensive bed of Halophila stipulacea
occurs along the northern shore of the Gulf
of Elat, probably extending towards and
beyond the nearby Jordanian town of Al
Agabah. The plants grow at depths from 5 m
to more than 45 m, with the highest densities

monospecific prairies in the lower intertidal zone of
muddy coasts. In the subtidal zone, pure stands of this
seagrass were much denser, and the plants were
larger. Mixed stands of Halodule uninervis with
Halophila stipulacea, and sometimes also Halophila
ovalis, were common in the two gulfs as well °°. Four
other communities dominated by Halodule uninervis
were reported from the Sinai coast of the Gulf of Elat:
the Halodule uninervis-Syringodium isoetifolium
community, the Halodule uninervis-Syringodium
isoetifolium-Halophila stipulacea community, the
Halodule uninervis-Cymodocea rotundata community
and the Halodule uninervis-Halophila ovalis
community. Vegetation types dominated by Halophila
stipulacea occupy a wide range of habitats. Mostly
Halophila stipulacea is represented by rather dense
monospecific beds that extend between the lower
intertidal zone and depths of 50-70 m at the Gulf
of Elat.

Density in these beds decreases below 10 m'".
Here and there mixed stands occur, in which Halophila
stipulacea is accompanied by Halodule uninervis or
Halophila ovalis, and in one small patch near Zeit Bay
(Ghubbel ez-Zeit) at the mouth of the Gulf of Suez, also
with Thalassodendron ciliatum*. The Thalasso-
dendron ciliatum community is the most complex of
Red Sea seagrass communities, and probably the most
important for other life forms. The roomy space under
the seagrass canopy and between its woody vertical
stems harbors larvae of many pelagic animals, as well
as its own assemblage of sciaphilic plants and animals.
The height of these vertical stems, varying with depth

{and the largest-leaved shoots) occurring
from 18 to 25 m. The extent of the bed, as
well as biomass within the bed, has been
observed to fluctuate during the last few
years, with a general decline during the last
Six years.

Several sites are located near the navy base
and the commercial harbor. Plants grow at
depths from 8 to more than 25 m.

A further site is near the harbor where oil
and petrol are unloaded. Plants grow at 20-
30 m depth.

A substantial site extends from just south of
the Steinitz [Interuniversity] Marine
Laboratory to the Egyptian border. Plants
grow at depths from 7 m to over 30 m.
Between this and the site near the harbor,
there are sporadically occurring smaller
(<100 m*) beds.

The eastern Mediterranean and the Red Sea

from around 15-20 cm at the shallows to more than 1m
at 30 m depth, determines the volume of this under-
canopy space.

Thalassodendron ciliatum is unique among Red
Sea seagrass communities in extending right up to
coral reefs, without the usual “halo” zone that typically
separates reefs from seagrass beds in their proximity.
This halo is formed by reef fishes grazing on the other
seagrasses. Standing stock of the Thalassodendron
ciliatum community is by far the highest among Red
Sea seagrass communities; its productivity, however, is
among the lowest. This seeming contradiction stems
from the extremely low consumption of most of the
organic matter produced by the seagrass and by
epiphytic algae in the under-canopy space. The only
highly productive and quickly consumed element in this
community is that of photophilic epiphytic algae of the
upper, well-illuminated surface of the canopy, on which
many herbivorous fishes and invertebrates, mainly
snails, graze °°"),

The Syringodium isoetifolium community is rare
in the Gulf of Elat, where it forms small patches.
However, the plant accompanies other seagrasses in
communities they dominate. Monospecific stands of
sparse vegetation of Halophila ovalis usually appear in
the Gulf of Elat as a narrow belt at the lee margins of
larger stands of Halophila stipulacea, or in clearings
within wide beds of the latter. Mixed stands of Halophila
ovalis, Halophila stipulacea and Halodule uninervis
appear in wider areas. Cymodocea rotundata beds are
the second least common seagrass community in the
Gulf of Elat, forming monospecific dense stands down
to 2m.

Thalassia hemprichii, although the least common
seagrass on the Sinai coast of the Gulf of Elat,
dominates in four communities at the southern part of
this coast. The first is represented by dense mono-
specific beds growing ona layer, about 30 cm thick, of
very coarse-grained substrate made of gravel-sized
coral debris covering the underlying rock. Beds of
Thalassia hemprichii and Halophila stipulacea in equal
proportions occurred on the same type of substrata,
but the unconsolidated layer was somewhat thicker.
Wide areas of Thalassia hemprichii with Thalasso-
dendron ciliatum appeared at Ras Muhammad, on the
tip of the Sinai Peninsula, to the seaward of mono-
specific Thalassia hemprichii stands on a thin 20-cm
layer of even coarser unconsolidated material. Finally,
large areas of dense vegetation of Thalassia
hemprichii, with 20-40 percent Halodule uninervis,
covered large stretches of wide reef flats between
Marsa abu Zabad and Shorat el Mangata’, growing on
coarse coralligenous sand at 0-30 cm below the low
water of spring tides".

The total populations of Halophila stipulacea on

Sea, Jordan

the Israeli Red Sea coast [only about 5 km long)
probably occupy some 0.5-1.0 km’.

EFFECTS OF POLLUTION

Most of the few reports on pollution effects on seagrass
beds in the eastern Mediterranean and the Red Sea
refer to chemical pollution. Haritonidis et al.” in 1990
reported considerable declines in the sizes of beds of
Posidonia oceanica and Cymodocea nodosa in the
Thermaikos Kolpos (northern Aegean Sea) during the
preceding two decades, with the former suffering
greatest losses. They also remarked that the density of
the shoots had decreased, and that marked changes in
the seagrass epiphytic communities had taken place.
The authors attributed these phenomena to the
increased amounts of domestic and _ industrial
pollutants discharged into the gulf during that period.
In contrast, Zostera noltii, the least common of the
three seagrasses that occur in the gulf, seemed to have
benefited from the increased discharge of sewage, as
the area covered by its beds had increased.

A similar decline in the area occupied by
Posidonia oceanica beds, and their thinning, was
reported for Cyprus‘, but here the authors attributed
these phenomena to competition with the invading
green alga Caulerpa racemosa. Between 1992 and
1997, dense stands of the latter replaced Posidonia
oceanica in part of the area it had covered at the
beginning of this period [total plant cover in the
Posidonia oceanica beds decreased from 70-90
percent to 40-60 percent), and a number of algae, not
previously found in the thinned beds, penetrated into
them, not replacing Caulerpa prolifera, an accom-
panying species in some of the Posidonia oceanica
beds during the earlier period. Similarly, Fishelson et
al." reported that Halophila stipulacea meadows,

Photo: M. Kochzius

WORLD ATLAS OF SEAGRASSES

formerly widespread, dramatically retreated at the
northern end of the Gulf of Elat, in the northern Red
Sea. Here the source of pollution was fish culture in
cages in the gulf.

Dando et al.” dealt with the effects of thermal
pollution. They reported that Cymodocea nodosa
replaced Posidonia oceanica near hydrothermal
discharge vents at the bottom of the Aegean Sea.

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AUTHORS

Yaacov Lipkin and Sven Beer, Department of Plant Sciences, Tel Aviv
University, Tel Aviv 69978, Israel. Tel: +972 (0|3 640 9848. Fax: +972 (0)3
640 9380. E-mail: lipkin{@post.tau.ac.il

David Zakai, Israel Nature and Parks Protection Authority, P.O. Box 667,
Elat 88105, Israel. The Interuniversity Institute for Marine Sciences, P.O.
Box 469, Elat 88103, Israel.

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WORLD ATLAS OF SEAGRASSES

6 The seagrasses of

THE ARABIAN GULF AND ARABIAN

REGION

(hereafter called “the Gulf") is a unique biotope.

The Gulf is a shallow semi-enclosed sea
measuring ca 1000 km by 200-300 km''*. The average
depth is only 35 m. The maximum depth of 100 m
occurs near the entrance to the Strait of Hormuz. There
are vast areas in some of the Gulf States, such as the
United Arab Emirates (UAE), Saudi Arabia and Bahrain,
with shallow areas less than 15 m deep suitable for
seagrass growth.

Seagrass habitats have been designated a critical
marine resource in the Gulf”. They have also been
listed as a key renewable resource” “|.

There are only three species of seagrass in the
Gulf. It is considered to be a very stressful habitat for
seagrasses", characterized by large seasonal air and
water temperature variations, fluctuating nutrient
levels and high salinities. The three species found are
considered to be tolerant of such conditions (Table 6.1).
Outside the Gulf, as many as 11 seagrass species have
been described for the Red Sea area’. Seven species
are known in the Arabian Sea” '”'“, seven species in the
Gulf of Aqaba’ "*'' and eight in the Gulf of Suez”.

Jones’ observed that seagrasses occur at only
six locations in Iran. He stated that the Iranian coastline
was mainly rocky. No seagrasses have been reported
for Iraq. Seagrass occurrence in Kuwait is quite
sparse’. Jones’ stated that Halodule uninervis was
the principal species in Kuwait and reported that large
beds of seagrasses extended along the coasts of Saudi
Arabia. However, IUCN-The World Conservation
Union"! diagrammed seagrasses along the entire Gulf
coastline occurring in scattered locations. As a whole,
the resulting report stated that seagrasses were of only
limited occurrence along the Saudi Arabian coast.
Price'’” sampled at 53 sites along the entire coastline
and found seagrasses at only 15 sites. The largest beds
of seagrass occurred in the north between Safaniyah

Ts seagrass ecosystem of the Arabian Gulf

R.C. Phillips

and Manifah, in Al-Musallamiyah, south of Abu’Ali, in
Tarut Bay", in the Dawhat Zalum (Halfmoon Bay), parts
of Al Ugayr and in the Gulf of Salwah'’. Seagrass
occurrence around Bahrain is extensive”. Sheppard et
al." stated that seagrasses were extensive along the
coasts of Qatar, but failed to provide documentation or
maps. The seagrass occurrence in the UAE is also
extensive'”. An estimated seagrass occurrence of 5500
km? occurs in Abu Dhabi Emirate alone.

Jones" stated that while the coastline of Iran was
mainly rocky, the western and southern coastlines of
the Gulf were soft sediments. It also appears that the
Gulf has its most extensive shallow flats on the western
and southern coastlines. From an analysis of the
largest seagrass beds within the Gulf, the beds
increase in size as one proceeds eastward along the
southern shoreline.

BIOGEOGRAPHY

The Arabian Gulf is characterized by large seasonal
temperature variations. The area is arid and very hot for
many months of the year. There are few rivers that
drain into the Gulf. There is little rainfall and very little
freshwater runoff. In addition, the evaporation from
Gulf waters leads to salinities averaging 40 psu, but
which exceed 70 psu in the Gulf of Salwah"'. Price and
Coles'”” reported that inshore waters of the Gulf vary
seasonally in temperature from 10°C to 39°C and
offshore from 19°C to 33°C, with salinities varying from
38 psu to 70 psu. The three species which are found in
the Gulf can tolerate these extreme conditions:
Halodule uninervis, Halophila ovalis and Halophila
stipulacea.

Very few studies on seagrasses in the Gulf have
been produced reporting density, biomass and primary
production values. Basson et al.” calculated the aver-
age dry weight of seagrass leaves in Tarut Bay (Saudi
Arabia) to be 128 g/m’. They doubled this value for an

annual average. They calculated the energy content of
the 175-km‘’ seagrass bed in the bay to be 1.4 x 10"' kcal,
an energy equivalent of about 95000 barrels of oil.

Price and Coles'’' took samples from a series of
sites along the entire Gulf coast of Saudi Arabia. They
took triplicate samples at eight stations during four
seasons in 1985 and three seasons in 1986. Seagrass
biomass values ranged from 6.0 to 435 g dry weight/m’
(means for each station ranged from 53.3 to 234.8
g/m’). They reported significant correlations between
seagrass biomass and depth, sediment hydrocarbons
and sediment grain size, but no significant correlations
between biomass and season, salinity, or nutrient
concentrations and heavy metals.

Kenworthy et al.'" reported total biomass of
Halodule uninervis from two heavily oiled sites at Ad
Dafi and Al-Musallamiyah (northern Saudi Arabia),
ranging from 50 to 116 g dry weight/m’. At one non-

Table 6.1
Seagrass species in the Arabian region

Arabian Gulf © Number of species
Iran i
Iraq 0
Kuwait 2

Species

Halodule uninervis
No seagrass
Halodule uninervis
Halophila ovalis
Halodule uninervis
Halophila ovalis
Halophila stipulacea
Halodule uninervis
Halophila ovalis
Halophila stipulacea
Halodule uninervis
Halophila ovalis
Halophila stipulacea
Halodule uninervis
Halophila ovalis
Halophila stipulacea

Saudi Arabia

Bahrain

United Arab
Emirates

ArabianSea Number of species
Oman 4

Species

Halodule uninervis
Halophila ovalis
Syringodium isoetifolium
Thalassodendron ciliatum
Cymodocea serrulata
Enhalus acoroides
Halodule uninervis
Halophila ovalis
Syringodium isoetifolium
Thalassia hemprichii
Thalassodendron ciliatum

The Arabian Gulf and Arabian region

a
2 ‘
KUWAIT {RABIAN
4. Karant CULR
Manifah—_%s Jana |
At-Musallamiyah—“@go Turi Buy ~~

=
Ad Daf / & BAHRAIN
ba S Hawar Is

Jubail Marine _—
Wildlife Sanctuary Strait of
© lore

A Aaziyah 4)” QATAR

Al Ugayr ~~ Abu Dhabi* » ,,

eal
‘asht Adhm UAE
Gulf of Salwah

SAUD! ARABIA

0 100 200 300 400 500 Kilometers
as

Map 6.1
The Arabian Gulf and Arabian region

oiled outer bay site nearby, the biomass was 188 g dry
weight/m*. For Halophila ovalis, the lowest values were
observed in the oiled inner bay stations (12 and 17 g dry
weight/m‘], while the largest biomass was found in the
non-oiled outer bay site (39 g dry weight/m’}. The
biomass of Halophila ovalis was nearly three times
greater at another heavily oiled site (Jinnah Island) as
compared to an unoiled site (Tanequib) (34 compared
with 12 g dry weight/m’). Densities of Halodule
uninervis varied from a high of 5879 shoots/m’ at oiled
inner bay and mid-bay stations at Dawhat Al-
Musallamiyah to the lowest densities recorded for oiled
inner bay and mid-bay sites at Dawhat Ad Dafi (1960 to
3250 shoots/m’). Densities for Halophila ovalis at
heavily oiled inner and mid-bay sites at Dawhat Al-
Musallamiyah and Dawhat Ad Dafi ranged between
1530 and 2533 leaf pairs/m’. A similar range of values
existed for Halophila stipulacea. At oiled sites at
Tanequib and Jinnah Island, densities ranged from
1721 to 3776 leaf pairs/m* for Halophila ovalis, with a
single value of 2772 leaf pairs/m* for Halophila
stipulacea at Tanequib. This study was conducted in
1991, one year after the Gulf War oil spill.

In Tarut Bay, Basson et al.” derived tentative
productivity values by converting from biomass values
of seagrass leaves. They estimated the production

WORLD ATLAS OF SEAGRASSES

value of the leaves to be 100 g carbon/m*/year. These
calculations did not include the productivity of roots and
rhizomes. These values included many assumptions
and were largely hypothetical”.

Kenworthy et al. determined the net leaf

Case Study 6.1
THE BAHRAIN CONSERVANCY

In the summer of 1982, civil engineers won a
contract to build a roadway from Saudi Arabia
across 25 km of sea to the island state of
Bahrain””. The causeway, consisting of five bridges
linked by seven solid embankments, carries two
parallel roads from Jasrah on the northeast coast
of Bahrain, across Umm Na’san Island, over the
Gulf of Bahrain to join the Saudi coastline at Al
Aziziyah. The largest of the bridges weighs 1200
metric tons, and passes 28.5 m above the water. It
can carry 3000 vehicles per hour. Halfway between
Umm Na’san and Al Aziziyah, an artificial island
was built to house coastguards, customs and
immigration offices. Madany et al.*"' stated that the
total cost of the project was US$564 million, and
was one of the largest projects undertaken in the
Middle East during the 1980s.

At least half of the causeway’s span consists
of embankments of dredged rocks and fine mud
spoil. In consideration of the massive negative
impacts which this project could have on the
extensive seagrass beds of Bahrain, the Regional
Organization for the Protection of the Marine
Environment from Pollution (ROPME) arranged to
cooperate with Bahrain's Directorate of
Environmental Affairs to carry out an ecological
study on the possible effects of building the
causeway. A team from the Tropical Marine
Research Unit at the University of York carried out
the study through IUCN and the United Nations
Environment Programme (UNEP].

SAMPLING THE SITES

Sampling was done in three visits in 1983, each of
about one month. Flora and fauna, and
temperature, salinity, turbidity and chlorophyll
concentrations, and zooplankton were sampled at
six coastal and six offshore sites.

Many of the sites sampled were deemed to
be critical habitats. In the immediate vicinity of the
causeway between Umm Na’san and the main
island of Bahrain, the water was found to be 9 psu
more saline in the now partly enclosed bay on the
south side of the road than just to the north, less

productivity of Halodule uninervis at a single oiled
station at Dawhat Ad Dafi. Values ranged from 0.094 to
0.250 g dry weight/m*/year.

Durako et al." exposed plants of all three species
from a well-flushed area seaward of the south of

than 100 m away. Of greater concern were the
more obvious physical impacts of dredging and
reclamation. The water became more turbid the
closer the team moved to the construction work.
Long plumes of sediment stretched downstream
from the construction areas. Just to the north of
the causeway, it found a layer of very fine silt mud
20 cm thick, with a complete absence of surface
flora and fauna, but a high abundance of infaunal
polychaete worms dominated by Ceratonereis.
Below the silt was a once healthy bed of seagrass,
now almost completely dead. This was probably
once a part of a large nursery of shrimp within the
bay area, as large numbers of juveniles and fish
thrived in the nearby intertidal flats. These flats
also supported a rich fauna, including crabs and
mollusks. At two sites south of the causeway on
the west coast of Bahrain there was no clear
evidence of damage.

SYMPTOMS OF STRESS

At the offshore sites on the east coast, where
relatively unspoiled conditions were expected, the
team instead found turbid water. On calm days,
visibility was only 60 cm into the water, and a layer
of fine silt covered the seabed out to the coral
reefs. These reefs were already displaying the
classic symptoms of sedimentary stress, with
horizontal faces showing bleached skeletons
devoid of polyps. The round heads of Platygyra
looked like a monk's head with a tonsured haircut,
with the top bleached white. Dead and dying
branches of Acropora were covered with sea
urchins or were turned green by colonies of
epiphytic algae.

Madany et al." did not state whether this
project was regulated by the Environmental
Protection Committee of Bahrain. This committee
has established specific rules and regulations to
control dredging and reclamation projects before
implementation. However, the authors found that
some projects were carried out without the
permission of the committee, due to the lack of
legislation to support the regulations.

Dawhat Al-Musallamiyah, Saudi Arabia, to un-
weathered Kuwait crude oil. The treatment duration
was 12 to 18 hours. There were no significant
photosynthesis as against irradiance response effects,
nor were there any effects noted on respiration rates.
Their conclusion was that the Gulf War oil spill
primarily impacted intertidal communities, rather than
the submerged plant communities of the northern Gulf
region.

Phillips et al." found density values of Halodule
uninervis from five sites in the UAE to vary from 1745 to
21590 shoots/m’, while leaf pair densities of Halophila
ovalis from two sites varied from 166 to 1108/m’.

Outside the Gulf, Wahbeh’” and Jones et al."
using oxygen release methods, estimated values of
1326 g carbon/m’/year for Halodule uninervis in the
Gulf of Aqaba, 617 g carbon/m*/year for Halophila
stipulacea and 11 g carbon/m*/year for Halophila
ovalis’”’.

The studies of Basson et al.’ and Price et al.’
suggested that primary production from seagrass and
shallow water benthic algae may be of greater
importance in the Gulf than that from phytoplankton.

Coles and McCain’ identified a total of 834
species associated with seagrass and sand/silt
substrates at seagrass stations north of Al Aziziyah
(Saudi Arabia). Mean numbers of benthic organisms in
the seagrass beds averaged nearly 52000/m’, an
average of 36000/m’ in the Manifah-Safaniyah area”
and up to around 67000/m* in Tarut Bay.

Basson et al.’ reported a total of 530 floral and

Case Study 6.2
RAPID ASSESSMENT TECHNIQUE

Price” devised a simple, rapid assessment
technique for coastal zone management
requirements. The method was based on semi-
quantitative [ranked] data on coastal resources,
uses and environmental impacts. He recorded
data at 53 geographically discrete sites, at
intervals of usually less than 10 km along virtually
the entire 450-km Saudi Arabian Gulf shoreline.
Each sampled site comprised a quadrat 500 m x
500 m, bisecting the beach. Within each quadrat,
the abundance or magnitude of the mangroves,
seagrasses, halophytes, algae and freshwater
vegetation were estimated and recorded semi-
quantitatively. The attributes were scored using a
ranked scale of 0-6 {0 was no impact; 6 was the
greatest impact]. For the resources, abundance
scores were based on estimates of areal extent
(m?) for flora, or of estimated number of

The Arabian Gulf and Arabian region

faunal species associated with the seagrass beds in
Tarut Bay, an area of 410 km’. McCain! found 369
species of benthic organisms in the seagrass beds on
the Saudi Arabian coast between Manifah and Bandar
Mishab.

The major associated animal species of the
seagrass beds of the Gulf are dugongs, green sea
turtles, pearl oysters and shrimp" * °°". Jones"
stated that the collapse of the shrimp fishery in the
northern Gulf has been largely attributed to the loss of
the critical seagrass habitat.

The preliminary studies done by Basson et al."”
suggested that the annual production of the Tarut Bay
seagrass beds may be about 230 million kg wet weight
per year. This, in turn, might be expected to yield 2.3
million kg of fish, at a value of US$8 million annually, or
the same quantity of shrimps at a value of US$12
million per year {conversion rate of 1 percent efficiency
for use of seagrass for fish and shrimps).

IUCN estimated that the industrial shrimp
fishery in the Saudi Arabian Gulf and the Red Sea
totaled some 6800 metric tons, with a value of
US$35.28 million. The net profit was US$13.94 million,
an increase of US$4.78 million from 1982. The IUCN
report concluded that this economic value of the Saudi
Arabian fisheries would be maintained and increased,
but only if managed on a sustainable basis. It also noted
that shrimp production had dropped over the five years
previous to the date of the report. This was the result of
either the resource being overexploited, or a
destruction of the critical seagrass habitat, or both.

individuals for fauna, both within each sample
area of the quadrat. Cluster analysis was applied
after the scores were recorded. The method
chosen for analyzing the biological resource data
and the resource uses/impacts was the Bray-
Curtis similarity index, followed by a hierarchical
clustering of sites, using the arithmetically
determined centroid. The results of the cluster
analyses were depicted as dendrograms.

Correlations were determined between, and
within, the following groups of variables: biological
resources and latitude/salinity; and biological
resources and uses/environmental impacts.
Price” concluded that the method can be of value
to managers and scientists alike, to determine
associations between different environmental
variables, and is especially useful for
management.

Photo: L. Murray

WORLD ATLAS OF SEAGRASSES

Dugong feeding on seagrasses.

Vousden” linked the extensive seagrass beds
surrounding Bahrain to juvenile stages of commercially
important penaeid shrimp and to a number of adult fish
species, e.g. Siganus spp., a popular local food
resource. Seagrasses also provided a habitat for the
settlement of high densities of pearl oyster spat
(Pinctada sp.), an important commercial species in
Bahrain. Vousden"” reported a herd of 700 dugongs at
one location over seagrass beds in Bahrain.

HISTORICAL AND PRESENT DISTRIBUTION
Jones"! stated that seagrasses were sometimes present
in the upper subtidal zone (2-3 m deep) along the Saudi
Arabian coast as a band some 1-20 m wide. In these
situations, seagrasses were recorded at 57 percent of
the shore sites inspected, but seldom in luxuriant
stands. The report estimated an areal extent of sea-
grasses along Saudi Arabia of 370 km’. De Clerck and
Coppejans™ studied seagrass distribution in the Gulf
sanctuary between Ras az-Zaur and the northeast point
of Abu Ali. They found that Halodule uninervis formed
extensive meadows from the low-water mark to 3 m
deep. Locally, it was replaced by Halophila ovalis and
Halophila stipulacea. In some places near Dawhat Ad
Dafi, seagrass cover declined rapidly below 3 m deep.
At the Jubail Marine Wildlife Sanctuary (Saudi
Arabia), Richmond! found that Halodule uninervis was
again the dominant species, with the best developed
beds at 3-4 m deep. Both species of Halophila were
also found. Seagrasses were not found below 5 m.
Vousden” mapped the seagrasses of Bahrain
using satellite imagery. He reported that, as far as
percentage cover was concerned, seagrass beds were
the major soft-bottom habitat type within the 2-12 m
subtidal zone. He found areas where the seagrasses
went to 14 m deep. Seagrass distribution was

widespread around the islands, covering most of the
east coast, from south of Fasht Adhm to the Hawar
Islands. Seagrasses also covered significant areas
around Fasht Jarim and along the west coast, south
and north of the Saudi-Bahrain causeway and along the
southwestern coast. He also reported that the seagrass
beds died back to low cover in winter, but found the
beds to be healthy in March 1986. He concluded that the
majority of well-developed beds occurred to the
southeast of Bahrain. Halodule uninervis was the most
common species. In summer, Halodule uninervis cover
was as high as 90 percent. More than 50 percent of the
sites at which seagrasses occurred supported 40
percent or greater cover.

In the UAE, Phillips et al."* performed an
extensive study of seagrass distribution and extent of
growth in 1999 and 2000. Halodule uninervis was the
most abundant species in the Gulf waters of the UAE.
Seagrasses occurred from 1.5 m to 15 m deep. Even
though Halodule uninervis was occasionally found at 15
m deep, Halophila ovalis tended to become the
dominant species in depths greater than 11 m.
Extensive continuous meadows were found wherever
water depths were suitable {for Halodule uninervis
from 1.5m to 11 m deep). Digitized estimates show that
there were 5500 km’ of seagrasses in the Gulf waters
of Abu Dhabi Emirate.

PRESENT THREATS AND LOSSES

Sheppard et al” listed a variety of coastal and marine
uses and their major environmental impacts which
affect or could affect seagrasses in the Gulf. They
ranked them as short-term to medium-term impacts,
medium-term to long-term impacts, and possible
longer-term impacts.

Except for my own observation on the effects of oil
globules and oily black films over the bottom near an oil
processing plant west of Jabel Dannah [seagrasses
absent under the films], none of the literature records
any negative impacts from oil-related pollution in the
Gulf.

Vousden" stated that the agricultural industry
was one of the major sources of organic non-
petrochemical pollution to the marine environment. He
found that the agricultural sector contributed 50
percent of the total biological oxygen demand (BOD)
loading to the waters around Bahrain. An oil refinery
discharged 19 percent of the loading, with domestic
discharges amounting to some 25 percent. The
remaining discharges came from other industries.

Sheppard et al." stated that coastal reclamation
and dredging represented one of the most significant
impacts on the coastal and marine environments of
the Arabian region. They reported that coastal
development and infilling have been far greater along

Case Study 6.3

The Arabian Gulf and Arabian region

MARINE TURTLES AND DUGONGS IN THE ARABIAN SEAGRASS PASTURES

The seagrass beds in the Gulf are home to the world’s
second largest assemblage of endangered dugongs
(Dugong dugon) - upwards of 7000 individuals” (the
largest population is off the coast of Australia],
distributed mostly in the southern and southwestern
regions of the Gulf. The dugongs belong to the
monotypic order Sirenia and are the only herbivorous
marine mammals, feeding directly on seagrasses.
They can live to be 70 years of age and grow to over 3
m in length and 400 kg in weight. Their nearest living
non-sirenian relative is believed to be the elephant.
Dugongs have extremely low reproductive capacities
as they do not become sexually mature until about ten
years of age, with subsequent calving only occurring
at intervals of seven or more years.

The most important foraging habitats for
dugongs in the Gulf are on either side of Bahrain, off
Saudi Arabia between Qatar and the UAE, and off Abu
Dhabi"!. Outside the Gulf, the nearest population is in
the Gulf of Kutch, northern India, suggesting the Gulf
population is genetically and physically isolated. Until
some 30 years ago, dugongs formed the staple diet of
many Gulf-bordering villages, and had been used for
their leathery skin and fats rendered into oils’. This
suggests that populations were significantly larger
than at present, and further reduction in population
size might adversely impact their chances of survival

FEEDING GROUNDS

Significant populations of herbivorous green turtles
(Chelonia mydas} also depend on the seagrasses of
the Gulf. They nest on Karan and Jana Islands off the
Saudi Arabian coast {ca 1000 females/year)™,
outside the Gulf at Ras Al-Hadd, Oman (ca 4000
females/year]", and to a smaller extent off the
southern coast of Iran, and are believed to feed
among the seagrass pastures bordering the
southern Gulf. Evidence of this is supported by re-
cent tag returns from Saudi Arabia and Oman" *”.
The green turtles in the Gulf also have low repro-
ductive capacities, with estimates of sexual
maturation periods of 15-40 years, and a survival
rate of hatchlings of roughly only one in a thousand.
These turtles have several key physiological features
that set them apart from other Testudines, such as
non-retractile limbs, extensively roofed skulls, limbs
converted to paddle-like flippers, and salt glands to
excrete excess salt. As with other reptiles, the sex of
hatchlings is dependent on temperature during

incubation, Adults can reach over 1 m in length
and weigh over 190 kilograms, and feed nearly
exclusively on seagrasses. The Gulf green turtles
exhibit strong nesting site fidelity, returning to the
same beaches to nest within and over several
seasons". This fidelity coupled with a relatively low
emigration rate from the Gulf, other than to the
Omani nesting site, suggests that populations which
nest and feed within the Gulf are, much as the
dugongs, genetically and physically isolated.

Threats to the turtle populations in the Gulf
include moderate egg and adult harvesting,
mortality in commercial and artisanal fishing gears,
loss of nesting habitats, and significant loss or
alteration of foraging grounds. While most Gulf-
bordering nationals do not generally eat turtles or
their eggs, many fishing boat crews are being
replaced with a number of other nationalities who
do, and unless the nesting beaches are patrolled the
fishermen frequently dig up clutches of eggs.
Fishermen are also known to take adults on an
opportunistic basis”. An important modern impact
is the extensive dredging and landfilling projects of
several Gulf-bordering nations, which are altering or
completely destroying foraging [seagrass) pastures.
As in the case of the dugongs, the seagrasses upon
which the green turtles in the Gulf depend are of
Supreme importance to the survival of these
isolated, regionally important populations.

CALL FOR PROTECTION

Based on the genetic isolation and population sizes
of these two species, a recent meeting of experts in
Hanoi, Viet Nam, concluded that the Gulf seagrass
habitats are of outstanding universal value at a
global level, and recommended they should be
protected through international instruments such as
the World Heritage Convention. Although there are a
number of national conservation programmes and
regional initiatives, they tend to be species-specific
and not, as yet, directed at preserving marine habi-
tats other than coral reefs. There is a need for
focused attention on the remaining habitats, par-
ticularly seagrass pastures, if the populations of
dugongs and green turtles are to survive.

Nicolas J. Pilcher
Community Conservation Network, P.O. Box 1017, Koror, Republic of
Palau

Photo: R.C. Phillips

WORLD ATLAS OF SEAGRASSES

Halodule uninervis, Abu Dhabi area

the Gulf coast than in the Red Sea or other parts of the
Arabian region".

IUCN"! and Sheppard and Price’ reported that
approximately 40 percent of the Saudi Arabian coast
had been developed, involving extensive infilling and
reclamation. They found that conditions were similar in
other Gulf States, such as Bahrain and Kuwait. More
than 30 km’ (3306 ha) of Bahrain was either reclaimed
or artificial land'*"'. In the late 1980s, there were plans
for further infilling on an area of almost 200 km’ in
Bahrain”. | have observed extensive dredging
activities around the UAE. These activities involved
maintenance channel dredging, dredging for new
channels and land reclamation. They were being
carried out inshore in the most extensive continuous
seagrass beds in Abu Dhabi Emirate.

Price” noted that dredging and coastal infilling
projects were occurring throughout Saudi Arabia, e.g.
Tarut Bay and the Jubail area, and also in Bahrain and
Kuwait. He conjectured that such activity was likely to
affect not only the shrimp and fish stocks, but also the
ecology of coastal habitats generally.

Vousden" stated that the effects of coastal
development represented a significant problem to the
marine environment of Bahrain. He noted that the
shallow intertidal flats next to a reclamation site
became smothered in a thick glutinous silt often many
centimeters deep and of little biological value due to its
anoxic nature. Offshore, the benthic communities
became choked by the anoxic sediments. Primary
productivity was reduced drastically by the high
sediment loads and consequent increase jn water
turbidities. Price et al’ noted that seagrass had
become smothered as a result of the sedimentation
caused by dredging.

Thus, many studies have recorded the large-scale
and continuing dredging and land reclamation projects

throughout the Gulf States. However, no one has
documented the amount of historical loss of
seagrasses as a result of this activity. Such studies are
needed. The study of Phillips ef al." in the UAE
appears to be the only study that has precisely
documented the extent of seagrass distribution in any
of the Gulf States. Such studies are also needed.

POLICY AND MANAGEMENT

Each Gulf State has a varying number of authorities
designed to study and/or protect seagrasses. However,
one can still see massive and continuing dredging and
land reclamation in all countries. Since there is so little
effective cooperation between the states as concerns
marine conservation of seagrasses, the feeling within
the Gulf is that this conservation and protection effort
would be best accomplished at the regional level. There
is a plan, the Kuwait Action Plan [KAP], based on the
Kuwait Regional Convention for Cooperation on the
Protection of the Marine Environment from Pollution.
All countries within the KAP region are signatories of
the convention. |IUCN/UNEP"' reported that the priority
concern was the current extensive loss or severe degra-
dation of seagrass habitats, and the probable reduction
in natural resources associated with this habitat.

The reports of Price’, the Coral Reef and Tropical
Marine Research Unit’! and Price et al.’ contained
detailed recommendations for conserving seagrass
beds in the Gulf area. These focused largely on
preventing further uncontrolled habitat destruction and
widespread pollution. IUCN/UNEP"! concluded that any
legislation aimed at preventing impacts must be
followed by enforcement. Little has been done to
implement these recommendations. Except for the
UAE, none of the countries has taken any steps to
implement the beginning of an effective management
program that would start with baseline mapping,
followed by periodic monitoring and mapping efforts.
The distribution and rate of seagrass loss needs to be
determined in the various KAP countries. As of 1985,
the conservation status of seagrass habitats had been
considered in Bahrain’! and Saudi Arabia’ *", but not in
detail in any of the other KAP countries.

Sheppard et al." stated that in addition to the
UNEP Regional Seas Programme, there were other
regional agreements, including those of the GCC (Gulf
Cooperative Council], the GAOCMAO (Gulf Area Oil
Companies Mutual Aid Organisation] and others. These
agreements relate to environmental management and
pollution control.

AUTHOR

Ronald C. Phillips, Florida Marine Research Institute, 100 Eighth
Avenue, S.E., St Petersburg, Florida 33701, USA. Tel (home): +38 (0) 692
413086. E-mail: ronphillips67(@hotmail.com

The Arabian Gulf and Arabian region 81

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Jones DA [1985]. The biological characteristics of the marine
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Jones DA [2002]. Personal communication.

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ios

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MEPA, Jeddah. 289 pp.

WORLD ATLAS OF SEAGRASSES

7 The seagrasses of

KENYA AND TANZANIA

productive coastal and marine ecosystems in the

East African region. The Kenyan (600 km) and
Tanzanian (800 km) coastlines have a shallow and
relatively narrow continental shelf bordering the Indian
Ocean and are characterized by extensive fringing coral
reefs, several sheltered bays and creeks, limestone
cliffs, mangrove forests, sand dunes and beaches'”.
The tidal amplitude is rather large - up to 4 m near
Mombasa” - and therefore there is a fairly extensive
intertidal zone between the fringing reefs and the coast
in many places. The substrate in this zone consists
mainly of carbonate sands derived from eroding reefs.
The productivity of these intertidal areas is determined
predominantly by the presence of seagrasses and
macroalgae, which grow wherever shallow depressions
retain a covering of water during low tide.

The most extensive seagrass meadows occur in
back-reef lagoons, which are found between the
beaches or cliffs and the adjacent fringing reefs.
Narrow channels connect the lagoons with the sea
during low tide, but high-tide waters pass over the reef
crest into the lagoon. Apart from many fish species that
reside permanently inside such lagoons, many other
species feed there during high tide, leaving for deeper
offshore waters during the ebbing tides.

At several places along the East African coast,
these lagoons grade into sheltered semi-enclosed bays
(e.g. at Mida, Kilifi, Mtwapa, Tudor, Gazi and Funzi in
Kenya, and at Tanga, Bagamoyo, Mohoro, Kilwa and
Mtwara in Tanzania) where mangroves, seagrass
meadows and coral reefs occur as adjacent and
interrelated ecosystems. Where the supply of
terrigenous sediments is limited, seagrass vegetation
is also common in the creeks and channels that run
through the mangroves, possibly functioning as traps
and reducing the extent of the fluxes of particulate
matter and nutrients between the mangroves and the
ocean. In Gazi Bay (Kenya), for example, it is possible to

S eagrasses are a major component of the rich and

C.A. Ochieng
P.L.A. Erftemeijer

snorkel in creeks and small rivers inside the
mangroves, where the water is very clear and the
bottom is covered in a luxuriant growth of seagrasses.
In the delta areas of major rivers, such as the Tana
River in Kenya and the Rufiji River in Tanzania,
seagrass growth is minimal.

BIOGEOGRAPHY

The following 12 seagrass species have been
encountered during several studies in Kenya and
Tanzania“: Halodule uninervis, Halodule wrightii,
Syringodium isoetifolium, Cymodocea_ rotundata,
Cymodocea serrulata, Thalassodendron ciliatum,
Zostera capensis, Enhalus acoroides, Halophila minor,
Halophila ovalis, Halophila stipulacea and Thalassia
hemprichii. All species appear to be widely distributed
along the entire coastline of both countries, even those
with only a limited number of observations, such as
Zostera capensis, Halophila minor and Halophila
stipulacea. Seagrasses often occur in mixed
communities consisting of two to several of the 12
species. Thalassodendron ciliatum is often the most
dominant species, forming pure stands with high
biomass. Three additional seagrass species (Halodule
pinifolia, Halophila ovata and Halophila beccarii) have
been reported for the region” '”, but these observations
may constitute misidentifications and need further
confirmation.

There is some controversy over the occurrence of
the species Halodule wrightii in East Africa. Most
authors have included Halodule wrightii in their species
descriptions for the region based on leaf width and tip
morphology““®!. However, field observations in Florida”
indicated that leaf tips in Halodule spp. vary widely from
bicuspidate to tridentate on shoots of the same
rhizome. Experimental culture!” revealed that leaf tips
of Halodule are environmentally variable, related to
nutrient variability or tidal zone. Furthermore, isozyme
analyses of diverse collections throughout the tropical

> Lamu Island

Mambrui +

: Ungwana Bay
Malindi \ \e Formosa Bay
Mida Creek~_~e
*___ Watamu Manne

National Park

Bamburi 4°
~_ Mombasa Marine National

~ Park and Reserve

Kile

Mombasa ¢
Gazi Bay.
Funzi

v« Diani-Chale Lagoon

#é Kilindini
=" Pemba Island

Tanga

?
Zanzibar
ae
° B- Chwaka Bay
sae
Bagamoyo"®.

% Dar es Salaam

INDIAN
OCEAN

Kinondoni

Mohoro e

+ 2" Mafia Island

0 40 80 120 160 200 Kilometers Mtwara®
la

Map 7.1
Kenya and Tanzania

western Atlantic as well as the Indo-Pacific revealed a
clear genetic difference between the two ocean
systems, but genetic uniformity within each of the two
ocean systems'”’. Based on these results it was
concluded that all plants {with this morphology] from
the Indo-Pacific are Halodule uninervis while those in
the tropical western Atlantic are Halodule wrightii"”.
Nevertheless, Halodule wrightii continues to be
reported in literature despite these field, culture and
isozyme findings'’ '” '”'. It appears therefore that there
is a need for further analyses of chromosomal
differences and physiological studies to determine the
relationship between nutrients and leaf morphology of
Halodule species.

The seagrass beds in East Africa, as indeed
elsewhere, harbor a diverse array of associated plant
and animal species. Detailed studies on seagrass
associates in this region have identified over 50
species of macroalgae and 18 species of algal
epiphytes” at least 75 species of benthic
invertebrates?" especially gastropods and
bivalves - several species of sea cucumbers” and at
least seven sea urchin species”, various shrimp,
lobster and crab species”** and over 100 fish
species’’*” in association with seagrass beds. This
clearly underscores the importance of seagrass
meadows for biodiversity conservation.

Kenya and Tanzania

Seagrass beds in the region also support sizeable
populations of two endangered species, i.e. the green
turtle Chelonia mydas®”*' and the dugong Dugong
dugon”'***”, both of which feed on seagrasses. In 1994,
a total of 443 sea turtles was recorded along the
Kenyan coast, among which the green turtle was by far
the most common species’. In Tanzania, there are no
recent population studies®". Similar surveys along the
Kenyan coast revealed ten dugongs during November
1994 and six dugongs during February-March 1996,
representing a significant decline in comparison to
earlier counts of over 50 animals in the 1960s and
1970s'":*”. The most important dugong habitat in Kenya
can be found in the Lamu Archipelago. In Tanzania, the
main centers of dugong population have been reported
along the Pemba-Zanzibar channels and in the Rufiji-
Mafia area’. The need for protection and management
of sea turtle and dugong habitats (seagrass beds] has
been stressed”.

The importance of East African seagrass
ecosystems for fisheries is gradually emerging from an
increasing research effort on the role of the seagrass
meadows in this region as nursery, breeding and
feeding grounds for marine fish and crustacean species
of economic importance such as shrimps [Penaeus]
and spiny lobster (Panulirus)'”***". Several fish species
graze on seagrasses, notably rabbitfishes (Siganidae]
and surgeonfishes (Acanthuridae}, while parrotfishes
(Leptoscarus spp.) preferentially graze the epiphytes
on the seagrass. Adult fishes, such as snappers,
groupers, grunts and barracuda, feed on the infauna of
seagrass beds while the diet of their juvenile stages is
mainly seagrass-derived detritus. Portunus pelagicus,
an important contributor to the crab fishery in
Bagamoyo and Dar es Salaam, is said to inhabit shallow
coastal habitats such as estuaries, sheltered bays and
open sublittoral waters (all of which may include
seagrass], where all stages of its life cycle are found”.

Significantly higher fish abundance and catch
rates were found in seagrass beds in comparison to
bare sand areas in a study of dema trap fishery in the
coastal waters of Zanzibar, Tanzania’. Similarly, 11 of
the 99 fish species of Tudor Mangrove Creek {Kenya}
are typically associated with seagrass (6 percent of the
total catch)”, while 74 species of fish (in a total of 39
families) and 15 species of macro-crustaceans were
reported for the seagrass beds of Chwaka Bay and Paje
on Zanzibar”. At both of these latter sites, Gerres
oyena was the dominant fish species in the seagrass
beds (>60 percent of the total catch).

Harvesting of bivalves (notably Anadara antiquata,
Anadara natalensis and Anadara uropigilemana,
Gardium assimile, Gardium pseudolina, Gardium
flavum and Scapharca_ erythraeonensis) and
gastropods (including Murex ramosus, Pleuroploca

fy gl

WI Fe

WORLD ATLAS OF SEAGRASSES

Case Study 7.1
GAZI BAY, KENYA: LINKS BETWEEN SEAGRASSES AND ADJACENT ECOSYSTEMS

Gazi Bay, a semi-enclosed bay (15 km’) ca 50 km
south of Mombasa, Is characteristic of the creeks and
bays along the East African coastline. Mangroves,
seagrass meadows and coral reefs occur here as
adjacent ecosystems. Mangroves are found along
small seasonal rivers on the landward side of the bay
and are drained by two tidal creeks. Extensive sea-
grass vegetation is common among and between the
mangroves, where it functions as a trap reducing the
flux of sediment, organic material and nutrients from
the mangroves to the ocean. Snorkeling in creeks and
small rivers among the mangroves can be a sens-
ational experience: the water can be very clear and
the bottom is covered in a luxuriant growth of
seagrasses, traversed by mangrove roots where
schools of juvenile fish hide from predators. Adjacent
to the mangroves on the seaward side are intertidal
flats, intersected by some channels, and shallow
subtidal areas which stretch to the fringing reef. Most
of this area is covered by various species of sea-
grasses and macroalgae, with the exception of a few
sandy patches” '. Seagrasses in Gazi Bay cover an
estimated total area of approximately 8 km*. The
maximum tidal range in Gazi Bay is 250 cm.

All the 12 seagrass species of eastern Africa
are found in Gazi Bay. Macroalgae are among their
most conspicuous floral associates. Sixteen species
of Chlorophyta, 4 species of Phaeophyta and 31
species of Rhodophyta associated with seagrass beds
in Gazi Bay have been identified®!. Among these were
Euchema, Gracilaria, Ulva and Sargassum, all of
which include species of potential economic value.
Average leaf production of Thalassodendron ciliatum,
the most dominant seagrass species, ranges from
4.9 to 9.5 g/m?/day”"""”. A separate study of the growth
and population dynamics of Thalassodendron
ciliatum has shown that its vertical growth is the
fastest reported for any seagrass to date [42 inter-
nodes, i.e. 42 leaves/year), whereas the horizontal
growth rate (16 cm/year] is among the slowest'*”. As
a result of the slow horizontal rhizome growth, shoot
recruitment through branching of vertical shoots is
an important part of the clonal growth of this
population and so an essential component of the
production of Thalassodendron ciliatum.

Seagrass meadows are open systems subject
to nutrient impoverishment due to export processes
mediated by tidal inundation. The intriguing feature of
the occurrence, in very close proximity to one
another, of mangroves, seagrasses and corals in Gazi

Bay attracted scientists to study the interlinkages
between these systems in terms of dissolved
nutrients and seston fluxes as well as shuttle move-
ments of fish”. Analysis of the stable isotope signa-
ture of the sediment carbon in the seagrass zone
revealed significant carbon outwelling from the man-
groves, but deposition of particulate organic matter
rapidly decreased with distance from the forest, with
most litter trapped within 2 km of the mangroves”.
However, marked decreases in the carbon signature
of seston flowing over the seagrass zone during flood
tides pointed to a reverse flux of organic particles
from the seagrass zone to the mangroves, with the
nearby coral reefs existing in apparent isolation.
Direct flux measurements of both mangrove and
seagrass litter showed that trapping of mangrove
litter by adjacent seagrasses is reciprocated by a
retention of seagrass litter in the mangrove, and this
give-and-take relationship is mediated by tides.
Further research has indicated that the detrital
cycling in the inner parts of the mangrove forest
forms part of a rather closed system based on local
inputs, whereas cycling in the outer parts of the forest
is tightly connected with the adjacent seagrass
ecosystem. Despite the presence of tide-mediated
chemical fluxes which allow one system to influence
another, the input of mangrove carbon did not co-
incide with enhanced leaf production of the dominant
subtidal seagrass Thalassodendron ciliatum'*'.
Presumably, carbon outwelling from the mangrove
coincides with only limited export of nitrogen and
phosphorous, and the restricted effects of these
nutrients on the seagrass [if any] are masked by other
local factors.

Gazi Bay is typical of the major fishing grounds
in Kenya, most of which are located in shallow near-
coastal waters due to a lack of sophisticated gear and
motorized boats which would allow exploitation of
deeper waters. Carbon isotope and delta '°N studies
into trophic relationships in Gazi Bay allowed the
identification of three trophic levels, i.e. herbivores,
zoobenthiplanktivores and piscivores/benthivores.
Seagrass beds were found to be the main feeding
grounds providing food for all fish species studied in
Gazi Bay, Kenya”. Seagrass plants were the major
source of carbon for four fish species studied in the
bay. They also contribute [together with mangroves)
to the particulate organic carbon for prawn larvae,
zooplankton, shrimps and oysters, hence their
support for food webs”.

trapezium and Oliva bulbosa) for food is common on
many of the intertidal areas (with or without seagrass)
in Tanzania. No data currently exist on the quantities
collected from seagrass areas. Strombus gibberulus,
Strombus trapezium and Cypraea tigris, all of which
are popular curio goods, are common in seagrass
areas around Dar es Salaam”. Twenty species of sea
cucumbers, the most common of which are Holothuria
scabra, Holothuria nobilis, Bohadschia_ vitiensis,
Bohadschia argus, Thelenota anax, Stichopus
chloronotus, Stichopus variegatus and Stichopus
hemanni, are harvested from intertidal areas [including
seagrass beds] along the Tanzania coast for export’? *”.

PRODUCTIVITY AND VALUE

Studies on the ecological processes and functioning of
seagrass ecosystems in Kenya and Tanzania have
provided a better understanding of the natural factors
limiting the growth and geographical distribution of
seagrasses, environmental stresses and indirect
values of seagrass ecosystems in this region.

Leaf productivity of Thalassodendron ciliatum
ranges from 4.9 to 9.5 g/m’/day”'''“"!, Vertical growth
rates of Thalassodendron ciliatum (42 internodes, i.e.
42 leaves/year] measured in Kenya are among the
fastest reported for any seagrass species to date,
whereas its horizontal growth rates (16 cm/year) rank
among the slowest'. Shoot recruitment rates
measured in seagrass meadows along the coasts of
Kenya and Zanzibar were either the same as or larger
than shoot mortality rates, suggesting that the
environmental quality in this region is still suitable for
sustaining vigorous seagrass vegetation”.

Most factors that govern primary production,
including light and temperature, are relatively constant
throughout the year in this region. However, the
composition of the oceanic water and the amount of
freshwater which enters the coastal areas are variable.
At several sites along the coast substantial seepage of
freshwater occurs, as a result of which brackish water
is often found in areas of seagrass beds”. Using
nitrogen stable isotope signatures, groundwater was
found to influence seagrass species diversity and
abundance where’ Thalassodendron ciliatum
dominated high groundwater outflow areas as opposed
to Thalassia hemprichii.

Photosynthetic studies carried out in Zanzibar,
Tanzania, indicate that seagrasses may respond
favorably to any future increases in marine carbon
dioxide levels due to global climate change“* “. The
enhanced photosynthetic rates by Halophila ovalis and
Cymodocea rotundata in the high, frequently air-
exposed, intertidal zone may have been related to a
capacity to take up the elevated HCO, levels directly”.
Furthermore, these tropical intertidal seagrasses were

Kenya and Tanzania

found to be more sensitive to desiccation than subtidal
seagrasses with the exception of the species
Syringodium isoetifolium“”. Desiccation tolerance,
however, may not be a trait that determines the vertical
zonation of tropical seagrasses. The ability to tolerate
high irradiances, as well as the high nutrient inputs
from the shore, apparently allows the shallow species
to occupy the uppermost intertidal zone.

Seagrass beach cast material may contribute
significantly to beach stability, as implied by a study
along the Kenyan coast’ “‘! [see Case Study 7.2).

Detailed studies in Gazi Bay, Kenya, revealed
significant carbon outwelling from the mangroves into
the adjacent seagrass meadows and a reverse flux of
organic particles from the seagrass zone to the
mangroves, with nearby coral reefs existing in apparent
isolation’ as far as particulate organic matter is
concerned. Export of organic matter from mangroves in
Chwaka Bay (Tanzania) was also limited to a narrow
fringe of seagrasses immediately adjacent to the
mangroves”. Despite the presence of tide-mediated
chemical fluxes, which allow one system to influence
another, the input of mangrove carbon did not coincide
with enhanced leaf production of the dominant subtidal
seagrass Thalassodendron ciliatum™.

Carbon isotope and delta '°N studies on trophic
relationships showed that seagrass beds were the
main feeding grounds for all fish species studied in Gazi
Bay, Kenya“’. An experiment on feeding preference

showed that Calotomus carolinus (Scaridae), the
second most abundant fish in Watamu Marine National

nie

The catch from a trap fishing trip in the seagrass beds - mainly the
seagrass parrotfish Leptoscarus vaigiensis, some pink ear emperor
Lethrinus lentjan, and a grouper Epinephelus flavocaeruleus.

Photo: F. Gell

WORLD ATLAS OF SEAGRASSES

Park, preferred pioneering short-lived seagrass
species to climax species. The study also highlighted
the role of grazing fish in influencing seagrass
abundance’.

Sea urchins mediate the competitive success of
different seagrass and fish species, in terms of
distribution and abundance. Sea urchins can reduce
grazing rates of some species of parrotfish'”, while the
relative dominance of some of the sea urchin species
indicates a high fishing pressure on herbivorous
fish species”. Tripneustes gratilla, for instance, can
graze at a rate of 1.8 seagrass shoots/m//day at fronts
that support a sea urchin abundance of 10.4
individuals/m*"“!. The species composition of seagrass
communities in reef environments appears to be
partially affected by prey choices of the dominant
grazers. Parrotfishes and the sea urchin Echinothrix
diadema appear to favor seagrass beds dominated by
Thalassodendron ciliatum, while other sea urchin
species such as Diadema setosum, Diadema savignyi
and Echinometra mathaei favor areas high in Thalassia
hemprichii®”.

There have been few studies on western Indian
Ocean seagrasses to date. A recent bibliographic survey
of marine botanical research outputs from East Africa
between 1950 and 2000 yielded only 44 papers and
reports that dealt with seagrasses'". Even baseline data
on distribution are largely lacking’. In recent years,
however, the number of seagrass publications from
studies in the region has increased and efforts are
under way for integrated coastal zone management and
participatory management of marine protected areas
including seagrass beds, indicating a growing
recognition of the important value of seagrass
ecosystems.

Massive beaching of seagrass litter was reported
as early as 1969 by an expedition to Watamu on the
Kenyan coast’, rendering it unlikely that these
accumulations have increased over past or recent
years"),

No direct utilization of seagrasses in East Africa
has been reported’ except for anecdotal reference to
the small-scale use of the leaves of Enhalus
acoroides for weaving mats and thatching huts, and
the harvesting of their rhizomes by people of the
Lamu Archipelago in Kenya, who dry and then grind
them into flour for cooking what is locally known as
mtimbi*™'. Quantitative data on such direct uses as
well as catch statistics of the seagrass-associated
fisheries in this region are lacking, making it
impossible to draw any conclusions regarding trends.
There are no published data on estimates of area loss
or degradation from the East African region’”*". At
present, there are insufficient data for even a crude
estimate.

ESTIMATED COVERAGE

There are very few area estimates for seagrasses in
this region. Distribution maps of seagrasses are only
available for Mida Creek, Gazi Bay, Diani-Chale Lagoon
and Chwaka Bay. The recent UNEP Atlas of Coastal
Resources shows that seagrass beds occur throughout
the 600-km-long Kenyan coastline in sheltered tidal
flats, lagoons and creeks, with the exception of the
coastal stretch adjoining the Tana Delta’. The testing of
a remote-sensing methodology for seagrass mapping
in southern Kenya estimated the net area of vegetation
cover to be approximately 33.63 km’ within a stretch of
around 50 km of coastline’. Ground-truthing revealed
that most of these areas were dominated by pure
stands of Thalassodendron ciliatum.

Chwaka Bay on the eastern side of Unguja Island
(Zanzibar), which covers more than 100 km’, has
extensive mixed seaweed-seagrass areas, with
seagrasses representing between 50 and 80 percent of
the macroflora biomass”. In Gazi Bay, which covers
approximately 15 km’, seagrass beds cover an area of
approximately 8 km? from the lower margin of the
mangrove forest through the intertidal and subtidal
flats up to the fringing reef, with the exception of a few
sandy patches”. The Diani-Chale Lagoon along the
Kenyan coast measures roughly 6 km* with seagrass
beds covering up to 75 percent’. The Nyali-Shanzu-
Bamburi Lagoon, with a total area of approximately 20
km’, is 60 percent covered by seagrass beds”.

At present, there are insufficient data for even a
“best guess” of total seagrass coverage in Kenya and
Tanzania, but new mapping data are expected to
become available from a recently started regional
seagrass research project under the Marine Science for
Management Programme (MASMA)].

THREATS

The lack of a true continental shelf, stretching out no
more than a few kilometers from the Kenyan and
Tanzanian shores, makes the coastal resources all the
more vulnerable to overexploitation and influences
from activities on land'”’. In general, seagrasses
appear to have experienced fewer direct negative
impacts than mangroves or coral reefs in the region,
but this may merely reflect the lack of any reliable
(quantitative) data. Deepening of channels for ships at
harbors results in uprooting and burial of seagrass
plants by dredge-spoil™.

Several beaches and adjacent coastal areas in
Kenya and Zanzibar are under increasing pressure
from expanding tourism development®”. High hotel
density in close proximity to the beach is common”.
Seagrass beds are locally damaged by motor boat
propellers and anchoring in the waters near these
highly intensive tourist areas'“’. While mooring buoys

have been deployed within the marine park to protect
the coral reef, the seagrass beds remain unguarded. In
some areas very popular with tourists stretches of
seagrass meadow (deemed a nuisance to swimmers]
are cleared by cutting and/or uprooting’™’. In addition,
the cumulative effects of raking, burying and removing
seagrass beach cast material may have negative
impacts on the functioning of the adjacent seagrass
meadows”.

Direct destruction of seagrass vegetation occurs
by trawling activities. Commercial trawlers operating in
the Rufiji Delta, Mtwara and coastal areas between
Bagamoyo and Tanga (Tanzania), as well as Ungwana
Bay in Kenya {where they reportedly have a fishing
effort well beyond the potential sustainable yield’, are
non-selective and are destructive to the seabed. Illegal
trawling - even during the closed season - occurs in
Bagamoyo, Tanzania, where up to 80 percent of prawn
bycatch is seagrass”. Trawling has also been reported
as a major cause of mortality of the green turtle along
the Kenyan coast"”.. Artisanal fishermen often connect
separate navigable channels by digging through
intertidal flats in order to make way for their canoes,
causing damage to seagrass, albeit at a small scale’.
Overfishing could pose a likely threat to seagrass
communities, as has been reported for the coral reefs
in this region®”, although there are no direct reports to
confirm this.

Recent agricultural activities in the Sabaki
catchment have resulted in accelerated soil erosion
and a tremendous increase in river sediments from
some 58000 tons/year in 1960 up to as much as 7-14
million metric tons/year at present”. Considerable
amounts of sediment brought down by the river to the
coral reefs and seagrass beds have been implicated in
the low seagrass species composition at Mambrui'™’.
The apparent absence of seagrass beds in Ungwana
Bay and northern Rufiji Delta’: ’! might also be related
to siltation by the Tana and Rufiji Rivers, but no studies
have been conducted here.

Oil pollution is one of the potential threats to
seagrasses in East Africa owing to spillage of crude oil
in harbors and the risk posed by a large fleet [over 200
oil tankers per day) from the Middle East across the
coastal waters. There have been no major oil spills to
date, except in 1988 when 5000 metric tons from a
pierced fuel tank in Mombasa destroyed a nearby area
of mangroves and associated biotopes. The seagrass
species Halophila stipulacea and Halodule wrightii
have not reappeared at the site since the spill™!. In
Tanzania, oil pollution along the coast - though not
severe - is heaviest during the southwest monsoon""!
The extent and specific effects of oil pollution on
seagrass ecosystems in East Africa's largest harbors,
Kilindini and Dar es Salaam, especially in creeks and

Kenya and Tanzania

Impacts of tourism industry on seagrasses. Seagrass cover has
declined in front of a Mombasa north coast beach hotel

sheltered lagoons, may be high but remain uninves-
tigated to date.

Increasing populations in coastal towns and
cities, such as Mombasa, Malindi and Dar es Salaam,
present a potential (but localized) threat to the coastal
seagrass resources from domestic solid waste, sewage
disposal and dredge spoil dumping, all of which are
responsible for the declining water quality”. Seasonal
blooming of Enteromorpha and Ulva species occurs
locally, especially in areas close to sewage discharge
points from hotel establishments and municipal
sewage”), Although low organic loading is a feature
of the well-flushed lagoon system, eutrophic conditions
and high bacterial contamination in the sheltered and
semi-enclosed creeks have been reported’.
Significant heavy metal pollution from urban and
industrial effluents has been reported in coastal waters
around Dar es Salaam", affecting edible shellfish
populations’. Reclamation of tidal flats, such as
proposed by the Selander Bridge coastal waterfront
reclamation project in Dar es Salaam, constitutes
another potential threat to seagrass ecosystems.

The expanding open-water mariculture farms of
the seaweed Eucheuma spinosa currently cover around
1000 ha of intertidal area on Zanzibar (Tanzania). The
various adverse effects that seaweed farming has on
intertidal areas could well mar the positive picture of its
socioeconomic benefits to coastal people. A marked
decline in seagrass cover from physical clearing of
seagrass vegetation by seaweed farmers has been
reported’. Seaweed farming areas on Zanzibar appear

Photo: PL.A. Erftemeijer

WORLD ATLAS OF SEAGRASSES

Case Study 7.2

A NUISANCE OR A VITAL LINK?

The Mombasa Marine National Park and Reserve
(Kenya] encompasses a major part of the Nyali-
Shanzu-Bamburi Lagoon (20 km’) which has a
maximum depth of 6 m. It is bordered by white
sandy beaches on the landward and a fringing reef
on the seaward sides. Mixed seagrass com-
munities (dominated by Thalassodendron
ciliatum) and associated seaweeds cover 60
percent of the lagoon, which Is typical for most of
such lagoons along the Kenyan coast. Turbulent
water motion (exposure) in these areas is relatively
high compared with the sheltered creeks and bays
and, due to hydrodynamic forcing, the spatial and
temporal concentrations of nutrients and chloro-
phyll a do not reach eutrophic levels because the
lagoon is well flushed.

Large banks of macrophytes, 88 percent of
which is seagrass, are deposited on the beaches
(beach cast] as the plants become detached from
the sea bottom by the surge effect from waves.
This phenomenon is seasonal and controlled by
tides and monsoon winds'” “!. The most intense
accumulations - as much as 1.2 million kg dry
weight along a 9.5-km stretch of beach - are
washed ashore during the southeast monsoons
when wind and current speeds, water column
mixing and wave height are usually greatest’.

The Mombasa Marine Park is “fenced” by a

to have a lower abundance of meio- and macrobenthos
than unvegetated sandy areas, and may cause declining
seagrass productivity due to shading’*°”!.

POLICY RESPONSES

Kenya has been one of the most active countries in
marine conservation in Africa. The first marine
protected area was gazetted as early as 1968. Kenya's
guidelines for establishing parks and reserves,
safeguarding marine ecosystems and preserving rare
species have been adopted from the United Nations
Environment Programme's (UNEP’s) Action Plan for
the East African Regional Seas Programme".

There are no existing management practices to
protect existing seagrass beds from overexploitation or
pollution per se. However, concern for the marine
environment is demonstrated by the establishment of
six marine protected areas covering a total area of 850
km? while an additional marine reserve has been
proposed. All protected areas are under the

SEAGRASS BEACH CAST AT MOMBASA MARINE PARK, KENYA:

stretch of about 30 hotels, whose guests enjoy the
white sandy beaches and other water sports
within a stone's throw of their rooms. Although the
beach cast phenomenon is seasonal and only
peaks during the low season, the burgeoning
tourism industry in this area considers it a
nuisance and would prefer its removal. Some of
the hotels employ staff to rake the seagrass
material from the beach in the immediate vicinity
of the hotel and bury it under the sand. A detailed
study on the beach cast phenomenon showed that
burying the material does not significantly affect
decomposition rates’.

The same study, however, also pointed to the
role of seagrass beach cast in contributing to
beach stability. By filtering out wave action, the
beach cast material can reduce erosion of
beaches caused by swash/backwash processes.
The beach cast material may also reduce beach
erosion due to wind. Furthermore, the cumulative
effects of removing seagrass beach cast may
intensify beach erosion either through the export
of sand in the process or the loosening up of
compact sand, or through removal of the
protecting material that slows wave action. The
potential rate of beach erosion in this study was
estimated at 492450 kg of beach sand (per
removal) if beach cast material at any given

custodianship of the Kenya Wildlife Service, a well-
equipped parastatal organization that has received
much donor support. Most, if not all, of the marine
protected areas in Kenya contain seagrass beds, but
detailed distribution maps of seagrasses in these
protected areas are not available.

In addition, several legal and administrative
instruments address aspects related to the protection
and management of marine protected areas and thus
(indirectly) of seagrass ecosystems. These include the
protection of wildlife species, regulation of fisheries,
land planning and coastal developments, research and
tourism. Dugongs and turtles are both listed as
“protected animals” under the Wildlife Conservation
and Management Act and various initiatives for their
conservation have been implemented. By working
closely with respective local authorities, the Kenya
Wildlife Service may avoid approval of activities that
could impact negatively on marine parks, as provided
for under the Land Planning (1968) and the Physical

moment was removed from the entire beach (9.5-
km stretch]

The total annual deposition of seagrass
beach cast was estimated to be in the order of 6.8
million kg dry weight, indicating that about 19
percent of the annual production of seagrass
meadows [14.7 million kg carbon/year) in the

lagoon passes through the beach, where
decomposition is accelerated through exposure to
oxygen availability, drying and vigorous

fragmentation by wave action'”. These processes
speed up the release of dissolved nutrients and
particles back into the adjacent ecosystems and
thus contribute to the detrital or energy pathways
The material was further found to contain over
23000 amphipods/m?, 3100 isopods/m? and
various other faunal groups, providing an
important food source for fishes during high tide
The role of seagrass beach cast accumulations in
nutrient regeneration processes and beach
stability, and as nursery sites and a source of food
for fish, crabs and shorebirds in the nearshore
zone, is thus highly significant. Removing
seagrass beach cast, though desirable for
tourism, would have negative impacts on the
health and functioning of adjacent seagrass beds,
on which artisanal fisheries and tourism itself rely.

Seagrass beach cast in Mombasa Marine National Park, 1995 -
significant amounts of seagrass litter are washed up
on the Kenyan beaches with each tide

Planning [1996] Acts. Efforts are being made to
encourage environmentally sensitive tourism as one of
the measures to achieve protection goals. A draft
national strategy for sea turtle conservation is currently
under review while seagrasses have been considered in
the most recent management plan of the Mombasa
Marine National Park and Reserve.

Outside marine protected areas, however,
management and control over the exploitation of coastal
and marine resources are virtually non-existent.
Conservation of coastal and marine systems has
concentrated its attention on either tourism-related or
directly exploitable marine resources such as shells and
coral reefs. Therefore it would seem that the important
functions of seagrass beds related to fisheries nursery
grounds, or to marine primary production, their
contribution to energy pathways [involving a diversity of
organisms], or linkages with land-based activities are
not at the top of the conservation agenda.

Since the recommendations to establish marine

Kenya and Tanzania

Photo: P.LA. Erftemeijer

(69)

protected areas in Tanzania’”, the first two marine
parks, of which seagrass ecosystems are part, were
only recently gazetted in 1995. Despite considerable
effort, the management of protected areas in Tanzania,
as in many developing countries, suffers from
insufficient capacity and law enforcement. One of the
stated objectives of the National Fisheries Policy and
Strategy, provided for by the Fisheries Act (1970), is to
protect the productivity and biological diversity of
coastal and aquatic ecosystems by preventing habitat
destruction, pollution and overexploitation.

Tanzania's Coastal Management Partnership,
whose goal is to establish a foundation for effective
coastal zone governance, has produced the first
national programme for Integrated Coastal Manage-
ment. Among the first outputs of this program are a
State of the Coast Report, a National Mariculture Issue
Profile, guidelines and a conflict resolution forum
dealing with such issues as trawling and dynamite
fishing. A draft national Integrated Coastal Manage-

WORLD ATLAS OF SEAGRASSES

ment Strategy is awaiting government approval. These
initiatives and, more so, the process have raised the
profile and level of understanding of the importance of
coastal and marine resources, including seagrass
beds. Implementation of integrated coastal zone
management initiatives in Tanzania is currently under
way in Tanga (by IUCN-The World Conservation Union),
Zanzibar (Menai Bay Conservation Project], Mafia

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N
\
& VR

8 The seagrasses of

Mozambique and southeastern Africa

MOZAMBIQUE AND
SOUTHEASTERN AFRICA

and 12 in the remaining southeastern African

region. Madagascar has nine common species.
Five species occur in South Africa, seven in Mauritius
and up to ten in Comoros and Seychelles!" **. Ruppia
maritima, recently defined as a seagrass, is also a
dominant species in the southeastern Africa region.

[oe seagrass species occur in Mozambique

BIOGEOGRAPHY

Mozambique

The Mozambican coast can be divided into three
regions: a sandy coastline from the southern end of the
country to the Save River; an estuarine coastline from
the Save River up to around 500 km north of the
Zambezi River; and a rocky limestone coastline,
typically surrounded by coral reefs, which runs from
the Zambezia province up to the northern end of the
country, and also covers the Tanzanian and Kenyan
coasts’). Seagrasses abound in the sandy and
limestone areas.

Seagrasses in general occur in mixed seagrass
stands, especially in intertidal areas. The three
dominant mixed-seagrass communities on the sandy
substrates of southern Mozambique consist of
combinations of Thalassia hemprichii, Halodule
wrightii, Zostera capensis, Thalassodendron ciliatum
and Cymodocea serrulata”’.

In contrast, the seagrass communities of the
more northerly limestone areas are quite different, with
seagrasses tending to occur intermingled with
seaweed species”. Here, the dominant botanical
communities also include Thalassia hemprichii and
Halodule wrightii, but species such as Gracilaria
salicornia, Halimeda spp. and Laurencia papillosa
occur mixed with Thalassia hemprichii, and Sargassum
spp. with Thalassodendron ciliatum. Elsewhere
Zostera capensis and Halodule wrightii also form
mixed beds.

In general Thalassodendron ciliatum and

S.0. Bandeira
F. Gell

Thalassia hemprichii are the dominant subtidal sea-
grass species in Mozambique. A detailed comparison
has been made of the former growing along the rocky
and sandy coasts of southern Mozambique”. Leaves
appear to grow faster on plants in the rocky areas (20-
26 g/m’/day and up to 57 mm/‘/day) than in sandy (8-10
g/m*/day and up to 22 mm’/day). Leaf biomass in rocky
areas is more than twice that of sandy (258 g/m? and
124 g/m’ respectively) and beds are characterized by a
much higher shoot density (4561 shoots/m* and 888
shoots/m* respectively).

The underground biomass of Thalassodendron
ciliatum is presumably relatively high in sandy
environments because total biomass (862 g/m’], while
significantly lower than in the rocky seagrass beds
(1070 g/m}, is comparable. Although possibly slower
growing, the Thalassodendron ciliatum plants in the
sandy habitat have wider (1.4 cm +0.1) and longer
(12.51 cm +0.6) leaves than in the rocky habitat (0.7 cm
+0.1 and 8.2 +0.5 respectively). The biomass of
epiphytes on Thalassodendron ciliatum plants is an
order of magnitude higher in the rock (512 g/m’) than in
the sand (40 g/m’), and consequently these organisms
account for nearly half (48 percent) of the combined
seagrass and epiphyte biomass, compared with just 5
percent in the southern sandy-bottom beds.

Enhalus acoroides, Halophila stipulacea and
Halophila minor are found only in northern
Mozambique while pure stands of Zostera capensis are
found only in the south”. Pioneer species observed in
Mozambique include Halodule wrightii, Halophila
ovalis and Cymodocea serrulata. The first two species
act as pioneers in exposed sandy areas close to the
coastline, whereas Cymodocea serrulata is a pioneer in
silted channels.

South Africa
Zostera capensis is most widespread and one of the
dominant seagrass species in South Africa. It occurs

94 WORLD ATLAS OF SEAGRASSES

* Quirimba Archipelagd O° S)
COMOROS
re -

¢
.
MOZAMBIQUE, Montepuc= Bay

+
Fernao .
Lum Veloso J

‘ Goa

ZIMBABWE red MADAGASCAR

Mozambique
Channel

qinhassoro
BOTSWANA ;

Bazaruto |
Inhambane Bay

Maputo Bay. «®%
Ne Xai-Xai

of Inhaca Island
?

°
® Kwazulu-Natal

INDIAN OCEAN

0 200 400 600 800 1000 Kilometers
40

Map 8.1
Mozambique and southeastern Africa

INDIAN OCEAN

SEYCHELLES
Praslin

La Digue

yevchelle
SiJhouette Seychelles Bank

=?
e Anse aux Pins

Mahé

45 Kilometers

Map 8.2
The Seychelles

® Poudre d'Or

Poste Lafayette

INDIAN
OCEAN

MAURITIUS

10 15 20 25 Kilometers
98° E

Map 8.3
Mauritius

Table 8.1

Area cover and location for the seagrass Zostera capensis in

South Africa

Estuary
name

St Lucia
Mbashe
Mlalazi
Mngazana
Mtakatye
Xora
Knysna
Klein
Swartvlei
Keiskamma
Keurbooms
Krom Oos
Qora
Swartkops
Hartenbos
Kabeljous
Ngqusi\Inxaxo

Area
{km’)
1.81
0.01
0.04
0.02
0.04
0.01
3.48
0.37
0.23
0.12
0.64
0.02
0.08
0.16
0.01
0.02
0.01

Climate

Subtropical
Subtropical
Subtropical
Subtropical
Subtropical
Subtropical
Warm temperate
Warm temperate
Warm temperate
Warm temperate
Warm temperate
Warm temperate
Warm temperate
Warm temperate
Warm temperate
Warm temperate
Warm temperate

Estuary
classification
Estuarine lake
Permanently open
Permanently open
Permanently open
Permanently open
Permanently open
Estuarine bay
Estuarine lake
Estuarine lake
Permanently open
Permanently open
Permanently open
Permanently open
Permanently open
Temporarily closed
Temporarily closed
Temporarily closed

Total 7.07

(12)

Source: Colloty

mostly in estuarine waters along a number of estuaries
from Kwazulu-Natal to the western Cape region.

Another important location with seagrass
species is found off Kwazulu-Natal. Here, a number of
rocky protuberances into the sea are mostly
dominated by Thalassodendron ciliatum adapted to
live in rocky habitat together with seaweeds". These
rocky areas generally experience strong water
dynamics and winds similar to those of southern
Mozambique".

The distribution of Zostera capensis in southeast
South Africa is well recorded. It grows in 17 estuaries
(Table 8.1]. Individual beds are small, generally only a
few hectares, and the total area covered by seagrass is
about 7 km’.

Madagascar

Little is known about the relative dominance
of seagrass species in Madagascar although it is
likely that in the southwest of the country they are
similar to the species from the limestone areas of
Mozambique, with most of the meadows being domin-
ated by Thalassodendron ciliatum and Thalassia
hemprichii. Seaweeds are also a common feature in
the intertidal and subtidal seagrass areas of
Madagascar”.

Mauritius

Thalassodendron ciliatum, Halodule uninervis and
Syringodium isoetifolium appear to be the most
common seagrass species in Mauritius’.

Comoros

Little is known about the seagrass meadows of
Comoros. Being located less than 400 km east of the
coastline of Mozambique and sharing a similar climate,
Comoros may have similar meadows to northern
Mozambique with mixed seagrass species in intertidal
areas and subtidal seagrass species dominated by
broad-leaved species such as Thalassodendron
ciliatum.

Seychelles

Seychelles is composed of 115 granite and coral
islands. Seagrass meadows are dominated by
Cymodocea serrulata. Syringodium isoetifolium and
Thalassia hemprichii occur at Anse aux Pins”! on the
main island of Mahé. Shoot density varies from 1093 to
1107 shoots/m’ in Cymodocea serrulata plants, 1123 to
1761 in Syringodium isoetifolium and 540 to 627 in
Thalassia hemprichii*. Thalassodendron ciliatum is
also common in subtidal areas down to depths of 33 m
throughout the Seychelles!”

SEAGRASS FISHERIES IN MOZAMBIQUE

The Quirimba Archipelago is a chain of 32 islands off
the coast of northern Mozambique, running from north
of the town of Pemba up to the Tanzanian border. One of
the largest and most populated islands in the chain is
Quirimba. Quirimba is 6 km long by 2 km wide and has
a population of 3000. This island is separated from the
mainland by the Montepuez Bay. The island’s main
fishery is located in the shallow seagrass beds of the
bay, and this seagrass fishery is the main source of
income and protein for people on the island. In 1996
and 1997 part of the Darwin/Frontier Quirimba
Archipelago Marine Research Programme studied the
Quirimba fishery which is dependent on a diverse
seagrass ecosystem!"

Montepuez Bay is between 1 and 10 m deep and
has extensive intertidal flats and banks, large areas of
which are covered in seagrass. The bay takes its name
from the Montepuez River, which enters the southwest
of the bay from the Mozambique mainland. Ten species
of seagrass are present in the bay: Enhalus acoroides,
Thalassodendron ciliatum, Cymodocea rotundata,
Cymodocea serrulata, Syringodium isoetifolium,
Halodule uninervis, Halodule wrightii, Halophila ovalis,
Halophila stipulacea and Thalassia hemprichii.

The intertidal seagrass beds are dominated by
Thalassia hemprichii. Subtidally, the most abundant
species are Enhalus acoroides and Thalassodendron

Mozambique and southeastern Africa

ciliatum, both of which can grow to over 1 m in height,
and the smaller species Cymodocea rotundata and
Cymodocea serrulata. Small seagrass species (e.g.
Syringodium isoetifolium, Halophila spp. and
Halodule spp.) are present in small quantities, often
forming an understorey in stands of larger species. In
quadrat surveys of the Montepuez Bay seagrass beds,
the most common seagrass types were stands
dominated by Enhalus acoroides. The most common
combination of seagrasses found was Enhalus
acoroides with Halophila ovalis, which were mainly
found together in areas that were exposed to the air at
very low tides.

Such a predominance of Enhalus acoroides is
unusual in the region and, even within the Quirimba
Archipelago which has extensive seagrass beds,
Montepuez Bay was the only area dominated by
Enhalus acoroides. Other subtidal seagrass beds in the
Quirimba Archipelago were dominated by Thalasso-
dendron ciliatum. Dense meadows of tall [often
between 50 and 100 cm) Enhalus acoroides were home
to a diverse range of invertebrates and fish, and the
seagrass itself was covered in epiphytes, altogether
constituting a complex habitat. Over 30 species of algae
were identified living on or in association with the
seagrass'”. Fishers in Montepuez Bay target shallow
areas of Enhalus acoroides for their main fishing
activities, whilst women collect invertebrates in the
intertidal seagrass beds dominated by Thalassia
hemprichii. Although the direct use of seagrass plants
has been reported from other places, this was not
observed in the Quirimba Archipelago.

Fishing methods

Seine nets were set from small sail-powered boats by
teams of between five and 12 men. Fishermen in the
water kept the net in place and drove the fish into the net
as it was hauled into the boat. Seine net fishing was
carried out in shallow water, from 1 to 8 meters deep, in
areas of Enhalus acoroides. The nets used were
approximately 100 m in length with a main mesh size of
4 cm stretch and a cod-end of 2 cm stretch, or less. The
mean duration of a fishing trip was about five hours and
the mean catch per trip was 75 kg. Catch per unit effort
was 3.6 kg of fish per man-hour spent fishing or 2 kg of
fish per man-hour spent at sea. The net catches were
highly diverse, with a total of 249 fish species in 62
families identified from more than 46 600 fish sampled’.
The fishers also caught invertebrates in the seine nets,
particularly squid. Approximately 30 fish species were
common in the catch. The most important species in the
net fishery in terms of weight were the African
whitespotted rabbitfish Siganus sutor (24 percent); the
pink ear emperor Lethrinus lentjan (12.2 percent); the
seagrass parrotfish Leptoscarus vaigiensis (11 percent);

=—

WORLD ATLAS OF SEAGRASSES

A marema fish trap in an Enhalus acoroides bed, Mozambique

the variegated emperor Lethrinus variegatus (7.4
percent); the blacktip mojarra Gerres oyena (6.3 percent]
and the spinytooth parrotfish Calotomus spinidens (3.2
percent). The majority of fish caught in seine nets were

Case Study 8.1

Seagrasses at Inhaca Island and Maputo Bay area
cover more than 80 km’. At Inhaca Island the
seagrasses alone cover around 50 percent of the
entire intertidal area”. The diversity of seagrasses is
very high, especially at Inhaca Island where eight
seagrasses species can be found in just one
hectare”. Nine seagrass species have been
identified in the area namely: Cymodocea rotundata,
Cymodocea serrulata, Halodule uninervis, Halodule
wrightii, Halophila ovalis, Syringodium isoetifolium,
Thalassia hemprichii, Thalassodendron ciliatum and
Zostera capensis”. These seagrass species are
grouped in three main dominant seagrass com-
munities: Thalassodendron ciliatum/Cymodocea
serrulata, Thalassia hemprichli/Halodule wrightii
and Zostera capensis”™'. Zostera capensis shoot
density is higher at Inhaca (2880 shoots/m/) than at
Maputo Bay [1285 shoots/m’) as are leaf, rhizome
and root biomass?”

The species Thalassia hemprichii and
Thalassodendron ciliatum tend to occupy deeper
areas far from the coastline whereas Halodule
wrightii and Cymodocea serrulata tend to occupy
shallow areas closer in. Thalassodendron ciliatum,

less than 15 cm long and many were juveniles. Virtually
all the fish caught in the seine net fishery were eaten.
Amongst the more unusual food species that were
common in the fishery were the tailspot goby
Amblygobius albimaculatus and the three-ribbon
wrasse Stethojulis strigiventer.

The traps used in Montepuez Bay are known
locally as marema. They are of an arrowhead design
and constructed from woven bamboo panels secured
together with palm fibers. Marema were set by
fishermen from outrigger canoes in shallow areas of
Enhalus acoroides at low tide, and were hauled the
following day at low tide. The traps were sometimes
baited with crushed TJerebralia snails collected from
mangrove areas, or with squid, but often the traps were
not baited at all. The traps were weighed down with
stones and placed amongst long, densely growing
Enhalus acoroides (the fishermen said that this
seagrass was very important for keeping the traps in
place in the strong tidal currents]. The mean daily catch
for a fisherman setting 40 traps was nearly 7 kg of fish,
although catches could be as high as 27 kg per trip.
The catch per unit effort for the trap fishery was 2.2 kg
of fish per hour spent fishing and the mean catch for a
trap set for 24 hours was 0.2 kg of fish. Trap catches

INHACA ISLAND AND MAPUTO BAY AREA, SOUTHERN MOZAMBIQUE

in the subtidal fringe, occurs in homogeneous stands
except in some areas where it is also accompanied
by a band of Syringodium isoetifolium parallel to the
coastline. When Thalassia hemprichii and Halodule
wrightii co-occur in mixed species communities,
Thalassia hemprichii is found in small depressions
whereas Halodule wrightii occupies elevated areas
which are exposed at low spring tides.

Seagrass meadows in Maputo Bay region are
widely used by the people who collect, by hand,
seafood from them, the most common being
mussels {Anadara natalensis, Cardium flavum,
Modiolus phillipinarum), oysters (Pinctada capensis),
gastropods (Conus betulinus, Strombus gibberulus)
and sea urchins le.g. Salmacis bicolores,
Tripneustes gratilla). They also use the meadows for
fishing using traditional techniques, for species such
as Crenidens crenidens, Gerres acinaces,
Leiognathus equulus, Lithognathus aureti, Liza
macrolepis, Lutjanus fulviflamma, Platycephalus
indicus, Pseudorhombus arsius, Rhabdosargus
sarba, Scarus ghobban, Siganus sutor and Terapon
Jarbua, and crustaceans such as Matuta lunaris and
Portunus pelagicus®*“*!. The sea cucumber

were dominated by the parrotfish Leptoscarus
vaigiensis, which accounted for over 74 percent of the
fish caught by weight. Other important species included
the parrotfish Calotomus spinidens (5 percent by
weight], the rabbitfish Siganus sutor (4 percent), the
dash-dot goatfish Parupeneus barberinus (4 percent),
the blackspot snapper Lutjanus fulviflamma (3 percent]
and the flagfin wrasse Pteragogus flagellifera (2.5
percent]. A total of 61 species of fish were identified
from 3500 fish sampled from the trap fishery, with
about 16 of these species appearing commonly in the
fishery. A wide variety of invertebrates entered the
traps, including swimming crabs (Portunidae) which
were kept for use as food.

Spatially referenced catch data from the seine net
fishery was used to identify the fishing sites in
Montepuez Bay with the highest mean fish catch per
unit effort. These were also the sites with the highest
mean percentage cover of seagrass and highest
seagrass biomass. This suggests that seagrass cover
and biomass may influence fish biomass and fishery
productivity. In experimental trap fishing, the prefer-
ence of trap fishermen for areas of Enhalus acoroides
to other species of seagrass was shown to be well
founded. In these experiments the mean catch per trap

Holothuria scabra, presently endangered in many
parts of the country, was earlier heavily collected by
the local people at Inhaca and north of Maputo city
and sold for export to Asia. The same is true of
Holothuria atra, but to a lesser extent.

More than 20 nets are set daily around Inhaca
Island from boats and by people walking on the
beach, and around 100 people may be seen collecting
edible organisms during the spring low tides”. To the
north of Maputo city, at the fishing village of Bairro
dos Pescadores, close to 50 people dug up seagrass
meadows at spring low tide for collection of
invertebrates, mainly bivalves, in the mid-1990s".
Recent counting estimated around 200 people
involved in this activity, which includes digging the
intertidal areas for the same purpose. Seagrasses
have also been reported as being used for alluring
and bewitching at Inhaca Island” and the dried
detached leaves of Thalassodendron ciliatum as
being used to fill pillows.

The seagrasses of the area are under consider-
able stress from a variety of sources. Sewage
disposal along the Maputo coastline threatens sea-
grasses there, with polluted areas tending to be
covered by seaweeds Ulva spp. and Enteromorpha
spp. instead of seagrass. Additional pollution,
especially oil spills, comes from the city harbor and

Mozambique and southeastern Africa

for Enhalus acoroides greatly exceeded that for other
common seagrass species, Thalassodendron ciliatum
or Cymodocea spp. Catch compositions from the three
different seagrass species were also different. Catches
from Enhalus acoroides beds were dominated by the
parrotfish Leptoscarus vaigiensis as the fishermen’s
catches were, but catches from Thalassodendron
ciliatum beds were dominated by the file fish
Paramonacanthus barnardi, and catches from
Cymodocea spp. by the snapper Lutjanus fulviflamma.

Invertebrate fishery

Women did most of the collecting of seagrass inver-
tebrates that could be achieved without a boat. They
walked out over the seagrass beds at low tides and
collected bivalves by hand. On spring tides, some women
traveled in groups by boat to some of the larger banks in
the bay that become exposed at low tide.
The main species they collected were the ark shell
Barbatia fusca and the pinna shell Pinna muricata, found
in sand in seagrass beds, and the oyster Pinctada nigra
which grows on the seagrass plant itself. These shellfish
were dried and most of them were sold on the mainland
for higher prices than they would fetch on the island,
particularly the pinna shell which is a local delicacy”.

industrial area. Sedimentation due to erosion and
floods further diminishes local seagrass coverage
around Maputo. Trampling and the heavy concen-
tration of fishing and tourist activities directly disturb
seagrass meadows at Inhaca Island's main village.
Fishing in very shallow water is another disturbance.
The combination of all these factors places heavy
pressures on the extensive seagrass meadows, and
has already caused a disappearance of Zostera
capensis from in front of Inhaca’s main village”.
Some priority areas for intervention to reduce
these disturbances include increased monitoring
and reduction of sewage disposal, industrial pollu-
tants and port activities. At Inhaca Island, only the
seagrass beds located close to coral reefs are under
protection. This protection should be reviewed to
target the conservation of seagrass areas with a high
concentration of threatened and depleted in-
vertebrate species such as holothurians and
seastars, e.g. Holothuria scabra and Holothuria atra.
The Thalassodendron ciliatum communities occur-
ring in rocky protuberances in the sea habitats have
only recently been described. This form of seagrass
only occurs in sandstone rocks facing the strong
waves of the Indian Ocean"! Few similar areas exist
in Mozambique and therefore some kind of pro-
tection should be put in place for their conservation.

*}
TEN

WORLD ATLAS OF SEAGRASSES

Some fishermen went out on the seagrass beds
in small canoes to dive with a mask to collect
invertebrates, mainly sea cucumbers, and mollusks
such as the tulip shell Pleuroploca trapezium and the
murex Chicoreus ramosus. Sea cucumbers were one
of the more valuable seagrass residents and were
dried and sold across the border in Tanzania, to be
exported to markets in the Far East. During the study
period fishermen reported the virtual disappearance
of sea cucumbers from the seagrass beds of
Montepuez Bay, and attributed this to overexploitation
by local and itinerant fishers. Fishermen involved in
the seine net and trap fishery would also collect
murex, tulip shells and sea cucumbers when they got
the opportunity. Tulip shells were collected for their
opercula which were sold to traders in Tanzania.
Murex were eaten and the shells of these and other
mollusks were collected and burnt for lime that was
used locally in building.

Subtidal surveys identified 34 species of large
invertebrates which were associated with the seagrass
beds. Commonly observed invertebrates that were not
collected locally included the sea urchins Diadema
setosum and Tripneustes gratilla, the sea cucumber
Synapta maculata and the starfish Pentaceraster
tuberculatus and Protoreaster lincki.

Local value of seagrass resources
The seagrass fisheries of Montepuez Bay supported
over 400 fishermen on Quirimba Island alone and many
more in the mainland villages and from other islands in
the vicinity. More than a hundred women from Quirimba
also collected invertebrates in the seagrass beds. In
total over 500 people were involved in the seagrass
fisheries of Quirimba, out of a total population of 3000.
The total fish catch from the 35 km? seagrass beds of
the whole bay was estimated at around 500 metric tons
per year, or 14.3 metric tons per km* per year.
This figure does not include invertebrates, but is still
high compared with many tropical reef and estuarine
fisheries. A minimum estimate for annual invertebrate
collection from seagrass beds around Quirimba was 40
metric tons per year.

In the study period, the fish caught in Montepuez
Bay had an estimated annual saleable value of ca
US$120000, based on prices paid for fish locally. Roughly
half the fish caught was consumed by the fishers and
their families or exchanged for other goods or services.
The other half was dried and traded on the mainland by
the owners of the net fishing boats, or other traders who
buy the surplus from trap fishermen.

Management issues
During the study period the local fishery seemed to
have a relatively low impact on the seagrass beds and

was apparently sustainable. The seine net fishery did
appear to have some negative effects on the seagrass
beds. The nets were often dragged along the bottom
and substantial amounts of seagrass, sponges and
small corals were sometimes brought up with the nets.
Trampling of intertidal seagrass was kept to a
minimum by the use of small paths across the
seagrass that restricted the trampling damage to a
small area. The main threats to the sustainability of the
seagrass fishery came from external sources, mainly
unregulated itinerant fishers and commercial sea
cucumber fishing for international trade. On a larger
scale, potential threats came from upstream activities
in the catchment of the Montepuez River - particularly
deforestation leading to changes in sedimentation
rates.

With so many people relying on the seagrass beds
of Montepuez Bay for their livelihoods, and with the
paucity of alternative employment or sources of
protein, their conservation and sustainable use is vital.
One of the reasons that the resources of the Montepuez
Bay seagrass beds are so widely used is that the habitat
is so accessible, even to those with the most limited
resources. Much of the seagrass can be reached on foot
at low tide, and even the deeper areas are close to
shore and are sheltered from the heavy seas that the
eastern coast of the island is subject to. At the time of
this study Quirimba Island had rich and diverse marine
resources including mangrove forests and extensive
coral reefs on the east coast. However, few fishers
utilized the reef resources because of the difficulties of
accessing the exposed reefs in their traditional fishing
vessels. This issue of the accessibility of seagrass beds
is seen in other places where fishers with small boats,
or on foot, are able to fish in seagrass beds in shallow
sheltered bays or lagoons. A priority for seagrass
research should be to look at how best to manage
open-access, multi-user seagrass systems such as
Montepuez Bay, to ensure their sustainable use, and to
conserve biodiversity. The Quirimba Island seagrass
fishery is a clear, and rare, example of the direct value
of seagrasses to local communities.

HISTORICAL PERSPECTIVES AND LOSS

The digging of Zostera capensis beds to collect bivalves
has dramatically depleted the seagrass cover at Bairro
dos Pescadores {near Maputo, Mozambique] from a
cover of around 60 percent or more to 10 percent or
less in the last ten years (Figure 8.1]. This activity lasts
for the entire spring tide period spanning about 15 days
each month. The bivalves are collected mainly for food.
It is expected that this activity will eventually
completely destroy the Zostera capensis beds at Bairro
dos Pescadores, and that the food security of the local
population will suffer as a consequence.

Photos: S.0. Bandeira

Sedimentation due to floods has buried sea-
grasses in Maputo Bay and Inhassoro. In the heavy
floods in southern Mozambique in 2000 around 24 km’
of seagrasses may have been buried here. Harbor
development, sewage and coastal development in
areas of southern Mozambique have further diminished
seagrass coverage. Heavy concentrations of artisanal
fishing boats in combination with intense trampling in
low tides have also caused reduction of seagrass
species at Inhaca Island.

In Mauritius seagrasses are threatened by the

Figure 8.1
Digging of Zostera capensis meadows at Vila dos Pescadores, near
Maputo city

a. Photo taken in 1994 - hunks of plants being lifted, washed an:
then placed upside down - plant cover is still high.

b. Photo taken in 2002 - plant cover is very low and in most areas
the seagrass has already disappeared.

Mozambique and southeastern Africa

high use of fertilizers in the sugar cane industry, and
specifically by the eutrophication of coastal lagoons
that is caused when they leach into these shallow
contained areas. Seagrass beds are being dredged
and destroyed to provide bathing and skiing areas for
tourists. Sedimentation, sewage disposal and sand
mining are among other threats to Mauritius
seagrasses.

In Anse aux Pins, Seychelles, sedimentation,

Table 8.2
Seagrass cover and area lost in Mozambique

Site name Main seagrass Area Area lost
species (km) {km’}
Quirimba Cr, Cs, Ea, Hm, 45
Archipelago Ho, Hs, Hw, Tc, Th
Mecufi-Pemba Hm, Ho, Hs, Hu, 30
Hw, Si, Tc, Th, Zc
Fernao Veloso Cr, Cs, Ea, Hm,
Ho, Hu, Hw, Si,
Tc, Th
Quissimajulo Th
Relanzapo Tc, Th,
macroalgae
Matibane- Cr, Hw, Tc, Th
Quitagonha
Island
Chocas Mar-
Cabaceira Grande-
Sete Paus Island
Mozambique Cr, Cs, Hm, Ho,
Istand-Lumbo- Hu, Hw, Si,
Cabaceira Pequena Tc, Th, Zc
Goa Island Tc
Inhassoro- Cs, Tc, Th
Bazaruto Island
Inhambane Bay Hw
Xai-Xai Tc, macroalgae
Bilene Rm, Hu
Maputo Bay Ho, Hw, Tc, Th, Zc
Inhaca Island Cr, Cs, Ho, Hu,
Hw, Si, Te, Th, Zc
Inhaca-Ponta Tc, macroalgae
do Ouro
Total 439.04 27.55

Notes: Cr Cymodocea rotundata; Cs Cymodocea serrulata;
Ea Enhalus acoroides; Hm Halophila minor; Ho Halophila ovalis;
Hs Halophila stipulacea; Hu Halodule uninervis; Hw Halodule

wrighti; Rm Ruppia maritima; Si Syringodium isoetifolium;
Tc Thalassodendron ciliatum; Th Thalassia hemprichii;
Zc Zostera capensis.

100

WORLD ATLAS OF SEAGRASSES

salinity and decreased water quality associated with a
river effluent discharge have adversely affected

seagrasses". Flooding in estuaries is the main threat to

the survival of Zostera capensis on the South African
east coast.

Other areas where seagrass cover has been lost
include Pemba, Mozambique Island, Inhambane Bay
and Inhaca Island (Table 8.2). The total known historical
loss of seagrasses in Mozambique is 27.55 km’,
although some of the areas affected by the 2000 floods
have already regained seagrass cover.

In Mauritius, seagrasses have diminished from
areas such as Albion (Halodule uninervis), Poudre
d'Or, Mont Choisy and Poste Lafayette (Syringodium
isoetifolium) though the actual area lost is unknown.
Similarly areas covered by Zostera capensis in
estuaries in Kwazulu-Natal, South Africa, are believed
to have been seriously depleted by periodic heavy
floods"! without measurements being available.
Nothing is known about the loss of seagrass from
Madagascar, Comoros or Seychelles.

REFERENCES

1 Titlyanov E, Cherbadgy |, Kolmakov P [1995]. Daily variations of
primary production and dependence of photosynthesis on
irradiance in seaweeds and seagrass Thalassodendron ciliatum of
the Seychelles Islands. Photosynthetica 31: 101-115.

2 Bandeira SO (2000). Diversity and Ecology of Seagrasses in
Mozambique: Emphasis on Thalassodendron Ciliatum Structure,
Dynamics, Nutrients and Genetic Variability. PhD thesis, Goteborg
University.

3 Ingram JC, Dawson TP [2001]. The impacts of a river effluent on a
coastal seagrass habitat of Mahe, Seychelles. South African
Journal of Botany 67: 483-487.

4 Short FT, Coles RG, Pergent-Martini C [2001]. Global seagrass
distribution. In: Short FT, Coles RG [eds] Seagrass Research
Methods. Elsevier Publishing, Amsterdam. pp 5-30.

5 Hartnoll RG [1976]. The ecology of some rocky shores in tropical
East Africa. Estuaries Coastal Marine Science 4: 1-21.

6 Gove DZ [1995]. The coastal zone of Mozambique. In: Lindén 0 (ed)
Workshop and Policy Conference on Integrated Coastal Zone
Management in Eastern Africa including the Island States.
Conference Proceedings. Coastal Management Center (CMC),
Metro Manila. pp 251-273.

7 Bandeira SO [1995]. Marine botanical communities in southern
Mozambique: Sea grass and seaweed diversity and conservation.
Ambio 24: 506-509.

8 Bandeira SO, Antonio CM [1996]. The intertidal distribution of
seagrasses and seaweeds at Mecufi Bay, northern Mozambique. In:
Kuo J, Phillips RC, Walker DI, Kirkman H (eds) Seagrass Biology:
Proceedings of an International Workshop. University of Western
Australia, Nedlands. pp 15-20.

9 Bandeira SO [2002]. Leaf production rates Thalassodendron
ciliatum from rocky and sandy habitats. Aquatic Botany 72: 13-24.

10 Bandeira SO, Bjork M [2001]. Seagrass research in the eastern
Africa region: Emphasis to diversity, ecology and ecophysiology.
South African Journal of Botany 67: 420-425.

11 Barnabas AD [1991]. Thalassodendron ciliatum (Forsk.) den
Hartog: Root structure and histochemistry in relation to apoplastic
transport. Aquatic Botany 40: 129-143.

PRESENT COVERAGE

Mozambique has a total of 439 km’ of seagrasses (Table
8.2]. There are 25 km? around Inhassoro and Bazaruto
Island, 30 km? at Mectifi-Pemba and 45 km’ in the
southern Quirimba Archipelago. The largest seagrass
beds occur at Fernao Veloso, Quirimba and Inhaca-
Ponta do Ouro. Additional inventories are needed,
particularly in remote coastal areas. In South Africa
Zostera capensis covers a total area of just over 7 km’:
other seagrasses species cover smaller areas. While
extensive seagrass meadows do occur in Madagascar,
Mauritius, Comoros and Seychelles, the exact area is
unknown.

AUTHORS

Salomao 0. Bandeira, Department of Biological Sciences, Universidade
Eduardo Mondlane, P.0. Box 257, Maputo, Mozambique. Tel: +258 (0}1
491223. Fax: +258 (0)1 492176. E-mail: sband(@zebra.uem.mz

Fiona Gell, Environment Department, University of York, Heslington, York
Y010 5DD, UK.

12 Colloty BM [2000]. Botanical Importance of Estuaries of the Former
Ciskei/Transkei Region. PhD thesis, University of Port Elizabeth. 202 pp.

13 Rabesandratana RN [1996]. Ecological distribution of seaweeds in

two fringing coral reefs at Toliara (SW of Madagascar). In: Bjork M,

Semesi AK, Pedersen M, Bergman B [eds] Current Trends in

Marine Botanical Research in East African Region. SIDA/SAREC,

Uppsala. pp 141-161.

Dulymamode. Personal communication.

Parnik T, Bil K, Kolmakov P, Titlyanov E [1992]. Photosynthesis of

the seagrass Thalassodendron ciliatum: Leaf anatomy and carbon

metabolism. Photosynthetica 26: 213-223.

Gell FR [1999]. Fish and Fisheries in the Seagrass Beds of the

Quirimba Archipelago, Northern Mozambique. PhD thesis,

University of York.

Whittington MW, Antonio CM, Corrie A, Gell FR [1997]. Technical

Report 3: Central Islands Group - lbo.

Antonio MC. Unpublished data.

Gell FR, Whittington MW [2000]. Diversity of fishes in seagrass beds

in the Quirimba Archipelago, northern Mozambique. Marine and

Freshwater Research 53: 115-121.

20 Barnes DKA, Corrie A, Whittington M, Carvalho MA, Gell FR [1998].
Coastal shellfish resources use in the Quirimba Archipelago,
Mozambique. Journal of Shellfish Research 17(1}: 51-58.

21 Adams JB, Bate GC, O'Callaghan M [1999]. Estuarine primary
producers. In: Allanson BR, Baird D [eds] Estuaries of South Africa.
Cambridge University Press, Cambridge. pp 91-118.

22 Martins ARO, Bandeira, SO [2001]. Biomass and leaf nutrients of
Thalassia hemprichii at Inhaca island, Mozambique. South African
Journal of Botany 67: 439-442.

23 Martins AR [1997]. Distribuicdo, estrutura, dinamica da erva
marinha Zostera capensis e estudo de alguns parametros fisicos
em duas areas da Baia de Maputo. Licenciatura thesis, Eduardo
Mondlane University, Maputo. 49 pp.

24 Kalk M [1995]. A Natural History of Inhaca Island, Mozambique.
Witwatersrand University Press, Johannesburg. 395 pp.

25 de Boer WF, Longomane FA [1996]. The exploitation of intertidal
food resources at Inhaca bay, Mozambique by shorebirds and
humans. Biological Conservation 78: 295-303.

aoe

9 The seagrasses of

INDIA

ndia has coastal wetlands of ca 63 630 km’, mostly

consisting of estuaries, bays, lagoons, brackish

waters, lakes and salt pans'’. The intertidal and
supralittoral shallow sheltered regions of these wet-
lands harbor various marine macrophytic ecosystems
such as seaweed, seagrass, mangrove and other obli-
gate halophytes. Coastal wetland habitats are of a
productive nature, and are of immense ecological and
socioeconomic importance. Marine macrophytes sup-
port various kinds of biota, and produce a considerable
amount of organic matter, a major energy source in the
coastal marine food web; they play a significant role in
nutrient regeneration and shore stabilization processes.

The major seagrass meadows in India exist along
the southeast coast (Gulf of Mannar and Palk Bay) and
in the lagoons of islands from Lakshadweep in the
Arabian Sea to Andaman and Nicobar in the Bay of
Bengal (Table 9.1]. The flora comprises 14 species and
is dominated by Cymodocea rotundata, Cymodocea
serrulata, Thalassia hemprichii, Halodule uninervis,
Halodule pinifolia, Halophila beccarii, Halophila ovata
and Halophila ovalis (Table 9.2). Distribution occurs
from the intertidal zone to a maximum depth of ca
15 m. Maximum growth and biomass occur in the lower
littoral zone to a depth of 2-2.5 m. Greatest species
richness and biomass of seagrass occur mainly in open
marine sandy habitats.

Seagrasses, though one of a predominant and
specialized group of marine flora, are poorly known in
India, compared to other similar ecosystems such as
mangroves. Earlier studies dealt mainly with the
distributional and taxonomic aspects of Indian
seagrasses”. Over the last 20 years, efforts have been
made to understand the community structure and
function of seagrass ecosystems in India“. However,
the structure and function of Indian seagrass
ecosystems remain poorly understood'*'”. Inadequate
information and almost total lack of awareness might
be the reasons for this lack of knowledge in India.

India

T.G. Jagtap
D.S. Komarpant
R. Rodrigues

Surprisingly, seagrasses have not been introduced
even at the level of plant science education programs.
Hence, large number of students, researchers and
coastal zone managers in India may be unaware of the
existence of seagrass ecosystems. Here, we present an
overall account of seagrass habitats from India.

Epiphytes form an important constituent of
seagrass ecosystems in India, though very limited
information is available”'". The floral epiphytes
comprise a few species of marine algae belonging to
Cyanophyceae, Chlorophyceae, Rhodophyceae and
Bacillariophyceae. The Rhodophyceae, particularly
Melobesia sp., occur frequently and are a dominant
part of epiphytic biomass” ". Cyanophycean members
such as species of Microcoleus, Mastogocoleus and
Oscillatoria were observed to be dominant epiphytes.
Ten species of diatoms have been reported on seagrass
blades and roots. The oldest leaves and roots were
found to be more infested and Navicula, Nitzschia and
Pleurosigma form the characteristic diatoms assoc-
iated with seagrasses”. Large numbers of fungi have
also been reported in association with seagrass'”. Nine
species of fungi have been recorded in association with
Thalassia hemprichii in India'“'. Microbial flora actively
mineralize seagrass litter and constitute about 1-3
percent of detrital biomass'’. The epiphytes contribute
7.5-52 percent of total seagrass ecosystem biomass in
shallower (1-3 m] depths. The higher epiphytic biomass
(Figure 9.1b) results mostly from algal genera such as
Melobesia, Hypnea, Ceramium and Centroceros. The
intensity of epiphytization increases with shoot age and
decreases at depths of more than 3 m.

Epifauna mostly consist of protozoans,
nematodes, polychaetes, rotifers, tardigrades, cope-
pods, amphipods and chironomid larvae. Very few
attempts have been made to explore the faunal
diversity of the seagrass beds of India. Harpacticoids,
nauplii and nematodes are rarely found on seagrasses
from India’.

102

WORLD ATLAS OF SEAGRASSES

Most of the algal groups in marine seagrass beds
grow on coral or shell debris, and on seagrass stems
and roots, in their earlier stages. Later stages of these
algae become detached and float in the waters overlying
the meadows. Some 100 species of algae have been re-
ported from seagrass in various regions of India {Table
9.3). The algal flora in general is dominated by Ulva
lactuca, Ulva fasciata, Boodlea composita, Chaeto-
morpha linum, Halimeda spp., Chnoospora implexa,
Chnoospora minima, Dictyota bartayresiana, Dictyota

Table 9.1
Quantitative data for major seagrass beds in Indian waters

Region No. of Biomass Area
species (g dry weight/m’) (km?)

Southeast coast 14 2.5-21.8 30

(Gulf of Mannar

and Palk Bay)

Lakshadweep

group of islands

Nicobar group

of islands

West coast

Notes: - no data available

Source: Various sources’® *2%2")

dichotoma, Dictyota divaricata, Hydoclathrus clathratus,
Gracilaria edulis, Hypnea musciformes, Amphiroa
fragillissima, Amphiroa rigida, Centroceros clavilatum
and Centroceros spp. Coralline algae, particularly
Halimeda spp., contribute substantially to the formation
of sediments suitable for the growth of the seagrasses”.
Most of the associated algal biomass contributes organic
matter to the seagrass environment.

Phytoplankton in the water column over the
seagrass beds largely belong to Bacillariophyceae and
Dinoflagellata; their occurrence is mostly patchy and
the population density remains very low. The
phytoplankton from the seagrass beds of Lakshadweep
was reported to comprise 13 species (Table 9.3},
commonly represented by Achnanthes longipes,
Asterionella japonica, Diploneis weisfloggi, Navicula
hennedyii, Pinnularia sp., and Trichodesmium sp.
Absolutely no information exists on nanoplankton and
picoplankton from the seagrass environment of India.

The regions of India that are colonized by sea-
grasses support rich and diverse fauna! 7". Hard
corals, sea anemones, mollusks, sea cucumbers, star-
fishes and sea urchins are common invertebrates.
Vertebrates such as fish and turtles commonly occur in

seagrass beds; however, Dugong dugon, the marine
mammal ({dugong), has been very rarely reported in
recent years”. The fish fauna is reported to consist of
192 species, dominated by sardine, mullet, eel, cat- and
parrotfishes and grouper™'. The mollusks (143
species}, crustaceans (150 species) and echinoderms
(77 species] are also found in large numbers (Table 9.3).
Mollusks are mostly represented by Acanthopleura
spiniger, Acniaea stellaris, Conus generalis, Cypraea
figris and Nerita costata. There are four species of sea
turtle, with Chelonia mydas and Lepidochelys olevacea
being common.

The biomass and species richness of meiofauna
and macrofauna in general is relatively very high in the
seagrass beds compared to unvegetated areas in the
vicinity". Sediment organic content from seagrass
beds varies from 4 to 13 percent, ten times higher than
the sediments from unvegetated areas.

The textural characteristics of the sediment may
be of great significance in determining density of
seagrass growth. Well-established seagrass meadows
influence mean size, sorting, skewness and shape of the
accumulated sedimentary particles’. The sediments
from seagrass beds of the Lakshadweep Islands show a
significant correlation coefficient (r = 0.85, p<0.05)
between kurtosis and total biomass, indicating
prevalence of a relict environment'™!. This means that
the depositional environment, which developed from
coral reef biota over geological time, is most suitable for
seagrass growth, a concept supported by the occurrence
of major seagrass beds in association with coral reef
regions *:** Halophila beccarii, an estuarine sea-
grass, acts as pioneer species in the succession process
leading to mangrove formation in India’”*. Thus,
seagrasses play a very important role as basic land
builders and shore stabilizers, in a similar way to sand
dunes and mangroves.

BIOGEOGRAPHY

Seagrass habitats are mainly limited to mud flats and
sandy regions from the lower intertidal zone to a depth
of ca 10-15 m along the open shores and in the lagoons
around islands’®. The major seagrass meadows in
India occur along the southeast coast (Gulf of Mannar
and Palk Bay), and a number of islands of
Lakshadweep in the Arabian Sea and of Andaman and
Nicobar in the Bay of Bengal. The largest area (30 km’)
of seagrass occurs along the Gulf of Mannar and Palk
Bay, while it is estimated that ca 1.12 km’ occur in the
lagoons of major islands of Lakshadweep" (Table 9.1).
A total 8.3 km* of seagrass cover has been reported
from the Andaman and Nicobar Islands, a large portion
of which is confined to islands like Teressa, Nancowry,
Katchall and Great Nicobar”. Seagrasses have been
reported to occur in long or broken stretches, or small

Regional map: Africa, West and South Asia

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WORLD ATLAS OF SEAGRASSES

IMPACTS TO SEAGRASS ECOSYSTEMS

Photo: J. Brock

Patch reef in Florida (USA). Dark areas are seagrass meadows. Light areas around the coral heads (25-50 m diameter] are haloes created by
herbivorous fish which live in the corals and graze on the seagrass

Photo: FT. Short

Photo: R. Coles, DPI

Commercial ship aground on a seagrass flat in Australia’s Great Barrier Reef.

Photo: F.T. Short

Seagrass beds on the flats adjacent to an Indonesian community are
Epiphytic algae growing on Zostera marina, Ninigret Pond, being destroyed by boat traffic, fishing activities and waste discharge, in
Rhode Island, USA contrast to the healthy seagrasses across the channel (lower left}

70°E
— Gulf of Kutch

Gulf of
Khambhat

1RABIAN
SEA

Bay of
Bengal

.* Kadmatl %
Lakshadweep Palk Bay
(Laccadive Islands) 2
Kalpeni | “
Pi s SRi 4
0 100 200 300 400 500 Kilometers Mannar® ANA
Cs |
Map 9.1
India

to large patches”’*". The maximum seagrass cover,
abundance and species richness are generally found in
the sandy regions along the seashores, and in the
lagoons of islands, where salinity of overlying waters
remains above 33 psu throughout the year (Table 9.2).
The estuaries, bays, lakes and gulf regions harbor a
limited number of seagrass species in the lower
intertidal mud flats in regions of moderate to high (10-
40 psu) salinity during pre-monsoon (March-June) and
post-monsoon (November-February) periods”. During
the monsoon itself (July-October) the seagrass beds,
particularly estuarine seagrasses, are subject to
freshwater flooding and become silted and decay’.
The new growth of estuarine seagrasses starts during
August-September with a gradual increase in salinity,
and attains maximum growth during November-

December, and May-June”.

PRESENT DISTRIBUTION

The seagrasses of India consist of 14 species belonging
to seven genera (Table 9.2]. The Tamil Nadu ({southeast]
coast harbors all 14 species, while eight and nine
species have been reported from the Lakshadweep and
Andaman-Nicobar groups of islands, respectively. The
mainland east coast supports more species than the
west coast of India. The main seagrasses are Thalassia
hemprichii, _Cymodocea_ rotundata, Cymodocea
serrulata, Halodule uninervis and Halophila ovata.
Species such as Syringodium isoetifolium
and Halophila spp. occur in patches as mixed
species. Meadows are mostly heterospecific. However,

India

North
Andaman

Middle

Andaman #
Andaman

} Islands
Y
Ss

South
Andaman

Little Andaman

1NDAMAN
SEA

Ten Degree Channel

« Car Nicobar

leressa *

a) a
\ ; Camora
eS Nancowry

Nicobar
Islands

Katchall

Little Nicobar

.
Great Nicobar

0 20 40 60 80 100 Kilometers
EL las

Map 9.2
Andaman and Nicobar Islands

from Kalpeni and Kadmat Islands of Lakshadweep,
plant composition is bispecific and monospecific,
respectively'”. Gulf and bay estuaries mostly harbor low
numbers of species, dominated by Halophila beccarii in
the lower intertidal regions, and by Halophila ovalis in
the lowest littoral zones. Enhalus acoroides has
restricted distribution in the mid-intertidal swampy
regions and shallow brackish waters” ''”.

Seagrasses grow from the regularly inundated
intertidal zone to ca 15 m depth in the sandy subtidal
zones". Unlike other species, Halophila beccarii is
found in the upper intertidal. The maximum number
of species and highest biomass usually occur at the

ay,

103

104

WORLD ATLAS OF SEAGRASSES

depth of 1-2.5 m (Figure 9.1]. The biomass of major
seagrass beds has been reported to be significantly
(r = -0.63 and -0.71, p<0.05) correlated with depth” '”.
Thalassia hemprichii, Cymodocea_ rotundata,
Cymodocea serrulata and Halophila ovata are
well adapted to the poor ambient light at greater
depths [>3 m].

Biomass of Indian seagrasses varies from 180 to
720 g wet weight/m’* [see also Table 9.1]. Halodule
uninervis and Cymodocea rotundata in the shallower
depths (0.5-2.5 m), and Thalassia hemprichii and
Cymodocea serrulata from the deeper [>3 m) waters,
are the main contributors to biomass along the
southeast coast (Figure 9.1]. A similar trend of
distribution and abundance was observed from major
seagrass beds of Lakshadweep Islands in the Arabian
Sea". The lower biomass and reduced number of taxa in
seagrasses deeper than 2 m is mainly attributed to
insufficient ambient light. The older plants provide sub-
stratum for colonization by epiphytes, which make a

Table 9.2
Occurrence of seagrasses in coastal states of India

Seagrass sp.

Cymodocea rotundata
Cymodocea serrulata
Enhalus acoroides
Halodule pinifolia
Halodule uninervis
Halodule wrightii
Halophila beccarii
Halophila decipiens
Halophila ovalis
Halophila ovalis var. ramamurtiana
Halophila ovata
Halophila stipulaceae
Syringodium isoetifolium
Thalassia hemprichii
Ruppia maritima

Total no. of species

Status of seagrass ecosystem
Salinity (psu)

Notes:

considerable contribution to total seagrass system
biomass” '”. Biomass of Halophila beccarii is reported
to vary from 4 to 24 g wet weight/m* with a minimum in

the month of August and a maximum in October™.

PRESENT THREATS

The natural causes of seagrass destruction in India are
cyclones, waves, intensive grazing and infestation of
fungi and epiphytes, as well as “die-back” disease.
Exposure at ebb tide may result in the desiccation of
the bed. Strong waves and rapid currents generally
destabilize the meadows causing fragmentation and
loss of seagrass rhizome. The decrease in salinity due
to excessive freshwater runoff also causes dis-
appearance, particularly of estuarine seagrass beds in
the confluence regions.

Anthropogenic activities such as deforestation in
the hinterland or mangrove destruction, construction of
harbors or jetties, and loading and unloading of
construction material as well as anchoring and moving

States

States: GJ Gujarat; MH Maharashtra; G Goa; KA Karnataka; KL Kerala; LD Lakshadweep Islands; WB West Bengal; OR Orissa; AP Andhra Pradesh;

TN Tamil Nadu; A&N Andaman and Nicobar Islands.

Frequency of occurrence: - absent; + very rare; ++ rare; +++ common; ++++ dominant.
Status of seagrass ecosystem: VG very good; G good; D degraded; MD most degraded; C in the process of formation.

Source: Various sources ® % 12. 20.291.

Table 9.3
Associated biota of seagrass beds of India

Group Number of species
Fauna

Bait fishes 21
Ornamental fishes 138
Fin fishes

Crustaceans

Mollusks

Echinoderms

Turtles

Mammals

Flora

Marine algae

Phytoplankton

Fungi

Source: Various sources!” ® 720-22)

of boats and ships, dredging and discharge of sediments,
land filling and untreated sewage disposal, are some of
the major causes of seagrass destruction in India. As a
result of the above natural and anthropogenic activities,
the sediment load in the overlying waters of seagrass
beds increases, reducing the amount of ambient light,
resulting in lower productivity because of a decline in
photosynthetic processes and increased respiration. The
excess sediment input in the region results in the
siltation and decline of seagrass beds. The siltation of
seagrass beds has been commonly observed in the Gulf
of Kutch, Gujarat, Andaman and Nicobar Islands, and in
most of the estuaries.

Seagrass beds in the lower intertidal region in the
Gulf of Kutch and a number of islands have experienced
decline. Halophila decipiens, reported earlier” along
the west coast, has totally disappeared, which might be
due to its elimination during natural succession.
Overexploitation of fisheries, particularly sea cucum-
bers and sea urchins, has impacted the resources
associated with seagrass beds. Dugong dugon, which
was abundant five decades ago’, has totally dis-
appeared along the Indian coast. The last report of
dugong sightings dates back to 1994-95 in Andaman
waters”. The loss of this mammal from the Indian
coast could be attributed to overexploitation for fat and
meat, as well as the obvious declines in seagrass beds.

POLICY RESPONSES

In India, seagrass regions, along with mangroves and
corals, have been categorized as ecologically sensitive
ecosystems under the Coastal Regulation Zone
Notification to the Environment (Protection) Act’.

However, seagrasses in India have been largely left out
of education, research and management compared to
other ecologically sensitive habitats such as mangroves,
sand dunes and corals. Considering the lack of
awareness, limited distribution and rising anthropo-
genic pressures, it is imperative to develop a national
educational and conservation management plan for the
seagrass ecosystem with the following objectives:

) quantification, mapping and regular monitoring to

evaluate changes over time;

) education, research and awareness programs;

fo) environmental impact assessments;

) mitigation of adverse impacts;

) identification and conservation of areas as
germplasm centers;

) rehabilitation.

Figure 9.1

Abundance of seagrass species at various depths in the Gulf of
Mannar (southeast coast)

\ Halodule
\uninervis
\

Thalassia
hemprichii

Cymodocea
serrulata

Syringodium
isoetifolium

a
Oo

Cymodocea
rotundata

nD
i=)

Depth (m)

5 Total
ls Epiphytic
Ml Seagrass

Average biomass (g dry weight/m?]

Figure 9.1b

106

WORLD ATLAS OF SEAGRASSES

Case Study 9.1
KADMAT ISLAND

Kadmat Island is located at 11°10°52"-11°15°20"N
and 72°45'41"-72°47 29'E. It stretches ca 8 km from
north to south, ranging in width from ca 50 to ca 400
m, with an area of 3.12 km*. The lagoon is on the
leeward [western] side, with a depth of 2-3 m. The
storm beach along the eastern side has an average
width of ca 100 m. A coralline algal ridge occurs
along the breaking zone of the storm beach. The
island is a submarine platform with a coral reef in
the form of an atoll. It is crescent-shaped, having a
north-south orientation. The western margin of the
lagoon is a submarine bank marked by a narrow
reef below.

Sampling and observations occurred along five

fixed transects laid down from -10 m on the reef
slope up to ca 150-200 m above high-tide line on the
island. The length of the transect varied from ca 1 to
3.5 km depending upon the topography or the
contour. The samplings were done during the post-
monsoon [November 1998] and pre-monsoon (May
1999] seasons. The collections and observations
were made from depths of -10 m and -5 m on the
reef slope and from -1.5 and -2.5 m in the lagoon,
and from exposed flats of reef and storm beach .
The seagrass bed in Kadmat Lagoon occurs In
patches as well as longer stretches along the shore.
A dense meadow occurs towards the northwest
region of the lagoon covering some 0.14 km? and

Characterization of a seagrass meadow at Kadmat Island, Lakshadweep

Period November 1998
Zone Lagoon Mid-lagoon
towards region
fore reef
Depth (m) 1-1.5 1.5-2.5
Substratum S+CD S
Thickness of substratum (cm) >2.5 5-10
Sand % (range) 97.1-97.95 97.8-98
Silt % {range} 0.23-2.8 1.67-1.82
Clay % (range) 0.1-2.03 0.32-0.42
Organic carbon (%) 0.11-0.27 0.21-0.23
Nature of seagrass beds SP LP

Quantitative aspect of seagrasses

Number of seagrass species 1 2
Thalassia hemprichii
% frequency of occurrence 10-20 10-20
Biomass (g dry weight/m’) N 5
Cymodocea rotundata
% frequency of occurrence A 10-20
Biomass (g dry weight/m’) NA 15
Total biomass (g dry weight/m’) NA 20
Average total drifted biomass NA NA
(g dry weight/m?)
Notes:

- data not collected

March 1999
Lagoon Lagoon Mid-lagoon Lagoon
towards towards region towards
land fore reef land
0-0.5 1-1.5 1.5-2.5 0-0.5
S S+CD S S
>10 >2.5 5-10 >10
94.8-97.6 - - -
2.02-2.48 - - -
0.41-2.74 - - -
0.36-0.42 1.08-1.4 1.52-1.96 0.92-1
BS SP LP BS
1 2 2 1
A 10-20 50-70 A
NA N 75 NA
50-70 - 50-70 >70
17 - 23 26
17 N 30.5 26
N NA NA 195

S sandy; CD coral debris; SP small patches; LP large patches; BS broken stretches

A absent; N negligible; NA not applicable

Source: Desai et al.'°*!

exhibiting marked zonation. Mostly sparse and small
patches of Thalassia hemprichii occur in the shallow
sandy regions towards the fore reef, while the mid-
lagoon deeper region [1.5-2.5 m] harbors mixed
dense beds of Thalassia hemprichii and Cymodocea
rotundata. The shallow region (0.5-1.5 m) towards
land supports intensive growth of Cymodocea
rotundata. A similar kind of distribution trend has
been reported from the other islands on the
Laccadive Archipelago”. The seagrass flora of
Kadmat comprises two species with higher biomass
(20-35 g dry weight/m*) occurring from the mixed
zone in the mid-lagoon (see table, left]. A biomass of
drifting seagrasses {195 g dry weight/m*] was
recorded during March when the biomass of the
seagrass standing crop was higher (26 g dry
weight/m’]. The frequency of occurrence of drifting
seagrass increased from 20 percent to 70 percent
during March, reflecting seagrass maximum bio-
mass; it is during this pre-monsoon period that high
wind speeds cause disturbances in the state of the
sea, including lagoon waters. Previously, five species
of seagrasses were recorded from the lagoons of
Kadmat”". It has been observed that the small-sized
seagrasses, such as Halophila spp., commonly grow
as pioneer species and form a suitable substratum
for other larger-sized seagrasses to follow during the
succession process". The absence of such species
from Kadmat Lagoon during this study might be due
to competition by the existing species during
succession.

A considerable amount of seagrass biomass
contributes to the detrital food chain’. The benthic
faunal population from the seagrass beds has been
reported to be higher due to high organic carbon in
the sediments". The organic carbon in the sedi-
ments, particularly from the seagrass beds, varied
from 0.11 to 1.96 percent (see table, left]. Macro-
fauna from the seagrass bed of Kadmat Island
consisted of eight groups [see table, right).
Macrofauna were largely Oligochaeta (40.17
percent), but the maximum number of species (22)
were from Polychaeta group™’. It was reported
earlier that Polychaeta [44.6 percent] and Crustacea
(42 percent] constitute the major macro-
invertebrates in the seagrass beds of India'™”.

The composition of meiofauna in seagrasses
varies seasonally"”. The meiofauna from the
seagrass bed of Kadmat'™” is represented by 19
groups dominated by Turbellaria (34.2 percent),
Nematoda (37.3 percent] and herpacticoid copepods
(10.1 percent).

Thalassia hemprichii

Benthic macrofauna in the seagrass bed at Kadmat Island,
Lakshadweep

Macrofauna No.of No. of % Dominant

group genera species composition taxa

Polychaeta 20 22 18.96 | Lumbriconeries,
Syllis, Onuphis,
Polydora

Nematoda 1 1 18:71 =

Oligochaeta 1 1 40.17 -

Pelecypoda 3 3 2.96 |Mesodesma,
Donax

Gastropoda 8 8 2.32 Cerithium,
Cerithidea

Crustacea 6 6 11.36 | Amphipoda,
Isopoda

Ophiuroidea i 1 0.61 Echiurida

Ascheliminthes - - 447 -

Unidentified = = 0.44 -

Note: - not identified to genus/species level

Source: Branganza et al.'*”

India

107

108

WORLD ATLAS OF SEAGRASSES

The Ministry of Environment and Forests,
Government of India, coordinates environment and
biodiversity-related coastal zone management
programs in the country. This department has a vital
role in adapting and implementing educational and
management plans for the seagrass environments of
India, similar to those for mangrove and coral reef
habitats. The necessary inputs based on research
would be of great importance in the formation of a
national seagrass management plan. Hence, the
ministry must encourage universities and national

REFERENCES

1 Anon [1992]. ‘Coastal Environment’ A Remote Sensing Application
Mission. A Scientific Note by Space Application Center (ISRO),
Ahmedabad, funded by Ministry of Environment and Forests,
Government of India, SAM/SAC/COM/SN/11/92. 100 pp.

2 Santapu H, Henry AN [1973]. A Dictionary of the Flowering Plants
in India. CSIR Publication, New Delhi.

3 Untawale AG, Jagtap TG [1978]. A new record of Halophila beccarii
(Aschers] from Mandovi estuary, Goa, India. Mahasagar, Bulletin of
the National Institute of Oceanography 10: 91-94.

4 Lakshmanan KK [1985]. Ecological importances of seagrass in
marine plants, their biology, chemistry and utilization. In:
Krishnamurthy V (ed) All India Symposium Marine Plants,
Proceedings. Donapaula, Goa. pp 277-294.

5 Ramamurthy K, Balakrishnan NP, Ravikumar K, Ganesan R [1992].
Seagrasses of Coromandel Coast, India. Flora of India, ser. 4. BSI,
Coimbatore. 79 pp.

6 Jagtap TG, Untawale AG [1981]. Ecology of seagrass bed Halophila
beccarii (Aschers} in Mandovi estuary, Goa. /ndian Journal of
Marine Sciences 4: 215-217.

7 Jagtap TG [1987]. Distribution of algae, seagrass and coral
communities from Lakshadweep Islands, Eastern Arabian Sea.
Indian Journal of Marine Sciences 16: 56-260.

8 Jagtap TG [1991]. Distribution of seagrasses along the Indian
Coast. Aquatic Botany 40: 379-386.

9 Jagtap TG [1996]. Some quantitative aspects of structural
components of seagrass meadows from the southeast coast of
India. Botanica Marina 39: 39-45.

10 Jagtap TG [1998]. Structure of major seagrass beds from three
coral reef atolls of Lakshadweep, Arabian Sea, India. Aquatic
Botany 60: 397-408.

11 Untawale AG, Jagtap TG [1989]. Marine macrophytes of Minicoy
(Lakshadweep) coral atoll of the Arabian Sea. Aquatic Botany 19:
97-103.

12 Ansari ZA [1984]. Benthic macrofauna of seagrass (Thalassia
hemprichii) bed at Minicoy, Lakshadweep. Indian Journal of Marine
Sciences 13: 126-127.

13. Ansari ZA, Rivonker CV, Ramani P, Parulekar AH [1991]. Seagrass
habitat complexity and microinvertebrate abundance in
Lakshadweep coral reef lagoons, Arabian Sea. Coral Reefs 10: 127-
131.

14 Sathe V, Raghukumar S [1991]. Fungi and their biomass in detritus

of the seagrass Thalassia hemprichii (Ehrenberg) Ascherson.

Botanica Marina 34: 271-277.

Jacobs RPWM [1982]. A Report: Component Studies in Seagrass

Ecosystems along West European Coasts. DRUK: Drukkerij verweij

BV, Mijdercht. pp 11-215.

Bortone SA [1999]. Seagrasses: Monitoring, Ecology, Physiology

and Management. CRC Press, New York. 309 pp.

Larkum AWD, McComb AJ, Shepherd SA [1989]. Biology of

Seagrasses. Elsevier, New York. 841 pp.

laboratories to undertake investigations on the various
aspects of seagrass ecosystems.

ACKNOWLEDGMENTS
The authors are grateful to the Director of the National Institute of
Oceanography (CSIR), Donapaula, Goa, for his encouragement.

AUTHORS

T.G. Jagtap, D.S. Komarpant and R. Rodrigues, National Institute of
Oceanography, Dona Paula, Goa - 403004, India. Tel: +91 (0)832 456700
4390. Fax: +91 (0}832 456702/456703. E-mail: tanaji(@csnio.ren.nic.in

18 Cuomo V, Jones EB, Grasso S [1988]. Occurrence and distribution
of marine fungi along the coast of the Mediterranean Sea. Progress
in Oceanography 21:189-200.

19 Siddique HN [1980]. The ages of the storm beaches of the
Lakshadweep (Laccadive]. Marine Geology 38: M11-M20.

20 Das HS [1996]. Status of Seagrass Habitats of Andaman and
Nicobar Coast. SACON Technical Report No. 4, Coimbatore. 32 pp.

21 Jagtap TG, Inamdar SN [1991]. Mapping of seagrass meadows from
the Lakshadweep Islands [India], using aerial photographs. J Ind
Soc Remote Sensing 19: 77-81.

22 James PSBR [1989]. Marine living resources of the union territory
of Lakshadweep - an indicative survey with suggestions for
development, Cochin, India. CMFRI Bulletin 43: 256 pp.

23 Swinchatt JP [1965]. Significance of constituent composition,
texture and skeletal breakdown in some recent carbonate
sediments. Journal of Sedimentary Petrology 35: 71-90.

24 Rajamanickam GV, Gujar AR [1984]. Sediment depositional

environment in some bays in the central west coast of India. Indian

Journal of Marine Sciences 53-59.

Hackett HE [1977]. Marine algae known from Maldive Islands. Atoll

Research Bulletin 210: 2-37.

26 Fortes MD [1989]. Seagrass: A Resource Unknown in the Asian

Region. ICLARM, Manila. 46 pp.

Jagtap TG [1985]. Ecological Studies in Relation to the Mangrove

Environment along the Goa Coast, India. PhD thesis, Shivaji

University, Kolhapur. 212 pp.

28 Untawale AG, Jagtap TG [1991]. Floristic composition of the deltaic
regions of India. In: Vaidyanadhan R led) Quaternary Deltas of India,
Memoir 22. Publication GSI, Bangalore. pp 243-265.

29 Jagtap TG [1992]. Marine flora of Nicobar group of Islands,
Andaman Sea. Indian Journal of Marine Sciences 22: 56-58.

30 Parthasarthy N, Ravikumar K, Ramamurthy K [1988]. Halophila
decipens Ostenf. Southern India. Aquatic Botany 32: 179-185.

31. Nair RV, Lal Mohan RS, Roa KS [1975]. The Dugong {Dugong
dugon). CMFRI Bulletin. 42 pp.

32 Anon [1990]. Coastal area classification and development
regulations. Gazette Notification, Part II, Section 3 [ii], Govt of India,
No. SC 595 (F] - Desk - 1/97.

33 Birch WR, Birch M [1984]. Succession and pattern of tropical
intertidal seagrasses in Cockle Bay, Queensland, Australia: A
decade of observation. Aquatic Botany 19: 343-368.

34 Mann KH [1988]. Production and use of detritus in various fresh
water, estuarine and marine ecosystems. Limnology and
Oceanography 33: 910-930.

35 Branganza C, Ingole BS, Jagtap TG. Unpublished data.

36 Desai W, Komarpant DS, Jagtap TG [Accepted manuscript].
Distribution and diversity of marine flora in coral reef ecosystems
of Kadmat Island in Lakshadweep Archipelago, Arabian Sea, India.
Atoll Research Bulletin.

10 The seagrasses of

Western Australia

WESTERN AUSTRALIA

km, from the temperate waters of the Southern

Ocean at 35°S to the tropical waters of the Timor
Sea at 12°S, with the contiguous coastline of the
Northern Territory extending across to Queensland.

T« coastline of Western Australia extends 12500

ECOSYSTEM DESCRIPTION

The long coastline has a diversity of environments that
support seagrass, ranging from those tropical species
associated with coral reefs and mangroves in the north
to large temperate seagrasses, in the shelter of
limestone reefs and in large embayments, on the west
and south coasts. These are exposed to different tidal
conditions {amplitudes 9 m in the north to less than 1m
on the west and south coasts"), substratum types and
exposure to wave energy. Although some areas of the
Western Australian coast, such as Cockburn Sound,
have been the subject of much research, a great deal of
the rest of the marine environment is poorly described
or understood.

This chapter will provide a brief description of the
coastal geomorphology, seagrass species and habitats,
and their biogeography. Current uses will be described
and current and potential threats to these habitats/
uses considered. Extensive use of Environment
Western Australia 1998: State of the Environment
Report” and of The State of the Marine Environment
Report®“ has been made in compiling the latter section
of this review. Issues of seagrass management will also
be discussed.

Geomorphology of the coast

The underlying geology of the coast consists of granitic
rocks in the south and southwest, with extensive
mantling of tertiary limestone, and sandstones in the
northwest and north. In the southeast of the state, the
vertical limestone cliffs of the southern edge of the
Nullarbor Plain delimit a narrow coastal plain. For

D.1. Walker

almost 300 km, offshore reefs protect sandy beaches
and high foreshore sand dunes from oceanic swell,
producing a calmer habitat between the reefs and the
shore, suitable for seagrass growth. At Twilight Cove
the cliffs again approach the sea and follow the
coastline to just east of Israelite Bay. From there to
Esperance, beaches and seagrass beds are sheltered
by the granitic islands of the Recherche Archipelago, 5-
50 km offshore.

From Esperance to Albany, sheltered beaches are
broken by granite outcrops although occasionally
limestone reefs and eroded cliffs occur. Small rivers
flow into a number of bays along this 500-km coastline,
but they have relatively low discharge rates,
particularly during the summer dry season. Offshore of
these estuaries, seagrasses of the Posidonia
ostenfeldii group occur as they can withstand swell and
sediment movement.

From Albany to Cape Naturaliste, limestone
overlies granitic rocks for much of the coast.
Seagrasses occur in this region in sheltered inshore
lagoons protected by offshore reefs.

Geographe Bay, east of Cape Naturaliste, is north
facing and the prevailing southwesterly swell is
refracted into the relatively sheltered embayment. The
embayment has a thin sediment veneer (mean
thickness: 1 m] overlying Pleistocene limestone”. It
provides an ideal habitat for seagrasses, and
extensive meadows are found to depths of 25 m.
A number of estuaries, larger than those further east,
also afford habitat for seagrasses and other submerged
aquatic plants such as Ruppia”" and their associated
invertebrates.

The western coastline, from Geographe Bay to
Kalbarri, is relatively straight and continuous, as it has
been eroded by the action of winds and currents which
have built up sand dunes and bars parallel to the coast.
There is also a fringe of limestone reefs running

110

WORLD ATLAS OF SEAGRASSES

parallel to the coast which are relict Pleistocene dune
systems composed of aeolianite; these break the Indian
Ocean swells, forming relatively calm, shallow (4-10 m
deep) lagoons up to 10 km wide, in which the tidal
range is small {<1 m), and the waters generally clear.
These lagoons are dominated by seagrasses.

From Kalbarri to Steep Point (the most westerly
point of the mainland], along Dirk Hartog Island,
Bernier and Dorre Islands and up to Quobba Point,
there are high cliffs composed of sandstone to the
south and limestone to the north. These cliffs shelter
Shark Bay, a large (13000 km’), shallow, semi-
enclosed embayment (see Case Study 10.1). This is an
area of intense carbonate sedimentation, which is
affected by wind and tidal-driven water movement,
leading to high turbidity. It also has relatively low water
temperatures in winter (down to 13°C)".

North of Quobba Point, the Pilbara coastline has a
low relief with gently sloping beaches, numerous
headlands and many small offshore islands. Headlands
are composed of isolated patches of very hard
hematite-bearing quartzite, which is more resistant to
erosion than the surrounding rocks. Normal erosion
processes, combined with submergence, have led to a
broken, rough coastline. Mangroves become conspic-
uous. Coral reefs and atolls occur north of Quobba
Point (near the Tropic of Capricorn), where tropical
seagrasses are found in lagoons, as well as in
mangrove swamps and around islands’. There is a
progressive increase in tidal amplitude with decreasing
latitude. Large tides affect seagrass distributions by
resuspending sediments; the high turbidity limits

Table 10.1
Western Australian endemic seagrass species

Species Distribution

Cymodoceaceae
Amphibolis antarctica
Amphibolis griffithii
Cymodocea angustata

Southern Australian endemic
Southern Australian endemic
Tropical Western Australian
endemic
Thalassodendron pachyrhizum Southern Australian endemic
Hydrocharitaceae
Halophila australis
Posidoniaceae
Posidonia angustifolia
Posidonia australis

Australian endemic

Southern Australian endemic
Southern Australian endemic
Western Australian endemic
Southern Australian endemic
Western Australian endemic
Western Australian endemic
Southern Australian endemic

Posidonia coriacea
Posidonia denhartogii
Posidonia kirkmanii
Posidonia ostenfeldii
Posidonia sinuosa

seagrass growth to shallow water. On broad intertidal
flats, seagrasses are restricted to those species which
can tolerate high temperatures and desiccation, as well
as periodic freshwater inundation from rainfall.

The Kimberley coast is a typical ria (drowned river
valley) system, characterized by resistant basement
rock, with faults oriented at angles to the shore,
creating a rugged coastline. The area is subject to large
tidal amplitudes and is remote and sparsely populated,
with little information available about the marine
habitats. Embayments and sounds grade shorewards
into mangrove-covered tidal flats, and there are many
offshore islands. Extensive terracing of these expanses
of the intertidal zone often results in seagrass,
particularly Enhalus acoroides", high in the intertidal
just below the mangroves.

Much of the Kimberley landscape is of
extraordinary natural beauty, extending to its coastal
regions. With a vast land area and a small population,
the Kimberley has been, until recently, largely
unexplored by biologists. Its isolated coastline is
devoid of settlement along the 2000-km stretch
between Derby and Wyndham. The area is receiving
growing attention from tourists, with increasing
activity by small private boats and charter operators.
As part of the development of a marine park and
reserve system in Western Australia, several areas are
being considered as potential marine parks. In
addition, some of the areas have been designated as
potential Aboriginal reserves. These designations have
been based on severely limited data available from the
few scientists and other people who have traveled in
the area. The only substantial data on marine
organisms in the Kimberley relate to salt water
crocodile populations and turtles. Marine plants, fish
and invertebrates are largely unknown. Recent surveys
by the West Australian Museum, the University of
Western Australia and the Northern Territory Museum,
and by CSIRO [Australia’s Commonwealth Scientific
and Industrial Research Organisation], have yet to be
published, but will help provide a basis for future
research.

BIOGEOGRAPHY

Seagrasses recorded from Western Australia fall into
two general distribution patterns. Twelve species are
endemic to Western Australia or to the southern
Australian coast, and are confined to temperate, clear
waters [Table 10.1). Twelve species are tropical and
are found throughout the Indian Ocean and tropical
Pacific Ocean.

Australia’s seagrasses can be divided into
temperate and tropical distributions, with Shark Bay on
the west coast and Moreton Bay on the east coast being
located at the center of the overlap zones. Temperate

species have been studied most extensively,
particularly the large genera Amphibolis, Posidonia
and Zostera, but there are other species which have
been little studied. Temperate species are distributed
across the southern half of the continent, extending
northwards on both the east and west coasts. The
highest biomasses, and highest regional species
diversity, occur in southwestern Australia, where
seagrasses are found in the coastal back-reef
environments within the fringing limestone reef, or in
semi-enclosed embayments.

In areas of northern Australia with a high tidal
range, visibility is often poor, and conventional remote-
sensing techniques are of limited value for mapping.
The Northern Territory coastline is largely unexplored
for seagrass distribution, and their associated animal
communities, especially the Northern Territory prawn
fisheries, remain largely unstudied. Recent research in
the Kimberley region of Western Australia has provided
some distribution information. Seagrasses in that
region either occur sparsely in coral reef environments
or can attain high biomasses within high intertidal
lagoons, where seawater is ponded during the falling
tide". The environments are otherwise too extreme
(tidal movements/turbidity/freshwater runoff in the wet
season] for seagrass survival”. Again, the significance
of these seagrass communities for any associated
fisheries species is unknown.

In general, our knowledge of shallow water
(<10 m) temperate seagrass distributions is reasonably
good, but our understanding of deep water [>20 m)
seagrasses throughout Australia is rudimentary. Areas
subject to more extreme water movement, either tidal
or wave induced, are also poorly studied compared with
seagrasses in more protected areas.

The main habitats for seagrasses are very
extensive shallow sedimentary environments that are
sheltered from oceanic swell, such as embayments
(e.g. Shark Bay, Cockburn Sound), protected bays (e.g.
Geographe Bay, Frenchman’s Bay] and lagoons
enclosed by fringing reefs {e.g. Bunbury to Kalbarri).
Seagrasses occupy approximately 20000 km* on the
Western Australian coast', ranging in depth from the
intertidal to 45 m'“!, making up a major component of
nearshore ecosystems. The diversity of seagrass
genera (10) and species (25) along this coastline is
unequaled elsewhere in the world'”, mainly due to the
overlap between tropical and temperate biogeographic
zones, and the extent of suitable habitats.

Large, mainly monospecific meadows of
southern Australian endemic species form about one
third of the habitat in the coastal regions of Western
Australia. These meadows have high biomasses
(500-1000 g/m*) and high productivities (>1000
g/m*/year)'"!. Southern Australian seagrasses occur in

Western Australia

400 600 Kilometers
—

Rowley «
Shoals

Montebello Is.

Barrow |
Ningaloo
Marine,

Park/ 4a

Ee Quobba Pt.

y Shark Bay Western Australia

~ Steep Pt.

South
Australia

30°S

Jurien Bay

Cockburn Sound. \, a
Geographe Bay. (

Cape Naturaliste va Ey

Esperance Twilight Cove

vn- Israelite Bay

Cape Leeuwin Recherche

atts aN Archipelago

Frenchman's Bay Princess Royal Harbour

Albany Harbour and Oyster Harbour
120° E *

140° E
Map 10.1
Western Australia

water bodies exposed to relatively high rates of water
movement. Nevertheless, Australian species also
occur where there is some protection from extreme
water movement and most are found in habitats with
extensive shallow sedimentary environments, shel-
tered from the swell of the open ocean, such as
embayments [e.g. Shark Bay and Cockburn Sound},
protected bays (e.g. Geographe Bay and Frenchman's
Bay) and lagoons sheltered by fringing reefs (e.g. the
western coast from 33° to 25°S).

MECHANISMS OF SEAGRASS DECLINE IN WESTERN
AUSTRALIA

Seagrass declines have been well documented from
around Australia. There are a variety of mechanisms of
seagrass loss, but the most ubiquitous and pervasive
cause of decline is the reduction of light availability.
Seagrasses are rather unique plants in that they have
high minimum light requirements for survival
compared with other plants'. These high minimum
light requirements (10-30 percent incident light) are
hypothesized to be related to the significant portions of
seagrass biomass that can be in anoxic sediments.
Reduction in light availability can occur as a result of
three major factors: chronic increases in dissolved
nutrient availability leading to proliferation of light-
absorbing algae, either phytoplankton, macroalgae or
algal epiphytes on seagrass leaves and stems; chronic

fas

111

D. Walker

Photo

WORLD ATLAS OF SEAGRASSES

Intertidal Enhalus acoroides, Leonie Island, Kimberley, Western
Australia

increases in suspended sediments leading to increased
turbidity; and pulsed increases in suspended
sediments and/or phytoplankton that cause a dramatic
reduction of light penetration for a limited time period.

Loss of habitat

Seagrasses are limited to the photic zone, extending up
to 54 m'”. Reductions in water quality can lead to a
reduction in the depth of the photic zone’, and hence
to a direct loss of habitat. Seagrasses in Cockburn
Sound, for example, are limited to a depth of less than
9 m, whereas in unpolluted areas the depth limit would
be 11-15 m. Increasing population pressure in Western
Australia leads to increasing pressure on the coast.
Development of the coastal zone, all along the Western
Australian coastline, in the form of construction of
marinas, port facilities and canal estates, results in
degradation of coastline causing direct destruction of
seagrass communities as well as indirect changes in
hydrodynamics and sedimentation.

Habitat removal

Coastal development in Western Australia is localized
to centers of population, and takes the form of
construction of ports, marinas and groynes. Housing
developments impact on coastal water quality, whereas
canal estates, such as in Carnarvon, have greater direct
impact on the marine environment. All these develop-
ments have potential consequences for seagrass
habitats and associated fauna.

Some developments have resulted in direct
destruction of seagrass communities, by smothering or
deterioration in water quality, e.g. construction of the
causeway at the southern end of Cockburn Sound",
where construction destroyed existing reef environ-
ments, and resulted in loss of seagrass habitat due to
reduced flushing. The construction of ports and
marinas in the Perth Metropolitan area has degraded
existing seagrass and reef habitats, as well as
fragmenting the remaining distributions. Subsequent
dredging and sediment infill has often reduced the
water quality and resulted in further losses.

Impacts of pollution

Pollution of coastal environments can result in major
changes to water quality, either from point or diffuse
sources which can influence marine community
structure, especially in relation to seagrass. Marine
disposal of sewage from the Perth Metropolitan
region's three outfalls contributes excess nutrients to
coastal areas”. The Kwinana Industrial Strip along the
shores of Cockburn Sound still relies on marine
disposal of the industries’ effluents, although now
under license conditions to regulate the amounts of
toxicants.

Water quality, especially nutrients
The Western Australian coastal environment is
particularly sensitive to nutrient enrichment from
human activities. The effects of this anthropogenic
eutrophication include an increase in frequency,
duration and extent of phytoplankton and macroalgal
blooms", low oxygen concentrations in the water
column, shifts in species composition’*", loss of
seagrass and benthic vegetation’, decrease in
diversity of organisms present’ and an increase in
diseases in fish and waterfowl. Western Australian
marine waters are generally low in nutrients and
biological productivity. Serious seagrass losses
resulting from increased nutrient loading have
occurred in the Albany Harbours, Cockburn Sound and
parts of Geographe Bay. Cockburn Sound is the most
degraded marine environment in Western Australia,
having experienced the second largest loss of seagrass
in Australia (more than two thirds].

The major human-induced declines of seagrass

in Western Australia are summarized in Table 10.2, with
suggested principal causes - in most cases, other
factors interact to make the process of loss more
complex. The general hypothesis for all these instances
of seagrass decline is that a decrease in the light
reaching seagrass chloroplasts reduces effective
seagrass photosynthesis. The decrease may result
from increased turbidity from particulates in the water,
or from the deposition of silt or the growth of epiphytes
on leaf surfaces or stems’. Seagrass meadows occur
between an upper limit imposed by exposure to
desiccation or wave energy, and a lower limit imposed
by penetration of light at an intensity sufficient for net
photosynthesis. A small reduction in light penetration
through the water will therefore reduce the depth range
of seagrass meadows, while particulates on leaves
could eliminate meadows over extensive areas of
shallower water [e.g. Princess Royal Harbour, Western
Australia)?*7!

Increasing turbidity of water above seagrasses
may occur directly, by discharge or resuspension of fine
material in the water column from, for example, sludge
dumping. Indirect effects on attenuation coefficients
occur through increased nutrient concentrations
resulting from the discharge of sewage and industrial
wastes, or from agricultural activity in catchments,
which in turn increase phytoplankton biomass reducing
light penetration significantly’. The extent of phyto-
plankton blooms associated with nutrient enrichment
will be determined by water movement, and mixing will
dilute nutrient concentrations. Deeper seagrass beds
further from the sources of contamination may show no
influence of turbidity.

Epiphytes

In Cockburn Sound, nutrient enrichment has led not
only to enhanced phytoplankton growth but also to
enhanced growth of macroscopic and microscopic
algae on leaf surfaces”. Macroalgae dominate over
seagrasses under conditions of marked eutrophication,
both as epiphytes and as loose-lying species (e.g. the

Table 10.2

Western Australia

genera Ulva, Enteromorpha, Ectocarpus) which may
originate as attached epiphytes””. Increased epiphytic
growth results in shading of seagrass leaves by up to 65
percent”, reduced photosynthesis and hence leaf
densities”. In addition, the epiphytes reduce diffusion
of gases and nutrients to seagrass leaves.

Light penetration

As photosynthetically active radiation passes through
water, it is attenuated by both absorption and
scattering. Attenuation is increased by the presence of
suspended organic matter (e.g. phytoplankton) and
inorganic matter, particularly in eutrophic systems
when phytoplankton concentrations are high'”, thus
reducing light penetrating to benthic primary
producers. In Cockburn Sound, where this continued
for extended periods of time, reduction in density and
loss of benthic macrophytes resulted!’”,

The requirement of light by benthic macrophytes
makes the presence of submerged aquatic vegetation
an indicator of water quality {adequate light penetra-
tion} and hence, nutrient status [i.e. low nutrient
concentrations)'"”. Light reduction for extended
periods, which is common in eutrophic systems, causes

loss of benthic macrophyte biomass”.

Siltation

Changes in landuse practices often result in increased
sediments in runoff from land, e.g. in Oyster Harbour.
Larger sediment loads reduce light penetration, as
detailed above. Increased sedimentation can result in
changes in the abundance and percentage cover of
seagrass due to increased sediment deposition or
scour”.

Toxic chemicals

In general the Western Australian coastal environment
is not subjected to large-scale inflows of toxic
chemicals. The 1998 Western Australian State of the
Environment Report does not consider them a threat”.
Awareness of toxic, human-produced chemicals and

Summary of major human-induced declines of seagrass in Western Australia

Place Seagrass community
Posidonia sinuosa
Posidonia australis
Posidonia australis
Amphibolis antarctica

Cockburn Sound,
Western Australia
Princess Royal and Oyster Harbours,
Western Australia

Extent of loss Cause
7.2 km’ lost (more than
two thirds}

8.1 km? lost [46%]

Increased epiphytism blocking light

Decreased light, increased epiphyte
and drift algal loads

Source: Cockburn Sound: Cambridge et al.'""), Silberstein et al. ”'; Princess Royal and Oyster Harbours: Walker et al'"*", Wells et al”)

113

114

Photo: D. Walker

WORLD ATLAS OF SEAGRASSES

Underwater meadow of Posidonia australis abutting a limestone
reef, Rottnest Island, Western Australia

their impacts on marine organisms has increased, and
such industrial inflows are controlled by Licence
Conditions from the Western Australia Department of
Environmental Protection. Urban runoff may include
such chemicals, but in Western Australia the runoff is
separated from the sewage system. Some direct runoff
may still influence groundwater or the coastal
environment, and increasing population pressure will
result in increased risk of contamination.

Fortunately, the aquaculture industry in Western
Australia has avoided the use of antibiotics in fish
foodstuffs. The potential effects of antibiotics” may
result in widespread changes in microbial activities,
with consequences up the food web, as well as for
nutrient recycling in coastal sediments.

The effects of antifouling compounds are also a
concern. Tributyltin [TBT] has been recorded from
Western Australian locations’, highest near marinas
and ports. TBT contamination is present at various
levels in all major ports in Western Australia. TBT
contamination is widespread throughout Perth
Metropolitan marine environment”. The use of TBT has
been banned in Western Australia on vessels longer
than 25 m.

Introduction of exotic (alien) species

Exotic marine organisms have been introduced to
Western Australia via ballast water and hull fouling
from shipping, and threaten natural distributions of
organisms, including seagrass. It is estimated that 100

million metric tons of ballast water are discharged into
this region's marine waters each year. Currently,
controls are only voluntary. Introduced marine species
may threaten native marine flora and fauna and human
uses of marine resources such as fishing and
aquaculture. Knowledge of species introduced and
their distribution has recently been updated. The risk of
damage to marine biodiversity is largely unknown but
international experience suggests that the potential for
significant environmental impact is high”.
Displacement of existing flora and fauna by introduced
species, intentional or accidental, has been widely
reported elsewhere’.

The 1998 Western Australian State of the
Environment Report estimated that over 27 exotic
species have been introduced to Western Australia”.
Twenty-one of these are known to have been introduced
into Perth Metropolitan waters, the most highly visible
being a large polychaete worm Sabella spallanzani
(Sabellidae family). This worm occupied up to 20 ha of
the seafloor and most of the structures in Cockburn
Sound, outcompeting the native Posidonia species, but
its incidence has been declining’.

ESTIMATE OF PRESENT COVERAGE

Large, mainly monospecific meadows of southern
Australian endemic species form about one third of the
habitat in the coastal regions of Western Australia and
amount to some 20000 km’. The tropical species are
less abundant but add a further 5000 km’.

THREATS

Human utilization of seagrass in Western Australia is

relatively restricted. Few commercial and recreational

species are taken from seagrass habitats. According to
the 1998 Western Australian State of the Environment

Report’, human activities most affecting coastal

seagrass habitats in Western Australia are:

) direct physical damage caused by port and
industrial development, pipelines, communi-
cation cables, mining and dredging, mostly in the
Perth Metropolitan and Pilbara marine regions;

() excessive loads of nutrients, causing seagrass
overgrowth and smothering by epiphytes, from
industrial, domestic and agricultural sources,
mostly in the Lower West Coast, Perth Metro-
politan and South West Coast marine regions;

fo) land-based activity associated with ports,
industry, aquaculture and farming, mostly in the
Pilbara, Central West Coast, Lower West Coast,
Perth Metropolitan and South West Coast marine
regions;

to) direct physical damage caused by recreational
and commercial boating activities including
anchor and trawling damage, mostly in the

Kimberley, Pilbara, Shark Bay, Perth Metro-
politan and Geographe Bay areas. Trawling nets
remove sponges and other attached organisms
from the seafloor.

The marine environment receives most of the
surface water from land. The quality of this water is
affected by activities and the environment of the
catchments through which it flows. Soil and nutrients
can be carried by river discharges to coastal waters,
causing water quality deterioration. Groundwater can
also carry terrestrial pollution into the marine
environment. Direct discharges such as sewage and/or
treated wastewater and industrial outfalls, and
accidental discharges such as spills and shipping
accidents, also influence coastal water quality”.

These land-based activities, their impacts on
ground and surface water and the ultimate movement
of these waters into nearshore marine environments
are the major human influence on the Western
Australian coast. They result in most pollution of the
marine environment and the resulting chronic
degradation of marine habitat. Degradation of the
marine environment leads to reductions in the area of
seagrass, as well as corals and mangroves.

Growing land- and marine-based tourism
development in Western Australia and the central-
ization of population growth will cause these impacts to
increase unless adequate protection and management
of the coast occurs.

Fisheries impacts

Most fishing methods in Western Australia are
suggested to have a limited effect on the shallow
coastal environments where seagrasses occur”.
Methods that may significantly affect the environment,
for example dredging and pelagic drift gill-netting, are
banned. Other methods, such as trawling, that alter the
benthic environment are restricted to prescribed areas.
Currently, many of these impacts cannot be
quantified”, but current assessments of the
sustainability of fisheries practices suggest that
damage to seagrass beds is minimal.

At present there are fewer than 100 trawlers
Operating in a series of discrete managed fisheries
within the total Western Australian fishing fleet of
around 2000. The number of these trawl licenses will be
reduced over time. Areas available to trawling within
each trawl fishery management area are also restric-
ted. There are significant demersal gill-netting closures
in areas of high abundance of vulnerable species such
as dugong (for example, Shark Bay and Ningaloo Reef).

Pollution, loss of habitat, sedimentation from
dredge spoil and agricultural runoff can impact heavily
on fish stocks, primarily in nearshore waters and

Western Australia

estuaries. Nutrient enrichment of some Western
Australian estuaries continues to be a problem. The
introduction of exotic marine organisms from ballast
water and via the aquarium industry remains an area
of concern.

SEAGRASS MANAGEMENT

Protected areas

All the marine parks in Western Australia contain
significant seagrass habitats. In particular the Shark
Bay World Heritage Property (see Case Study 10.1}
contains more than 4 000 km’ of seagrass beds of high
diversity”, as well as a population of more than 10 000
dugong, and turtles.

Two marine parks in the Perth area, Marmion and
Shoalwater Islands, contain about 20 percent seagrass.
The Swan River has small sections of marine park,
mainly declared for their migratory bird populations but
also including areas of the paddleweed, Halophila
ovalis. Two coral reef areas to the north of Western
Australia, Ningaloo and Rowley Shoals Marine Parks,
contain small but relatively diverse seagrass

populations’. Three areas to be declared as marine

LS coet Wa acm alo
aa ry oy .# . =
Divers airlifting sediment samples from a Posidonia sinuosa
meadow, Princess Royal Harbour, Western Australia

parks, Jurien Bay, Cape Leeuwin-Cape Naturaliste and
Montebellos-Barrow Island, also have diverse seagrass
ecosystems represented.

The establishment of the West Australian Marine
Parks and Reserves Authority, in which marine
conservation reserves are vested, should help facilitate
the development of a comprehensive series of
reserves. This process is, however, slow, and current

Photo: D. Walker

115

116

WORLD ATLAS OF SEAGRASSES

Case Study 10.1

Shark Bay is a large (13000 km’), shallow (<15 m],

hypersaline environment, dominated by seagrasses.

Situated on the West Australian coastline, at about

26°S, it contains the largest reported seagrass

meadows as well as the most species-rich seagrass
assemblages. Shark Bay is also a World Heritage

Property, one of only 11 World Heritage sites in the

world to have been listed under all four categories

for nomination:

) outstanding examples representing the major
stages of the Earth's evolutionary history;

fo) outstanding examples representing significant
ongoing geological processes, biological
evolution and humans’ interaction with their
natural environment;

) superlative natural phenomena, formations or
features, for instance outstanding examples of
the most important ecosystems, areas of
exceptional natural beauty or exceptional
combinations of natural and cultural
elements;

fo) the most important and significant natural
habitats where threatened species of animals
or plants of outstanding universal value still
survive.

issues such as extensive plans for aquaculture
developments being implemented by another section
of government (Fisheries) may compromise the
effectiveness of the Parks Authority. The development
of marine conservation reserves within Western
Australia must form part of the framework being
developed federally for Australia, and it must be
assessed to see if it provides the necessary
comprehensiveness, adequacy and representativeness
for marine conservation to be effective.

Policy

On an urgent basis, more detailed studies of the
Western Australian marine environment are required if
a sound basis for management is to be developed, both
within the marine park and reserve system and outside
it. There have been few coherent, broad-based studies
{both in time and space] that have researched the
cumulative impact of pollution, siltation, habitat
fragmentation and introductions of invasive species on
the community structure of marine communities”.
Further effort is needed on the influence of these
human activities on the whole community, although it

SHARK BAY, WESTERN AUSTRALIA: HOW SEAGRASS SHAPED AN ECOSYSTEM

Although the area also has terrestrial
significance, and is home to dolphins, the world’s
largest stable population of dugongs and living
stromatolites, the seagrasses are responsible for
some of the most impressive illustrations in the
world of the interaction between seagrasses and
their environment. Shark Bay provides an out-
standing example of the role that seagrasses can
play in influencing the physical, chemical and
biological evolution of a marine environment.

DESCRIPTION OF SHARK BAY

Shark Bay is a semi-enclosed basin, with restricted
exchange with the Indian Ocean, situated in an arid
landscape where evaporation exceeds precipitation
by a factor of ten. There are two gulfs, the eastern
and western, formed by pleistocene dunes, creating
a series of inlets and basins. Astronomical tides are
less than 1 m, thus atmospheric conditions influence
water levels. In summer, strong southerly winds
transport about 1-1.5 m of water northwards out of
the bay, exposing sand flats up to 2 km wide. There is
a well-developed salinity gradient developed as the
marine waters cross the shallow carbonate banks of
the Faure Sill. Salinities in Hamelin Pool may reach

will take a long-term commitment to fund these
multidisciplinary studies.

A more coherent approach to managing the
marine environment is required by government
agencies. Some 15 different government agencies have
some responsibility for management of the Western
Australian marine environment. The 1998 State of the
Environment Report” recommends that the state
government should establish a formal framework to
coordinate environmental management within Perth’s
Metropolitan marine region and between these waters
and their land catchments. This should be used as a
pilot program for expansion to other areas under
pressure from domestic and rural discharges.

A recent change in state government in Western
Australia has seen major changes to the structure of
government departments that may alleviate some of
the previous problems.

AUTHOR

Diana Walker, School of Plant Biology, University of Western Australia,
WA 6907, Australia. Tel: +61 (0)8 9380 2089/2214. Fax: +61 (0}8 9380 1001.
E-mail: diwalker(dcyllene.uwa.edu.au

REI
1

70 psu. Strong tidal currents, up to 8 knots, flow
through channels in the Faure Sill.

Seagrasses, particularly the southern
Australian endemic species Amphibolis antarctica
and Posidonia australis, dominate the subtidal
environment, to depths of about 12 m. The intertidal
flats are composed of mixed Halophila ovalis and
Halodule unjnervis. The 12 species of seagrass in
Shark Bay make it one of the most diverse seagrass
assemblages in the world. Seagrass covers more
than 4000 km’? of the bay, about 25 percent, with the
1030-km? Wooramel Seagrass Bank being the
largest structure of its type in the world.

A STABILIZING ROLE

The presence of extensive, monospecific beds of
these large, lengthy [2 m) seagrasses, baffle the
currents and modify the sediments underlying the
seagrass. The plants trap and bind the sediments
accreting from calcareous epiphytes and associated
epifauna. The plants can significantly slow the rate
of water movement over the bottom, and stabilize
the otherwise unstable sediments. Rates of
sediment accretion associated with Amphibolis
antarctica are higher than those associated with
coral reefs. This is related to high rates of leaf
turnover, depositing more calcareous sediments.
Over geological time, this had led to the build-up of

FERENCES
Anon [1994]. Australian National Tide Tables 1995. Australian
Government Publishing Service, Canberra. 256 pp.
Anon [1998]. Environment Western Australia 1998: State of the
Environment Report. Department of Environmental Protection,
Western Australia. 135 pp.
Zann LP, Kailola P {eds} [1995]. The State of the Marine
Environment Report. Technical Annex |. The Marine Environment.
Zann LP [1996]. The State of the Marine Environment Report for
Australia. Technical Summary. Department of Environment, Sport
and Territories, Commonwealth of Australia. 515 pp.
Searle JD, Logan BW [1978]. A Report on Sedimentation in
Geographe Bay. Research Project R T 2595. Department of Geology,
University of Western Australia. Report to Public Works
Department, Western Australia. 72 pp.
McMahon K, Young E, Montgomery S, Cosgrove J, Wilshaw J,
Walker DI [1997]. Status of a shallow seagrass system, Geographe
Bay, south-western Australia. Journal of the Royal Society of
Western Australia 80: 255-262.
Congdon RA, McComb AJ [1979]. Productivity of Ruppia: Seasonal
changes and dependence on light in an Australian estuary. Aquatic
Botany 6: 121-132.
Carruthers TJB, Walker DI, Kendrick GA [1999]. Abundance of
Ruppia megacarpa Mason in a seasonally variable estuary.
Estuarine Coastal and Shelf Science 48: 497-509.
Walker DI [1989]. Seagrass in Shark Bay - the foundations of an
ecosystem. In: Larkum AWD, McComb AJ, Shepherd SA [eds]

Western Australia

banks under the seagrass, forming the Faure Sili, as
well as the extensive sand flats.

The build-up of the banks underlying the
seagrass, in turn, has restricted the circulation of
oceanic seawater, which with high evaporation and
low rainfall results in the hypersalinity gradient in
the inner reaches of the bay. This makes the
southern areas of Hamelin Pool unsuitable for
seagrasses, but has allowed the development of
stromatolites.

HIGH RATES OF PRODUCTION

The waters flowing over the seagrasses are
depleted in phosphorus by the seagrasses them-
selves. For Shark Bay as a whole, the seagrass
meadows represent an enormous pool, with some
86 million kg of nitrogen and 6 million kg of
phosphorus being required to support the seagrass
growth. Only about 10 percent of this can be
supplied from the oceanic inflow, so the high rates
of production must be supported by tight recycling,
both from decomposition in situ and from internal
retranslocation.

Seagrasses in Shark Bay thus represent “an
outstanding example representing significant on-
going geological processes, and biological evolu-
tion”, demonstrating how important seagrasses are
throughout the world.

Seagrasses: A Treatise on the Biology of Seagrasses with Special
Reference to the Australian Region. Elsevier/North Holland,
Amsterdam. pp 182-210.

10 Walker DI, Prince RIT [1987]. Distribution and biogeography of
seagrass species on the north-west coast of Australia. Aquatic
Botany 29: 19-32.

11 Walker DI [1997]. Marine Biological Survey of the Central
Kimberley, Western Australia. Report to the National Estates
Committee. 159 pp.

12 Dennison WC, Kirkman H [1996]. Seagrass survival model. In: Kuo

JJS, Phillips R, Walker DI, Kirkman H leds) Seagrass Biology:
Proceedings of an International Workshop, Rottnest Island,
Western Australia, 25-29th January 1996. Faculty of Science,
University of Western Australia, Perth. pp 341-344.

13 Kirkman H, Walker DI [1989]. Western Australian seagrass. In:
Larkum AWD, McComb AJ, Shepherd SA {eds} Biology of
Seagrasses: A Treatise on the Biology of Seagrasses with Special
Reference to the Australian Region. Elsevier/North Holland,
Amsterdam. pp 157-181.

14 Cambridge ML [1980]. Ecological Studies on Seagrass of South
Western Australia with particular reference to Cockburn Sound.
PhD thesis, University of Western Australia, Perth. 326 pp.

15 Hillman K, Walker DI, McComb AJ, Larkum AWD [1989].

Productivity and nutrient limitation. In: Larkum AWD, McComb AJ,

Shepherd SA (eds) Seagrasses: A Treatise on the Biology of
Seagrasses with Special Reference to the Australian Region.
Elsevier/North Holland, Amsterdam. pp 635-685.

117

118

WORLD ATLAS OF SEAGRASSES

Dennison WC, Orth RJ, Moore KA, Stevenson JC, Carter V, Dollar S,
Bergstrom PW, Batiuk RA [1993]. Assessing water quality with
submersed aquatic vegetation. Bioscience 43: 86-94.

Kirk JTO [1994]. Light and Photosynthesis in Aquatic Ecosystems.
Cambridge University Press, Cambridge.

Walker DI, McComb AJ [1992]. Seagrass degradation in Australian
coastal waters. Marine Pollution Bulletin 25: 191-195.

Cambridge ML, Chiffings AW, Brittan C, Moore L, McComb AJ
[1986]. The loss of seagrass in Cockburn Sound, Western Australia.

Il. Possible causes of seagrass decline. Aquatic Botany 24: 269-285.

Lord DA [1994]. Coastal eutrophication: Prevention is better than
cure. The Perth Coastal Water Study 45: 22-27.

Lukatelich RJ, McComb AJ [1989]. Seasonal Changes in
Macrophyte Abundance and Composition in a Shallow
Southwestern Australian Estuarine System. Waterways
Commission, Perth, Western Australia.

Lukatelich RJ, McComb AJ [1986]. Distribution and abundance of
benthic microalgae in a shallow southwestern Australian estuarine
system. Marine Ecology Progress Series 27: 287-297.

Lavery PS, Lukatelich RJ, McComb AJ [1991]. Changes in the
biomass and species composition of macroalgae in a eutrophic
estuary. Estuarine Coastal and Shelf Science 33: 1-22.

McMahon K, Walker DI [1998]. Fate of seasonal, terrestrial nutrient
inputs to a shallow seagrass dominated embayment. Estuarine
Coastal and Shelf Science 46: 15-25.

Bastyan G [1986]. Distribution of Seagrasses in Princess Royal
Harbour and Oyster Harbour on the Southern Coast of Western
Australia. Technical Series 1. Department of Conservation and
Environment, Perth, Western Australia. 50 pp.

Walker DI, Hutchings PA, Wells FE [1991]. Seagrass, sediment and
infauna - a comparison of Posidonia australis, Posidonia sinuosa
and Amphibolis antarctica, Princess Royal Harbour, South-Western
Australia |. Seagrass biomass, productivity and contribution to
sediments. In: Wells FE, Walker DI, Kirkman H, Lethbridge R {eds}
Proceedings of the 3rd International Marine Biological Workshop:
The Flora and Fauna of Albany, Western Australia. Vol 2. Western
Australia Museum. pp 597-610.

Wells FE, Walker DI, Hutchings PA [1991]. Seagrass, sediment and
infauna - a comparison of Posidonia australis, Posidonia sinuosa
and Amphibolis antarctica in Princess Royal Harbour, South-
Western Australia Ill. Consequences of seagrass loss. In: Wells FE,
Walker DI, Kirkman H, Lethbridge R leds] Proceedings of the 3rd
International Marine Biological Workshop: The Flora and Fauna of
Albany, Western Australia. Vol 2. Western Australian Museum. pp
635-639.

Chiffings AW, McComb AJ [1981]. Boundaries in phytoplankton
populations. Proceedings of the Ecological Society of Australia 11:
27-38.

Silberstein K, Chiffings AW, McComb AJ [1986]. The loss of
seagrass in Cockburn Sound, Western Australia. Ill. The effect of
epiphytes on productivity of Posidonia australis Hook. f. Aquatic
Botany 24: 355-371.

Kendrick GA [1991]. Recruitment of coralline crusts and
filamentous turf algae in the Galapagos archipelago: Effect of
stimulated scour, erosion and accretion. Journal of Experimental
Marine Biology and Ecology 147: 47-63.

Coyne R, Hiney M, O'Connor B, Kerry J, Cazabon D, Smith P [1994].
Concentration and persistence of oxytetracycline in sediments
under a marine salmon farm. Aquaculture 123(1-2): 31-42.

Kerry J, Hiney M, Coyne R, Cazabon D, Nicgabhainn S, Smith P
{1994]. Frequency and distribution of resistance to oxytetracycline
in micro-organisms isolated from marine fish farm sediments
following therapeutic use of oxytetracycline. Aquaculture 123(1-2):
43-54.

Kohn AJ, Almasi KN [1993]. Imposex in Australian Conus. Journal
of Marine Biology Association UK 73: 241-244.

Sindermann CJ [1991]. Case histories of effects of transfers and
introductions on marine resources - Introduction. Journal du
Conseil 47: 377-378.

Chaplin G, Evans DR [1995]. The Status of the Introduced Marine
Fanworm Sabella spallanzanii in Western Australia: A Preliminary
Investigation. Technical Report 2. Centre for Research on
Introduced Marine Pests, Division of Fisheries, Hobart, Tasmania.
34 pp.

Regional map: Australasia

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vi WORLD ATLAS OF SEAGRASSES

SEAGRASS ECOSYSTEMS

A manatee (Trichechus manatus], feixe-boi in Portugese,
over a Halodule wrightii bed in Recife, Brazil

A sea horse, Hippocampus whitei, amongst Zostera capricorni in Sydney

Harbour, Australia

Photo: J. Harmelin

to: F.T. Short

Pho

Mediterranean Posidonia oceanica seagrass beds with
saupe (Sarpa sarpa) and bream [Diplodus spp.)

Sea star in Enhalus acoroides and

Snails grazing epiphytes on Zostera
Thalassia hemprichii, Micronesia

Photo: F.T. Sho

marina blades in southern Norway.

King helmet in Thalassia :
testudinum, Turks & Caicos Lizard fish in Amphibolis antarctica, Western Australia

11 The seagrasses of

Eastern Australia

EASTERN AUSTRALIA

eastern Australian coastline which extends from

the tropics (10°S) to the cool temperate zone
(44°S) and includes the Great Barrier Reef World
Heritage Area. The area includes the Gulf of Carpentaria
to the north and around the coastline of Australia to
Tasmania and to Spencer Gulf. There are extensive
seagrass habitats in this region including tropical and
temperate seagrass assemblages. An overlap between
these two zones occurs in Moreton Bay, southern
Queensland". Both tropical and temperate species in
Australia are mostly found growing in water less than 10
m below mean sea level”. Some species of tropical
Halophila can be found to depths of 60 m".

The eastern Australian coast includes areas of
diverse physical characteristics. The tropical north
coast and Gulf of Carpentaria are monsoon influenced,
mostly with muddy sediments, low human population
and low levels of disturbance. The tropical and most of
the temperate subtropical Queensland east coast is
sheltered by the Great Barrier Reef and is effectively a
long lagoon. The temperate east and south coasts are
sandier and more exposed and include the large [by
Australian standards) population centers of Brisbane,
Sydney, Melbourne and Adelaide with a standard suite
of associated anthropogenic coastal disturbances.

The highest species diversity of seagrass is found
near the tip of Cape York in the very north, with a
gradual decline in diversity moving south down the
east coast'!. This is thought to be a result of geo-
graphic distance from a center of diversity in the
Malaysian/Indonesian region driven by the east
Australian current which runs roughly north to south”,
combined with changes in temperature, topography
{available substrate), past changes in sea level and
exposure to wave action".

The temperate species in the southern half of the
region include members of the genera Amphibolis,
Posidonia and Zostera which are found predominately in

Seen meadows are a prominent feature of the

R. Coles
L. McKenzie
S. Campbell

sheltered estuaries and bays. Amphibolis is an
Australian endemic. They possibly had a much wider
distribution in the early Paleocene (64 million years ago)
with rapid climatic and tectonic changes since that time
restricting their distribution to southern Australia’.
Posidonia has a fractured distribution at the present
time (southern Australia and the Mediterranean], also
likely to be the result of localized extinctions in the
past”. The genus Zostera has both temperate and
tropical species in Australia.

The tropical meadows are highly diverse, but
generally have lower biomass than those in temperate
parts. While bays such as Hervey Bay and Moreton Bay
have large areas of seagrass, most tropical seagrasses
are found in the intertidal or shallow subtidal environ-
ments of the Gulf of Carpentaria and the central and
southern Great Barrier Reef World Heritage Area
lagoon with extension into deeper waters in the central
and northern sections.

The importance of seagrass meadows as struc-
tural components of coastal ecosystems has resulted
in research interest being focused on the biology and
ecology of seagrasses and on the methods for mapping,
monitoring and protection of critical seagrass habitats.
Seagrasses of eastern Australia are important for
stabilizing coastal sediments, providing food and
shelter for diverse organisms, as a nursery ground for
shrimp and fish of commercial importance, and for
nutrient trapping and recycling”. In eastern Australia
the marine mammal, Dugong dugon, and the green sea
turtle, Chelonia mydas, feed directly on seagrasses.
Both animals are used by traditional Australian
communities for food and ceremonial use. Both species
have declined in number, and protection of their habitat
and food source Is vital.

The extent of seagrass areas and the ecosystem
values of seagrasses are the basic information required
for coastal zone managers to aid planning and
development decisions that will minimize impacts on

120

WORLD ATLAS OF SEAGRASSES

seagrass habitat. In general, our knowledge of intertidal
and shallow subtidal {down to 10 m]) distributions is
good; however, we have only a basic understanding of
deepwater (>10 m] seagrasses throughout the region. It
is important to document seagrass species diversity and
distribution and identify areas requiring conservation
measures before significant areas and species are lost.

BIOGEOGRAPHY

Gulf of Carpentaria and Torres Strait

The Gulf of Carpentaria is a large, shallow, muddy
marine bay. Extensive open coastline seagrass
communities, mainly of the genera Halodule and
Halophila intertidally, and Syringodium and Cymodocea
subtidally, are found along the southern and western
sides of the gulf”. Along the exposed eastern coast of
the gulf, seagrasses are generally sparse and
restricted to the leeside of islands, protected reef flats,
and estuaries and protected bays. The coastline of the
eastern gulf is extremely shallow and regularly
disturbed by prevailing winds. Sediments throughout
the gulf are predominately fine muds, and these are
easily resuspended due to the shallow bathymetry
resulting in increased turbidity, which restricts
seagrass distribution and growth. Reef flat communi-
ties are dominated by Thalassia. Meadows in estuaries
and sheltered bays are mostly of the genera Halodule,
with Cymodocea and Enhalus.

The Torres Strait is a shallow (mostly 10-20 m
depth) body of water 100 km long and 250-260 km
wide [east-west], formed by a drowned land ridge
extending from Cape York to Papua New Guinea. The
area has a large number of islands, shoals and reefs.
Reefs are generally aligned east-west, streamlined
by the high-velocity tidal currents that pour through
the inter-reef channels. Seagrass communities occur
across the open seafloor, on reef flats and subtidally
adjacent to continental islands. A well-defined line of
large reefs runs northwards from Cape York,
including the Warrior Reefs with extensive seagrass-
covered reef flats. Mixed species occur on these flats,
most commonly of the genera Halodule, Thalassia,
Thalassodendron and Cymodocea. The large ex-
panses of open water bottom are covered with either
sparsely distributed Halophila or mixed species
(Halodule, Thalassia and Syringodium) communities.
Lush Halophila ovalis and Halophila spinulosa
communities are also found in the deep waters
(>30 m) of the southwestern Torres Strait.

Northeast coast

Tropical seagrass habitats in northeastern Australia
are extensive, diverse and important for primary and
secondary production’. A high diversity of seagrass
habitats is provided by extensive bays, estuaries, rivers

and the 2600-km Great Barrier Reef with its reef
platforms and inshore lagoon.

Carruthers et al." classified the northeast coast
seagrass systems into river estuaries, coastal,
deepwater and reef habitats. All but some of the reef
habitats are significantly influenced by seasonal and
episodic pulses of sediment-laden, nutrient-rich river
flows, resulting from high-volume summer rainfall.
Cyclones, severe storms and wind waves, as well as
macrograzers (dugongs and turtles) influence all
habitats in this region to varying degrees. The result is
a series of dynamic, spatially and temporally variable
seagrass meadows.

River estuary habitats include a wide range of
subtidal or intertidal species and can be highly
productive. The species mixture, growth and distri-
bution of these seagrass meadows are influenced by
terrigenous runoff as well as temperature and salinity
fluctuations. Increased river flows in summer cause
higher sediment loads and reduced light, creating
potential light limitation for seagrass. Associated
erosion and unstable sediments make river and inlet
habitats a seasonally stressful environment for
seagrass growth. These meadows often have high
shoot densities but low species diversity”. Differences
in life history strategies, resilience to habitat variability,
and the physical characteristics of the inlet act to
control species assemblages in different river and inlet
systems.

Coastal habitats also have extensive intertidal
and subtidal seagrasses. Intertidal environments are
impacted by sediment deposition, erosion, tidal
fluctuations, desiccation, fluctuating and sometimes
very high temperature, and variable salinity”. Tidal
range can be as large as 6 m. These communities are
affected rapidly by increased runoff with heavy rain or
cyclone events'', but a large and variable seed bank
can facilitate recovery following disturbance’. Inshore
seagrass communities are found in varying quantity
along the eastern Queensland coastline, mostly where
they are protected from the prevalent southeast winds
by the Great Barrier Reef. Along the southern
Queensland coast, the Great Barrier Reef offers little
protection and coastal seagrass meadows are
restricted to sheltered bays, behind headlands and in
the lee of islands. Extensive coastal seagrass meadows
occur in north-facing bays such as Moreton Bay, Hervey
Bay and Shoalwater Bay.

Increasing distance from the coast decreases the
impacts from pulsed terrigenous runoff, and in these
regions clear inter-reef water at depth (>15 m] allows
for deepwater seagrass growth. Throughout the Great
Barrier Reef region, approximately 40000 km? of
lagoon and inter-reef area has at least some seagrass,
most of low density (<5 percent cover)”.

Deepwater seagrass areas are dominated by
species of Halophila®*"*. Large monospecific mead-
ows of seagrass occur in this habitat composed mainly
of Halophila decipiens or Halophila_ spinulosa.
Halophila spp. display morphological, physiological and
life history adaptations to survival in low-light environ-
ments. Halophila spp. can be annuals in the Great
Barrier Reef region, have rapid growth rates and are
considered to be pioneering species'’”. An important
characteristic of this strategy is high seed production.
Rates of 70000 seeds/m*/year have been estimated
from field observations of Halophila tricostata"”.

The distribution of deepwater seagrasses
appears to be mainly influenced by water clarity and a
combination of propagule dispersal, nutrient supply
and current stress. High-density deepwater sea-
grasses occur mostly on the inner shelf in the central
narrow-shelf section of the east coast which
experiences a moderate tidal range and is adjacent to
high-rainfall rainforest catchments. Where there are
large tidal ranges, just to the south of Mackay, no major
deepwater seagrass areas exist, but some meadows
occur further south in Hervey Bay where tide ranges
moderate again’. Deepwater seagrasses are uncom-
mon north of Princess Charlotte Bay, a remote area of
low human population and little disturbance. This may
be the result of the east Australian current diverging at
Princess Charlotte Bay and the far northern section
may not receive propagules for colonization from
southern meadows. Much of this coast is also silica
sand and low in rainfall and stream runoff, and it is
possible that limited availability of nutrients restricts
seagrass growth”.

Reef seagrass communities support a high
biodiversity and can be extensive and highly productive.
Shallow unstable sediment and fluctuating tempera-
ture characterize these habitats. Low nutrient availa-
bility is a feature of reef habitats, and seagrasses are
likely to be nitrogen limited'”. Seagrasses are more
likely to be present on reefs with vegetated cays than on
younger reefs with highly mobile sand. Intermittent
sources of nutrients arrive when seasonal runoff
reaches the reef. In some localized areas, particularly
coral cays, seabirds can add high amounts of
phosphorus to reef environments. The more successful
seagrass species in reef habitats of the Great Barrier
Reef include Thalassia hemprichii, Cymodocea
rotundata, Thalassodendron ciliatum, the colonizing
species Halophila ovalis, and species of the genus
Halodule.

New South Wales, Victoria and Tasmania

Ten species of seagrass (excluding Lepilaena cylindro-
carpa) are recorded in this region’. Species of the
genus Zostera (including the former Heterozostera) are

Eastern Australia

Torres* Strait
Cape York

Gulf of
Carpentaria CORAL SEA

Green Island

Great Barrier Reef
« World Heritage Area

Queensland

Hervey
Bay

Deception Bay’
Brisbane, &

Moreton
dy

South
Australia
30° S

Port Macquarie »

Tom, f
-
, Zs Sydney ¢ Botany Bay
x N Adelaide 2
)

.
Spencer 9° .
Gulf Victoria

, Melbourne » y

oP Rig

Port Hacking > — Westernport Bay
Bass Sirait

Port Phillip Bay a

2
a
m

Coorong Mallacoota
Lakes

TASMAN SEA

ania
® Freycinet
600 Kilometers Hi

Bnuny Island

Map 11.1
Eastern Australia

the most common as they dominate in estuaries and
coastal lagoons". In Victoria and Tasmania, Posidonia
and Amphibolis are also found, mainly near estuary
entrances, or in sheltered bays adjacent to Bass Strait
Islands.

The distribution and occurrence of seagrasses
depends on the estuary type, i.e. drowned river valley,
barrier estuary or coastal lagoon'"'. Seagrass species
composition and distribution is associated mostly with
sediment type and with differing exposure to wave
energy from the open ocean. Seagrasses are generally
more abundant several kilometers upstream from the
estuary entrance due to lesser tidal and wave
disturbance. Seagrasses in coastal lagoons may also be
affected by the frequency with which the lagoon
entrance is open to the ocean or closed by shifting sand
banks, changing conditions from brackish to saline.
Agricultural development and poor catchment practices
in some regions have resulted in high sediment and
nutrient loads reducing light availability and favoring
species which can tolerate lower light levels. In other
localities, reduced freshwater flows (due to industrial
and agricultural extraction) have increased salinities.

In protected sites, mixed stands of Zostera

121

I
™
OSA

—~

122

WORLD ATLAS OF SEAGRASSES

tasmanica, Zostera capricorni (formerly Zostera
muelleri) and Halophila ovalis dominate. Ruppia
meadows are common in areas of high freshwater
input. A feature of estuarine habitats in this region is
heavy winter-spring rains with associated high turbidity,
followed by high salinity and low rainfall in summer.

In less-protected areas dominated by sandy
sediments [e.g. north coast of Tasmania, Bass Strait
islands) mixed seagrass communities consist of larger,
slower growing species such as Posidonia australis, with
small, faster growing species such as Zostera tasmanica
and Halophila ovalis occupying the gaps between
meadows and areas close to freshwater inputs. At the
mouth of some bays and in areas dominated by sandy
siliceous sediments and exposed to ocean swells in
Victoria, the slow-growing seagrass Amphibolis
antarctica (Amphibolis griffithii fills the same role in
South Australia) forms patches of varying sizes rather
than extensive monospecific meadows. In these areas,
nutrient inputs are low and sediments are nutrient poor.

Large oceanic bays in southeast Tasmania have
meadows of Halophila and Zostera species. Seagrass
distribution is influenced by biogeography and geo-
morphology as well as wave energy. Deep, oceanic
seagrass beds of Posidonia australis and Amphibolis
antarctica are also present to depths of 22 m in clear
non-polluted water. Their distributions are influenced by
depth, bottom type, wave energy and geomorphology.
Most seagrasses in southeastern Australia are restric-
ted to depths of less than 20 m by light availability.

South gulf coast of South Australia
Seagrass distribution in South Australia is dependent
on coastal topography, bathymetry and environment”.

.The most extensive meadows are found in the large

expanses of sheltered shallow water in Spencer Gulf
and Gulf St Vincent. These are predominantly Posidonia
and Amphibolis meadows, with Halophila and Zostera
species. Large seagrass meadows which are
dominated by species of Zostera also occur along the
southeastern coast of South Australia in coastal
lagoons [e.g. Lake Alexandrina and Lake Albert).

HISTORICAL PERSPECTIVES

Australia has had a relatively stable climate with the
northward movement of the continent compensating
during past episodes of global cooling. The biomass
and diversity of seagrass seen today is most likely to
have remained relatively unchanged on a continental
scale for tens of millions of years.

Agriculture and coastal development started in
Australia with the arrival of European migrants only
200 years ago and coastal influences on seagrass
before that date would have been almost entirely
natural. Sediment and nutrient loads to estuaries and

enclosed waters such as Moreton Bay and Westernport
Bay have undoubtedly influenced the modern
distribution of seagrasses, particularly in temperate
waters. Less easy to determine is the likely effect in
tropical waters where turbidities are already naturally
high. Dramatic declines in grazer populations [turtle
and dugong) from increased hunting would be expected
to allow an increase in seagrass, particularly of
biomass where climax communities can now develop.

Traditionally, the fruit of Enhalus acoroides was
eaten in the northern islands and the leaf fibers were
possibly used to make nets and cord. This use was
likely to have been infrequent and of low importance to
seagrass distribution as the human population was
very small before European migration. Seagrasses
were used to make matting and for bed mattresses
during the Second World War. They were also used for
fertilizer, such as in Lacepede Bay in southeastern
South Australia, where Posidonia angustifolia leaf drift
and wrack is still harvested from the beach for soil
conditioner and compost mixes”. Such activities are
now illegal in many parts of Australia where both live
and dead seagrasses are protected.

There are reports from the southern and eastern
Australian coastline that seagrass communities have
declined in recent decades’. Anecdotal reports of 30
years ago from residents in the Hervey Bay and Great
Sandy Strait region describe large long-leaved (>30 cm)
Zostera capricorni meadows abundant over the
intertidal banks. Long-time residents report abundant
fishing and bird life [especially black swans) and say
that the seagrass wrack was so plentiful that it was
harvested from the beaches for garden mulch. Today,
much of the seagrass on the intertidal banks in the
region is sparse or low-cover Zostera capricorni with
short [<10 cm) and narrow leaves. Fishing is reported
to have declined and black swans no longer frequent
the region. Unfortunately, accurate mapping programs
were not instigated until the late 1980s so these types
of report are impossible to verify and may well be
overstated.

In Victoria there are unquantified reports of
Zostera loss in Westernport Bay during the 1950s. The
decline coincided with a reduction in fish catches.
Anecdotal reports and photographs from local
residents in the north and eastern regions of
Westernport Bay, prior to the loss of seagrasses,
describe “lush seagrass meadows”. Similarly in Corner
Inlet, Victoria, a decline in Posidonia australis in the
1960s was followed by a reduction in fishermen

operating in the region””.

AN ESTIMATE OF HISTORICAL LOSSES
More than 450 km’ of seagrass have been lost from
Australian coastal waters in recent years, largely

attributed to eutrophication, natural storm events, and
reductions in available light due to coastal
development. It is worth noting that there is a high
probability of bias towards reporting decline, and that
increases in biomass and area are often not reported.

There have been several well-documented cases
of seagrass loss in eastern Australia over the past 50
years”. In Port Macquarie (New South Wales] 11.3 km?
of seagrass was lost between 1953 and 1985 due to
increased turbidity from human activity, resulting in
declining fish stocks’. Similarly in Botany Bay, a loss
of 2.5 km’ of Posidona sinuosa, representing 58 percent
of the bay’s seagrass, was lost between 1942 and
1986, a consequence of dredging activities and
eutrophication”.

In South Australia there has been a significant
decline in seagrasses on the eastern side of Gulf St
Vincent due to sewage effluent. Approximately 60 km?
of Posidona sinuosa and Ampbhibolis antarctica
meadows were lost between 1935 and 1987! In
Spencer Gulf, fishermen and local residents have
reported widespread loss of Amphibolis close to the
intertidal zone. Recent loss (1992-93) of mixed
meadows of Posidonia australis, Zostera tasmanica
and Zostera capricorni were due to sediment accretion
and desiccation caused by exposure to high air
temperatures and low humidity”.

In Victoria, the recorded loss of seagrass has
been from the large marine bays of Westernport Bay,
Port Phillip Bay and Gippsland Lakes. In Westernport
Bay, persistent high turbidity and poor water quality
due to agricultural runoff, sediment inputs and
resuspension of sediments caused seagrass to decline
from 196 km? in the early 1970s to 67 km’ in 1984'”.
Seagrass recovery has occurred (154 km? by 2001)'",
but seagrass meadows have failed to recolonize the
intertidal mud flats in north and western regions and in
some areas seagrass meadows have at least 45 percent
lower biomass compared to 25 years ago”. A near
complete loss of seagrass (ca 31 km’] in the Gippsland
Lakes from the 1920s to 1950s coincided with reduced
commercial fish catches”. More recent estimates of
seagrass abundance suggest that there has been little
decline over the past 30 years®" except for some
localized replacement by algae. Similarly, in Port
Phillip Bay, little change in seagrass area was recorded
from 1957 (76 km’) to 1981 (96 km’)°**". From 1981 to
2000, the area of seagrass in Port Phillip Bay declined
from 96 km? to 68 km’, possibly due to increased
turbidity and eutrophication in Corio Bay and Swan Bay
(early 1990s) in the west and southwest of Port Phillip,
respectively. Drifting algal communities have replaced
some areas of seagrass vegetation.

In Queensland, declines of seagrass area resulted
from flooding and sedimentation. In Moreton Bay,

Eastern Australia

thousands of hectares of seagrass, which were present
prior to the 1980s, have been destroyed by the effects of
canal estate development. Deception Bay seagrasses
have declined since 1996 in what may be a cyclic
pattern. Both cases were due to low light and poor

Rob Coles visually estimating seagrass abundance and mapping
distribution (using differential GPS], Shoalwater Bay, Queensland

water quality associated with urban development and
possibly agriculture’. Loss from climatic events
(storms, flooding and cyclones] has occurred in a
number of regions including Hervey Bay (1000 km? and
27.75 km’ in separate events in the 1990s) and
Townsville. Anecdotal evidence and evidence collected
during lobster fishery surveys suggests that thousands
of hectares have been lost in the northwest Torres
Strait due to flooding and sedimentation from Papua
New Guinea, but these are remote locations and
difficult to track effectively.

In northeastern Australia, most seagrass losses
have been followed by significant recovery. For
example, approximately 1000 km’ of seagrasses in
Hervey Bay were lost in 1992 after two major floods and
a cyclone within a three-week period added to
pressures on the system from agricultural
development and land development associated with
increases in human populations'. The deepwater
seagrasses died, apparently from light deprivation
caused by a persistent plume of turbid water from the
floods and the resuspension of sediments caused by
the cyclonic seas. The heavy seas uprooted shallow-
water and intertidal seagrass. Recovery of subtidal
seagrass [at depth >5 m) began within two years of the
initial loss'“’, but recovery of intertidal seagrasses was
much slower. These seagrasses only started to recover
after four to five years and did not fully recover until
December 1998".

The capacity of tropical seagrasses to recover
appears to be a consequence of morphological,

% Ww Ww
= A 4
SH] YG y
\
\

123

Photo: L. McKenzie, DPI

124

WORLD ATLAS OF SEAGRASSES

physiological and life history adaptations; the plants can
be fairly resilient in unstable environments. Halodule
uninervis and Halophila ovalis are considered pioneer
species, growing rapidly and surviving well in unstable
or depositional environments'”:'”. Halophila tricostata
is an annual, only appearing in late September through
to February and being sustained by a sizeable seed
bank". Cymodocea serrulata occurs in deeper
sediments and has been linked to increased rates of

Case Study 11.1

BARRIER REEF LAGOON

Seagrasses in waters deeper than 15 m in the Great
Barrier Reef World Heritage Area were surveyed
between 1994 and 1999. A real-time video camera
and dredge were towed for four to six minutes on
1 426 sites to record bottom-habitat characteristics
and seagrasses. In conjunction with the camera tow,
a sled-net sample of benthos and a grab sample of
the sediment were collected.

Sampling included the Great Barrier Reef
province from the tip of Cape York Peninsula at 10°S
to approximately 25°S, or 1000 nautical miles of
coastline. Sites were located from inshore out to the

Probability of
seagrass occurrence

148
Longitude

Probability of occurrence of deepwater seagrasses in the Great
Barrier Reef Lagoon (contours obtained by spatial smoothing).

sediment accretion”. Zostera capricorni meadows

were found to recolonize through vegetative growth and
can therefore survive small-scale disturbances”.
Queensland's east and gulf coasts have areas
where seagrass meadows have expanded. Little is
known about long-term cycles in seagrass meadow
size and biomass. The losses and gains being
measured may fall within a natural range. In heavily
grazed coastal waters with high dugong and green

MAPPING DEEPWATER (15-60 M) SEAGRASSES AND EPIBENTHOS IN THE GREAT

reef edge up to 120 km from the coast. Seagrass
presence, species and biomass were recorded with
depth, sediment, Sechii disk depth, associations
with algae and epibenthos, and proximity to reefs.

Five seagrasses were present, all from the
genus Halophila, in depths down to 60 m. Sea-
grasses were present at 33 percent of sites
sampled. The species Halophila ovalis, Halophila
spinulosa, Halophila decipiens, Halophila tricostata
and Halophila capricorni were found. Halophila
tricostata is a species endemic to northern
Australia and Halophila capricorni is found only in
the southern Indo-Pacific. All other species are
broadly distributed throughout the Indo-Pacific
region”. Most seagrass seen in video tows was of
low density {<5 percent cover] and biomass ranged
from less than 1 g to 45 g dry weight/m’ (the highest
was recorded from a Halophila spinulosa-dominant
meadow in 21 mJ]. Mean biomass was 3.26 +0.36 g
dry weight/m’.

The map of seagrass was generated using
generalized additive models incorporating Loess
smoothers'”. The degree of smoothness was
minimized but sufficient to account for both spatial
effects and spatial correlation. The location of the
data points was recoded based on the proportion of
the distance the point was located between the coast
and the outer edge and the proportion from 10°S to
the southern edge. The model estimated that as
much as 40000 km? of lagoon and inter-reef area
may have at least some seagrass”. This type of map
or statement of probability is necessary when
factors such as depth make it impossible to plot
around the edge of the meadow even if that could be
defined. With areas of very low biomass and very
large areas with patchy seagrass, the concept of a
defined meadow is not always appropriate. Using
probability to estimate the likelihood of seagrass
presence must be explained with care as the

turtle populations, increases in meadow size and
biomass may reflect simply changes (decreases) in
herbivore populations and be an indicator of
disturbance rather than a positive measure.

AN ESTIMATE OF PRESENT COVERAGE

Gulf of Carpentaria and Torres Strait
Approximately 779 km’ of seagrass in the western Gulf
of Carpentaria were mapped in 1984. In 1986,

outcome may be scale dependent and the outcome
is definitely not a “map” in the sense it is normally
used. If you define the sampling unit as the entire
Great Barrier Reef Region, the probability of finding
seagrass in that sampling unit will be 100 percent. A
smaller unit will have a lower probability. Typically
the ability of a map drawn this way can be improved
if physical factors such as light and bottom-type
location can be incorporated in the model.

DEEPWATER SEAGRASSES
Deepwater seagrasses were most common in the
central narrow shelf regions which experience a
moderate tidal range and are adjacent to high-
rainfall rainforest catchments. Highest densities
occurred between Princess Charlotte Bay and
Cairns, and south of 23°S. Halophila tricostata was
found only between Princess Charlotte Bay and
Mackay. Other species were spread throughout.
Seagrasses (Halophila ovalis, Halophila spinulosa,
Halophila decipiens and Halophila capricorni)
occurred to 60 m depth. The frequency of occurrence
of seagrasses declined below 35 m. Halophila
decipiens was the most commonly found species at
all depths. Dense algae beds (mainly Caulerpa and
Halimeda) were found on the outer shelf north of
Cooktown. Where there are large tidal velocities and
ranges [4-6 m tidal range], just to the south of
Mackay, no major deepwater seagrass areas occur.
Some seagrass habitats were apparent further
south in Hervey Bay where tidal ranges moderate.
The ecological role of inter-reef seagrasses
and algae is not well understood. Some deepwater
meadows [<25 m] of Halophila ovalis and Halophila
spinulosa are important dugong feeding habitat.
Commercial fish and crustacean species were
uncommon in deep water compared to catches in
coastal intertidal and shallow subtidal meadows”.
This seagrass and benthic community
information is one of the major databases
supporting development of a multi-use marine park
plan for maintaining the biodiversity of the Great
Barrier Reef World Heritage Area based on the

Eastern Australia

Queensland Department of Primary Industries (QDPI)
mapped 184 km’ in the eastern gulf®” and 225 km?
around the Wellesley Island Group {southern gulf) in
1984").

Using probability models and ground-truthing,
the Torres Strait is estimated to contain 13425 km‘? of
seagrass habitat on reef platforms and non-reef soft
bottoms’ *, much of which is valuable habitat for
juvenile commercial shrimp.

BB Halophila decipiens
35 Halophila spinulosa
©) Halophila ovalis
— GBB Halophila tricostata. —
Halophila capricorni
WB Seagrass present ——

Frequency of occurrence (%]

15-25 25-35 35-45 45-55 55-65
Depth strata (m)

Frequency of probability of occurrence (percent adjusted for
sampling frequency) of seagrasses within each depth stratum.

Note: Seagrass present = all species combined lincluding
unidentified).

principles of comprehensiveness, adequacy, and
representativeness. This “representative areas”
program has used two processes: a data-based
statistical approach and a delphic expert
experience-based questionnaire approach. Thirty-
eight relatively homogeneous inter-reef bioregions
have been identified based on the presence and
distribution of seagrasses, algae, other benthos,
sediment and habitat descriptions. This information
will be used to select areas to protect in “no-take”
zones and to minimize the loss of economic use of
reef areas by the tourist and fishing industries and
by recreational users. The deepwater seagrass and
epibenthos mapping is an excellent example of
seagrass maps being used directly to support good
management decisions.

Source: Coles et al."!

125

126 WORLD ATLAS OF SEAGRASSES

SE OEE .-—0—_—0—0_.0.0—_—___ —eoeoaOrcvV138”Tnw ——

Northeast coast

The northeastern Australia coastline is either within
the Great Barrier Reef World Heritage Area with high
conservation values or includes coastline with sea-
grass meadows supporting valuable shrimp fisheries,
green turtle or dugong populations. The perceived
importance of seagrasses in these regions, as well as
concern about the downstream effects of agriculture,
effects of fishing and the possibility of shipping
accidents! have led to an extensive mapping program.
Broad-scale surveys conducted between 1984 and 1989
mapped seagrass habitats down to 15 m depth in
estuaries, shallow coastal bays and inlets, on some
fringing reefs, barrier reef platforms, inner reef and
Great Barrier Reef Lagoon". Since 1989 there have
been repeated surveys at finer scales of resolution in
certain localities as a result of specific issues (e.g. port
developments, dugong protection areas]. Some studies
have repeated surveys at a locality once or twice yearly

for up to four or more years””.

Case Study 11.2
WESTERNPORT BAY

Westernport Bay is a large estuarine tidal bay in
southern Victoria. It encloses two large islands and
has an area of 680 km’ of which 270 km’ is intertidal
mud flat. Intersecting the mud flats is a series of
complex channels where sediment movement Is
influenced by the water movement patterns in a net
clockwise direction.

Westernport Bay is an area of high biological
diversity because of its wide range of habitats,
including seagrass meadows, mangroves, salt
marsh and deepwater channels. It is an inter-
nationally significant coastal wetland acknowledged
by nomination to the Ramsar Convention on
Wetlands. The bay consists of extensive intertidal
seagrass meadows, subtidal meadows and macro-
algal communities. The dominant seagrasses are
Zostera tasmanica and Zostera capricorni. The
dominant macroalga associated with seagrass is
Caulerpa cactoides, which, with other algae,
comprises about 16 percent of the total marine
vegetation.

The catchment to the north of Westernport Bay
was cleared of vegetation in the late 1800s for
agriculture, and the bay is now subject to inputs of
nutrients and suspended particulates! Change in
seagrass distribution from 1956 to 2000 was
examined using aerial photography at four sites in
Westernport Bay! The four sites were Rhyll
(southern region), Corinella [eastern region], Stony

It is difficult to estimate the exact seagrass area
as published information is from overlapping zones and
information is being constantly updated as mapping
improves. The most accurate estimates of seagrass
meadows along the northeast coast are 5668 km’?
intertidal and shallow subtidal (down to 15 m water
depth)": 39-50)

From Cape York to Cairns, seagrass communities
are predominantly subtidal Halophila species with
approximately equal area of sparse and dense cover.
Species of Cymodocea and Syringodium are found in
shallow subtidal areas where there is shelter from the
southeast winds. Between Cairns and Bowen, around
70 percent of the area of seagrass is less than 10
percent cover and mostly a mixture of Halodule and
Halophila species, both intertidal and subtidal.
Between Bowen and Yeppoon approximately 50 percent
of the area of the mainly intertidal Halodule
communities is between 10 and 50 percent cover. South
of Yeppoon, the seagrass communities are mostly

Point [eastern region] and Point Leo {southwest
region). From 1956 to 1974, there was a decrease in
seagrass distribution at three [Rhyll, Corinella and
Stony Point) of the four sites. From 1973-74 to 1983-
84 an 85 percent reduction of seagrass and
macroalgal biomass, from 251 km? to 72 km’, was
reported in the bay”””!, much of it on intertidal
banks. A number of studies examined the causes of
this dramatic loss of seagrass habitat”””*”” focusing
on the effects of light reduction on seagrass
communities as a result of increased sediment
loads in the water column. These studies also
examined the increased elevation of intertidal banks,
the loss of pooling and the increased exposure of
seagrasses to desiccation, a consequence of
increased sediment inputs from catchment sources
and resuspension of sediments in the water column.
Annual sediment inputs from the northeastern
catchment [>86 200 m‘/year) were found to be six to
seven times the loads of sediments into other
regions of the bay (13000 m’/year|" leading to
decline in light availability in this region. Other
causes such as the effects of industrial effluents on
invertebrate fauna and subsequent reduced grazing
of epiphyte loads were examined. No conclusive
evidence was found that identified a single major
factor as the cause of seagrass loss. The effects of
seagrass loss on fish populations were also studied
and findings suggested that Westernport Bay
seagrass meadows play an important role in
enhancing fish production and marine invertebrate
numbers”.

denser, with approximately 60 percent of the area of
seagrass greater than 50 percent cover. These
seagrass areas are dominated intertidally by
Zostera/Halodule communities and subtidally by
Halophila communities.

Waters of the Great Barrier Reef World Heritage
Area deeper than 15 m have been surveyed and it is
likely that as much as 40000 km’ of habitat that may
support seagrass populations is present in the reef
lagoon". The map in this case was based on spatial
probability and cannot be compared with a map drawn
from global position system points taken on the edge of
a meadow.

New South Wales, Victoria and Tasmania

Estimates of seagrass area in New South Wales from
mapping exercises prior to 1985 were 155 km’ in 111
estuaries. In New South Wales the Conservation
Division of New South Wales Fisheries is presently
mapping seagrasses in large estuaries of the

Subsequent mapping of seagrass and
macroalgal habitats in Westernport Bay in 1995
showed that seagrass and macroalgal cover in the
bay had partly recovered, from an area of 72 km? in
1983-84 to 113 km? in 1995. A further increase to 154
km? was recorded in 1999" Despite these
increases, the seagrasses in the north and
northeast regions of Westernport Bay either remain
in poor condition or have not recovered”. This is
likely to be a result of poor water quality as
chlorophylla and suspended sediment concen-
trations increased in the northeastern waters of
Westernport Bay between 1975 and 2000. This
trend has reduced light availability and reduced the
biomass and productivity of seagrasses.

In April 2000, the effects of poor catchment
practices and water quality again resulted in
hundreds of hectares of seagrasses being lost during
a flood event. Although some recovery of seagrasses
has occurred over the last 15 years, seagrass
meadows in Westernport Bay would still appear to be
threatened by flooding and high turbidity even over
time periods as short as days to weeks.

The range of information from published
papers and technical reports on Westernport Bay
fails conclusively to attribute a single cause to the
dramatic loss of seagrass from 1974 to 1984. By
1999, seagrasses in the region had shown some
recovery, more than doubling the area present in
1984. Nevertheless, there are vast regions in West-
ernport Bay that have failed to recover, or they are at
their threshold of survival during high turbidity?”

Eastern Australia

Hawkesbury region and Port Hacking, but this
information is not yet available.

The Victorian Department of Natural Resources
and Environment has recently produced maps for bays
and inlets of Victoria that include 470 km’ of seagrass.
Fine-scale maps (1:10000) detailing seagrass species
composition and estimates of abundance have been
produced for large bays including Gippsland Lakes,
Corner and Nooramunga Inlets, Westernport Bay and
Port Phillip Bay. Smaller inlets that have been mapped
include Anderson, Mallacoota, Shallow, Sydenham,
Tamboon and Wingham Inlets. The dominant seagrass
communities include sparse to dense meadows of
Zostera tasmanica, Zostera capricorni and Posidonia
australis’”.

The Tasmanian Aquaculture and Fisheries
Institute mapped areas of seagrass in six bioregions of
Tasmania. The total area of mapped seagrass was 845
km’. The Boags, Flinders and Freycinet bioregions have
been mapped primarily from aerial photographs and

These regions are closest to inputs of nutrients and
sediments from a rapidly expanding urbanized
catchment with extensive agricultural activities.
Management strategies are being implemented to
improve water quality in the northeast region by
reducing flows of freshwater and loads of nutrients
and sediments. These strategies are useful, but
existing sediment resuspension issues and changes
to intertidal bank topography will limit the possibility
of full recovery of seagrass in this region.

127

128

WORLD ATLAS OF SEAGRASSES

LANDSAT (1:100000 or greater). The Bruny bioregion
has been recently mapped in detail from aerial
photography with extensive ground-truthing’ *”. No
mapping has been conducted in the Davey, Franklin and
Otway bioregions, but it is unlikely there is much
seagrass in these because of exposure to ocean swells
and because of high tannin loadings in estuaries (i.e.
Port Davey and Macquarie Harbour)".

South gulf coast of South Australia

Seagrasses in South Australia cover an area of
approximately 9620 km’. Shepherd and Robertson”
recognize three seagrass zones: exposed coasts, gulfs
and bays, and coastal lagoons, each with different
species composition. The exposed coasts are mainly
patchy Posidonia typically where islands or reefs give
local protection. The two gulfs which are a main feature

Case Study 11.3

Seagrasses are an integral and important part of
coral reef systems. The Green Island seagrass
meadows are one of many seagrass meadows found
on reef platforms in the Great Barrier Reef waters'”!
At a time when declines in seagrass biomass and
distribution have been widely reported, Green Island
is one of the few localities in the eastern Australian
region where expansion of seagrasses has been
recorded.

Green Island is a vegetated coral cay located
approximately 27 km northeast of Cairns. Ground-
truthing and mapping of seagrass distribution was
conducted in 1992, 1993 and 1994. Systematic
mapping by transects was adopted on each occasion
and vertical aerial photography (1:12000) was used if
captured within the same season that ground
surveys were conducted. Transects were located
along compass bearings from permanent markers.
A theodolite was used to accurately determine
geographic location of survey sites [+1.5 ml.
Estimates of above-ground seagrass biomass (three
replicates of a 0.25 m? quadrat), species composition
and sediment depth were collected every 20 m.
Underwater video and still photography were used to
provide permanent records. All data were entered
onto a geographic information system. Boundaries
of seagrass meadows were determined based on
the geographic position of a ground-truthed site and
aerial photograph interpretation. Digitally scanned
and rectified vertical aerial photographs were used
to map the past (1936, 1959 and 1972] seagrass
distribution to the northwest of Green Island Cay.

of the coast have a species gradient from entrance to
head with Posidonia species being replaced with
Amphibolis along the gradient. Three genera, Zostera,
Ruppia and Lepilaena, are also found where intertidal
mud flats occur. Coastal lagoons with a marine
environment, such as the Coorong which is 100 km long
and less than 2 m deep, are unique in this region. They
feature an association of marine and brackish water
genera such as Ruppia, Zostera and Lepilaena together
with some marine algae’.

USES

Seagrass habitats in this region are noted for their
importance as nursery areas for juvenile fish and for
the commercial penaeid shrimp fishery in
northeastern Australia. Coles et al.” recorded 134
taxa of fish and 20 shrimp species in the seagrasses

EXPANSION OF GREEN ISLAND SEAGRASS MEADOWS

From the interpretation of aerial photographs,
a high-density seagrass meadow of 0.39 +0.3 ha was
first visible in 1936 as an isolated patch near the
northwest tip of the cay. It appears to have expanded
into the back-reef area northwest of Green Island in
the 1950s to a small patch covering approximately
1.1 +0.3 ha in 1959. It increased from the 1950s to 6.5
+1.3 ha in 1972, 15.31 +2.29 ha in 1992, 22.71 +3.3 ha
in 1993 and 22.9 +2.4 ha in 1994. A survey in 1997
found little change”.

In 1994 Halodule uninervis {average above-
ground biomass, all sites pooled, 16.61 +1.4 g dry
weight/m’) was the dominant species in the meadow.
Cymodocea rotundata was the next most common
species (3.95 +1.6 g dry weight/m’), with Cymodocea
serrulata and Syringodium isoetifolium occurring in
small patches of the meadow (4.12 +0.7 g dry
weight/m’). Halophila ovalis (0.91 +0.3 g dry weight/
m*) occurred intermixed with Halodule uninervis
beyond the intertidal and subtidal edges of the main
meadow. Thalassia hemprichii was uncommon in the
meadow (0.03 +0.02 g dry weight/m’).

It has long been believed that the expansion of
Green Island seagrass meadows was the result of
biological and anthropogenic disturbances on the
reef. It was first thought that the increases in area of
the dense seagrass meadows to the northwest of
Green Island Cay were linked to increases in tourist
visitation and increased nutrients from the adjacent
sewage outfall. This is because low nutrient
availability dominates reef habitats such as Green
Island and seagrasses are nitrogen limited".

of Cairns Harbour. Seagrasses also provide food for
dugong and green sea turtle which are the subject of
conservation measures.

Apart from licensed worm and bait collecting
there is little or no gleaning activity on seagrasses in
eastern Australia.

Larkum et al.’ sum up the values of seagrass in
six basic axioms:
stability of structure;
provision of food and shelter for many organisms;
high productivity;
recycling of nutrients;
stabilizing effect on shorelines;
provision of a nursery ground for fish.

(sy (6) (S) fe} (©) e)

In our view this remains an excellent summary of
the uses and values of seagrass.

In 1972, a sewage system for hotel buildings
and public toilets on Green Island was established”
Sewerage effluent from this was discharged onto
the Green Island reef for 20 years, until December
1992 when a tertiary treatment facility was
completed. It is estimated that approximately 70-100
m* of sewage was discharged per day". With no
treatment to the effluent, it was essentially raw
sewage (nutrient loads unknown] being dumped
onto the western edge of the reef platform.

It was, however, unlikely that sewage provided
the major nitrogen source, as in September 1994,
Udy et al") measured leaf tissue '"°N and recorded
values from 1.3 to 1.7 parts per thousand suggesting
that the primary nitrogen source comes from either
fertilizers or No fixation®™. If the primary nitrogen
source was from sewage, the seagrass would have
had a leaf tissue 'N value closer to 10 parts per
thousand. It could be assumed that '"N values
would have been higher prior to the cessation of raw
sewage discharge in 1992, but '°N values tend to be
highly conservative due to internal recycling of
nitrogen in the seagrass.

Also, the expansion of the seagrass meadow
before the sewage pipe was installed indicates that
increased nutrient availability associated with the
sewage outfall in 1972 was not a primary cause of
the meadow expansion. This suggests other factors
including water seepage and nutrient translocation
from the cay, as well as regional changes
(agriculture and urban development) in nutrient
availability in Great Barrier Reef water may have
caused the observed expansion prior to 1972. The
continued expansion of the seagrass meadow after
1972 may have been influenced by the sewage

Eastern Australia

THREATS

Most Australian recorded losses of seagrass are
probably the result of light reduction due to sediment
loads in the water'“'. Quantifying loss of seagrass has
been difficult in many locations as maps are often
imprecise or unreliable and local change may be
indistinguishable from map error’. Long-term data
sets are not common so the extent to which loss of
seagrass can be attributed to natural long-term
cycles is impossible to estimate. Improved mapping of
seagrass meadows will enable losses to be more
accurately measured and tracked.

Coastal development, dredging and marina
developments are generic threats to seagrass in the
tourist regions of Australia’s east coast. While these
issues raise considerable public interest and concern
they are usually closely managed through legislative

discharge in addition to regional changes in nutrient
availability.

Seagrass composition at Green Island con-
tinues to change, with a rapid increase in the area of
Syringodium isoetifolium which was first recorded at
the island in the mid-1980s. With detailed maps and
geographic information system (GIS) formats,
changes in the future can be readily quantified and
the dynamics of reef island seagrass meadows
better understood.

(19)

Source: Udy et al
Industries

and Queensland Department of Primary
(35)

ia yyy
: Zo Breen sland

“,

kilometers

14598"
r

1936 ER 1959

reef-flat

129

130

oles, DPI

Photo: R. {

WORLD ATLAS OF SEAGRASSES

Thalassia hemprichii meadow on flat adjacent to Rhizophora forest,
Piper Reef, Queensland

processes and the actual areas of seagrass destroyed
are generally small.

Coastal agriculture may add to sediment loads in
catchments and the presence of herbicides in seagrass
sediments’ is a worrying trend, as unlike small-scale
coastal developments, this has the potential to destroy
large areas. Often the risk factors for the seagrass
environment are many kilometers away in upper water-
sheds. The Coorong Lakes seagrasses are affected by
changes in nutrients and freshwater flows in the Murray
River catchment which extends from South Australia up
to central Queensland thousands of kilometers north.

Port development and the management of risk
can influence seagrass survival and many sheltered
seagrass sites are also important port locations. The
configuration of shipping lanes in northeastern
Australia directs large ships transiting south of Papua
New Guinea into Great Barrier Reef Lagoon waters.
Shipping accidents remain a major concern for coastal
habitats and, while infrequent, can be potentially
devastating. Major programs exist in the western Pacific
to provide advice on shipping-related incidents'*".

Estuarine seagrass communities are increasingly
the most threatened of the seagrass habitats in eastern
Australia *’. As provincial centers develop along the
Queensland coast, rivers and inlets are often highly
affected and need careful management to maintain
these seagrass habitats and the fisheries they support’”.

Coastal habitats are threatened by coastal
development as well as the impacts of runoff from
poorly managed catchments, particularly when
associated with large bays such as Botany Bay,
Moreton Bay and Hervey Bay.

Reef seagrass habitats are the least threatened
seagrass community with minor damage from boating
and shipping activities. High tourist visitation rates and
associated sewage and poor anchoring practices are
identified as a threat at some localities. Acute impacts
such as ship groundings and associated spills would
impact heavily on reef platform seagrasses.

Although deepwater seagrasses are the least
understood seagrass community, they could be
impacted by coastal runoff (and associated light
reduction] and to some extent prawn/shrimp trawling
activities” “’, although the scale of any impact is largely
unknown and difficult to determine.

SEAGRASS PROTECTION

Seagrasses are habitat for juvenile fish and
crustaceans that in many parts of the world form the
basis of economically valuable subsistence and/or
commercial fisheries. The need to manage fisheries in
a sustainable way has itself become a motivating factor
for the protection of seagrasses’.

Approaches to coastal management decision-
making are complex, and much of the information
exists only in policy and legal documents that are not
readily available. Local or regional government author-
ities have control over small jurisdictions with
regulations and policies that may apply.

Approaches in eastern Australia to protecting
seagrass tend to be location specific or at least state
specific. The approach used depends to a large extent
on the tools available in law and to the cultural approach
of the community; in Australia these tools and
approaches have their origin in British common law.

While there is no international legislation, there is
a global acceptance through international conventions
(e.g. the Ramsar Convention on Wetlands, the
Convention on Conservation of Migratory Species of
Wild Animals and the Convention on Biological
Diversity) of the need for a set of standardized data on
the location and values of seagrasses. Numerous
studies worldwide have presented ideas for seagrass
protection. Cappo et al.'' summarized the main
pressures on fish habitats and seagrasses in Australia.
Leadbitter et al.’, Lee Long et al." and Coles and
Fortes’ expanded the implications for research and
management, a discussion that has Australian as well
as global relevance.

Protection by legislation
In the eastern Australian states of New South Wales
and Queensland, marine plants cannot be damaged
without a permit” *. In Queensland, the legislation
directly protects marine plants. Marine plants are
defined as “a plant [a tidal plant] that usually grows on,
or adjacent to, tidal land, whether living, dead,
standing, or fallen”, a definition which includes living
plants as well as seagrass plant material washed up on
the beach. This definition recognizes the role of even
dead plant material in the bacterial cycle that
ultimately supports fisheries productivity.

The Queensland Fisheries Act allows for
destruction or damage of seagrass only when a permit

has been assessed and issued. All permit issue is
directed by a policy that must be taken into account by
the person delegated under the Act to make the
decision. The policy requires that no reasonable
alternative exists. In states such as Queensland, fines
well in excess of US$0.5 million are applicable for
damaging seagrasses, with the possibility of associated
restoration orders.

All eastern Australian states have similar
protections in either Fisheries Acts or in National Park
or Marine Park Acts. Australia, in fact, has approxi-
mately 40 legislative instruments that directly influence
marine plant and/or seagrass management’, not
including regulations and management plans that as
subsidiary legislation may also be operationally vital to
seagrass protection. An example of this would be
fisheries legislation that limits areas where bottom
trawling can take place.

Protection by marine protected areas (MPAs)
Overlying state and local approaches, Australia also
has national legislation addressing international issues
such as treaties and conventions including the
Convention on International Trade in Endangered
Species of Wild Fauna and Flora (CITES) and world
heritage area declarations. The Great Barrier Reef
World Heritage Area is protected in legislation by the
world’s largest MPA, the Great Barrier Reef Marine
Park. This is unique in that it possibly has as much as
40000 km’ of seagrass”, much of which is afforded a
level of protection by the MPA. This can lead to
confusingly high levels of regulation; a seagrass
scientist working in east coast tropical Queensland
requires permits and must meet conditions from
national and state authorities.

However, the Great Barrier Reef Marine Park
model would not be appropriate in many situations as
the money to fund a large administrative authority,
legislative support, ongoing research and long-term
monitoring, and compliance is not available. More

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Eastern Australia

common are MPAs specific to a site and designed to

protect an area identified as having important

ecosystem functions.

The Queensland Fisheries Act‘ allows for the
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In recent years there has been a growing
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() maintain ecological processes or systems.

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base for future protective decisions and implementation.

AUTHORS

Rob Coles, Len McKenzie and Stuart Campbell, Queensland Department
of Primary Industries, Northern Fisheries Centre, P.O. Box 5396,
Cairns, Queensland 4870, Australia. Tel: +61 (0)7 4035 0111.
Fax: +61 (0]7 4035 4664. E-mail: rob.colesr{ddpi.qld.gov.au

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issues and new research directions. Marine Pollution Bulletin 41:
428-434.

Haynes D, Ralph P, Prange J, Dennison B [2000b]. The impact of
the herbicide Diuron on photosynthesis in three species of tropical
seagrasses. Marine Pollution Bulletin 41: 288-293.

Rasheed MA, Coles RG, Thomas R [2001]. Fisheries habitat
monitoring in Queensland tropical ports - a tool for port
management. In: Proceedings of the 15th Australasian

Coastal and Ocean Engineering Conference and the 8th
Australasian Port and Harbour Conference, 15th-18th September
2001. pp 89-95.

Lee Long WJ, McKenzie LJ, Rasheed MA, Coles RG [1996b].
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Proceedings of an International Workshop, Rottnest Island,
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University of Western Australia, Perth. pp 345-350.

Coles RG, Lee Long WJ, Squire BA, Squire LC, Bibby JM

[1987]. Distribution of seagrasses and associated juvenile
commercial penaeid prawns in north-eastern Queensland

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103-119.

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68
69
70

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Eastern Australia

133

Coles RG, Fortes M [2001]. Protecting seagrass - approaches and
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Synthesis of Australian Fisheries Habitat Research. FRDC Project
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Leadbitter D, Lee Long W, Dalmazzo P [1999]. Seagrasses and their
management - implications for research. In: Butler A, Jernakoff P
(eds) Seagrass in Australia: Strategic Review and Development of
an R & D Plan. CSIRO, Collingwood. pp 140-171.

Smith A, Pollard D [1998]. Fish Habitat Protection Plan No. 2;
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Brisbane, 137 pp. http://www.legislation.qld.gov.au/legislation.htm
http://chrisweb.dpi.qld.au/chris

Great Barrier Reef Marine Park Authority [1999]. An Overview of
the Great Barrier Reef Marine Park Authority Representative Areas
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Fortes MD [1989]. Seagrasses: A Resource Unknown in the ASEAN
Region. International Center for Living Aquatic Resources
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Hastie TJ, Tibshirani RJ [1990]. Generalized Additive Models.
Chapman and Hall, London.

Derbyshire KJ, Willoughby SR, McColl AL, Hocroft DM [1995]. Small
Prawn Habitat and Recruitment Study - Final Report to the
Fisheries Research and Development Corporation and the
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Department of Primary Industries, Cairns.

Bulthuis DA [1983b]. Effects of in situ light reduction on density and
growth of the seagrass Heterozostera tasmanica (Martens ex
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Experimental Marine Biology and Ecology 67: 91-103.

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Ministry for Conservation, Victoria.

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Committee on the Project 88/91: Consequences for Commercial
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Institute of Marine Sciences, Victoria.

Sargeant | [1977]. A Review of the Extent and Environmental Effects
of Erosion in the Westernport Catchment. Environmental Studies
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Lee Long WJ, Coles RG, Helmke SA, Bennett RE [1989]. Seagrass
Habitats in Coastal, Mid Shelf and Reef Waters from Lookout Point
to Barrow Point in North-eastern Queensland. QDPI Report to the
Great Barrier Reef Marine Park Authority. Queensland Department
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Baxter IN [1990]. Green Island Information Review. Report to the
Great Barrier Reef Marine Park Authority - August 31. Great
Barrier Reef Marine Park Authority, Townsville.

Morissette N [1992]. Identifying Areas of Seagrasses within the
Great Barrier Reef Region Threatened by Anthropogenic Activities.
Great Barrier Reef Marine Park Authority, Townsville.

Udy JW, Dennison WC [1997]. Growth and physiological responses
of three seagrass species to elevated nutrients in Moreton Bay,
Australia. Journal of Experimental Marine Biology and Ecology 217:
253-277.

Grice AM, Loneragan NR, Dennison WC [1996]. Light intensity and
the interaction between physiology, morphology and stable isotope
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Biology and Ecology 195: 91-110.

134 WORLD ATLAS OF SEAGRASSES

12 The seagrasses of

NEW ZEALAND

ew Zealand (Aotearoa) is an isolated archi-
N pelago, consisting of two main islands and a

number of smaller islands which lie in the
southern Pacific Ocean. Until quite recently, the
seagrass flora of New Zealand was thought to consist
of two species of Zostera: Zostera capricorni, which
also occurs in eastern Australia, and an endemic
species, Zostera novazelandica. {Two species of Ruppia
- Ruppia polycarpa and Ruppia megacarpa - also occur
in brackish and freshwater wetlands in New Zealand",
but are not considered further here.) Zostera
novazelandica was originally described by Setchell in
1933 on the basis of morphological variation in
vegetative characters, using a relatively limited sample
of plants”. In fact, there is quite large morphological
variation within natural stands of Zostera in New
Zealand and reproductive structures occur infrequently
in many populations’®. This variation has caused
considerable uncertainty in identification over the past
century, and workers have variously referred to the
New Zealand Zostera as Zostera nana, Zostera
muelleri, Zostera marina and Zostera tasmanica“”"'. A
recent molecular phylogeny of the Zostera group,
however, demonstrated that Zostera capricorni and
Zostera novazelandica are, in fact, conspecific and that
there is likely to be only a single species in New
Zealand, hereafter referred to as Zostera capricorni”.

DISTRIBUTION

Zostera capricorni occurs throughout the mainland
coast of New Zealand, from Parengarenga Harbour in
the north to Stewart Island in the south (Tables 12.1 and
12.2). It is found predominantly between mid and low
tidal levels in estuaries and sheltered harbors". On the
eastern coastline of the two main islands, patchy
stands of Zostera capricorni also occur on the tops of
siltstone platform reefs in open coastal areas, where
they are interspersed with algal beds and biotic
assemblages more characteristic of rocky, intertidal

G.J. Inglis

assemblages” |". Stands vary in extent, biomass and
stability, depending upon their location” * '”. In large,
shallow estuaries subject to wind fetch, and on
platform reefs exposed to oceanic waves, stands of
Zostera capricorni typically consist of a mosaic of
patches that range in size from less than 1 m’ to 15 m*
and which exhibit large interannual fluctuations in
extent '* "|. The largest persistent stands appear to
occur in estuaries and embayments with relatively
clear, tidal waters that are situated away from major
urban centers, such as Parengarenga Harbour,
Farewell Spit, Whanganui Inlet and estuaries of the
eastern Coromandel Peninsula.

Despite the wide geographic distribution of
Zostera capricorni in New Zealand, there have been
relatively few published studies of its extent,
demography or ecology. Part of the reason for this may
be its relative scarcity in many New Zealand estuaries.
Zostera capricorni is absent from, or occurs in
relatively small areas within, many of the shallow,
turbid estuaries in New Zealand. Seagrass habitats
have been mapped in only 22 of New Zealand's 300-
plus estuaries (Table 12.1). The areas that have been
mapped typically represent less than 3 percent of the
total intertidal area of each estuary. Exceptions include
tidally dominated embayments, such as Whanganui
Inlet and Whangamata, where seagrass meadows
cover up to 31 percent and 18 percent of the intertidal
area, respectively. Just over half (54 percent] of New
Zealand's estuaries are unsuitable for seagrass growth
as they are shallow, barrier-formed estuaries, built
around the mouths of rivers'“', so Zostera capricorni is
likely to be a relatively uncommon benthic habitat in
many estuarine environments.

ECOSYSTEM DESCRIPTION

Zostera capricorni stands in New Zealand, like those
elsewhere in the world, support a diverse and abundant
assemblage of invertebrates that is often richer than

unvegetated habitats nearby” ' 7". The composition

of the invertebrate assemblages varies with the size
and stability of the seagrass stand and its position
relative to other habitats’. Bullomorph and proso-
branch gastropods are distinctive components of the
epibenthic fauna’. Small crustaceans and polychaetes,
which are particularly abundant within seagrass
meadows, are important sources of food for wading
birds, such as the South Island pied oystercatcher, bar-
tailed godwit, pied stilt and royal spoonbill; and for
fishes such as mullet, stargazers and juvenile
flatfish®. Seagrass fragments are also a common
food of garfish (family Hemirhamphidae], which are
popular with recreational fishermen”.

Large densities of small cockles, Austrovenus
stutchburyi, and other bivalves are common in
seagrass habitats” *”*'. Many of these species are not
restricted exclusively to seagrasses, but are often
more abundant within them as juveniles. Several
authors have also drawn a_ strong historical
association between the distribution of seagrasses
and beds of the New Zealand scallop, Pecten
novazelandiae™ *". However, the life cycle of the Pecten
novazelandiae is not dependent on seagrass habitats
and commercial stocks exist in areas where Zostera
capricorni is not present’.

A recent survey of more than 25 harbors in
northern New Zealand suggests that seagrasses may
be important nursery habitats for newly settled
snapper (Pagrus auratus, family Sparidae]”. Snapper
is arguably New Zealand’s most sought-after marine
fish and is the subject of a large commercial and
recreational fishery. Adult snapper spawn in large bays,
but juveniles are found predominantly in sheltered bays
and shallow estuaries during their first summer, before
they move to deeper coastal waters’. Snapper under
one year old have been found in few other coastal
habitats and appear to occur mostly in clear-water,
sandy reaches of estuaries, the areas most favorable to
seagrass growth. Juveniles of other estuarine and
coastal fishes are also abundant in seagrass
meadows”.

The presence of Zostera capricorni on siltstone
platform reefs allows some estuarine species to inhabit
these open coastal environments. For example, the
endemic burrowing crab Macrophthalamus hirtipes
occurs exclusively in Zostera capricorni on siltstone
reefs, where it feeds on seagrass detritus and
associated invertebrates”. On estuarine mud flats,
Macrophthalamus hirtipes is more widespread and not
necessarily restricted to seagrasses.

HISTORICAL CHANGES IN DISTRIBUTION
The lack of detailed mapping and long-term study of
seagrass habitats in New Zealand makes it difficult to

New Zealand

+ Parengarenga Harbour
Houhora Harbour "Ue NSarensa 1%
"

Whangarei Harbour
35°§

Kaipara Harbour Firth of Thames

.
Auckland Coromandel Peninsula

Manukau Harbour £
@ Whangamata

«Tauranga Harbour
.

TASMAN SEA
HO? s Kawhia Harbour .

Waimea Inlet North Island
Farewell Spit
Whanganui Inlet ¢

.
» Te Angiangi
Marine Reserve

Oharito Lagoon Pee or

¢ Kaikoura Peninsula
South Island Christchurch
e » Purau Bay
fkaroa Harbour

NEW ZEALAND

Waituna
Lagoon ,

Otago Harbour

a. 0 100 200 300 Kilometers
Stewart Island “Awarua Bay —
165° E 170° E

175° E 180° E
Map 12.1
New Zealand

determine how their distribution and extent have
changed over time. Seagrass meadows undoubtedly
supported elements of the economies of pre-European
and early European life in New Zealand. The name
given to Zostera capricorni by New Zealand's

Table 12.1
Area of seagrass in New Zealand estuaries where benthic
habitats have been mapped

Estuary Total area of
Zostera capricorni km’)
Mahurangi Harbour''”! 0.03
Whangateau Harbour!” 0.33
Pahurehure Inlet (Manukau Harbour)!”
Arm of Kaipara Harbour'”®!
New River Estuary'"®!
Matakana Harbour
Manaia Estuary'””!
Whitianga Harbour
Tairua Harbour”
Whangamata Estuary
Wharekawa Estuary'*””
Otahu Estuary”
Te Kouma Estuary
Firth of Thames?”
Tauranga Harbour”
Ohiwa Estuary"®!
Waimea Estuary
Havelock'"®!
Whanganui Inle
Avon-Heathcote Estuary
Kaikorai Estuary!"
Harwood, Otago Harbour

(19)

{20}

(20)

(18)

!23)

(18)

(24)

135

136

WORLD ATLAS OF SEAGRASSES

indigenous Maori - rimurehia - suggests that they may
have recognized the food value of its starchy
underground rhizome. Rimu is the general term for
seaweed or sea plant and réhia was a type of jelly-like
stew that was made by boiling marine plants [more
usually algae] with tutu berries, the fruit of a wetland
plant (Coriaria spp.)'“'. Seagrass leaves were also
occasionally used by Maori to adorn items of clothing.
Hamilton in 1901 described widows wearing mourning
caps (potae taual that had veils made from seagrass’.

Historical accounts by early European naturalists
suggest that meadows were quite widespread at the
end of the 19th century. Colenso in 1869 described
them as “very plentiful” and occurring in “many places
in the colony” from the top of the North Island to
Stewart Island’*°”. Leonard Cockayne (1855-1934)

Table 12.2

Location Description

Parengarenga Harbour'"!
and bird populations

Muriwhenua Wetlands?"

Whangarei Harbour’ *"!

(21)

described Zostera as “extremely common in shallow
estuaries” where it “covers the muddy floor... for many
square yards at a time”. At that time, seagrass was
apparently so abundant that at least two authors
proposed harvesting it for export to London, where
dried Zostera fetched between £7 10s and €10 per ton
as a stuffing for mattresses and upholstered
furniture’ *’. This suggestion does not appear to have
been acted upon. Other accounts describe Zostera as
“common in many of the lagoons and estuaries which
occur along the coast"”’, and as covering “extensive
areas of sheltered mud flats between the tides””.
Oliver in 1923 described extensive meadows of Zostera
in Parengarenga Harbour, Tauranga Harbour and
Golden Bay, Stewart Island”. According to him,
"masses of Zostera” were occasionally torn up by

List of locations where seagrasses have been recorded in New Zealand

Extensive tidal sand flats (42 km’) mostly covered in seagrass. Important feeding grounds for large fish

Includes Houhora (10.5 km’) and Rangaunu Harbours (74 km’). Extensive tidal sand flats mostly
covered in dense beds of seagrass, supporting abundant mollusks, polychaetes, anemones, asteroids
and crustaceans. Important feeding grounds for large fish and bird populations

Lush seagrass beds present until late 1960s. Some recent recovery

Whangapoua Wetlands
Waitemata Harbour”!
Tairua Estuary?”
Whangamata Estuary
Wharekawa Estuary”
Kaipara Harbour"!
Manukau Harbour

(20)

(12, 13, 21)

Firth of Thames")
Kawhia Harbour?”
Tauranga Harbour"!
Maketu-Waihi Estuaries"!
Ohiwa Harbour'"® 2°21)

Ahuriri Estuary and Wetlands:

Te Angiangi Marine Reserve-East’”

Te Tapuwae 0 Rongokako
Pauatahanui Inlet!**!

Farewell Spit?"

Seagrass present on mud flats (ca14% of the area]. Significant site for shellfish gathering

Seagrass meadows much reduced since 1960s, now in small abundance in a range of locations
Around 1.25 km? in 1995, covering ca 23% of the tidal flats

Around 0.51 km’ in 1995, covering ca 18% of the tidal flats

Around 0.50 km? in 1995, covering ca 32% of the tidal flats

Extensive mud flats and sand flats, but limited area of seagrass

Extensive intertidal mud flats with large beds of seagrass in the 1960s. Current stands are patchy and
temporally variable

Internationally important feeding area for waterfowl (Ramsar Site]. Around 0.3 km’ of seagrass on

tidal flats of ca 85 km* Traditional food gathering area. Important local fisheries for snapper and flounder
Seagrass beds often present on tidal sand and mud flats

Around 29.3 km? of seagrass remaining (1996). Decline of 34% overall from 1959 and 90% in subtidal
meadows. Important shellfishery, spawning and nursery areas for marine fishes

Intertidal mud flats and sand flats have local areas of seagrass

About 23.8 km’ of intertidal flats with 1.1 km? of seagrass. Outstanding

importance as an area for traditional shellfish collection

Patches of seagrass in the marine reaches of the estuary, along with

Ruppia and green algae. Important nursery for fish. High diversity and abundance of invertebrates,
especially cockles

Patches of seagrass on coastal reefs. Marine reserve

Large areas of Zostera capricorni on the banks of the inlet near deltas of Horokiwi and

Pauatahanui streams

Extensive areas of sand and mud flats. Large areas of seagrass.

Internationally important area for waterfowl (Ramsar site]

storms and washed onto beaches or swept out to sea in
these areas.

In the major South Island city, Christchurch, mud
flats of the Avon-Heathcote Estuary were reportedly
“covered in great expanses of eelgrass (Zostera]” prior
to European settlement". Early photographs clearly
show dense meadows lining the sand banks of the main
channels“ and accounts described seeing eels
feeding in “lush paddocks” of seagrass that grew in the
deep channels“). Later records document the rapid
disappearance and stuttering recovery of Zostera in the
estuary. By 1929, the “lush paddocks” had been
reduced to sparse, small patches’. Loss of the
meadows was associated with the decline of small
fisheries for shrimp and periwinkles in the estuary and
caused a “severe and rapid degradation” of feeding

New Zealand

grounds for wading birds, which were hunted
extensively at the time for food and sport” “". At least
ten families had made their living harvesting shrimp
from what they referred to as “shrimp grass"“”. By
1952, the seagrass had disappeared almost completely,
with only a few, very small patches remaining in the
northern channel of the Avon River'!. Since then,
patches have waxed and waned in abundance. By 1970
Zostera had almost completely disappeared'’*“”. In
1981, small patches covered around 14 percent of the
tidal flats, but these disappeared later in the same year
with almost complete defoliation occurring in many
areas”. The most recent surveys, in 1999, show a total
area of around 0.137 km’ that comprises around eight
consolidated patches'"”’.

Seagrass losses have also been reported in other

Location

Whanganui Inlet": 7!

Waimea Inlet!" 2”
Parapara Inle
Moutere Inlet'®?!

{621

Waikawa Bay (Queen Charlotte]'**’
Wairau Lagoons" *!

Kaikoura Peninsula’ ° *
Karamea Estuary’?
Saltwater Lagoon
Okarito Lagoon": °*!

(21)

Avon-Heathcote Estuary,
Christchurch'2": 4”

Akaroa Harbour'®”!

Purau Bay, Lyttleton Harbour”

Brooklands Lagoon'“* **!

Otago Harbour!” *”!

New River Estuary

Awarua Bay'"!

Toetoes Harbour

(21)
(21)

Freshwater?"

Paterson Inlet, Stewart Island!”
Moeraki Beach'*”!

Mahurangi Harbour
Whangateau Harbour
Whitianga Harbour”
Manaia Harbour”!
Te Kouma Harbour
Otahu Estuary”!

(15)

(16)

(20)

Description

Large seagrass beds (8.6 km’], especially in the northern part of the inlet.

Important nursery for marine fishes. Marine reserve

Extensive bar-built estuary. Around. 0.28 km’ of seagrass

Zostera capricorni on silt deposits on the rock platform and on mud flats

Large mud flats with extensive beds of Zostera capricorni and shellfish.

Important nursery for marine and freshwater fishes

Patches of Zostera capricorni present

Extensive areas of algae, Ruppia megacarpa and some Zostera. Nursery

habitat for marine and freshwater fishes

Zostera capricorni present on coastal siltstone reefs at Wairepo flats and Mudstone Bay

Mud flats with extensive areas of seagrass and large densities of invertebrates

Bare or sparsely vegetated tidal mud flats

Middle reaches of lagoon dominated by Zostera, upper reaches characterized by dense beds

of Ruppia, Lepidena and Nitella

Patches of seagrass grow between low and mid tide close to the Avon Channel. Seagrass more
abundant prior to 1929. Nationally important area for waterfowl. Among the most important food
gathering sites for South Island Maori in pre-European times

Extensive areas of seagrass on tidal flats at Duvaechelle and Takamatua Bays

Patches of seagrass

Scattered, large circular patches of Zostera capricorni prior to 1978. None recorded in 1991
Around 0.8 km? of seagrass on tidal flats at Harwood

Extensive mud flats with seagrass. Important source of kaimoana. Nationally important wildlife area
Extensive mud flats with seagrass. Important source of kaimoana. Nationally important wildlife area
Mud flats with extensive areas of seagrass and large densities of invertebrates. Nationally
important wildlife area

Mud flats beyond the river mouth support seagrass

Patches of seagrass on coastal reefs

Around 0.03 km? in 1999 in a single meadow.

Around 0.33 km? in 1999 consisting of two main beds in the southern arm
Around 0.5 km? in 1995, occupying ca 0.6% of the estuary area

Around 0.27 km? in 1995, covering ca 7.5% of the estuarine flats

Around 0.05 km? in 1995, covering ca 2% of the tidal flats

Around 0.002 km? in 1995, covering ca 0.4% of the tidal flats

137

138

WORLD ATLAS OF SEAGRASSES

parts of the country. Zostera was reputedly once very
abundant in Waitemata Harbour, the location of New
Zealand's largest city, Auckland (population ca 1
million). Before 1921, seagrass dominated large areas
of Hobson Bay and Stanley Bay, but by 1931, it had all
but disappeared” *'. Powell" associated this loss with
marked reductions in catches of snapper and other
carnivorous fishes. At the time, he speculated that “in
respect to depletion of harbour fishing grounds
generally [loss of seagrass] may be a more important
factor than either over-fishing or assumed harbour
pollution”. This hypothesis has been given greater
weight by research that suggests an important nursery
role of seagrasses for juvenile snapper'”.

Extensive meadows in the Tamaki Estuary,
Howick Beach, Okahu Bay, Kawakawa Bay, Torpedo
Bay and Cheltenham in the Auckland district that
were present during the early 1960s disappeared by
the 1980s""’. Well-developed stands of seagrass also
occurred on Te Tau Banks and along the northern tidal
flats of Manukau Harbour in the early 1960s!”
Descriptions at the time referred to “splendid Zostera
fields of the Manukau Harbour... in some places up to
a mile across". Most of these areas had also
disappeared or were severely reduced in size by the
early 1980s”,

Further north, “lush beds” of seagrass on mud
flats in Whangarei Harbour disappeared in the early
1960s'“*". In Tauranga Harbour, Park recorded a
decline of around 15 km* (about a third of the total area
of seagrass) between 1959 and 1996’. Subtidal
meadows were most affected, with just 0.46 km?
remaining out of the 4.79 km? present in 1959 (a 90
percent reduction).

The causes of these declines are generally
unclear. They have variously been attributed to a range
of different human activities and natural events. In the
Avon-Heathcote Estuary, the loss was linked to the
practice of “river sweeping” which began in 1925 to
clear silt and plant growth that had accumulated in the
two rivers which feed into the estuary’. Large
quantities of sediment were released during the 25
years that the sweeper operated, producing a muddy
sediment layer in the estuary up to 25 cm deep.
Untreated sewerage effluent and industrial waste from
the rapidly growing city of Christchurch were also
discharged into the estuary at this time and may have
contributed to the decline“. In Waitemata Harbour, the
disappearance of seagrass was attributed to waterfront
construction, channelization of tidal streams and runoff
of fine sediments from surrounding land develop-
ment’. In Whangarei Harbour, a major cement works
discharged around 106000 metric tons of limestone
washings each year into the surrounding waters. The
discharge significantly reduced water clarity and has

been implicated in the disappearance of extensive areas
of seagrass’ *"!

Armiger reported the widespread die-back of
seagrass throughout New Zealand during the 1960s'"".
In 1964, she isolated a slime mold from some of the
affected populations that resembled Labyrinthula
zosterae”, the pathogen responsible for the infamous
wasting disease epidemic in North Atlantic Zostera
during the 1930s'**. Subsequent collections and
observations showed that the mold and symptoms of
die-off were present throughout both the North and
South Islands*". Other studies have reported sporadic
outbreaks in some populations’**“”. Curiously, the first
recorded disappearance of seagrass meadows in New
Zealand, from Waitemata Harbour and the Avon-
Heathcote Estuary, occurred at much the same time as
the northern hemisphere epidemic and corresponded
with reports of the large-scale disappearance of

Zostera in South Australia".

PRESENT THREATS
There has been no recent assessment of the condition
of New Zealand's estuaries and, therefore, of
contemporary threats to seagrass habitats. New
Zealand is relatively sparsely populated {ca 3.8 million
people in a total land area of 268021 km‘) so that,
although most of its estuaries have settlements
nearby, only six are located within urban environments
that contain more than 80000 people’. Estuarine
habitats have, however, been progressively modified
since the times of Polynesian {ca 800 years ago) and
European [ca 200 years ago) settlement. Land
clearance, shoreline reclamation, harbor development,
flood mitigation works and discharge of pollutants have
had direct impacts. Less than 23 percent of the land
area of the country now remains in native forest with
significant areas converted to agricultural production
(51 percent] or plantation forestry (6 percent]!
Sedimentation is the most widespread problem in
New Zealand’s estuaries. New Zealand is a
predominantly mountainous and hilly country, with
nearly half of the land mass at slopes steeper than 28
degrees. Its rivers carry a particularly high load of
suspended sediments as a result of the steep terrain
and relatively high annual rainfall"!. Deforestation and
rural land management have exacerbated the delivery
of suspended sediments to coastal areas and many of
New Zealand's larger estuaries are very turbid (light
attenuation coefficients up to 0.75/m’‘), with compara-
tively high rates of sediment accretion. In some
northern estuaries, this has meant that the area of
intertidal habitat has slowly been reduced by increases
in the area of mangroves and supratidal salt marsh.
Losses of seagrass habitat have been attributed to
increased sedimentation and turbidity in a number of

estuaries'“*7“4°2° and it remains the biggest

challenge for restoration of submerged aquatic
vegetation.

Large areas of plantation forest are now coming
into production in New Zealand and harvests are
expected to double within the next ten years to more
than 600 km’ per year. The largest increases are likely
to occur in regional areas of the North Island
(Northland, Coromandel, East Cape, Hawkes Bay, and
southern North Island), and to include areas bordering
some of the most significant remaining areas of sea-
grass {e.g. Parengarenga, Houhora and Coromandel
Harbours). It will be important for industry and regional
authorities to manage sediment and nutrient runoff
from this activity to avoid additional impacts on the
ecology of these estuaries.

Nutrient enrichment from land-based sources is a
significant problem in some urban estuaries. Recurrent
blooms of macroalgae in Tauranga Harbour and the
Avon-Heathcote Estuary in Christchurch have been
attributed to nutrient loads from wastewater discharge
and urban runoff. No direct studies have been done of
the effects of nutrient loading from these sources on
seagrass growth, although both estuaries have had
significant seagrass meadows in the past”*“““”". Less
information is available on nutrient loads to estuaries
outside the major urban centers. The most widespread
sources of nitrates entering New Zealand rivers are
likely to be associated with effluent and runoff from
agricultural production’. It is unclear what impacts
these diffuse sources have had on seagrass habitats.

In some areas, recreational activities have had
localized impacts on seagrasses”. In Otago Harbour,

Figure 12.1

New Zealand

for example, horse riding and four-wheel drive bikes
occasionally rip up rhizomes and roots leading to the
formation of large bare patches that can take longer
than one year to regrow. Heavy trampling (more than
ten passes in one area) across the seagrass flats has
also been shown to cause trench formation and lasting
damage, but it is unclear how widespread this is”.

Occasional, recurrent outbreaks of wasting
disease appear likely in New Zealand seagrass
populations. Further study is required to understand
the epidemiology of these outbreaks and, in particular,
if they are exacerbated by human activities. In the first
instance, this requires an understanding of the
resilience of different meadow types (e.g. large versus
patchy, persistent versus ephemeral) to outbreaks of
the disease and the method of transmission of the
pathogen from one location to another.

Nevertheless, there are positive signs that
seagrass meadows are Slowly returning to some areas
from which they had been lost. In Whangarei Harbour,
improvements in water quality over the past two
decades have led to the re-establishment of
seagrasses in areas from which they had disappeared.
Discharges of limestone washings into the harbor
ceased in 1983 and, since then, improvements in
sewerage wastewater and other discharges have
greatly increased water quality’. This pattern has
been repeated in other estuaries as point sources of
pollution have been removed or have been better
managed over the past 20-30 years. Regrowth of
seagrasses in the Avon-Heathcote Estuary is no doubt
attributable, in part, to improvements in water quality
that have been made through upgrading treatment of

An example of changes in the historical distribution of seagrasses in New Zealand

Ref: 897 1/2

‘=
=)
a
a
=)
=
=i
=
5
=
2
=
o
oO
>
oO
ao
oO
=
oO
=
s
=
ie
oO
=)
a
uw
5
r=}
=
om

P{hoto: G. Inglis

Moncks Bay in the Avon-Heathcote Estuary, Christchurch at low tide in 1885 [left] and 2003 [right]. The channel morphology has changed
considerably since 1885 and the once extensive intertidal sand banks have all but disappeared. Seagrass meadows, which can be seen
clearly as dark bands lining the sand banks in 1889, are no longer present. It is unclear whether the change in channel morphology
preceded the loss of seagrass or resulted from it, as the root and rhizomes of seagrass meadows trap and hold soft sediments in place.

139

140

WORLD ATLAS OF SEAGRASSES

wastewater and urban runoff and ending disturbance of
river habitat’“*”. Non-point sources of pollution and
urban stormwater, however, remain significant
problems for many estuaries.

POLICY AND MANAGEMENT

Seagrasses and other aquatic macrophytes are not
specifically protected by legislation in New Zealand, but
are provided for under a variety of resource man-
agement and conservation legislation. Responsibility
for the protection and management of coastal habitats
is split among several national and regional
authorities.

The Resource Management Act 1991 [RMA] is an
overarching piece of legislation that governs the use of
most natural and physical resources [excluding
fisheries) in New Zealand. Under the RMA, regional
authorities have principal responsibility for managing
the use of coastal environments and are required to
prepare regional coastal plans as the strategic basis
for guiding decisions about resource use in these
areas. Development activities within the coastal
marine area require approval (“resource consent")
from the local authorities under the RMA and must be
consistent with the provisions of the coastal plan.
Priorities for coastal management were set by the
Minister of Conservation in the New Zealand Coastal
Policy Statement and these serve as a guide for

Case Study 12.1
A SEAGRASS SPECIALIST

An unusual seagrass specialist in New Zealand Is
the small endemic limpet, Notoacmea helmsi
(scapha] (see drawing, right). This species appears
to occupy an almost identical niche to the North
Atlantic species Lottia alveus, which reputedly
became extinct during the wasting disease epidemic
of the 1930s? Like Lottia alveus, Notoacmea
helmsi(scapha) is a small, elongate limpet (ca 4 mm
long x 1.75 mm wide) that fits perfectly onto the
narrow leaves of Zostera”.

Unfortunately, there have been no studies of
its life history, so it is unclear if it is as specialized as
its North American counterpart and, although it was
reportedly once widespread in New Zealand, there
is no contemporary information on its distribution
and abundance. The absence of detailed study also
means that there is some uncertainty about whether
Notoacmea helmsi {scapha) is a true species or
simply a morphological variant of the larger
estuarine limpet Notoacmea helmsi helmsi**.

The New Zealand limpet provides a unique

development of the regional coastal plans. Wetlands
are specifically identified as a “matter of national
importance” in the RMA that must be taken into
account when decisions are being made about
resource use. Because of this, many freshwater and
estuarine wetlands are specifically listed as “areas of
significant conservation value” in existing and
proposed coastal plans, and are subject to relatively
strict development controls. In some instances,
regional authorities have used regulatory measures
such as estuarine protection zones to exclude
damaging activities from sensitive environments.
Regional authorities are also responsible for
maintaining coastal water quality under the RMA and
regulate land-based activities that can detrimentally
affect water quality.

The New Zealand Fisheries Act 1996 provides for
the “utilization of fisheries resources while ensuring
sustainability”. This includes managing the current and
potential production of fisheries in New Zealand and
their impact on the habitats that support them.
Although marine vegetation is not specifically mention-
ed in the Act, it establishes environmental principles to
guide the utilization of fisheries resources. These
include the “maintenance of biological diversity” and
the "protection of habitat of particular significance for
fisheries management”. Provisions allow for the pro-
tection of specific areas that are important for local and

opportunity to study the causes of rarity and
extinction in marine environments and to determine
what impact [if any) loss of the North Atlantic limpet
may have had on other species that live and feed in
seagrass meadows.

Morphology and habit of the New Zealand seagrass limpet
Notoacmea helmsi(scapha).

Source: Redrawn from Morton and Miller)

customary fisheries (ta/apure}, traditional fishing
(mataitai) and for the protection of specific stocks or
their habitat.

Legal protection of coastal waters is mostly
administered by the Department of Conservation under
the Marine Reserves Act 1971. Marine reserves contain
the highest level of protection for natural marine
environments in New Zealand; all species and habitats
are protected from exploitation. There are currently 16
marine reserves in New Zealand that encompass
around 7633.5 km?. However, only two of these contain
significant areas of seagrass. Whanganui {Westhaven]
Inlet contains around 8.59 km? of seagrass”! which are
protected through a combination of a marine reserve
and a wildlife management reserve that cover a total
area of 26.48 km’. Te Angiangi Marine Reserve, on the
east coast of the North Island, also encompasses
extensive stands of seagrass on intertidal platform
reefs'''. The exact area of seagrass in the reserve is not
known, but in this open coast environment it is likely to
be highly variable”.

The Wildlife Act 1953 and Reserves Act 1977, also
administered by the Department of Conservation, have
been used to protect intertidal habitats in some
estuaries where there are important wildlife, scenic,
scientific, recreational or natural values.

Five wetlands in New Zealand are registered
under the Ramsar Convention as of special importance
to wading birds”". Three of these contain coastal or
marine environments that include areas of seagrass.
Farewell Spit, on the northwest of the South Island,
contains an extensive area of intertidal sand and mud
flats with Zostera capricorni meadows". It has been
protected as a Nature Reserve since 1938 and is a
significant area for a variety of wading birds and
waterfowl. In particular, it is the site of the major
molting congregation of the native black swan, Cygnus
atratus. More than 13000 swans have been recorded in
the area, at densities of up to 1000 birds per km’.
During these congregations, Zostera capricorni is the
largest component of their diet. The two other coastal
Ramsar sites are in the Firth of Thames in the North
Island and Waituna Lagoon at the southern tip of the
South Island.

CONCLUSION

The collage of historical and contemporary information
assembled in this review suggests strongly that
seagrass habitats were once much more widespread in
New Zealand's estuaries. Their demise appears to be
the result of a combination of disease and human
activities that have reduced the quality of estuarine
waters. Despite relatively limited information on the
ecological functions of these habitats in New Zealand,
historical information suggests that loss of seagrass

New Zealand

Photographers negotiating the tidal channels near New Brighton in
the Avon-Heathcote Estuary in the early 1900s. The elevated intertidal
banks are clearly vegetated with extensive stands of Zostera

has had similarly dramatic effects on the distribution
and abundance of invertebrates, fishes and other
estuarine wildlife that depend upon them, including
some species of commercial significance. The high
turbidity of many New Zealand estuaries - caused by a
combination of natural topography and changes in land
use - means that restoration efforts are likely to be long
term and broad based, necessitating changes in land
and catchment management. Immediate conservation
is, therefore, best focused on the relatively few areas
where there are large, persistent meadows. There are,
however, promising signs of improving water quality in
a number of estuaries and of the recent expansion of
seagrass habitats in some areas.

ACKNOWLEDGMENTS

Preparation of the review and attendance at the Global Seagrass
Workshop was supported by a Technical Participatory Programme grant
from the International Science and Technology Linkages Fund. Thanks
are due to Diane Gardiner {Ministry of Research, Science and
Technology), Megan Linwood [Ministry for the Environment) and Rick
Pridmore (National Institute of Water and Atmospheric Research Ltd) for
facilitating this. Valuable information from, and discussions with, Mark
Morrison, Anne-Maree Schwarz [NIWA], Paul Gillespie (Cawthron
Institute], Stephanie Turner (Environment Waikato) and Don Les
(University of Connecticut] improved the content of the manuscript.

AUTHOR

Graeme Inglis, National Institute of Water and Atmospheric Research
Ltd, P.0. Box 8602, Christchurch, New Zealand. Tel: +64 {0]3 348 8987.
Fax: +64 (0}3 348 5548, E-mail: g.inglis@niwa.cri.nz

141

142

WORLD ATLAS OF SEAGRASSES

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13 The seagrasses of

THAILAND

of Thailand and the Andaman Sea, and coastal

habitats support abundant populations of
commercial fish and associated nearshore fisheries.
Seagrasses occur in many locations along the Thai
shoreline. The occurrence, community structure and
biomass of seagrasses have been studied at different
locations in 19 provinces along the coastal areas of the
Gulf of Thailand and the Andaman Sea. Among the 12
species of seagrasses found in Thailand, Halophila
ovalis is the most widely distributed, because of its
ability to grow in different habitats. Enhalus acoroides,
the largest species, is also common in the major
seagrass areas. Seagrasses are more abundant in the
Andaman Sea than in the Gulf of Thailand.

Te coastline of Thailand is 2583 km along the Gulf

BIOGEOGRAPHY

Most of the seagrass beds are multispecies beds
located in enclosed or semi-enclosed embayments
from the intertidal area to 5 m in depth depending on
seagrass species, chemical and physical factors.
Distribution and habitat of the 12 seagrass species in
Thailand is summarized in Table 13.1. Seven species
are widespread in both the Gulf of Thailand and the
Andaman Sea. Enhalus acoroides occurs in brackish
water canals down to the lower intertidal and subtidal
zones on mud, muddy sand and sandy coral substrates;
Thalassia hemprichii grows on muddy sand or
fragmented dead coral substrates in the upper littoral
zone or coral sand substrate in subtidal areas;
Halophila beccarii grows on mud or muddy sand
substrates in estuarine and coastal areas in the
intertidal zone; Halophila decipiens was previously
thought only to occur in waters 9-36 m in depth but has
been found in the intertidal areas where it is exposed
during low tides; Halophila ovalis is found growing on
various substrates such as mud, muddy sand and dead
coral fragments in the upper littoral to subtidal areas;
Halodule pinifolia and Halodule uninervis both grow in

C. Supanwanid
K. Lewmanomont

sandy or muddy sand substrates from the upper littoral
to subtidal areas. Two species occur only in the Gulf of
Thailand: Halophila minor which grows on muddy sand
in the intertidal zone and Ruppia maritima in mangrove
areas or brackish water ponds. Cymodocea serrulata,
which grows on muddy sand, fine sand or sand with
coral rubble substrates in the intertidal zone, occurs in
both regions but is mainly distributed along the
Andaman Sea coastline. Two species are found in the
Andaman Sea and not the Gulf: Cymodocea rotundata,
which occupies the lower littoral zone on muddy sand
area or sandy bottom mixed with dead coral fragments
and Syringodium isoetifolium which occurs densely in
subtidal areas on fine sediment.

A total of 68.5 km’ along the coast of Thailand is
known to be covered by seagrasses, but actual
coverage must be much greater given the lack of
measurements in 11 of the 24 locations in Table 13.1.
Seagrass distribution is more extensive in the Andaman
Sea than in the Gulf of Thailand.

The four most important seagrass beds in
Thailand are Haad Chao Mai National Park, in Trang
province on the southern coast of the Andaman Sea and
just north of Malaysia, Ko Talibong (Talibong Island),
also in Trang province, Kung Krabane Bay, in
Chanthaburi province on the eastern coast of the Gulf of
Thailand near to Cambodia, and Ko Samui (Samui
Island), in Surat Thani province, and part of the
southern coast of the Gulf of Thailand.

The seagrass beds at Haad Chao Mai National
Park, Trang province are the largest of these seagrass
beds and cover 18 km’, with the highest species
diversity for a single area in Thailand”. The beds cover
a small area around a peninsula called Khao Bae Na
and a larger area between the islands of Ko Muk and
Laem Yong Lum on the mainland. There are nine
species in this area: Enhalus acoroides, Thalassia
hemprichii, Halophila decipiens, Halophila ovalis,
Halodule pinifolia, Halodule uninervis, Cymodocea

rotundata, Cymodocea serrulata and Syringodium
isoetifolium. Halophila decipiens is considered to be
a deepwater seagrass species in Thailand. However
this species occurs in the intertidal zone at Khao Bae
Na and pure stands of Halophila decipiens are
therefore exposed during low tide down to the depths of
5m"! Until recently the only available information on
the seagrass beds at Haad Chao Mai National Park was
qualitative and restricted to the intertidal zone, but in
2000 the distribution and biomass of seagrasses over
the entire subtidal and intertidal bed was
investigated’. The biomass was highest at shallower
depths [<2 m) all along the coastline. Enhalus
acoroides was the most abundant species, followed by
Halophila ovalis and Thalassia hemprichii. Both
Halophila ovalis and Thalassia hemprichii were
dominant at the upper intertidal area and formed
monospecific patches in sand dunes and tide pools
respectively. Average above-ground biomass of
seagrasses in the intertidal area (15 g/m’) was 1.5
times greater than the biomass of subtidal seagrass
beds (10 g/m’). Enhalus acoroides was the most
dominant species in the subtidal and lower intertidal
zones'. The sedimentation rate inside the Enhalus
acoroides beds was greater than those inside the
Thalassia hemprichii and Halophila ovalis beds
because of the shape and size of the Enhalus acoroides
plants". It has been suggested that distribution of
seagrass beds in this area is primarily controlled by the
physical conditions of the local environment, principally
the roughness of weather during the monsoon season
and the amount of shelter available at different
locations'"’. This is also true for the seagrass beds at
Ko Talibong. The strong southwest waves during the
monsoon season (May-October) induces instability of
bottom sediments and high turbidity preventing
seagrass settlement and growth in the area directly
facing offshore waters'. Consequently seagrasses
only flourish in areas sheltered by the offshore islands.

At the muddy flat of Ko Talibong, 15 km from the
southern end of the Haad Chao Mai National Park bed,
7.0 km? of nine seagrass species are distributed along
the northern, eastern and southeastern coasts of this
island. This bed is very important as a feeding ground
for the dugong (Dugong dugon)"”. One hundred and
twenty-three dugongs were found in Haad Chao Mai
National Park and Ko Talibong seagrass beds in 2001,
with the largest herd size being 53 dugongs in the Ko
Talibong seagrass bed'"”.

Compared to the seagrass bed at Haad Chao Mai
National Park, the seagrass bed at Ko Talibong is highly
affected by siltation from the Trang River. These
seagrasses grow in a highly turbid environment with a
transparency of about 1-2 m on mud and muddy sand
substrates. As a result the maximum depth of seagrass

Thailand

5 104° E
Chon Bun
CAMBODIA
Rayong
*» @Chanthabun

Kung Krabane Bay -9itat

MYANMAR » ®>rachuab Khiri Khan
Koh Kram

Indaman

)
# Ranong

Sea

F surat Thani
THAILAND Gulf of Thailand

Nakhon Si os
Thammarat ®

fh
Phuket i tren!
} 3 Tran,

ig Phatthalun:
Phangnga Bay .° 3

pe
Haad Chao Mai 2

National Park Pattani
Libong Island oatun \
Ko Talibong eT ‘e Narathiwat
’

Songkhla
es

0 50 100 150 Kilometers
aa

Map 13.1
Thailand

is limited to 2.5 m''". At the eastern end of the island,
seagrasses grow on muddy flats and are exposed to the
air during low tide. Nine seagrass species were found:
Enhalus acoroides, Thalassia hemprichii, Halophila
beccarii, Halophila ovalis, Halodule pinifolia, Halodule
uninervis, Cymodocea rotundata, Cymodocea serrulata
and Syringodium isoetifolium"”. Enhalus acoroides and
Halophila ovalis were the dominant species in intertidal
flats while Halophila ovalis was widely distributed in
the subtidal area to the southeast of the island.

In the Gulf of Thailand, two major seagrass beds
are located in the almost enclosed Kung Krabane Bay
in Chanthaburi province and Ko Samui in Surat Thani
province’ “*”!. Kung Krabane Bay has a small narrow
opening to the sea and an area of approximately 15 km*
which is surrounded by mangroves and shrimp ponds.
Five species of seagrasses grow here: Enhalus
acoroides, Halophila decipiens, Halophila minor,
Halophila ovalis and Halodule pinifolia, and cover
7.0 km?":'*" The deepest part of this bay does not
exceed 6 m. Enhalus acoroides and Halodule pinifolia
were the two dominant species among the five’.

Ko Samui Is the largest island on the west coast
of the Gulf of Thailand and a major destination for
foreign tourists. Five species of seagrasses grow in
beds that almost completely surround the island:
Halodule uninervis, Halophila minor, Halophila ovalis,
Halophila decipiens and Enhalus acoroides cover a
total area of 7.7 km’ and grow in association with
corals, mainly Acropora spp. and massive species of
coral, scattered around the island. Most of the seagrass

145

146

WORLD ATLAS OF SEAGRASSES

Table 13.1
Occurrence of seagrass species in Thailand

Province/major
seagrass area
Chon Buri 7
Rayong v
Makampom Bay
Chanthaburi
Kung Krabane Bay
Trat
Phetchaburi
Prachuab Khiri Khan
Chumphon
Surat Thani
Ko Samui
Nakhon Si Thammarat
Songkhla
Pattani
Ranong
Phangnga
Krabi
Phuket
Trang
Haad Chao Mai National Park
Ko Talibong
Satun
Phatthalung
Narathiwat

AES ES BSS SS SESS ESS,

Seagrass species
Hm Ho

/
v

v
v
v
v
v
v
v
v
/
v
v
v
v

No. of Area
Cs Si Rm species {km’)
if v 6 id

Hp Hu

42
1.2
40
10.0
47
27.1
18.0
7.0
0.06
id
0.04

NoOrFrF On SHY HN TK

SPSS ESS PSS Ts ESS BSS PSS

Notes: Ea Enhalus acoroides; Th Thalassia hemprichii; Hb Halophila beccarii; Hd Halophila decipiens; Hm Halophila minor, Ho Halophila ovalis;
Hp Halodule pinifolia, Hu Halodule uninervis; Cr Cymodocea rotundata; Cs Cymodocea serrulata; Si Syringodium isoetifolium,; Rm Ruppia

maritima.
id insufficient data.

Source: Various sources'

areas were formed outside the area of living corals or
on reef flats inside the coral reef. Enhalus acoroides
grows on coarse substrates ranging from medium and
coarse sand to coral rubbles at a depth of 0.5-1.0 m.
Halodule uninervis, Halophila ovalis, Halophila minor
and Halophila decipiens are distributed on fine to
medium sand at 2.5-7.0 m in depth.”

HISTORICAL PERSPECTIVES

The first report of Halophila ovalis and Halodule
uninervis in Thai water was made in 1902 when
Halophila decipiens was also described as a new
species. There were no further reports until 1970 when
den Hartog found five species in Thailand: Cymodocea
rotundata, Thalassia hemprichii, Halophila ovalis,
Halophila ovata and Halophila decipiens". \In 1976,

Lewmanomont reported the occurrence of seagrasses
belonging to Halophila, Enhalus and Cymodocea in the
mangrove areas’. Christensen and Anderson found
two seagrass species in Surin Island in 1977". Two
species were recorded in Koh Kram in Chon Buri
province”! After this, many reports were published on
the occurrence, community structure, biomass and area
of seagrasses. Many studies on the ecology and biology
of seagrasses have been initiated under the ASEAN-
Australia Marine Science project since 1988”.

For Thai people, the main importance of
seagrasses is their role as fishing grounds and as
habitats for many commercially important species and
endangered marine mammals, but the value of
seagrasses to provincial and national economies has
not been quantified. Indirect uses of seagrasses in

Thailand include their role in coastal protection and as
nursery grounds for marine species.

Before 1999 there was no information on the
importance of seagrasses in coastal protection in
Thailand. Then studies on the water flow and
hydrological factors in seagrass beds at Haad Chao Mai
National Park were conducted. The studies showed that
the intensity of bottom water movement in seagrass
beds at lower depths was less than that at the upper
depths. This study demonstrated the effectiveness with
which Enhalus acoro/des beds retard the intensity of
water motion: current speed inside the Enhalus
acoroides beds was 15 cm/s on the seafloor and 25
cm/s at 0.5 m in depth. This was a slower movement of
water than inside the other seagrass beds, and over
bare sand where currents speeds were 22.5 cm/s and
35 cm/s on the seafloor and at 0.5 m depth, respectively.
The width and length of Enhalus acoroides blades is the
greatest among the seagrass species of Thailand, and
the blades not only greatly reduce the rate of water flow
under and over the meadow but also induce a higher
sedimentation rate as a result. In this way, the seagrass
beds at Haad Chao Mai National Park create and

Case Study 13.1
THE DUGONG - A FLAGSHIP
SPECIES

In Thailand, most fishermen and local people know
that seagrass is an important food for the dugongs
(Dugong dugon). The dugong in Thailand is an
endangered species and Is protected under the Thai
Fishery Act 1947.

Before the first aerial survey for dugong in
1992, not many Thais knew what dugongs and
seagrasses were. During the first survey in 1993,
dugongs were found near the seagrass bed in Trang
Province and the Royal Forestry Department
announced that this was the last herd of dugong in
Thailand’. However, dugongs may still exist on the
eastern coast of the Gulf of Thailand”. Fishermen in

Rayong province have seen dugongs and their

feeding trails on small seagrass species.

More dugong feeding trails on Halophila ovalis
at Haad Chao Mai National Park were reported in
1996"! At that time, Thai people believed that
dugongs preferred feeding on small seagrass
species. In 1998, the study on dugong grazing on
Halophila ovalis beds at Haad Chao Mai National
Park was carried out. It was reported that in a 100 x
100 m quadrat, one dugong could produce 14.9
feeding trails (5.1 m*/day). The estimated grazing
rate of Halophila ovalis by a dugong was 1.1 kg dry

Thailand

maintain a unique physical environment in terms of
water motion and sedimentation which protects the
coastline from the adverse effects of high wave action
during the monsoon season”.

Thai seagrass beds are a nursery ground for
juvenile fishes and other marine animals. At Haad Chao
Mai National Park, 30 families of fish larvae have been
recorded in the nearshore seagrass bed. The
abundance of fish larvae in the seagrass bed, at 2064
individuals/1000 m*, was higher than in open sandy
areas, with 1217 individuals/1000 m*. Economically
important fish larvae found in this area were
Carangidae, Nemipteridae, Engraulidae, Mullidae and
Callionymidae”*. At Haad Chao Mai National Park
seagrass bed, juveniles of the Malabar grouper,
Epinephelus malabaricus, were collected by small fish
traps and cultured in net cages in the canals near the
seagrass bed”. Twenty-two species of juvenile fishes
were reported in the seagrass bed at Kung Krabane
Bay, Chanthaburi province. Among these, Serranidae
are the most abundant and are also the most important
species for fisheries. From October to December,
fishermen collect juveniles of Serranidae species

weight, 13.0 kg wet weight/day. Recently, other
seagrass species were found in the stomach content
of dugongs in Trang province. The species included
Halodule pinifolia, Halodule uninervis, Halophila
ovalis, Cymodocea rotundata, Cymodocea serrulata,
Syringodium isoetifolium, Thalassia hemprichii and
Enhalus acoroides*”.

The dugongs in the Andaman Sea are a
flagship species based on their specialized relation-
ship with seagrasses and they are further evidence
of the value and importance of the seagrass
ecosystem. Recent surveys have shown that more
than 60 percent of the people along the Andaman
Sea appreciate the importance of the dugongs and
seagrasses”,

Dugongs and seagrass on a Thai stamp.

147

148

WORLD ATLAS OF SEAGRASSES

{approximately 2.5 cm in length] in the morning using
scoop nets, and culture them in net cages until they
grow to marketable size, when each individual weighs
more than 0.8-1.5 kg'”.

Seagrass beds in Thailand are very important
areas for fisheries, over and above their role as nursery
areas, with both demersal and highly mobile species of
fish being harvested from seagrass areas throughout
the country. At least 318 species representing 51
families have been identified in seagrass beds in ASEAN
countries. They have economic value mainly as food and
aquarium specimens”. In Thailand the diversity of fish
is lower in seagrass beds in the Gulf of Thailand (where
38 species of fishes from 29 families have been
recorded from six seagrass beds’) than in the
Andaman Sea (where 78 species of fishes from 46
families have been recorded from the seagrass beds at
Haad Chao Mai National Park]. Many species are very
important in terms of economic value such as
Epinephelus malabaricus, orange-spotted grouper
(Epinephelus coioides), great barracuda (Sphyraena
barracuda), squaretail mullet (Liza vaigiensis), brown-
stripe red snapper (Lutjanus vitta), Russell's snapper
(Lutjanus russell], mangrove red snapper (Lutjanus
argentimaculatus}, oriental sweetlips (Plectorhinchus
orientalis), silver sillago (Sillago sihama) and Indian
mackerel (Rastrelliger kanagurta)””.

In addition to the fishes in the seagrass area,
crabs and sea cucumbers are also important to
fisheries. Since 1998, local fishermen have been
collecting sea cucumbers from many seagrass beds in
summer, during low tide. After drying the sea
cucumbers, the fishermen sell them to Malaysian
buyers. At present, three species of sea cucumber have
been harvested, namely, Holothuria scabra, Holothuria
atra and Bohadschia marmorata. Fresh sea cucumber
costs US$12-15 (500-600 Baht) per kg while the dried
ones cost US$25 per kg’. Eighty percent of the crabs
exported from Thailand are portunids, mainly Portunus
pelagicus, coming mostly from seagrass areas."

Direct use of seagrass is less apparent in Thailand
although the seeds of Enhalus acoroides are eaten by
Thai fishermen. They believe that someone who has a
chance to eat the seeds of Enhalus acoroides will be
lucky. However, they do not like to harvest the fruits of
Enhalus acoroides for food because of the time
necessary to collect enough seeds. Local people in
some areas in Thailand use dry seagrass leaves and
rhizomes for the treatment of diarrhea. At present,
extracts from many species are being screened for
biological properties. For example a group of research-
ers from Kasetsart University has been testing crude
seagrass extracts and conducting five bioassays (anti-
bacterial, antifungal, cytotoxicity, antialgal and toxicity
tests] on these extracts.

HISTORICAL LOSSES

It is very difficult to estimate the seagrass loss in
Thailand because there are no reports on historical
coverage or loss. Most of the studies on seagrasses in
Thailand were conducted recently and over very short
periods of one to two years. There has been no long-
term monitoring in the country. Even the present
seagrass coverage cannot be completely estimated.
However there is evidence showing that a small
seagrass bed at Khao Bae Na in Haad Chao Mai
National Park has been covered by sand.

Khao Bae Na is a small embayment of flat sand
which had a dense Halophila ovalis meadow extending
over approximately 30000 m’ and served in the past as
a feeding ground for dugongs. The feeding trails of
dugongs were clearly seen during low tide. Some
Cymodocea rotundata, Halophila decipiens and small
patches of Enhalus acoroides occurred in this area.
Tidal level of the meadow was about 1.8 m above mean
lower low water’. Since the monsoon season in 2000,
this seagrass bed has been covered with a high level of
sediment. Only small patches of Halophila ovalis and
Cymodocea rotundata have survived and their
distributions have been limited by the high
sedimentation rate. It is thought that the dugongs have
moved their feeding grounds to Ko Muk and Talibong
Island seagrass beds.

On 20 January 2002, damage to the seagrasses at
Baan Pak Krok in Phuket by the use of mechanized
push seines was reported in the press, but the area
affected was not estimated. The Natural Resource
Conservation Group of Baan Pak Krok requested the
government to strengthen law enforcement. There is
other anecdotal evidence of damage to seagrass areas
in Thailand but it would be impossible to determine the
actual loss.

THREATS

Seagrasses in Thailand are threatened by a
combination of illegal fisheries and fishing practices,
and land-based activities, especially mining. The
destruction of seagrass beds is caused by fishing gear
such as small-mesh beach seines and mechanized
push seines.

Before 1992, the local fishermen in five villages
near Haad Chao Mai National Park used mechanized
push seines that decreased the number of marine
animals and seagrass area. Paradoxically the
fishermen’s income also decreased while the use of
these illegal fishing gears increased. They started to
fish by using dynamite and cyanide in the seagrass bed.
After 1992, the Royal Forestry Department announced
the occurrence of dugong in Haad Chao Mai National
Park, and a mass media campaign helped to spread
awareness of dugong and seagrass conservation in

Thailand. Local organizations implemented dugong and
seagrass conservation projects to persuade local
fishermen to stop using beach and push seines in
seagrass areas. They can now only use traps for fishing.
One year later, the seagrass bed at Haad Chao Mai
National Park had increased in size and the fishermen’s
income had increased because of larger catches from
within the protected seagrass areas. However, the Royal
Forestry Department still found mechanized push seine
trails in other seagrass areas”.

In Thailand, tin mining is centered in Phuket,
Phangnga and Ranong provinces. It has been
suggested that sediments from tin mining in Phuket
cause chronic problems for seagrass beds in Phuket
and Phangnga provinces. Mining activities have now
decreased drastically in most areas, but the seagrasses
are still affected by other activities, such as land
development resulting in landfill, open topsoil on roads
and construction on hill slopes”.

A major threat to seagrasses in Thailand is
reduced water clarity in many areas resulting from
upland clearing, development along rivers and
destruction of mangrove forests.

LEGAL AND POLICY INITIATIVES
In Thailand, there are only two seagrass protected
areas. These are Haad Chao Mai National Park and
Libong Island Non-hunting Area. Haad Chao Mai
National Park is administered by the Royal Forestry
Department under the auspices of the Marine National
Park Division. Haad Chao Mai National Park was
established in 1981 and encompasses 230.9 km’ - 59
percent of the area is an aquatic zone. Hunting and
collecting are forbidden since this is the largest
seagrass bed with the highest diversity in Thailand.
Libong Island Non-Hunting Area (Ko Talibong Non-
Hunting Area) was established in 1960. The only activity
restricted here is hunting. Seven square kilometers of
seagrass bed distributed in this area serves as a
feeding ground for more than 53 dugongs. Most of the
officers of Libong Island Non-hunting Area are the local
people of the island. They not only protect the area from
hunting but also help other local people understand the
importance of seagrasses to the marine environment.
There have been several other policy initiatives
designed, in part, to conserve seagrasses. In 1972, the
Ministry of Agriculture and Co-operatives declared that
all mechanized fishing gears were prohibited within
3000 meters of the coastline in all coastal provinces. In
1993, Trang Provincial Notification was empowered
under Fisheries Act B.E. 2490 (Fisheries Act 1947]
Section 32” to declare that trawlers, mechanized push
seines, beach seines and gill nets were prohibited in
Haad Chao Mai National Park seagrass bed and at Ko
Talibong. In 1997, the Ministry of Agriculture and Co-

Thailand

Dugong feeding trails on Halophila ovalis at Haad Chao Mai
National Park

Seeds of Enhalus acoroides

operatives declared the prohibition of trawlers,
mechanized push seines, purse-seines and nets in the
area along Phangnga Bay which includes Phuket,
Phangnga and Krabi coastlines.

In 1998, the Office of Environmental Policy and
Planning proposed policies for the management of
seagrass resources including:

() accelerated management and control of water
pollution;

) increasing efficiency in management of seagrass
conservation through landuse planning;

149

Photo: C. Supanwanid

Photo: J.S. Bujang

150

WORLD ATLAS OF SEAGRASSES

) support for studies on seagrass research and
conservation;

fo) campaigns to heighten and improve public
awareness of the importance of conserving
seagrasses, at all levels of the community;

) review and adjustment of laws, regulations and
enforcement concerning seagrasses so that they
work more efficiently by recognizing the import-
ant roles of local authorities and communities;

) the monitoring of the status and problems of the
seagrass beds, with the cooperation of central
government, local authorities and local people”.

So far seagrass monitoring, restoration and
conservation in Thailand has not been widely
successful in the long term because of a lack of
funding and a suitable methodology. Law enforcement
alone has not led to the successful protection of the
seagrass ecosystem. It is necessary to involve local
people through information and education. A non-

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ACKNOWLEDGMENTS

We are grateful to Dr F.T. Short and Dr R.G. Coles for
their great support. Sincere thanks go to Assistant Professor Dr C.
Meksampan, P. Wisespongpand, S. Putchakarn, S. Wongworalak,
S. Pitaksintorn, K. Adulyanukosol, Assistant Professor Dr S.
Satumanatpan and N. Suksunthon for their information and help.

AUTHORS

Chatcharee Supanwanid and Khanjanapaj Lewmanomont, Department
of Fishery Biology, Faculty of Fisheries, Kasetsart University, Chatujak,
BKK 10900, Thailand. Tel: +66 (0}2 579 5575. Fax: +66 (02 940 5016.
E-mail: ffischs(@ku.ac.th

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Nateekanjanalarp S, Sudara S [1994]. Dugong protection
awareness: An approach for coastal conservation. In: Sudara S,
Wilkinson CR, Ming CL (eds) Third ASEAN-Australia

Symposium on Living Coastal Resources, 16-20 May 1994.
Department of Marine Science, Chulalongkorn University, Bangkok.
pp 915-525.

Pitaksintorn S. Personal communication.

Supanwanid C [1996]. Recovery of the seagrass Halophila ovalis
after grazing by dugong. In: Kuo J, Phillips RC, Walker DI, Kirkman
H leds) Seagrass Biology: Proceedings of an International
Workshop, 25-29 January 1996, Rottnest Island, Western Australia.
University of Western Australia, Nedlands, Western Australia. pp
315-318.

Mukai H, Aioi K, Lewmanomont K, Matsumasa M, Nakaoka M,
Nojima S, Supanwanid C, Suzuki T, Toyohara T [1999]. Dugong
grazing on Halophila beds in Haad Chao Mai National Park, Trang
Province, Thailand: How many dugongs can survive? In: Koike | {ed]
Effects of Grazing and Disturbance by Dugongs and Turtles on
Tropical Seagrass Ecosystem. University of Tokyo, Tokyo.

pp 239-254.

Adulyanukosol K, Poovachiranon S, Natakuathung P [2001].
Analysis of stomach contents of dugongs [Dugong dugon] from
Trang Province. Fishery Gazette 54(2): 129-137 {in Thail.

Hines E [2000]. Population and Habitat Assessment of the Dugong
(Dugong dugon) off the Andaman Coast of Thailand. Final report
submitted to the Ocean Park Conservation Foundation, Hong Kong.
Satumanatpan S, Sudara S, Navanugraha C [2000]. State of the
seagrass beds in Thailand. Biologia Marina Mediterranea 7(2):
417-420.

151

152

WORLD ATLAS OF SEAGRASSES

14 The seagrasses of

MALAYSIA

alaysia’s coastline is around 4800 km long,
M stretching along the Malay Peninsula, Sabah

and Sarawak, bounding much of the southern
part of the South China Sea. In and adjacent to this
coastline are three major coastal ecosystems -
mangroves, coral reefs and, less well known,
seagrasses. Corals are found on the outer edge of the
coastal zone while mangroves are on the inner edge. In
general, coastal areas between mangroves and corals,
from low-tide level to the coral reef fringe, form the
habitats for seagrasses in Malaysia. Seagrasses are
also found around offshore islands with fringing corals.
Here they are usually found in the outer region between
the corals and the semi-open sea. The earliest account
of seagrasses in the shallow bays all around the coast
of Peninsular Malaysia dates back to 1924".
Information on seagrasses is scattered and appears in
a number of books, scientific publications and
monographs” "". These have been largely taxonomic in
nature and list habitats of at least seven species of
seagrasses: Enhalus acoroides (then referred to as
Enhalus koenigii by Ridley and Holttum), Halophila
ovalis, Halophila minor (referred to as Halophila ovata
by Henderson], Halophila spinulosa, Halodule uninervis
{then referred to as Diplanthera uninervis), Thalassia
hemprichii and Ruppia maritima.

In recent years more research has been carried
out on seagrasses in Malaysia. Consequently there are
now a number of reports in the literature that describe
the extent and richness of flora’ and fauna!’?:*”*" in
Malaysian seagrass beds. Unlike other terrestrial
communities that can be lived in, managed or exploited,
seagrasses offer only a few direct uses. The ecological
role and importance of seagrasses has not been fully
understood. Much more effort has been spent on
quantifying and managing mangroves and corals.
Mangrove reserves have been established and coral
reefs are protected and conserved in marine parks and
marine protected areas. There are guidelines and

J.S. Bujang
M.H. Zakaria

policies governing the conservation and management
of mangroves by the National Mangrove Committee””
and corals under the Fisheries Act 1985. However the
importance of seagrasses at local and national levels,
and from the standpoint of conservation, has received
far less attention. There are no specific reserves or
legislation for seagrasses. Given the importance of
seagrass as fisheries habitat, nursery and feeding
grounds in Malaysia, this neglected and relatively
lesser known resource must be afforded the same
priority and be as well managed as mangroves and
corals to provide for future renewable resource
utilization, education and training, science and
research, conservation and protection.

ECOSYSTEM DESCRIPTION

The majority of seagrasses in Malaysia are restricted to
sheltered situations in the shallow intertidal associated
ecosystem, semi-enclosed lagoons and also in subtidal
zones. In these areas they sometimes form diverse
extensive communities. The overview of the seagrass
distribution and description in this section is given
separately for Peninsular and East Malaysia (Sabah).
We include specific examples to illustrate the types of
seagrass bed found in Malaysia.

Peninsular Malaysia

Along the west coast, patches of mixed species
seagrass communities usually occur on substrates
from the sandy mud to sand-covered corals in the
extreme northern region along the coast of Langkawi
Island, Kedah, to the central region of Port Dickson,
Negri Sembilan", extending as far as Pulau Serimbun,
Malacca’. The Port Dickson area, at Teluk Kemang, is
the only area in mainland Peninsular Malaysia that has
intertidal seagrass on reef platform. In the southern
region, around the Sungai Pulai area, Johore, mixed
species seagrass beds exist at depths of 2-3 m on both
sandy mud banks of the mangrove estuary” and

Pengkalan Nangka
seca Pulau Perhentian
ov Pulau Redang

« Gong Batu
.

Merchang
: SOUTH
* Paka CHINA
*~ Kemasik SEA

= Telaga Simpul
Kemaman

PENINSULAR
MALAYSIA

Strait of

Malacca © Kuala Lumpur Pulau Tengah
:

® Pulau Tioman

Teluk 4A Port Dickson
‘emang

Malacca

K
=> Pulau Tinggi
Pulau Pulau Sibu

Serimbun
ee” Merambong,

INDONESIA Tanjung
(Sumatra) Adang Laut

50 100 150 Kilometers

Map 14.1
Peninsular Malaysia

calcareous sandy mud_ subtidal shoals _ of
Merambong'”, Tanjung Adang Darat' and Tanjung
Adang Laut”. These subtidal shoals, at depths of

2-2.7 m, support nine species (Enhalus acoroides,
Halophila ovalis, Halophila minor, Halophila spinulosa,
Thalassia hemprichii, Cymodocea serrulata, Halodule
pinifolia, Halodule uninervis, Syringodium isoetifolium)
of seagrasses, the highest species number for any
locality in Peninsular Malaysia or East Malaysia’.
These beds measure 1-1.2 km in length and 100-200 m
in width according to estimates based on the visible
portion exposed several times in a year by low tides.
This is therefore probably the largest single seagrass
bed in Peninsular Malaysia. The south has a greater
diversity of seagrasses than the northern region with
just three species (Halophila ovalis, Cymodocea
serrulata and Halodule uninervis) in Tanjung Rhu and
Pantai Penarak in the north.

Intertidal areas of the eastern coastline are
devoid of seagrasses. Beds of two species, Halophila
beccarii and Halodule pinifolia, inhabit the fine sand
substrate of the shallow inland coastal lagoons from
Pengkalan Nangka, Kelantan, to Paka, Terengganu,
while Halodule pinifolia and Halophila ovalis inhabit a
similar substrate type at Gong Batu and Merchang.
Monospecific beds of Halodule pinifolia were found at
Kemasik, Terengganu, and pure stands of Halophila
beccarii grew on the mud flat of the mangroves in
Kemaman, Terengganu. Monospecific beds of Halodule
pinifolia, Halophila decipiens and mixed species
seagrass beds occur in the waters of the offshore

Malaysia

SOUTH 20 40 60 80100 Kilometers wy |
CIIINA A ]
SEA Bak-Bak 5
a = 7N

SULU |
SEA

Tanjung
Mengayau

Sungai Salut
.

*Tunku Abdul Rahman
~~ Marine Parks

Turtle Islands
oy

Pulau_—# B
Gaya *\ ‘Sungai Mengkabong
‘ Sepangar Bay

Pulau Tiga
' Sabah

Labuan Island SUN Lahad Datu,

Pulau Tabawan —* *

= Pulau Bohay

Pulau Maganting ~ /Dulang
dye

.
.
.

Kalimantan
INDONESIA

“
116°E Pulau Sipadan

Map 14.2
Sabah

islands with fringing coral reefs such as Pulau Sibu,
Pulau Tengah, Pulau Besar and Pulau Tinggi’, Pulau
Redang and Pulau Perhentian™! and Pulau Tioman™.
Seagrasses are usually found in the outer region
between the corals and the semi-open sea.

East Malaysia

The west and southeastern coasts of Sabah harbor
mixed species seagrass beds in the intertidal zone
down to a depth of 2.5 m. Seagrasses grow on
substrates ranging from sand and muddy sand to coral
rubble. There are six areas of intertidal mixed
associations of seagrass and coral reef along the west
coast at Bak-Bak, Tanjung Mengayau, Sungai Salut,
Sungai Mengkabong, Sepangar Bay and Pulau Gaya.
The four isolated offshore islands of Pulau Maganting,
Pulau Tabawan, Pulau Bohay Dulang and Pulau
Sipadan along the southeastern coast have subtidal
seagrasses growing on coral rubble! 77°»),

In Sarawak, other than records of herbarium
specimens of Halophila beccarii, collected by Beccari in
Sungai Bintulu”'”’, and Halophila decipiens collected at
Pulau Talang Talang, Semantan™', nothing much is
known about the seagrass habitats, distribution and
species composition.

BIOGEOGRAPHY

Peninsular Malaysia

The distribution of seagrasses in Peninsular Malaysia
has been detailed in various publications!” ''>"67)_ A
very broad distinction can be made between the
seagrass distribution of the west and east coasts.
Differences in the available habitats and prevailing
environmental characteristics along the east and west
coasts probably explain these distributions. On the west
coast seagrasses occur in the sandy mud sediments of

153

154

WORLD ATLAS OF SEAGRASSES

shallow coastal waters while on the east coast the
coastline is fringed with sandy to rocky areas which are
not suitable for the growth of seagrasses. On the east
coast seagrasses inhabit sandy mud lagoons, behind
the sand ridges in areas sheltered from the open sea.
Seagrasses are also found around relatively calm
offshore eastern islands with fringing reefs such as
Pulau Redang, Pulau Perhentian, Pulau Tengah, Pulau
Sibu, Pulau Tinggi and Pulau Besar. The west coast of
Peninsular Malaysia does not generally experience
strong wave action, whereas the east coast is exposed
annually to the northeast monsoon from November to
January”.

Clarity of water and sufficient light irradiance play
a significant role in the depth distribution of the
seagrasses. Coastal waters are often turbid or high in
suspended solids that limit the depth at which most
seagrasses grow, more so on the western coast of
Peninsular Malaysia than the east. This is reflected in
seagrass communities along the west coast which are
generally found inhabiting the shallow waters at depths
of less than 4.0 m. Seagrasses on the east coast, how-
ever, extend to deeper areas, 5.0-7.0 m. Seagrasses
will colonize greater depth if the water is clear. By way
of comparison, in the clear water of the east coast the
depth limit for Halophila decipiens ranged from 6 to
24 m in the Sungai Redang Estuary and Cagar Hutang
of Pulau Redang, Terengganu, respectively” while in
the turbid water of the west coast, at Teluk Kemang,

Port Dickson, it grows at 1.5-3.1 m!”.

Sabah, East Malaysia

Seagrass distribution along the west and
southeastern coasts of Sabah was described by
Ismail in 1993" and in the Tunku Abdul Rahman
Marine Parks (Pulau Gaya, Pulau Mamutik, Pulau
Sulug, Pulau Manukan and Pulau Sapi) by Josephine
in 1997", Almost all seagrasses are associated with
degraded coral reef, although a few are associated
with mangroves and habitats damaged through illegal
fishing by explosive. There were no broad differences
regionally with respect to species distribution and
composition.

HISTORICAL PERSPECTIVES

In Peninsular Malaysia seagrasses (Enhalus acoroides,
Halophila ovalis}) were apparently locally common all
around the coast on muddy shores and areas exposed
at low tide'’*“*”. Historical accounts of the distribution
of seagrass species at three places in Sabah, Labuan
Island, Sandakan and Lahad Datu, were given by den
Hartog in 1970'". Information on their abundance was
not given. Ismail’ described seagrass habitats that
were already degraded by human activities in Sabah,
East Malaysia, in 1993. Since the early reports, which

yom

indicated extensive seagrass beds, many of the habitats
(e.g. the west coast of Peninsular Malaysia, East
Malaysia, Sabah) have been exploited or have
deteriorated to a greater or lesser extent as a result of
coastal development, especially in the last 15 years!"""""
Such phenomena would explain the present seagrass
distribution, which is no longer extensive, and its patchy
distribution along the Malaysian coastline!” *”".

Known uses of seagrasses were few. Burkill” in
his book, A Dictionary of the Economic Products of the
Malay Peninsula, mentioned that Ridley recorded in
1924 that the leaves of Enhalus acoroides were one of
the chief foods of the dugong, Dugong dugon, which
was then common in Malaysia. Later the dugong
became rare because it was hunted for meat and hide”.
Presently dugongs are found in areas with abundant
seagrasses such as Pulau Sibu, Pulau Tengah, Pulau
Besar and Pulau Tinggi on the east coast and around
Merambong, Tanjung Adang Darat and Tanjung Adang
Laut shoals of Sungai Pulai, Johore. Enhalus acoroides
fruits are edible’) and the coastal communities of
Sungai Pulai, Johore, still collect them for con-
sumption. In addition the softer parts of Enhalus
acoroides form fibers that are made into fishing nets.
Ruppia maritima plants are used in fish ponds to aid in
the aeration of the water, and the milk fish (Chanos
spp.) feeds on it. This functional role, though
mentioned, has not been observed in Peninsular
Malaysia, and is probably based on observations made
in the fishponds of Java, Indonesia”. Ruppia maritima
is rare in Peninsular Malaysia".

Other forms of utilization include using seagrass
areas for fish (Lates calcarifer and Epinephelus
sexfasciatus) cage farming, for example at Pengkalan
Nangka, Kelantan, and Gong Batu, Terengganu, which
started in 1991, or oyster (Saccostrea cacullata)
farming as at Merchang from 1998'”'. Seagrass areas at
Pengkalan Nangka, Kelantan, Paka shoal, Terengganu,
and Tanjung Adang Laut shoal, Johore, are used as
collection and gleaning sites for food including fishes,
gastropods (Lambis lambis, Strombus canarium),
bivalves (Gafrarium sp., Meretrix sp., Modiolus sp.) and
echinoderms (sea cucumber e.g. Pentacta quadran-
gularis, Mensamaria intercedens). Gleaning for food in
seagrass areas associated with coral reefs is
widespread in Sabah, East Malaysia.

ESTIMATE OF HISTORICAL LOSSES

There is no information in the form of historical maps
or aerial photographs that can be used to determine
the loss of seagrass beds over time. The losses
reported here have been observed during repeated
visits to the various seagrass sites. On the west coast of
Peninsular Malaysia, at Port Dickson, localized
depletion of seagrass (narrow-leaved Halodule

uninervis and Enhalus acoroides) began in 1994,
representing about 50 percent of the area originally
present. This area was heavily utilized as a public
recreational area. At Teluk Kemang in 1997 there was
intensive sand mining for reclamation activities in
mangrove swamps as part of the construction of a
condominium. This caused the loss of Halophila ovalis
and Halodule pinifolia in the subtidal seagrass bed of
Teluk Kemang. Suspended particles in the water
settled on the leaves of the seagrasses, blocking light
for photosynthesis and causing considerable stress and
mortality through burial. The presence of an oil
refinery, intense shipping activity and frequent oil spills
in the adjacent waters have also been suggested as
potential causes for the decline or loss of seagrasses
along the coastline of Port Dickson. Tar balls in
significant quantities, frequently washed ashore, were
evidence of oil spills. In addition, petrogenic

Case Study 14.1
THE SEAGRASS MACROALGAE COMMUNITY OF TELUK KEMANG

At Teluk Kemang, Port Dickson, Negri Sembilan, the
intertidal community consists of non-uniform
patches of mixed seagrasses and macroalgae on a
coral reef platform 1.0-1.5 m deep. Seagrasses grow
in various substrates, from sand-covered coral to a
combination of silt, coarse sand and coral rubbles
(see photograph]. Halophila ovalis is dominant and
widespread, interspersed with Thalassia hemprichii,
Cymodocea serrulata, Enhalus acoroides and
Halodule pinifolia. Syringodium isoetifolium, a rare
species here, occurs in patches in the sand-filled
spaces amongst coral rubble areas. Macroalgae
coexist with these seagrasses.

The most common, and seasonal, macroalgae
species are (Chlorophytae] Caulerpa sertularioides,
Caulerpa prolifera, Caulerpa racemosa, Caulerpa
lentillifera; (Phaeophytae] Sargassum polycystum,
Sargassum cristaefolium, Sargassum ilicifolium
and Padina tetrastomatica; and {Rhodophytae]
Laurencia corymbosa and Jania decussato-
dichotoma™. This intertidal community extends into
the subtidal zone to depths of 3.5 m with a clear
zonation of seagrass species that are confined to
sandy mud and silty substrates. Pure stands of
Halophila ovalis and Halodule pinifolia with isolated
individuals of Enhalus acoro/des occur at a depth of
1.5 m. Halophila decipiens grows in small patches at
a depth of 1.5-2.0 m in association with Halophila
ovalis and Halodule pinifolia. Slightly deeper, at 2.0-
3.0 m, Halophila decipiens forms a continuous
meadow. Occasionally patches of pure Halophila

hydrocarbons were detected in the water and

sediments at Teluk Kemang™™”.

The Sungai Pulai seagrass beds Tanjung Adang
Laut and Tanjung Adang Darat are diverse and
extensive, and were only discovered in 1991 and 1994
respectively, yet by 1998 they were at risk from port
development involving dredging of shallow passage-
ways and land reclamation for new facilities, both
causing an increase in the suspended solids in the
water column. Localized losses were observed with the
death of sand-smothered Halophila ovalis clearly
visible. In addition dense overgrowth of the macroalgae
Gracilaria coronopifolia and Amphiroa fragilissima
caused the seagrasses in the area to die back.
However, recovery occurred with regrowth of sea-
grasses and the disappearance of the macroalgae.

On the east coast at Pengkalan Nangka, Kelantan,
the decline was the result of human activities such as

ovalis occur at depths of 3.2 to 3.5 m. Morphological
differences are observed in Halophila ovalis in these
two communities. Subtidal Halophila ovalis plants
possess much bigger leaf blades and more cross-
veins®” than plants of the same species growing in
the intertidal zone.

Another conspicuous seagrass is Halophila
decipiens which occurs at shallow depths of 1.5-3.0
m'*) Halophila decipiens was previously thought to
be a deepwater species growing at depths between
10 mand 30 m!"°173),

Photo: J.S. Bujang

The Teluk Kemang seagrass macroalgae community on coral
reef platform. Seagrasses occupy the sand-filled spaces of the
coral reef platform, and macroalgae dominated by Sargassum
spp. inhabit the boulders and coral rubbles.

Malaysia 155

156

WORLD ATLAS OF SEAGRASSES

the dredging of sand for landfills which have totally
removed two shoals of Halophila beccarii and Halodule
pinifolia, representing 30 percent of the total seagrass
area. At Merchang and Kemasik, Terengganu, the effect
of wind and resulting wave action on lagoon seagrass is
reduced by the sheltering presence of the sand ridges.
Despite this protection, 50-70 percent of Halodule
pinifolia and Halophila ovalis seagrass beds were
severely damaged by intense winds, waves and

Case Study 14.2

sediment movement during the northeast monsoon
storms of October 1998 to January 1999. No recovery to
the original areal extent has been observed yet. Mining
of sand at Telaga Simpul, Terengganu, in March 1997,
for the shoreline stabilization and protection of Kuala
Kemaman village, resulted in high total suspended
solids in the water column and sedimentation
smothered the dense Halophila beccarii bed there. The
bed was transformed to sparse and scattered patches

THE SUBTIDAL SHOAL SEAGRASS COMMUNITY OF TANJUNG ADANG LAUT

The subtidal shoal of Tanjung Adang Laut in the
Sungai Pulai estuary, Johore, is 1.5-2.7 m below
mean sea level and is vegetated with seagrasses
(see photograph)'’. This shoal is one of the feeding
grounds for dugongs around Sungai Pulai, Johore,
and their feeding trails can be seen clearly at low
tides. The shoal is made up of calcareous sandy mud
substrate and supports a mixed species community
dominated by Enhalus acoroides, Halophila ovalis
and Halophila spinulosa. This association occupies
the middle zone (1.5-1.8 m) and is exposed during
extreme low spring tides. Cymodocea serrulata,
Syringodium isoetifolium and Halodule uninervis
inhabit the deeper, narrow edge zones [1.8-2.1 m])
which remain unexposed.

The edge zone is bare at some places, while at
others isolated patches of Cymodocea rotundata,
Halophila spinulosa, Halophila minor or Halodule
pinifolia occur. In the deeper zone (2.1-2.7 m)
sparse, isolated patches of Enhalus acoroides and
Halophila ovalis are found. Enhalus acoroides and
Halophila ovalis occur at depths of 1.5-1.8 m, and
are also exposed during low spring tides, but are
able to withstand short periods of desiccating
conditions. Cymodocea serrulata and Syringodium
isoetifolium are less resistant and therefore tend to
occur in the unexposed edge zone (1.8-2.1 ml.

This seagrass bed also supports a total of 25
species of macroalgae. Rhizophytic macroalgae
such as Avrainvillea erecta, Caulerpa spp. and
Udotea occidentalis are set into the sandy or sandy
mud substrates whereas epiphytes such as Bryopsis
plumosa, Ceramium affine, Chaetomorpha spiralis,
Cladophora spatentiramea, Cladophora fascicularis,
Cladophora fuliginosa, Dictyota dichtoma, Hypnea
cervicornis, Gracilaria coronopifolia, Gracilaria
fisherii and Gracilaria salicornia are attached
directly to seagrasses. Species such as Entero-
morpha calthrata and Gracilaria textorii attach to
mollusk shells or polycheate tubes. Drift macro-

algae, such as Acanthophora spicifera, Amphiroa
rigida, Amphiroa fragilissima, Hypnea esperi and
Ulva spp. lie loosely amongst the seagrasses.
Attached (e.g. Gracilaria coronopifolia) and drift
macroalgae [e.g. Amphiroa fragilissima) form
important components of this shoal community and
seasonally, from April to July and in November, the
seagrass bed is overgrown with them.

The waters around Tanjung Adang Laut as well
as those of Tanjung Adang Darat and Merambong
shoals support the fisheries which feed the
inhabitants of coastal communities. Seventy-six
species of fishes [including the Indian anchovy
Stolephorus indicus, barramundi Lates calcarifer
and Spanish flag snapper Lutjanus carponotatus)
and others including prawn (e.g. Penaeus indicus)
and crabs (Portunus pelagicus and Scylla serrata)
have been reported in the area'””!. The locals also
used the shoal as a gleaning site for collection of
gastropods such as Strombus canarium and Lambis
lambis and bivalves such as Gafrarium spp. and
Modiolus spp.

Photo: J.S. Bujang

Tanjung Adang Laut subtidal shoal with mixed species
seagrass community. Nine species of seagrass inhabit the
calcareous sandy mud substrate of the shoal.

and Halophila beccarii has been largely replaced by the
more aggressive Halodule pinifolia which now forms a
monospecific bed. Standing biomass of Halophila
beccarii has been dramatically reduced from 0.89-4.34
g dry weight/m* (shoot density of 2078-6 798/m’) before
the mining in 1996 to 0.58-0.59 g dry weight/m? (shoot
density of 758-1 386/m*) from April 1997 until January
1999. Halodule pinifolia biomass and shoot density
fluctuated from 10.1 to 56.6 g dry weight/m? and 2145.3
to 8946/m’ respectively during that period.

In Sabah, no information on decline or loss of
seagrasses has been reported. However, symptoms of
a declining seagrass bed were visible at Sepangar Bay.
The middle sublittoral belt of Halodule uninervis and
Cymodocea rotundata was eroded by wave action. Edge
plants have exposed rhizomes and roots. Sediment
erosion and instability appear to be implicated in the
progressive decline of these seagrasses in the shallow
water.

PRESENT COVERAGE

Information on the total area, extent or size of seagrass
beds in Malaysia is incomplete. The individual and total
estimated areas presented [Table 14.1] are for the
known seagrass areas in Peninsular Malaysia. This is
an underestimate as seagrass areas in the offshore
islands are not included. Although Ismail’ has
reported that seagrass beds in Sabah occur in patches
ranging in size from 10 m to 150 m in diameter, no
further data are available, though it is known that,
compared with Peninsular Malaysia, seagrasses are
common in Sabah. An approximate estimate for
seagrass areas in Sabah would be many times that of
the known seagrass areas in Peninsular Malaysia.

PRESENT THREATS

The Malaysian coastal zone is being subjected to a high
degree of resource exploitation as well as pollution.
Seagrass beds grow in shallow, coastal zone waters
and this renders them susceptible to unplanned and
unmanaged urban and industrial development. These
problems are compounded by a lack of environmental
assessment procedures for developments and lack of
awareness about the importance of seagrasses. In the
past, and even at present, losses of seagrass
communities in the coastal areas of Malaysia caused
either by natural causes or human activities generally
Pass unnoticed or unrecorded. States such as Kedah
and Malacca are undertaking land reclamation and
expansion programs. Land reclamation and expansion
in Johore is occurring for the development of new port
facilities. With more expansion planned, the future
intention is to completely reclaim the stretch of
seagrass beds of Merambong-Tanjung Adang shoals,
the feeding ground of dugongs. Sourcing for sand on

Malaysia

the east coast is a common activity for landfill and
shoreline stabilization projects. Dredging is being
carried out in the Halophila beccarii and Halodule
pinifolia beds of Pengkalan Nangka, Paka shoal and
Telaga Simpul. This dredging will lead inevitably to
increased sedimentation and smothering of sea-
grasses. More bed removal will eventually occur if
dredging is to be continued to supply the increasing
demand for sand.

Small-scale destructive fishing by pull net at
Pengkalan Nangka, Kelantan, and Paka shoal,
Terengganu, dislodges the seagrasses and reduces the
seagrass cover. Harvesting of bivalves, Hiatula solida,
Meretrix meretrix and Geloina coaxans at Pengkalan
Nangka, Kelantan, has been shown to cause
mechanical damage, reduce seagrass cover and retard
the spread and colonization of seagrasses. Other
threats include the increasing public use of natural
seagrass areas, such as for recreational boating, fish-
ing and swimming in Port Dickson, Negri Sembilan,
and as avenues for transportation such as in the
narrow channels in the Paka Lagoon, Terengganu, and
Sungai Pulai-Merambong-Tanjung Adang_ shoals,
Johore.

In Sabah, seagrass and coral reef associated
ecosystems are areas of gleaning and collection for
food resources. Uncontrolled collection of flora such as

Table 14.1
Estimate of known seagrass areas in Peninsular Malaysia

State and location Area (ha)
Kelantan
Pengkalan Nangka Lagoon 40.0
Kampung Baru Nelayan-Kampung
Sungai Tanjung
Pantai Baru Lagoon
Terengganu
Sungai Kemaman
Chukai, Kemaman
Telaga Simpul
Sungai Paka Lagoon
Sungai Paka shoal
River bank of Sungai Paka
Merchang
Gong Batu
Negri Sembilan
Teluk Kemang
Johore
Tanjung Adang Laut shoal
Tanjung Adang Darat shoal
Merambong shoal
Total estimated area in Peninsular Malaysia

157

158

WORLD ATLAS OF SEAGRASSES

Case Study 14.3

COASTAL LAGOON SEAGRASS COMMUNITY AT PENGKALAN NANGKA,

KELANTAN

The intertidal area and two shoals in the lagoon all
harbor a mixed Halodule pinifolia and Halophila
beccarii community. Halodule pinifolia grows in pure
and extensive subtidal meadows on soft muddy
substrates at depths of 1.6 to 2.0 m. Halophila
beccarli grows in shallower parts, at depths of 0.9 to
1.5 m in monospecific and very dense meadows on
sandy substrates. The two species are able to
withstand a wide fluctuation of salinity from 0 to 18
psu. The meadow is a site for the collection of
bivalves [e.g. Hiatula solida and Geloina coaxans)
and artisanal fishing. Digging for bivalves has
caused a lot of damage to the meadow (see
photograph). Since 1991 the lagoon has also been
used for fish cage farming of Lates calcarifer and
Epinephelus sexfasciatus. Seasonally, from June to
July, the migrant wader, Egretta garzetta, used the
shoals as a feeding ground on its migrations until
two shoals were completely destroyed by sand
dredging in early 1999.

Caulerpa spp. and fauna such as sea cucumbers,
gastropods and bivalves, and illegal fishing with
explosives are among the major causes of damage to
coral reefs and associated seagrasses. Such activities
not only cause loss of flora and fauna but also create an
imbalance within the ecosystem from which seagrass
beds are unlikely to recover quickly.

POLICY RESPONSES
In the earlier part of this chapter, it was mentioned that
seagrass beds are the least protected of the three main
marine ecosystems in Malaysia. It is strongly
recommended that seagrass beds, especially those
around offshore islands that have been gazetted as
marine parks (Pulau Redang; Pulau Perhentian,
Terengganu; Pulau Tioman, Phang; Pulau Tengah;
Pulau Besar; Pulau Sibu; Pulau Tinggi, Johore) be given
protection as marine parks or reserves under the
Fisheries Act 1985. Under Part IX, Section 41(1) and (2)
of the Fisheries Act 1985 the Minister of Agriculture
may order in the Gazette the establishment of any area
or part of an area in Malaysian fisheries waters as a
marine park or marine reserve in order to:
“(a) afford special protection to the aquatic flora
and fauna of such area or part thereof and to
protect, preserve and manage the natural
breeding grounds and habitat of aquatic life, with

Photo: J.S. Bujang

Halophila beccarii meadow is a harvesting site for Hiatula solida
and Geloina coaxans. Digging has caused damage to
the bed

particular regard to species of rare or
endangered flora and fauna;

(b) allow for the natural regeneration of aquatic
life in such area or part thereof where such life
has been depleted;

{c) promote scientific study and research in
respect of such area or part thereof;

({d) preserve and enhance the pristine state and
productivity of such area or part thereof; and

({e) regulate recreational and other activities in
such area or part thereof to avoid irreversible
damage to its environment.”

Furthermore:
"(2) The limits of any area or part of an area
established as a marine park or marine reserve
under subsection (1) may be altered by the
Minister by order in the Gazette and such order
may also provide for the area or part of the area
to cease to be a marine park or marine reserve.”

The question of affording comprehensive
protection to marine ecosystems gazetted under the
present Fisheries Act 1985 has been the subject of
intense scrutiny by marine scientists, government
officials and conservationists. The bone of contention
has been the separation of the land on islands

gazetted as marine parks and reserves from the
waters surrounding the islands. Under these circum-
stances, while the authorities vested with the powers
to manage and enforce the marine park laws can do so
at sea, they have no jurisdiction whatsoever over what
happens on land.

This could be resolved based on practices
adopted by Sabah Parks and the present trend of
promulgating state parks enactment for the protection
of ecosystems. At present, Sabah Parks has under its
auspices three marine protected areas: Tunku Abdul
Rahman Marine Parks, Pulau Tiga Parks and Turtle
Islands Parks. All harbor seagrasses and were
gazetted as state parks under the State Parks
Enactment 1984. Marine areas gazetted as state parks
in Sabah are afforded more comprehensive protection
under the enactment than marine parks or reserves in
Peninsular Malaysia. These parks are protected in their
entirety without separating the marine and terrestrial
components.

Several states in Peninsular Malaysia have
promulgated enactments for the gazettement of state
parks. Johore has gazetted the National Parks (Johore)}
Corporation Enactment 1991. Terengganu has a
Terengganu State Parks Enactment.

Can the above policies be applied for the
management of marine protected areas in Peninsular
Malaysia? The answer lies in encouraging concurrent
gazettement of marine protected areas under both
federal and state legislation using the Fisheries Act
1985 to gazette the protection of the waters
surrounding the islands as marine parks or reserves,
and state park enactments to gazette the terrestrial
component of the marine protected areas as state
parks.

REFERENCES

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Malaysia

Boat unable to move because of thick Enhalus acoroides bed

ACKNOWLEDGMENTS
Support from the United Kingdom Department for International
Development (DfID) is gratefully acknowledged.

AUTHORS

Japar Sidik Bujang, Department of Biology, Faculty of Science and
Environmental Studies, Universiti Putra Malaysia, 43400 UPM, Serdang,
Selangor Darul Ehsan, Malaysia. Tel: +603 (0)8946 6626. Fax: +603
(0}8656 7454. E-mail: japar(@fsas.upm.edu.my

Muta Harah Zakaria, Faculty of Agricultural Sciences and Food, Universiti
Putra Malaysia Bintulu Campus, Jalan Nyabau, P.O. Box 396, 97008
Bintulu, Sarawak, Malaysia.

10 den Hartog C [1970]. Seagrasses of the World. North-Holland
Publishing, Amsterdam.

11 Phang SM [1989]. Seagrasses - a neglected natural resource in
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Proceedings 12th Annual Seminar of the Malaysian Society of
Marine Sciences. Research Priorities for Marine Sciences in the
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Advanced Studies, Universiti Malaya, Kuala Lumpur. pp 269-278.

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[1989]. The Sungai Pulai (Johore]: A unique mangrove estuary. In:
Phang SM, Sasekumar A, Vickineswary S [eds] Proceedings 12th
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Universiti Malaya, Kuala Lumpur. pp 191-211.

13 Mohd Rajuddin MK [1992]. The Areas and Species Distribution of
Seagrasses in Peninsular Malaysia. Paper presented at the First
National Symposium on Natural Resources, 23-26 July 1992, FSSA,
UKM, Kota Kinabalu, Sabah.

14 Ismail N [1993]. Preliminary study of seagrass flora of Sabah,
Malaysia. Pertanika Journal of Tropical Agricultural Science 16(2):
111-118.

Photo: J.S. Bujang

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WORLD ATLAS OF SEAGRASSES

Japar Sidik B [1994]. Status of seagrass resources in Malaysia. In:
Wilkinson CR, Sudara S, Chou LM [eds] Proceedings Third ASEAN
Australia Symposium on Living Coastal Resources, Status Reviews
1. Chulalongkorn University, Bangkok. pp 283-290.

Japar Sidik B, Arshad A, Hishamuddin 0, Muta Harah Z, Misni S
[1996]. Seagrass and macroalgal communities of Sungai Pulai
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DI, Kirkman H leds} Seagrass Biology: Scientific discussion from
an international workshop, Rottnest Island, Western Australia.
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pp 3-12.

Japar Sidik B, Lamri A, Muta Harah Z, Muhamad Saini S,
Mansoruddin A, Josephine G, Fazrullah Rizally AR [1997]. Halophila
decipiens (Hydrocharitaceae], a new seagrass for Sabah.
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Japar Sidik B, Muta Harah Z, Lamri A, Francis L, Josephine G,
Fazrullah Rizally AR [1999]. Halophila spinulosa (R. Br.) Aschers.:
An unreported seagrass in Sabah, Malaysia. Sabah Parks Nature
Journal 2: 1-9.

Japar Sidik B, Muta Harah Z, Mohd Pauzi A, Suleika M [1999].
Halodule species from Malaysia - distribution and morphological
variation. Aquatic Botany 65: 33-46.

Japar Sidik B, Muta Harah Z, Fazrullah Rizally AR, Kamin B [2000].
New observations on Halophila spinulosa (R. Br.) Aschers. in
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Japar Sidik B, Muta Harah Z, Misri K, Hishamuddin 0 [2000]. The
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Gopinath N, Ibrahim HM, Nik Mustapha RA (eds) Towards
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Japar Sidik B, Muta Harah Z, Kanamoto Z, Mohd Pauzi A [2001].
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Anisah A, Zulfigar Y [1998]. Seagrass of Pulai Sipadan, Sabah,
Malaysia: A preliminary survey. Malayan Nature Journal 52(3, 4):
223-235.

Muta Harah Z, Japar Sidik B, Hishamuddin 0 [1999]. Flowering,
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Seeding of Halophila beccarii Aschers. in Peninsular Malaysia.
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Mohd Rajuddin MK [1992]. Species composition and size of fish in
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pp 309-313.

Japar Sidik B, Arshad A, Law AT [1995]. Inventory for seagrass
beds in Malaysia. In: Japar Sidik B (ed) UNEP: EAS-35:

Malaysian Inventory of Coastal Watersheds, Coastal Wetlands,
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Ministry of Science, Technology and Environment, Kuala Lumpur.
pp 48-79.

Arshad A, Siti Sarah MY, Japar Sidik B [1994]. A comparative
qualitative survey on the invertebrate fauna in seagrass and non
seagrass beds in Merambong shoal Johore. In: Sudara S, Wilkinson
CR, Chou LM (eds) Proceedings Third ASEAN Australia Symposium
on Living Coastal Resources, Chulalongkorn University, Bangkok.
Department of Marine Science, Chulalongkorn University. Bangkok
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Arshad A, Japar Sidik B, Muta Harah Z [2001]. Fishes associated
with seagrass habitat. In: Japar Sidik B, Arshad A, Tan SG, Daud
SK, Jambari HA, Sugiyama S [eds] Aquatic Resource and
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pp 151-162.

National Mangrove Committee [1989]. Guidelines on the Use of the
Mangrove Ecosystem for Brackish Water Aquaculture in Malaysia.
The Working Group to the Malaysian National Mangrove Committee
and the National Council for Scientific Research and Development,
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Lumpur.

Phang SM [2000]. Seagrasses of Malaysia. Universiti Malaya,
Botanical Monographs No. 2. Institute of Biological Sciences,
Universiti Malaya, Kuala Lumpur.

Audery ML, Sasekumar A, Charles Leh MU, Chong VC, Rebecca D
[1989]. A Survey of the Living Aquatic Resources of the Sungai Pulai
Estuary, Johore.

Zelina ZI, Arshad A, Lee SC, Japar Sidik B, Law AT, Nik Mustapha
RA, Maged Mahmoud M [2000]. East coast of Peninsular Malaysia.
In: Sheppard C (ed) Seas at the Millennium. Vol. 2. Pergamon,
Amsterdam. pp 345-359.

Josephine G [1997]. A Study on Seagrass Biodiversity, Distribution
and Biomass in Tunku Abdul Rahman Park, Sabah, Malaysia. Final
year thesis, Universiti Kolej Terengganu, Universiti Putra Malaysia.
Lim LH, Hishamuddin 0, Japar Sidik B, Noro T [2001].

Seaweed community in degraded coral reef area at Teluk

Kemang, Port Dickson, Negeri Sembilan. In: Japar Sidik B, Arshad
A, Tan SG, Daud SK, Jambari HA, Sugiyama S [eds] Aquatic
Resource and Environmental Studies of the Straits of Malacca:
Current Research and Reviews. Malacca Straits Research and
Development Centre (MASDEC], Universiti Putra Malaysia, Serdang.
pp 99-110.

Lee CN [1998]. Seagrass Communities in the Coastal Waters of
Port Dickson. BSc thesis, Department of Biology, Universiti Putra
Malaysia, Serdang.

Japar Sidik B, Arshad A, Hishamuddin 0, Shamsul Bahar A [1995].
Halophila decipiens Ostenfeld (Hydrocharitaceae]: A new record of
seagrass for Malaysia. Aquatic Botany 52: 151-154.

Muta Harah Z, Japar Sidik B, Fazrullah Rizally AR, Mansoruddin A,
Sujak S (2002, in press]. Occurrence and systematic account of
seagrasses from Pulau Redang, Terengganu, Malaysia. In:
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Terengganu: Towards Sustainable Usage and Management of
Islands, Grand Continental Hotel, Kuala Terengganu. Department
of Fisheries Malaysia, Ministry of Agriculture Malaysia, Kuala
Lumpur.

15 The seagrasses of

The western Pacific islands

THE WESTERN PACIFIC ISLANDS

countries and island states of Micronesia,

Melanesia and Polynesia. These countries are
located in the tropical Pacific Ocean; almost all the
islands are in a zone spanning the equator from the
Tropic of Cancer in the north to the Tropic of Capricorn
in the south.

Most islands, with the exception of Papua New
Guinea and Fiji, are small by continental standards
and are separated by expanses of deep ocean waters.
It is no easy task estimating even the number of
islands in the western Pacific region. For example
there are in excess of 2000 islands in Micronesia
alone, some of which may not be permanent and can
be swamped by high tides. There are two main types
of islands - the high islands such as Fiji, Papua New
Guinea and most of the Solomon Islands, and the low
islands and coral reef atolls such as Majuro and
Kiribati. In the Pacific, as in the rest of the world, most
of the cities and towns are located in the coastal
region. Only in Papua New Guinea are there large
towns located away from the coast. There has been a
marked change away from mostly subsistence living.
As a consequence Pacific islanders are no longer
totally rural, and urban growth is outstripping total
growth. Human populations are increasing throughout
the region and can be as high as 23 000 people per km*
(e.g. Marshall Islands]".

Most countries in the Pacific list human waste
disposal as a significant issue and this is likely to
affect seagrass meadows. Only larger towns have
sewage systems, but most of the effluent discharges
into the sea". Along with septic systems and village
latrines, the eventual nutrient loads of sewage
systems to inshore and reef platform seagrasses may
be significant. Custom ownership of land [inherited
ownership of land and nearshore regions by
indigenous villages or families) gives the owners the
right to do as they wish with the land even if that leads

T=: western Pacific island region includes the

R. Coles

L. McKenzie
S. Campbell
M. Fortes

F. Short

to environmental damage. While these issues are
recognized and are being addressed by planning
legislation, enforcement is difficult or impossible in
many of the islands. This dilemma of land tenure may
be an obstacle to the environment planning needed to
ensure a sustainable habitat for seagrass.

There are 24 species of seagrasses, including
Ruppia”, found throughout the tropical Indo-Pacific”.
Our best estimate is that 13 of these are found in the
western Pacific islands. These include the genera of
Cymodocea, Enhalus, Halodule, Halophila, Syringo-
dium, Thalassia and Thalassodendron. \t is possible
that new species remain to be described from the
western Pacific, as collections from this region are
relatively few. Seagrass species distribution across the
western Pacific is believed to be influenced by the
equatorial counter-current in the northern hemi-
sphere and the equatorial current in the southern
hemisphere“, with the number of species declining
with easterly distance. The reduced bottom area
available and the effect of past changes in sea level
would also reduce species numbers along an easterly
gradient’. The numbers are greatest near the biggest
land mass, with 13 species in Papua New Guinea”, and
least in the easternmost islands; only one species is
known from Tahiti”.

Seagrasses across the region are also often
closely linked, with complex interactions, to mangrove
communities and coral reef systems. Dense seagrass
communities of Enhalus and Cymodocea are often
present on the intertidal banks adjacent to mangroves
and fringing reefs.

BIOGEOGRAPHY

Western Pacific seagrass communities grow on
fringing reefs, in protected bays and on the protected
side of barrier reefs and islands. Habitats most suited
to tropical seagrasses are reef platforms and lagoons
with mainly fine sand or muddy sediments enclosed

162

WORLD ATLAS OF SEAGRASSES

by outer coral reefs. These habitats are influenced by
pulses of sediment-laden, nutrient-rich freshwater,
resulting from seasonally high summer rainfall.
Cyclones and severe storms or wind waves also
influence seagrass distribution to varying degrees. On
reef platforms and in lagoons the presence of water
pooling at low tide prevents drying out and enables
seagrass to survive tropical summer temperatures.

Enhalus acoroides is the only species that
releases pollen to the surface of the water when
reproducing sexually. This feature restricts its
distribution to intertidal and shallow subtidal areas. It
is a slow-growing, persistent species with a poor
resistance to perturbation”, suggesting that areas
where it is found are quite stable over time. Cymodocea
is an intermediate genus that can survive a moderate
level of disturbance, while Halophila and Halodule are
described as being ephemeral genera with rapid
turnover and high seed set, well adapted to high levels
of disturbance”.

Thalassia hemprichii is the dominant seagrass
found throughout Micronesia and Melanesia, although
it is absent from Polynesia and Fiji. Thalassia
hemprichii is often associated with coral reefs and is
common on reef platforms where it may form dense
meadows. It is able to grow on hard coral substrates
with little sediment cover. It can also be found
colonizing muddy substrates, particularly where water
pools at low tide. In the Indo-Pacific region, Thalassia
hemprichii is commonly the climax seagrass species.
Species of Halodule, Cymodocea and Syringodium may
at times also be found in dense meadows associated
with reefs and on reef platforms. Enhalus acoroides
and Cymodocea rotundata are also widespread
throughout the region but absent from Polynesia and
Fiji. Halodule uninervis is abundant throughout
Melanesia and Polynesia, but is only found in Guam and
Palau in Micronesia. Both Cymodocea serrulata and
Cymodocea rotundata were recorded in intertidal
regions of Micronesia” and in Papua New Guinea,
eastern Micronesia and Vanuatu”.

Syringodium isoetifolium has only been recorded
in the most westerly islands of Micronesia (e.g. Palau
and Yap], in Tonga and Samoa in Polynesia, in Papua
New Guinea, and in Vanuatu and Fiji in Melanesia. In Fiji
Syringodium isoetifolium occurs as a widespread and
dominant seagrass species.

Halophila species are widespread through the
Pacific islands with the exception of the eastern
Micronesia islands. In the western islands of the west-
ern Pacific, Halophila ovalis is found in intertidal habitat
mixed with larger seagrass species like Enhalus
acoroides in Palau or Thalassia hemprichii in Yap.
Halophila ovalis is also commonly found in deep water
at the offshore edge of mixed seagrass meadows. The

only Halophila species present in Fiji is the subspecies
Halophila ovalis bullosa identified by den Hartog”.

Thalassodendron ciliatum has been recorded
from Palau, Papua New Guinea and Vanuatu'™”. It is
unusual in being restricted almost exclusively to rocky
or reef substrates. It is often found on reef edges
exposed to wave action, protected from damage by its
flexible woody stem and strong root system. It can be
difficult to locate because of its exposed reef edge habit
and is uncommon in records from most Pacific island
countries.

Generally low nutrient availability’ is a likely
determining factor in seagrass extent on reef habitats
across the western Pacific islands. Seagrasses
frequently grow more abundantly on intertidal reef
platforms and mud flats adjacent to populated areas
where they can utilize the available nutrients. Seagrass
communities in the western Pacific islands must
tolerate fluctuating and extreme temperatures, fluc-
tuating salinity during rainfall seasons, and exposure to
storm-driven waves and erosion. Often the sediments
are unstable and their depth on the reef platforms can
be very shallow, restricting seagrass growth and
distribution.

Most tropical species in the western Pacific are
found in waters less than 10 m deep. There is a complex
depth range for seagrasses as the availability of bottom
substrate and shelter for seagrass growth is controlled
by the topography of coral reef communities which often
protect the seagrass habitats from wave action. The
location of the seaward edge may be determined by the
depth or location at which coral cover becomes consis-
tent or by the edge of a platform that drops rapidly into
deeper water. This distribution and the topographic
features controlling it differ from many temperate
regions where availability of light for photosynthesis
controls the depth penetration of seagrasses.

Exposure at low tide, wave action and low salinity
from freshwater inflow determine seagrass species
survival at the shallow edge. Seagrasses survive in the
intertidal zone especially at sites sheltered from wave
action or where there is entrapment of water at low
tide (e.g. reef platforms and tide pools) protecting the
seagrasses from exposure (to excessive heat or drying)
at low tide. At the deeper edge, light, wave action and
the availability of suitable bottom substrate limit
distribution.

The stresses and limitations to seagrasses in the
tropics are generally different from those in temperate
or subarctic regions. They include thermal impacts
from high water temperatures; desiccation from
overexposure to warm air; osmotic impacts from
hypersalinity due to evaporation or hyposalinity from
wet season rain; radiation impacts from high irradiance
and UV exposure. Both Halophila ovalis and Thalassia

(11)

« Pikelot

Woleai «

Eaunpik *

FABIO ESR ANT ED

PACIFIC OCEAN

-
:

Inan Jaya
(West Papua)

INDONESIA

PAPUA NEW GUINEA

| at 2

BANDA SEA

ee Culfof Papua
Port Morea

Aes CORAL SEA

ARAFURA SEA

SOLOMON ISLANDS
J

Santa Cruz Is.

VANUATU

NEW CALEDONIA

600 800 1000 Kilometers

170° E
Maps 15.1 and 15.2
Western Pacific islands (west) (top) and Western Pacific islands (east)

hemprichii were found in intertidal regions in Yap,
Micronesia’, where tolerance to 40°C temperatures
and low salinity allow these species to colonize. Other
species present in Yap, Syringodium isoetifolium and
Cymodocea serrulata, were restricted to deeper water
by these conditions.

Reef platform seagrass meadows support a wide
range of mollusks, fish, holothurians and decapods.
The available literature does not focus on the ecological
role of seagrasses and information on complex

STATES

Wewalke BISMARCK SEA

The western Pacific islands

Nomwin

Chuuk
a (Truk) _Pohnpei

* Mwokil

* Satawan
* Kosrae

ODF MICRONESIA

0 100 200300400500 Kilometers 0
mE a ha

“\s Kavieng

SOLOMON
SOLOMON SEA ISLANDS

.
.

Milne Bay

150° E 160° ES

PACIFIC-OCEAN

AMERICAN
SAMOA

Nukubuco Reef

4 TONGA

community interactions presented for reef flat species
may not necessarily refer to areas with seagrass.
Munro’ lists 75 species of mollusks collected by
subsistence gleaners in the Solomon Islands, Papua
New Guinea and Fiji from mangroves, reefs, seagrass
meadows and sand flats. Other mollusks such as the
trochus shell {Trochus niloticus) found in seagrass
meadows are collected as a source of cash income.
Similarly the holothurians have been a valuable source
of cash income, although now heavily overfished'’. We

163

164

WORLD ATLAS OF SEAGRASSES

have found lower value species such as Holothuria atra
to be still common in seagrass meadows in parts of
Micronesia.

Pyle" lists at least 3 392 reef and shore fish from
the Pacific islands but it is not possible to distinguish
which species are from seagrass meadows. Klumpp et
al.'"' refer to 154 species of tropical invertebrates and
fish that feed directly on seagrasses and Coles et al.'"”
list and classify 134 taxa of fish and 20 shrimp species
found in tropical Australian seagrass meadows giving
some indication of the likely use of tropical Pacific
seagrass meadows.

Case Study 15.1
KOSRAE

The Federated States of Micronesia is made up of

~ four states: Kosrae, Pohnpei, Chuuk and Yap. Kosrae
is the easternmost state and consists of two islands:
a large mountainous island approximately 20 km
long and 12 km wide, and a smaller 70 ha island,
Lelu, approximately 1 km off the northeast coast of
Kosrae,

A detailed assessment of Kosrae reef
environments in 1989 (carried out by the US Army
Corps of Engineers, Coastal Engineering Research
Center] mapped approximately 3.5 km? of seagrass
meadows around the islands. Seagrass meadows
were restricted to reef tops. Large dense meadows
were mapped adjacent to Okat and Lelu Harbours.

——

Kilometers

Lelu Harbour ca 1900.

Seagrasses are also food for the green turtle
(Chelonia mydas), found throughout the Pacific island
region, and for the dugong {Dugong dugon), found in
small numbers feeding on seagrasses in the western
islands - Palau, Vanuatu and the Solomon Islands.

HISTORICAL PERSPECTIVES

The major changes in Pacific island seagrass meadows
have occurred mostly in the post-Second World War
period and are related to transport infrastructure,
tourist development and population growth. Some
islands have seagrass maps available but most do not

Species of seagrass found were Enhalus acoroides,
Thalassia hemprichii and Cymodocea rotundata.

Over the last three to four decades there has
been considerable coastal construction activity on
the islands to build modern transportation facilities,
and the seagrass meadows and reef flats at those
locations have been severely impacted. Two aircraft
runways and associated causeways have been
constructed on the only available flat area on the
island — the reef flat.

The first runway was constructed on the
shallow flat between Kosrae and Lelu Islands in
the late 1960s and early 1970s. Maragos'”!
reported that the causeway connecting to this
runway construction had adverse effects on Lelu
Harbour. The original causeway blocks the water
circulation and fish runs into inner Lelu Harbour,

Water
currents

Mangroves

od
=~

Kilometers =
Lelu Harbour 1975.

have information recorded with the precision required
to identify any historical change. It is likely that some
information exists in unpublished reports and
environmental assessments for areas subject to
development but, where it exists, this information is not
readily available.

Human population growth and the need to provide
tourist accommodation have led to filling in some
coastal areas to provide new land. Certainly port
developments and small boat marinas have been
constructed in locations without taking the presence of
seagrass meadows into account". Nutrient inputs

leading to a decline in seagrasses and fish catches
and increased pollution problems. Fill for the
runway expansion further reduced water circu-
lation, fish yields, water quality and seagrasses in
the harbor.

In the mid-1980s, a new airport and dock were
constructed in Okat Harbour on the north of Kosrae
Island. Construction buried a large area of the
offshore reef flat seagrass meadows (see sketch
maps below}. Also, during dredging activities, the
rate of slurry discharged into a retention basin
exceeded the basin’s capacity, causing the slurry to
overflow and burying an adjacent 10 ha of seagrass
and coral habitat under 0.25-0.5 m of fine mud.

The construction also changed the water
circulation, and the strong currents caused
shoreline erosion. These impacts are reported to

x
vtec
5

es, Harbour” ~_- yy
KOSRAE
ISLAND

Okat Harbour and Reef 1978.

The western Pacific islands

from expanding coastal urban development may have
increased the biomass of seagrass on nearby reef plat-
forms. In general, though, there is not sufficient histor-
ical written information from which to draw direct
conclusions on historic trends. Munro’ does report
that 2000-year-old mollusk shell middens in Papua
New Guinea have essentially the same species
composition as present-day harvests, suggesting
indirectly that the habitats, including seagrass habitats
and their faunal communities, are stable and any
changes occurring are either short term or the result of
localized impacts.

have reduced Okat reef’s fish harvest to half that of
pre-construction levels.

The unintended environmental effects of these
constructions are continuing with shore erosion and
restoration by revetment still occurring at Lelu
Harbour and adjacent to villages near the new
airport. While it is easy to criticize a decision to build
infrastructure on top of coral reef platforms, it is
hard to suggest a feasible land-based solution on
such a mountainous island. Flat areas available are
either inhabited or mangrove covered. It would be
hoped that if these projects or similar were under-
taken today, better environment management sys-
tems in place would at least reduce the unintended
effects and slurry overflow that occurred.

Source: Maragos'"”!.

Harbour
‘ — !

j a. a
/ , Ss Si
f A f i F

KOSRAE
ISLAND

Okat Harbour and Reef 1988.

165

166

Photo: FT. Short

WORLD ATLAS OF SEAGRASSES

Banded sea snake swimming over Syringodium isoetifolium and
Halodule uninervis meadow, Nukubuco Reef, Fiji

AN ESTIMATE OF HISTORICAL LOSSES

In the western Pacific, local coastal developments for
tourism or transport infrastructure are the major cause
of seagrass loss. In Kosrae and other members of the
Federated States of Micronesia the development of local
airports has contributed to a loss of seagrass on reef
platforms. The Kosrae airport, for instance, is placed on
landfill covering a reef platform and seagrasses’. In
Palau, the building of causeways without sufficient
consideration of the need for culverts to maintain water
flow has caused localized seagrass loss. In Fiji,
eutrophication and coastal development are the primary
causes of seagrass loss. Little information is available
on the loss of seagrass habitats in Papua New Guinea,
but away from major population centers losses are
likely to be small and again associated with transport
infrastructures.

Maragos'”'details the loss of mainly coral reef flat
habitat, but including seagrasses and mangroves, in
the Federated States of Micronesia from construction
activities associated with plantations, transportation,
military activity, urban development, aquaculture
development and resort development. Coastal road
construction around the islands of Pohnpei and Kosrae
resulted in the dredging of many hectares of seagrass
and mangrove habitat.

Losses of seagrasses such as these are likely to
be widespread across the Pacific islands as there has
been little attention paid to protecting seagrasses.
Modern mapping and monitoring techniques should in
the near future enable some baseline estimation of the
total areas of the seagrass resources of the region.

AN ESTIMATE OF PRESENT COVERAGE

Species lists are available for the western Pacific
region” but they are not available for many of the
individual islands. Coles and Kuo'” list seagrass
species from 26 islands [including the Hawaiian Islands
and Papua New Guinea) based on published records,
examination of herbarium specimens and/or site visits
by the authors. Species numbers ranged from 11 on
Vanuatu to a single species in the Marshall Islands. The
numbers in Coles and Kuo'” are conservative in some
cases because they do not include unpublished reports
or records. Maps of seagrass are not readily available
or are of relatively poor quality and/or reliability. Some
estimation might be possible based on the high
likelihood of almost all shallow [<2 m below mean sea
level) reef flats having at least a sparse seagrass cover,
but no numerical estimation of seagrass cover in the
western Pacific has been made to date.

Geographic information system (GIS) initiatives in
the Federated States of Micronesia by the South Pacific
Regional Environment Program should improve map
coverage. Simple GIS maps are already available for
Kosrae although they are based on earlier aerial
mapping and would not be precise enough for detailed
management purposes. Project assistance to update
and validate these maps would accelerate the process
of providing a publicly available set of maps for these
islands. Partial maps are available for other western
Pacific islands although their validity is uncertain and
likely to be variable.

CSIRO (Australia’s Commonwealth Scientific and
Industrial Research Organisation) has recently surveyed
Milne Bay Province in Papua New Guinea. Seagrass was
seen at 103 locations out of a total of 1126. Seagrass
was found at several areas throughout the province,
mostly on shallow areas adjacent to the larger islands
such as the Trobriand, Woodlark and Sudest Islands.
Cover was up to 95 percent in these areas. The
dominant species were Thalassia hemprichii, Enhalus
acoroides and Halophila ovalis with some Cymodocea
serrulata, Halodule uninervis and Syringodium
isoetifolium™”. To the best of our knowledge no other
broadscale surveys have been conducted for Papua New
Guinea outside individual published site descriptions.

USES AND THREATS

Traditional uses of seagrass by communities in the
western Pacific include manufacture of baskets;
burning for salt, soda or warmth; bedding; roof
thatch; upholstery and packing material; fertilizer;
insulation for sound and temperature; fiber
substitutes; piles to build dikes; and for cigars and
children’s toys’. Enhalus acoroides fiber is also
reported to be used on Yap, Micronesia, in the
construction of nets”. Enhalus acoroides fruit is

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_Vill WORLD ATLAS OF SEAGRASSES

SEAGRASSES AND PEOPLE

Recreational fisher standing in a seagrass bed, Bali, Indonesia Food [bivalves] collected from seagrass beds, Mozambique

Beach seine is
Ph uppines WW Cd

Harvesting abalone from

Phyllospadix Harvesting Zostera marina for

spp. ca 1914, Pacific coast of USA transplanting, Maine, USA =

Snorkeler over a long-bladed Zostera marina bed in New Hampshire, USA

Trap fisherman Anibal Amade in

A fisher family on Quirimba Island, Mozambique with the
catch from a trap fishing trip in the seagrass beds

eaten in some Australian traditional communities and
in some parts of the western Pacific.

Coastal development, dredging and marina
developments are generic threats to seagrass in the
tropical tourist regions but areas lost are generally
small. Causeway development in Palau'’” without
culverts to allow water flow has led to large seagrass
losses as water stagnates and sediment builds up.
Coastal agriculture may add to sediment loads in
catchments in Papua New Guinea and Fiji. Shipping
management influences seagrass survival adjacent to
shipping lanes and port locations.

Climate change and associated increase in storm
activity, water temperature and/or sea-level rise have
the potential to damage seagrasses in the region and to
influence their distribution causing widespread loss.
Reef platform seagrasses are already exposed to water
temperatures at low tide greater than 40°C and an in-
crease in temperature may restrict the growth of the
inner shallow edge of reef platform seagrass. Sea-level
rise and associated increased storm activity could lead
to large seagrass losses through increased water move-
ment over seagrass beds and erosion of sediments. It is
possible that with a rise in sea level areas that are now
seagrass habitat may be colonized by coral.

SEAGRASS PROTECTION

Many western Pacific island communities have
complex and at times unwritten approaches to land
ownership, custom rights and coastal sea rights. These
are partially overlaid by arrangements put in place by
colonizing powers during and after the Second World
War, leaving the nature and strength of protective
arrangements open for debate’. In implementing any
protective arrangements for seagrasses the challenge
will be to develop an approach that will suit all parties
and that will respect traditional ownership rights. This
must also be achieved in an area where enforcement, at
least in the sense it is used in North America and
Europe, is absent or ineffective and more of a
consensus approach will be required.

We are not able to find any legislation or
protective reserve systems that are specifically
designed to protect seagrasses. Existing reserves,
however, often include seagrasses and legislation to
protect mangroves or marine animals such as trochus
shell may indirectly protect seagrass meadows.

The South Pacific Regional Environment
Programme Action Strategy for Nature Conservation in
the Pacific Islands region lists 232 established protected
areas and community-based conservation areas in the
Pacific islands. Some, such as the Okat trochus sanc-
tuary in Kosrae and the Ngerukewid Islands reserve in
Palau, provide some level of indirect protection.

Under the Law of the Sea Treaty, coastal nations

The western Pacific islands

are bound to protect the marine environments under
their control. There are some 13 other international
conventions and treaties which could have some
bearing on seagrass management although in reality it
is hard to measure any quantifiable outcomes that
protect seagrasses whether the programs are ratified
or not.

At a regional level, laws relating to impact
assessment and town planning have an indirect ability
to protect seagrass from loss. In Fiji the Town Planning
Act deals with environmental impact assessments.

Halophila ovalis, a species commonly found in the western Pacific

Land below high water is administered by the Ministry
for Land and Mineral Resources through the
Department of Lands and Surveys. If a mangrove area
{and presumably also seagrasses] is be reclaimed, the
application is referred to the Department of Town and
Country Planning for comment, recommendation and
suggested conditions. It may also be referred to the
Department of Fisheries and the Native Fisheries
Commission for arbitration of compensation”.

In Papua New Guinea the Environmental Planning
Act requires a plan for a development project to be
submitted to the Department of Environment and
Conservation for approval”. Palau’s conservation laws
are cited in the Palau National Code Annotated and are
described by the Palau Conservation Society” in an
easy-to-understand form.

Two trends are emerging from the Pacific islands.
One is the recognition of the need for sanctuaries and
protected areas and the other the concept of traditional
or community management of these areas’. The role
being played by non-governmental organizations,
focused on conservation and environment protection
integrated with traditional leadership and government

Photo: J.S. Bujang

167

168 WORLD ATLAS OF SEAGRASSES

Case Study 15.2
SEAGRASSNET - A WESTERN
PACIFIC PILOT STUDY

SeagrassNet is a global monitoring program that
investigates and documents the status of seagrass
resources worldwide and the threats to this
important ecosystem. Seagrasses, which grow at
the interface of the land margin and the world’s
oceans, are threatened by numerous anthropogenic
impacts. There is a lack of information on the status
and health of seagrasses, particularly in the less
economically developed countries. SeagrassNet's
efforts to monitor known seagrass areas and to map
and record uncharted seagrasses in the western
Pacific are important first steps in understanding
and maintaining seagrass resources worldwide.
Synchronous and repeated global sampling of
selected environment and plant parameters is
critical to comprehending seagrass status and
trends; monitoring these ecosystems will reveal
both human impacts and natural fluctuations in
coastal environments throughout the world.

SeagrassNet was developed with two com-
ponents. Research-oriented monitoring methods
are based on recently compiled seagrass research
techniques for global application”, while
community-based seagrass monitoring effort is
modeled after Seagrass-Watch” - an Australian
seagrass community [citizen] monitoring program
that is conducted simultaneously with research-
based monitoring so that comparisons of the
resulting data are possible.

An important part of the communication
strategy for SeagrassNet is an interactive system
established on a website, with data entry, archiving,
display and retrieval of seagrass habitat-monitoring
data, ranging from plant species distribution to
animal abundance and records of localized die-offs.
SeagrassNet both acquires and provides monitoring
data in a format for information sharing.

A PILOT STUDY

Before the program can become fully established, a
pilot study is being conducted to develop a globally
applicable seagrass monitoring protocol, to
compare science-based with community-based
monitoring efforts and to test the feasibility and
usefulness of this publicly available database
retrieval network. The western Pacific was chosen
for the pilot because it has extensive and diverse
seagrass habitats and a myriad of coastal issues
with the potential to threaten seagrass growth and

survival. Challenges to seagrasses in the western
Pacific are numerous and, similar to those in most
parts of the world, range from human population
increase, fisheries practices, pollution and onshore
development to global climate change and sea-level
rise. The combination of these factors and the
remoteness of many locations provide a complex set
of circumstances that challenges our scientific
ability to monitor seagrass habitat and to test the
diversity of habitat impacts. The western Pacific
region includes underdeveloped countries that have
extensive seagrass habitat linked to important
economic activities such as fishing, tourism and
sports diving. The constraints of resources and the
relatively small number of seagrass scientists in the
western Pacific have to date precluded extensive
surveys and monitoring of the kind common in
Europe and parts of the US and Australian coast.

With funding assistance from the David and
Lucile Packard Foundation, eight locations, five of
which are western Pacific islands, were identified as
suitable. In mid-2001, long-term monitoring sites
were established in Kosrae, Pohnpei, Palau,
Kavieng (Papua New Guinea) and Fiji. Scientists
were identified at each location to take part in the
direct field monitoring aspect of the research.
Quarterly monitoring is now being conducted at
designated sites in each country. Sites chosen were
representative of the dominant seagrass habitat
existing in each location.

In Kosrae, a monitoring site was established in
a trochus sanctuary adjacent to Okat Harbour on the
north of Kosrae Island. The site is on an intertidal
fringing reef borded by mangroves landward and the
reef edge seaward. Seagrass meadows cover much
of the fringing reef where coral is absent. It is
predominately an Enhalus acoroides meadow
inshore, which changes to a meadow dominated by
Thalassia hemprichii and Cymodocea rotundata
seaward. The Fisheries Development Division is
monitoring the site with some assistance from the
Kosrae Development Review Commission.

On the island of Pohnpei, the largest island
and location of the capital of the Federal States of
Micronesia, a monitoring site was established on a
relatively remote fringing reef at the southernmost
point of the main island in an area free from physical
disturbance by human activity. The site is on a reef
flat where water pools at low tide, and is similar to
the site monitored on Kosrae, including the species
Enhalus acoroides and Thalassia hemprichil.
Scientists from the College of Micronesia are
monitoring the site.

In the Republic of Palau a monitoring site was
established on a fringing reef at the edge of the
shipping channel on Koror. The meadow extends
across the intertidal reef flat from the mangrove-
lined shore to the reef crest. Inshore, the meadow is
predominately Enhalus acoroides, becoming inter-
spersed with Thalassia hemprichii, which increases
in presence along with Halodule uninervis and
Halophila ovalis seaward. The site is adjacent to
coastal development and receives stormwater and
agricultural runoff. Scientists of the Palau Inter-
national Coral Reef Centre and Coral Reef Research
Foundation are monitoring this site.

In Papua New Guinea, seagrass monitoring
was conducted near Kavieng in New Ireland, an
island province in the northeast. With the permission
of the village leader a monitoring site was estab-
lished on the fringing reef flat of a small island,
Nusa Lik. The site is intertidal with a mixture of
Halodule uninervis, Enhalus acoroides, Thalassia
hemprichii, Cymodocea serrulata and Halophila
ovalis. The outer edge of the seagrass was deter-
mined by the edge of the coral reef. Staff attached to
the Fisheries Research Laboratory and local fish-
eries college are monitoring the site.

Fiji has environmental issues similar to the
other western Pacific island countries, such as
deforestation, soil erosion and sewage effluent. A
monitoring site was established on Nukubuco Reef
in Laucala Bay. This monitoring site is different from
sites at other localities, as it is on a barrier reef. No
suitable fringing reef sites similar to other
participating countries could be found. The site was
chosen because the seagrass distribution and
abundance of Nukubuco Reef have been mapped as
part of a University of the South Pacific postgraduate
project and the site was easily accessible from Suva.
The monitoring site is adjacent to a sand cay at the
northwestern edge of the reef. It is an intertidal site
with a mixture of Halodule uninervis, Halodule
pinifolia and Halophila ovalis subsp. bullosa close to
the cay, becoming a monospecific Syringodium
isoetifolium meadow seaward. The outer edge of the
meadow was determined by the edge of the channel.
Scientists from the University of the South Pacific
are monitoring the site.

The community-based seagrass monitoring
program that forms the second stage of the project
was initiated in the western Pacific islands in April
2002 in New Ireland, Papua New Guinea. In June and
July 2002 local citizens also began monitoring sites in
Kosrae, Palau and Fiji. Community participants were
mostly school students and local villagers.

The western Pacific islands

Community monitoring sites were established on
intertidal fringing reefs and local scientists,
government and non-governmental organizations are
providing support. The program is using the existing
Australian Seagrass-Watch program
data entry systems.

"5! brotocols and

Thalassia hemprichii and Cymodocea rotundata meadow on
intertidal fringing reef, Kosrae, Federated States of Micronesia.

ENCOURAGING RESULTS

Preliminary results from the scientific monitoring
indicate that the sampling protocols appear suitable,
although adjustments and refinements may occur
from time to time as the program develops. Data
entry via the website {www.seagrassnet.org] was
successful, although access to the Internet is limited
in some countries. Quality control and data
validation are being completed at the University of
New Hampshire's Jackson Estuarine Laboratory.
Photographic collections are being cataloged and
archived by the Queensland Department of Primary
Industry Marine Plant Ecology Group. Herbarium
samples were also verified at the University of New
Hampshire and sent to the International Seagrass
Herbarium at the Smithsonian Institution,
Washington, DC, USA.

The initial success of the pilot study has
encouraged scientists and coastal resource
managers in Africa, South America, Asia, Europe,
Australia and North America to participate. The goal
is to expand SeagrassNet to other areas of the globe
and, ultimately, to establish a network of monitoring
sites linked through the Internet by an interactive
database. The ultimate aim is to preserve the
seagrass ecosystem by increasing scientific
knowledge and public awareness of this threatened
coastal resource.

Photo: L. McKenzie, DPI

169

170

WORLD ATLAS OF SEAGRASSES

agencies, suggests that conservation measures and
the acceptance of enforcement will continue to
improve.

There is a growing understanding that community
types such as seagrasses are vital to the health of the
reef environment and that they are threatened by climate
change as well as direct human impacts. There is clearly
a need in the Pacific island nations to quantify the risks
to seagrass of present management practices and to
quantify the extent and value of seagrass protection
afforded by the present reserves and legislative
approach.

REFERENCES

1 Bryant-Tokalalu JJ [1999]. The impact of human settlements on
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and Coastal Biodiversity in the Tropical Island Pacific Region: Vol 2:
Population, development and conservation priorities. Workshop
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Honolulu. pp 215-235.

2 Short FT, Coles RG, Pergent-Martini C [2001]. Global seagrass
distribution. In: Short FT, Coles RG {eds] Global Seagrass Research
Methods. Elsevier Science BV, Amsterdam. pp 5-30.

3 Short FT, Coles RG (eds) [2001]. Global Seagrass Research
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4 Mukai H [1993]. Biogeography of the tropical seagrasses in the
western Pacific. Australian Journal of Marine and Freshwater
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5 Coles RG, Lee Long WJ [1999]. Seagrasses. In: Maragos JE,
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6 Fortes MD [1998]. Indo-West Pacific affinities of Philippine
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7 den Hartog C [1970]. The Seagrasses of the World. North Holland
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8 Walker DI, Dennison WC, Edgar G [1999]. Status of Australian
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9 Tsuda RT, Kamura S [1990]. Comparative review on the floristics,
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10 Coles RG, Kuo J [1995]. Seagrasses. In: Maragos JE, Peterson

MNA, Eldredge LG, Bardach JE, Takeuchi HF (eds) Marine and

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ie)

AUTHORS

Rob Coles, Len McKenzie and Stuart Campbell, DPIQ,
Northern Fisheries Centre, P.O. Box 5396, Cairns, Queensland 4870,
Australia. Tel: +61 (07 4035 0111. Fax: +61 (0)7 4035 4664. E-mail:
rob.coles(ddpi.qld.gov.au

Miguel Fortes, Marine Science Institute CS, University of the Philippines,
Diliman, Quezon City 1101, Philippines.

Fred Short, Department of Natural Resources, University of New
Hampshire, Jackson Estuarine Laboratory, 85 Adams Point Road,
Durham, NH 03824, United States.

JE, Peterson MNA, Eldredge LG, Bardach JE, Takeuchi HF leds)
Marine and Coastal Biodiversity in the Tropical Island Pacific
Region: Vol 2: Population, development and conservation priorities.
Workshop proceedings. Pacific Science Association, East-West
Center, Honolulu. pp 127-144.

14 Richmond RH [1999]. Sea cucumbers. In: Maragos JE, Peterson
MNA, Eldredge LG, Bardach JE, Takeuchi HF (eds) Marine and
Coastal Biodiversity in the Tropical Island Pacific Region: Vol 2:
Population, development and conservation priorities. Workshop
proceedings. Pacific Science Association, East-West Center,
Honolulu. pp 145-156.

15 Pyle RL [1999]. Patterns of Pacific reef and shore fish biodiversity.
In: Maragos JE, Peterson MNA, Eldredge LG, Bardach JE, Takeuchi
HF [eds] Marine and Coastal Biodiversity in the Tropical Island
Pacific Region: Vol 2: Population, development and conservation
priorities. Workshop proceedings. Pacific Science Association.
East-West Center, Honolulu. pp 157-176.

16 Klumpp DW, Howard RK, Pollard DA [1989]. Trophodynamics and
nutritional ecology of seagrass communities. In: Larkum AWD,
McComb AJ, Shepherd SA (eds) Biology of Seagrasses: A treatise
on the biology of seagrasses with special reference to the
Australian region. Elsevier, Amsterdam. pp 394-457.

17 Coles RG, Lee Long WJ, Watson RA, Derbyshire KJ [1993].
Distribution of seagrasses, their fish and penaid prawn
communities in Cairns Harbour, a tropical estuary, northern
Queensland, Australia. Australian Journal of Marine and
Freshwater Research 44: 193-210.

18 Coles RG [1996]. Coastal Management and Community Coastal
Resource Planning in the Asia Pacific Region. Final report to the
Churchill Fellowship Foundation. 51 pp.

19 Maragos JE [1993]. Impact of coastal construction on coral reefs in
the US affiliated Pacific islands. Coastal Management 21: 235-269.

20 Skewes. Personal communication.

21 Fortes MD [1990]. Seagrasses: A resource unknown in the ASEAN
region. United States Coastal Resources Management Project.
International Center for Living Aquatic Resources Management,
Manila, Philippines. ICLARM Education Series No. 6. 46 pp.

22 Falanruw MC [1992]. Seagrass nets. Atoll Research Bulletin (364):
1-12.

23 Palau Conservation Society [1996]. A Guide to the Conservation
Laws and Regulations of the Republic of Palau. Palau Conservation
Society, Koror. 19 pp.

24 Federated States of Micronesia [2001]. Preliminary Report to the
Conference of the Parties of the Convention on Biological Diversity.
24 pp.

25 McKenzie LJ, Campbell SJ, Roder CA [2001]. Seagrass-Watch:
Manual for mapping & monitoring seagrass resources by
community (citizen) volunteers. Northern Fisheries Service, Cairns,
Australia. 94 pp.

16 The seagrasses of

INDONESIA

[though seagrasses cover at least 30000 km?
Aevossnas the Indonesian Archipelago, from
Pulau Weh in Aceh to Merauke, Papua, they have
only been studied in relatively small areas and
information is therefore rather limited. Nonetheless an
encouraging and increased understanding of the
importance, ecology and biology of Indonesian
seagrasses has developed in recent years". Vast areas
of the archipelago [e.g. the north coast of Papua, the
southwest coast of Indonesia, the south and west
coasts of Kalimantan) are yet to be studied, however.
The diversity of marine habitats in Indonesia is
among the highest in the world and Indonesian sea-
grass diversity is comparable to other countries in the
region. Seven genera and 12 species of seagrasses
currently occur in Indonesian waters”. Two species,
Halophila spinulosa and Halophila decipiens, have
been recorded in just a few locations: Halophila
spinulosa in Sorong [Papua], Lombok, East Java, Sunda
Strait and Riau, and Halophila decipiens in Aru, Kotania
Bay, Lembata, Sumbawa and Jakarta Bay. Two further
species, Halophila beccarii and Ruppia maritima, are
known only through specimens at the Bogor Herbarium
and have not recently been found in the field.
Indonesian seagrasses either form dense
monospecific meadows or mixed stands of up to eight
species. Thalassia hemprichii, Enhalus acoroides,
Halophila ovalis, Halodule uninervis, Cymodocea serru-
lata and Thalassodendron ciliatum usually grow in
monospecific beds’, and muddy substrates on the
seaward edges of mangroves often have meadows of
high biomass. Mixed-species meadows occur in the
lower intertidal and shallow subtidal zones, growing best
in well-sheltered, sandy (not muddy], stable and low-
relief sediments. These beds are typically dominated by
pioneer species such as Halophila ovalis, Cymodocea
rotundata and Halodule pinifolia. Thalassodendron
ciliatum dominates the lower subtidal zone - this
species can grow in silt as well as in medium-to-coarse

Indonesia

T.E. Kuriandewa
W. Kiswara

M. Hutomo

S. Soemodihardjo

sand and coral rubble. High bioturbation by, for example,
burrowing shrimps tends to decrease seagrass density
and favor the pioneer species. Seagrasses growing in
terrigenous sediment are more influenced by the
turbidity, seasonality, fluctuating nutrient and salinity
concentrations, and subsequent light limitation, of land
runoff than those in reef-derived carbonate sediments
with less variable seasonal dynamics.

Monospecific beds of Thalassia hemprichii are
the most widespread throughout Indonesia and occur
over a large vertical range from the intertidal zone
down to the lower subtidal zone”. Halophila ovalis also
has a wide vertical range, from the intertidal zone down
to more than 20 m depth, and grows especially well on
disturbed sediments such as the mounds of burrowing
invertebrates. Enhalus acoroides, too, grows in a
variety of different sediment types, from silt to coarse
sand, in subtidal areas or localities with heavy
bioturbation. Halodule uninervis is a pioneer species,
usually forming monospecific beds on the inner reef
flat or on steep sediment slopes in both the intertidal
and subtidal zones.

ECOLOGY
The majority of detritus produced by Indonesian
seagrasses is believed to settle within the beds, with an
estimate of only 10 percent exported to other
ecosystems’. Most of the nutrients lost by leaf
fragmentation through decomposition or harvesting by
alpheid shrimps are translocated to the sediment and
about 80 percent of the nitrogen content is denitrified
there”. This retention of nutrients within the beds may
explain why seagrass beds in Indonesia maintain a high
level of productivity despite low nutrient availability.
Detailed studies of the nutrient concentrations at
six different locations in the Spermonde Archipelago of
South Sulawesi have indicated that there are structural
and functional differences between coastal beds
growing on the sand and mud deposited by rivers, and

eae 172

WORLD ATLAS OF SEAGRASSES

Table 16.1
Average biomass of seagrasses (g dry weight/m’) at various locations throughout Indonesia

Sunda Banten
Strait Bay

1976 353-560
Cymodocea rotundata 37-106 139
Cymodocea serrulata 48-104 15-35
Halodule pinifolia = cs
Halodule uninervis 10-36 6-80
Halophila ovalis 2-4 8
Syringodium isoetifolium 74 102-372
Thalassia hemprichii 87-193 120-257
Thalassodendron ciliatum - -

Species

Enhalus acoroides

Source: Kiswara"”

Table 16.2

Jakarta Flores Lombok
Bay Sea

250-663 155-546 393-2 479

18-23 34-113 39-243

45-174 111

29-126 47

13-516 29-128

1-3 4-46

33-127 85-262

115-322 53-263

231-444 -

Average density of seagrasses (shoots/m’] at various locations throughout the Indonesian Archipelago

Sunda Banten
Strait Bay

Enhalus acoroides 160 40-80
Cymodocea rotundata 38-756 690
Cymodocea serrulata 48-1 120 60-190
Halodule pinifolia = -
Halodule uninervis 10-335 40-1 160
Halophila ovalis 15-240 820
Syringodium isoetifolium 630 124-3 920
Thalassia hemprichii 30-315 220-464
Thalassodendron ciliatum = -

Species

therefore of terrestrial origin, and those growing
offshore on sediments derived from coral reefs.
Concentrations of dissolved reactive phosphate,
ammonium and nitrate+nitrite were low [<2 uM] in the
water column at all sites, often below detectable limits,
but considerably higher in sediment porewater™.
Porewater phosphate concentrations (3-13 uM) were
comparable between the two sediment types, but
exchangeable phosphorus contents were two to five
times higher in carbonate sediment [(18.2-23.6 mg
phosphorus/100 g versus 4.4-10.9 mg phosphorus/100
g) than in terrigenous sediments. Carbonate sediments
were extremely low in organic matter compared with
terrigenous sediments.

The more vigorous growth of coastal seagrasses
is attributed to a higher level of nutrients in the
sediment than offshore. Leaf size of Enhalus acoroides
is significantly larger in coastal than offshore beds”,
biomass and shoot densities are higher and epiphyte

Jakarta Flores
Bay Sea
36-96 60-146 50-90

26-1 136 220-1 800 253-1 400
1056 115-1 600 362

- 430-2 260 7120

604 360-5 600 80-160
18-115 100-2 160 400-1 855
144-536 360-3 740 1 160-2 520
68-560 160-1 820 200-865
- 400-840 -

Lombok

cover lower, factors attributed to the less severe
environmental fluctuations of offshore beds”.

Biomass

The below-ground rhizome biomass of Enhalus
acoroides is six to ten times larger than that of above-
ground biomass". Cymodocea rotundata, Cymodocea
serrulata and Halodule uninervis have higher below-
ground biomass when growing in established mixed
vegetation beds than in monospecific pioneer beds“. In
general, species characteristic of climax Indonesian
seagrass meadows (Thalassia hemprichii, Enhalus
acoroides and Thalassodendron ciliatum) invest two to
four times more energy into below-ground biomass
growth than the colonizing species (Halodule uninervis,
Cymodocea rotundata and Cymodocea serrulata)"’.
Biomass values show high variability (Table 16.1] due to
habitat differences, species composition, plant densities
between locations and sampling techniques’.

20
Manila Bay

SOUTH
CHINA
SEA

epulsuan BRUNE! <’

.
3

MALAYSIAJ — Anambas
: \

MALAYSIA.

=< Sha. - Riu
i) acl

cae Archipelago
., Bangka

Karimata

‘Sumatra «
INDONESIA = “*
>

“Belitung 4 f

Lampung Bay
Kepulauan Seribu 4
Gremang Bay JAVA SEA

gow Jakarta Bay
Sunda Strait—— 52, Jakarta
Banien Bay “s

& P
° Kangean

INDIAN
OCEAN

Java

Gilmanuk Bay
0 200° 400 +600 800 1000 Kilometers
—— a
Gerupuk Bay!
Map 16.1
Indonesia

Seagrass density also varies considerably
between locations (Table 16.2]. Kiswara found that the
density of Halodule uninervis depends on the phenotype
(normal shoots or thin shoots). In Gerupuk Bay,
southern Lombok, Halodule uninervis densities ranged
from 870 normal shoots/m’* to 6 560 thin shoots/m?
within the same seagrass bed". Nienhuis reported that
Halodule uninervis had the highest density of all
seagrass species in mixed as well as in monospecific
seagrass beds (Table 16.3). In seagrass beds where
foliage covers more than 70 percent of substrate, the
density of seagrasses frequently depends on the
species composition of the community and the relative
age of the seagrasses. In some species, such as
Thalassia hemprichii, biomass is frequently a function
of shoot density and total leaf area per leaf cluster”.

Seasonal studies of seagrass biomass and shoot
densities in Indonesian waters are scarce but
significant seasonal fluctuations are known to occur”.

Productivity

Growth studies have been carried out in Indonesia
using several techniques” * '*'”. Using the oxygen
evolution [photosynthesis] technique, Lindeboom and
Sandee’ demonstrated that gross primary production
rates of various seagrass communities in the Flores
Sea vary from 1230 mg carbon/m’/day to 4700 mg
carbon/m*/day. Seagrass respiration consumption
rates were between 860 mg carbon/m‘*/day and 3900
mg carbon/m*/day. They concluded that net primary
production rates of seagrass communities in the Flores

Puerto Galera

Spermonde P e
Arcipelago YL BANDA SEA *,

Lombok
Flores Sea pi
See:

Indonesia

ee Ce UUUEE EEE SEI SSSSSSSSISSSSSSSSSSS SISSIES

PACIFIC
OCEAN

t CELEBES
SEA

Ilalmahera
-
= + =«
= Aes
af ~* Fyor0ng .
oo -

Sulawesi, Ceram Sea sg:

Kotania Bay
eee

Ambon Bay oe

= Taka Bone Rate Atoll Pe

~ rer
7? {RAFURA

SEA

~~
‘EAST TIMOR

Lesser Sunda Islands

Table 16.3
Average shoot density of seagrass species in mixed and
monospecific seagrass meadows in the Flores Sea
Species Mixed seagrass Monospecific seagrass
meadow (number meadow [number
of shoots/m’] of shoots/m’}

324 (276) =

696 (767) 533 (543)

54 (86) 136 (58)
Halodule uninervis 2847 (5689) 14762 (6 076)
Halophila ovalis 69 (117) -
Syringodium isoetifolium 2504 (1736) -
Thalassia hemprichii 754 [748] 1459 (811)
Thalassodendron ciliatum - 692 (272)

Cymodocea rotundata
Cymodocea serrulata
Enhalus acoroides

Note: In all sampling locations foliage cover is >70 percent,
except for Thalassodendron ciliatum (>50 percent } [SD in
parentheses].

Sea vary between 60 mg carbon/m’/day and 1060 mg
carbon/m?/day which, assuming the same rates of
production throughout the year as during the study
period (October), translates to a maximum annual net
primary production of about 387 g carbon/m’. Epiphyte
production alone accounted for a maximum annual net
primary production of about 84 mg carbon/m‘ of leaf
surface area”, or 36 percent of the net primary
production rate of the seagrass communities studied.

173

174 WORLD ATLAS OF SEAGRASSES

ee een

A comparative study of two different seagrass
environments in the Spermonde Archipelago obtained
very similar results using the same techniques".
Gross primary production rates ranged from 900 mg
carbon/m*/day to 4400 mg_ carbon/m‘/day.
Interestingly, the bell-jar technique used in the
Spermonde Archipelago did not reveal any significant
difference in seagrass production rates between
coastal and reef environments. Net primary
production was slightly negative in a number of
stations and was. generally below 500 mg
carbon/m‘/day. Low net primary rates were attributed
to high community oxygen consumption rates. Higher
net primary production rates were obtained from
monospecific stands of Thalassia hemprichii, where
combined seagrass and epiphyte net production rates
reached 1.5 mg carbon/m’/day to 1.9 mg
carbon/m‘/day, equivalent to a maximum of 694 mg
carbon/m/’/year.

Nienhuis has suggested that Indonesian seagrass
communities are self-sustaining systems and export
very little of their photosynthetically fixed carbon to
adjacent ecosystems such as coral reefs”. The results
obtained from the Flores Sea and Spermonde
Archipelago seem to support this general hypothesis.
Erftemeijer points out that many seagrass communities
(58 percent of his study sites] seem to use more energy
than is actually produced by the autotrophic seagrass
community. This suggests that, while recycling of nutri-
ents and organic carbon is high, seagrass beds may not
be self-sustaining. Filter and suspension-feeding
macroinvertebrates constitute a significant consumer
component of the Indonesian seagrass community.

Marking methods have been used to measure leaf
production’ in seagrass meadows at Taka Bone Rate
Atoll”, Kepulauan Seribu'™”: \“’, Banten Bay'”' and, most
recently, in Lombok'® and the Spermonde

Table 16.4
Average growth rates (mm/day) of seagrass leaves using leaf-marking techniques

Species West Java

Spermonde

Archipelago”. Production rates obtained from these
studies are summarized in Table 16.4.

Erftemeijer” demonstrated that, while there was
no difference in primary production rates of coastal and
offshore seagrass beds in Sulawesi, the leaf growth
rate (3.1 mm/day) of Enhalus acoroides was
significantly higher in muddy coastal habitats than in
offshore reef habitats (1.6 mm/day]. Similar results
were obtained for Thalassia hemprichii.

ASSOCIATED BIOTA

Seagrass-associated flora and fauna remain one of the
most open and exciting fields of research for Indonesian
scientists. Recent studies have focused on establishing
species lists and measuring abundance and biomass of
various seagrass-associated taxa. With a few
exceptions’ “” the majority of seagrass-associated
faunal studies have dealt with infauna, macrofauna,
motile epifauna and epibenthic fauna [Table 16.5).

Algae

Fishermen at Benoa, Bali and West Lombok have
recorded seven economically important species of
seaweeds growing in the mixed seagrass meadow of
Cymodocea serrulata, Halodule uninervis, Thalassia
hemprichii and Thalassodendron ciliatum””. In South
Sulawesi 117 species of macroalgae are associated
with seagrasses, composed of 50 species of
Chlorophyta, 17 species of Phaeophyta and 50 species
of Rhodophyta. Thirteen species were exclusively

associated with seagrass vegetation”.

Meiofauna

The meiofauna associated with monospecific Enhalus
acoroides seagrass beds on the south coast of Lombok
consisted of nematodes, foraminiferans, cumaceans,

copepods, ostracods, turbelarians and polychaetes”,

Lombok Flores

Sea Archipelago

Cymodocea rotundata -
5.0 (0.6)
7.3 (3.6)

Cymodocea serrulata
Enhalus acoroides

Syringodium isoetifolium 4.1 (6.8)
Thalassia hemprichii 4.9 (1.5)
Thalassodendron ciliatum =

Notes:
Production rates in parentheses (g dry weight/m*/day).
* In mg ash-free dry weight/m?/day.

2.4 (2.3*)

1.6 (3.5")

= 5.5 (6.8)

6.5 (1.5)
3.8 [8.1] 5
2.7 (4.7)

Table 16.5
Indonesian seagrass-associated flora and fauna: number of species

Taxon Banten Bay Jakarta Bay Lombok
Algae 37

Meiofauna
Mollusks 55
Crustaceans 84
Echinoderms 45
Fishes 85
Fish larvae 53

Source: Various sources”

many of which were actively emergent. A high
abundance of nematodes was indicative of nutrient
enrichment. Benthic foraminifera are an important
component of Indonesian seagrass communities, but
have received only rudimentary attention”. In the
Kepulauan Seribu patch reef complex, seagrass beds
are abundant and frequently dominated by associations
of Enhalus acoroides and Thalassia hemprichii*”'.
Benthic foraminifera in this location are dominated by
the suborders Miliolina and Rotaliina’. The most
abundant rotaliinids were Ammonia beccarii, Ammonia
umbonata, Calcarina calcar, Elpidium advenum,
Elpidium crispum, Elpidium craticulatum and Rosalina
bradyi. The genus Ammonia is a euryhaline group,
common in shallow-water tropical environments, and
Calcarina calcar is indicative of coral reef habitats. The
abundance of Elpidium spp. is interesting, since this
euryhaline, shallow-water species is extremely tolerant
of low salinities and can be found far up estuaries. The
miliolinids are represented by Adolesina semistriata,
Milionella sublineata, Quinqueloculina granulocostata,
Quinqueloculina parkery, Quinqueloculina_ sp.,
Spiroloculina communis, Spirolina cilindrica and
Triloculina tricarinata. Both Quinquiloculina and
Triloculina are characteristic of shallow tropical waters.

Crustaceans

Crustaceans are a key component of seagrass food
webs. Recent gut analyses from the south coast of
Lombok" demonstrated that crustaceans are the
dominant food source for seagrass-associated fish.
Aswandy and Hutomo'" recorded 28 species of
crustaceans in Banten Bay seagrass beds. The
tanaidacean Apseudes chilkensis and an unknown
species of melitidae amphipod are the most abundant
crustaceans in Enhalus acoroides meadows in
Grenyang Bay”. Moosa and Aswandy”™” recorded 70
crustacean species from seagrass meadows in Kuta
and Gerupuk Bays but many specimens were

6 groups

Indonesia

Ambon Bay Kotania Bay South Sulawesi

34 117

143 [hermit crabs}
30

205

apparently collected from coral rubble areas adjacent
to the seagrass meadows. One hipollitid shrimp there,
Tozeuma spp., has special morphological adaptations
to live specifically in seagrass meadows. Its lancelet
body shape and coloration, green mottled with small
white spots, provides almost perfect camouflage when
it adheres to seagrass leaves. Many stomatopods are
found in Indonesian seagrass beds with Pseudosquilla
ciliata, an obligate seagrass-associated species'”.
Other stomatopods, such as Odontodactylus scyllarus,
leave the reefs to forage for mollusks in adjacent
seagrass beds”. Rahayu collected 30 species of hermit
crabs from Kotania Bay seagrass bed. Three were
species of Diogenes, one was a species of Pagurus and
four were undescribed species. It is believed that
crustaceans in the seagrass beds of Kotania Bay are
much more diverse than those of other locations.

Mollusks
The mollusks are one of the best-known groups of
seagrass-associated macroinvertebrates and perhaps
the most overexploited. Mudjiono et al. recorded 11
gastropods and four bivalves from the seagrass
meadows in Banten Bay”!. This rather impoverished
mollusk fauna was collected from monospecific Enhalus
acoroides beds, in mixed beds of Enhalus acoroides,
Cymodocea serrulata and Syringodium isoetifolium, and
mixed beds of Enhalus acoroides, Cymodocea rotundata,
Cymodocea serrulata, Halodule uninervis, Halophila
ovalis, Syringodium isoetifolium and _ Thalassia
hemprichii. The entire bay is heavily exploited and only
two gastropods were common to all locations, Pyrene
versicolor and Cerithium tenellum. Just four juvenile (3-
5 mm diameter] Trochus niloticus were collected”.
Seventy species were collected from less
disturbed sites in Lombok’, many of which are
economically valuable. Gastropod families included
Bullidae, Conidae, Castellariidae, Cypraeidae, Olividae,
Pyrenidae, Strombidae, Trochidae and Volutidae;

175

176

WORLD ATLAS OF SEAGRASSES

bivalve families were Arcidae, Cardiidae, Glycymeri-
dae, Isognomonidae, Lucinidae, Mesodesnatidae,
Mytilidae, Pinnidae, Pteridae, Tellinidae and Veneridae.
Pyrene versicolor, Strombus labiatus, Strombus
luhuanus and Cymbiola verspertilio were the most
abundant gastropod species and Anadara scapha,
Trachycardium flavum, Trachycardium subrugosum,
Peryglypta crispata, Mactra spp. and Pinna bicolor were
the most common bivalve species””. A number of Conus
species were found.

A high diversity of mollusks, 142 species from 43
families, has also been reported from seagrass beds in
Kotania Bay’.

Echinoderms
The most significant echinoderm species is a sea star,
Protoreaster nodosus, which feeds on seagrass
detritus and the surface of broken seagrass leaves.
Forty-five species of Echinodea, Holothuridae, Ophiur-
oidae and Crinoidae have been recorded in the
seagrass beds of Kuta and Gerupuk Bays. Several
economically important species of Holothuria and
Actinopyga, and the sea urchin Tripneustes gratilla,
have declined in abundance”.

Similar depletions in echinoderm populations
have been reported from Kotania Bay on west Ceram

Case Study 16.1
BANTEN BAY, WEST JAVA

Banten Bay covers 120 km?, and harbors several
coral islands. The biggest inhabited island is Pulau
Panjang; the other islands are small and uninhabi-
ted. The rivers Domas, Soge, Kemayung, Banten,
Pelabuhan, Wadas, Baros and Ciujung discharge
into the bay. Seagrass is found along the mainland
Java coast in the western part of the bay, on the reef
flat of the coral islands (Pulau Panjang, Pulau
Tarahan, Pulau Lima, Pulau Kambing and Pulau
Pamujan Besar] and on submerged coral reefs in
the intertidal area down to a depth of 6 m. The total
area of seagrass beds at Banten Bay is about 330 ha,
consisting of 168 ha on the mainland and 162 ha on
the coral islands.

The depth of the bay is not more than 10 m. Its
sediment consists of mud and sand” *) and the
salinity varies between 28.23 and 35.34 psu. The
rainy season Is from November to March. Mangrove
is found at Grenyang in the eastern part of the bay up
to Tanjung Pontang in the west part, and in the
southern part of Pulau Panjang. Eight species of
seagrasses occur here: Cymodocea rotundata,
Cymodocea serrulata, Enhalus acoroides, Halodule

Island, Moluccas, where seagrass meadows formerly
supported a high abundance of economically important
holothuroids. In 1983, the extensive seagrass meadows
in Kotania Bay supported high population densities [i.e.
1-2 individuals/m’) of nine economically important sea
cucumber species, namely Bohadschia marmorata,
Bohadschia argus, Holothuria (Metrialyta) scabra,
Holothuria nobilis, Holothuria vagabunda, Holothuria
impatiens, Holothuria edulis, Thelenota ananas and
Actinopyga miliaris. In a 1993 inventory of the same
area, only three sea cucumbers were recorded within a
distance of 500 m. The average body size of sea cucum-
bers decreased from around 22 cm in 1983 to less than
15 cm in 1993. The decline of the stock and size are
attributed to intensive collections by local people to
supply the lucrative teripang (béche de mer) trade.
Another heavily overexploited echinoderm species
whose population has declined sharply during the past
ten years is the edible sea urchin Tripneustes gratilla.

Fish

In 1977 one of the first studies of seagrass-associated
fish in Indonesia collected 78 species from Thalassia
hemprichii and Enhalus acoroides meadows amongst
lagoonal patch reefs in Pari Island, in the Kepulauan
Seribu complex”. Only six (Apogonidae, Atherinidae,

uninervis, Halophila ovalis, Halophila minor,
Syringodium isoetifolium and Thalassia hemprichii.
Beds between 25 and 300 m in length" are
continuous along the coast of Banten Bay, from the
beach to the reef edge.

They are nursery grounds for 165 species of
fish which feed either directly on algae and
seagrass or on seagrass-associated inverte-
brates), including six juveniles of grouper
(Epinephelus bleekeri, Epinephelus fuscoguttatus,
Epinephelus merra, Epinephelus septemfasciatus,
Epinephelus coioides and Plectropomus spp.'*)).
Dugongs also occur here“. The cultivation of
seaweeds in Banten Bay has increased enormously
in recent years along the coastline of all the islands,
on the coral reef and lately also outside the reef flat
area. Approximately 35 ha, including 25 ha or 10
percent of the reef flat area and 10 ha outside the
coral reef flat, are now used for the cultivation of
seaweeds and have been cleared of seagrass'”.
Transplantation studies using Enhalus acoroides
were conducted in Banten Bay in 1998". Only
rhizomes transplanted to muddy substrate survived
more than five months — these new seagrass beds
are now used by local fishermen to collect fishes
and prawns).

Labridae, Gerridae, Siganidae and Monacanthidae) of
the families recorded, however, could be considered as
important seagrass residents. The Pari Island study
was followed in 1985 by a long-term study of seagrass
fish assemblages in Banten Bay, southwest Java Sea.
The results from the Banten Bay study’ supported
earlier views that only small numbers of fish species
permanently reside in seagrass beds. However, it was
also reconfirmed that seagrass beds act as nursery

Case Study 16.2
KUTA AND GERUPUK BAYS, LOMBOK

Kuta and Gerupuk Bays are covered by gravel, small
pebbles, fine sand and mud in the river mouth,
where Enhalus acoroides grows. The tidal range in
the bays is about 2 m, tidal velocity and direction are
2.8-10.8 cm/min and 315°-350° at high tide and 4.5-
10.0 cm/min and 270°-310° at low tide. During the
wet season, December to April, salinity varies from
28 to 29 psu and surface water temperature from 18
to 24°C. In the dry season, May to November, these
measurements are approximately 34 psu and 27°C.

The most diverse seagrass beds in Indonesia
occur here, with 11 of the 12 species present in
Gerupuk (Cymodocea rotundata, Cymodocea serru-
lata, Enhalus acoroides, Halodule pinifolia, Halodule
uninervis, Halophila minor, Halophila ovalis,
Halophila spinulosa, Syringodium isoetifolium,
Thalassia hemprichii, Thalassodendron ciliatum).
Halophila spinulosa is absent from Kuta. Enhalus
acoroides and Thalassodendron ciliatum form
monospecific beds in both bays, and Halophila
spinulosa in Gerupuk Bay. Mixed beds of Cymodocea
rotundata, Cymodocea serrulata, Halodule pinifolia,
Halodule uninervis, Halophila minor, Halophila
ovalis, Syringodium isoetifolium and Thalassia
hemprichii occur at both locations.

Coverage area of habitat types at Kuta and Gerupuk Bays

Coverage area (ha)
Kuta Bay Gerupuk Bay

Enhalus acoroides 7.68 29.40
Thalassodendron ciliatum 10.50 id
Halophila spinulosa 11.07
Habitat types

Mixed vegetation 76.86
Sandy bar 42.97
Lagoon =
Dead coral 27.36
Live coral =
Volcanic stone -

Indonesia

grounds for many economically valuable fish species.
Beds with higher densities of seagrass supported
higher abundance of fish, and Enhalus acoroides
meadows supported higher fish abundance than
Thalassia hemprichii.

Studies on seagrass fish in Indonesia have been
gradually increasing since the late 1980s‘ %*°7).
Indonesian seagrass fish communities are commonly
dominated by Siganidae [rabbitfishes], such as Siganus

Large amounts of seagrass detritus wash up
and accumulate on the beach during the strong
winds of the east monsoon. Interestingly Thalasso-
dendron ciliatum at Kuta Bay is able to grow on
volcanic stone. During low tide the local community
collects milkfish, sea cucumbers, octopus, shellfish,
sea urchins and seaweeds (Caulerpa spp., Gracilaria
spp. and Hypnea cervicornis) from the seagrass
beds. The commercial alga, Kappaphycum alvarezi,
is cultivated here.

Associated flora and fauna of the seagrass bed of Lombok

Taxon group Number of species
Algae 37
Meiofauna™” 6 (higher taxa)
Mollusk”" 55
Echinoderm”” 45
Crustacean” vi)

Fish”! 85

Fish larvae 53

Source: Various sources - see references by groups.

Only four of the fish found here -
Syngnathoides biaculeatus, Novaculichthys spp.,
Pervagor spp. and Centrogenys valgiensis — are typi-
cal seagrass fishes. Halichoeres argus and Cheilio
enermis are abundant not only in seagrass but also
in algal beds. The dominance of Syngnathoides
biaculeatus and Cheilio enermis is unusual because,
more commonly, the fish populations of Indonesian
seagrass beds are characterized by abundant
rabbitfish, especially Siganus canaliculatus.

The main threat to the seagrass of Kuta and
Gerupuk Bays is the intensive collecting of intertidal
organisms during low tide, often involving digging
with sharp iron sticks which disturb the substrate,
cut the leaves of seagrasses and uproot their
rhizomes. Future threats may include hotel
construction and operation as the area has been
earmarked for development by the local
government.

177

178

WORLD ATLAS OF SEAGRASSES

Case Study 16.3
KOTANIA BAY

Kotania Bay, Ceram Island, contains five small
islands: Buntal, Burung, Marsegu, Tatumbu and Osi.
Only Osi has freshwater and Is inhabited, along with
two villages at Pelita Jaya and Kotania on Ceram
Island. The water around Pelita Jaya (40 m) is
deeper than that at Kotania village (20 m). The
intertidal area in the northern part of Kotania Bay is
very narrow [4 to 10 m) but wider in the east and
south (50 to 250 m). Seagrasses are found along the
whole coast area of the bay, except in the north. On
Buntal and Osi Islands the sediment trapped by
these seagrass beds has, over time, created “cliffs”
which have served as substrate for the development
and seaward expansion of mangrove communities.
The seagrass beds have been mapped using
remote-sensing techniques which estimated a total
area of 11.2 km’. The pattern of seagrass
distribution depends on the type of substrate.
Muddy substrate is mostly dominated by

Table 16.6
Present coverage of seagrasses in Indonesia
E
a
E) Geass
eee ca
a << ed
Coverage (hal 200-300 50-150 <2 5-150
Cover (%] 20-80 15-80 12-25 10-15 5
Recorded species [number] 9 8 5 7
Hydrocharitaceae
Enhalus acoroides C A R R
Halophila decipiens - - - -
Halophila minor - - - VR
Halophila ovalis R R R VR
Halophila spinulosa = = = =
Thalassia hemprichii C VA C R
Cymodoceaceae
Cymodocea rotundata R C R VR
Cymodocea serrulata R R - =
Halodule pinifolia R R = VR
Halodule uninervis R R = =
Syringodium isoetifolium R C VR VR
Thalassodendron ciliatum C = = =

Notes: C common; A abundant; R rare; VA very abundant; VR very rare.

Lampung Bay

De)
aoa i
onan

aw wD

monospecific beds of Enhalus acoroides. Mixtures
of mud, sand and coral rubble are usually covered by
Thalassia hemprichii. The highest density of
seagrass IS found in the area between Osi and
Burung. The eastern part of the bay, called Wai Tosu,
has two kinds of substrates. The sediment at the
mouth of a small creek is deep and muddy, and is
covered only by Enhalus acoroides {10-20 percent
coverage} while there is a thin layer of mud, sand
and coral rubble about 100 m in front of the
mangroves. Underneath this thin substrate is a hard
layer of coral rock. Thalassia hemprichii, Cymod-
ocea rotundata, Halodule uninervis, Halophila ovalis
and Enhalus acoroides grow sporadically here to
less than 35 percent coverage. Local people have Set
a fish trap around the seagrass area and bullt a
large cage to rear sea cucumbers.

In the southern part of Kotania Bay the
intertidal zone is very flat and almost all is exposed
during the lowest tides. The substrate near to the
mangrove area is mixed mud and sand dominated by
Thalassia hemprichii and Enhalus acoroides. Along

2 a
Bat coke ee aT =
BO ne es Ek, aay tasters
S 2 = PS 8 = >
o o = = oS s 5
ao ao e Oo a ee oO
05-18 336 20-80 30 1 73 36
5-15 25-45 30-70 15-50 5-10 30-70 20-50
9 Beato 5 9 10 1
© WA 2 R R VA VA
= = R ~ = = =
= R R = S R R
R R R R R R R
= - = 2 E = R
R VA VA R WA
R R R R R R R
vR VR R = R R R
R = R = R R R
R R R R R R R
R R R = R R R
c = A = R c R

Indonesia 179

Distribution of seagrass in Kotania Bay

Species of seagrass % cover Substrate type Depth (m) PJ TL Ol BRI BTI Tl Ml
Cymodocea rotundata 10-40 Sand +0.2-2.0 v v v Vv v v v
Cymodocea serrulata <5 Sand 0.5-2.0 v v v,
Enhalus acoroides 20-60 Mud, sand 0.5-2.5 v v J v v v v
Halodule pinifolia <5 Sand +0.2-1.5 v v v v / v
Halodule uninervis <5 Sand 0.5-2.0 v v v v v v v
Halophila decipiens 40-100 Coral rubble v J
Halophila ovalis <5 Sand +0.2-1.5 v v v v v v v
Halophila minor J

Syringodium isoetifolium <5 Mud, sand 0.5-2.0 v v v /
Thalassia hemprichii <5 Mud, sand +0.2-2.5 v / v J v

Notes: PJ Pelita Jaya; TL Tanjung Lalansoi; 0! Osi Island; BRI Burung Island; BT! Buntal Island; Tl Tatumbu Island; Ml Marsegu Island

the southern part of the bay up to Tanjung Lalansoi lata, Halodule pinifolia, Halodule uninervis, Halophila
the substrate in the deeper areas is a mixture of sand ovalis and Enhalus acoroides. The seagrass density
and coral rubble. The most common seagrasses is quite high and varies seasonally. Percent coverage
there are Thalassia hemprichii, Cymodocea rotun- ranges from 40 to 70 percent with the highest values
data, Syringodium isoetifolium, Cymodocea serru- always close to the mangrove areas.

2
a 2
wo = is a = cy) 4 = <7 a £
Seller, aE. ee ae Eh a Ce yt en
aoa Se Meas kt ee, ere oe ee Rea ne aie 2
Seen ee ee Beene a) a ad epee | ia
a <= a =< o = = = a = = =
Coverage (hal 10-50 0.3-1 4-5 212 25-75 100-1000 5-50 10-100 25-75 100-1000 5-50 10-100
Cover (%] 30-60 5-20 15-30 30-80 30-60 50-99 30-70 30-50 30-60 50-99 30-70 30-50
Recorded species (number) 9 7 8 10 8 8 8 8 8 8 8 8
Hydrocharitaceae
Enhalus acoroides VA R R A VA A VA VA VA A VA VA
Halophila decipiens - - - R - - - - - - - -
Halophila minor R VR = R - = = = = = = =
Halophila ovalis R R R R R R R R R R R R
Halophila spinulosa - - - - = = = = - = = -
Thalassia hemprichii VA C R VA VA R VA VA VA R VA VA
Cymodoceaceae
Cymodocea rotundata R C C C R R R R R R R R
Cymodocea serrulata R - R R R R R R R R R R
Halodule pinifolia R VR R R VR R R R VR R R R
Halodule uninervis R R R R R R R R R R R R
Syringodium isoetifolium R - R C R R R R R R R R

1
1
'
i)
'
1
1
1
1
'
'
1

Thalassodendron ciliatum

Notes: C common; A abundant; R rare; VA very abundant; VR very rare.

WORLD ATLAS OF SEAGRASSES

Photo: P. Erftemeijer

canaliculatus in Jakarta Bay'”, except in Lombok (see

Case Study 16.2). Indonesian seagrass fish have been

classified into four principal species assemblages:

1 permanent residents which spend most of their
lives in seagrass beds (e.g. the chequered
cardinalfish, Apogon margaritophorus);

2 residents which live in seagrass throughout their
life cycle but which spawn outside the seagrass
beds [e.g. Halichoeres argus, Atherinomorus
duodecimalis, Cheilodipterus quinquelineatus,
Gerres macrosoma, Stephanolepis hispidus,
Acreichthys hajam, Hemiglyphidodon plagio-
metopon, Syngnathoides biaculeatus);

3 temporary residents which occur in seagrass
beds only during their juvenile stage (e.g. Siganus
canaliculatus, Siganus virgatus, Siganus punc-
tatus, Lethrinus spp., Scarus spp., Abudefduf
spp., Monacanthus chinensis, Mulloidichthys
flavolineatus, Pelates quadrilineatus, Upeneus
tragula);

4 occasional residents or transients that visit
seagrass beds to seek shelter or food.

Measuring the primary productivity of seagrass meadows in
Sulawesi using enclosures equipped with oxygen electrodes

The first study on seagrass fish larvae and
juveniles took place in Kuta Bay and recorded 53
species belonging mainly to four families: Channidae,
Ambassidae, Engraulidae and Gobiidae. High numbers
of species and individuals were found in unvegetated
areas full of broken seagrass leaves, and in the Enhalus
acoroides beds.

HISTORICAL PERSPECTIVE

Herbarium collections of seagrasses from Indonesian
waters were made by Zollenger in 1847 and
Kostermans in 1962 and include both Ruppia maritima
from Ancol-Jakarta Bay and Pasir Putih, East Java, and
one specimen of Halophila beccarii from an unknown

location. The development of Jakarta has destroyed the
Mangrove swamp in Ancol, the only place that Ruppia
maritima had been reported, and this is thought to have
caused the disappearance of this species from
Indonesia.

For 15 years the Ancol Oceanorium in Jakarta kept
two male dugongs in captivity, feeding them with
seagrasses [(Syringodium isoetifolium and Halodule
uninervis) harvested from Banten Bay. Unfortunately
they died in November 1991”. There is one female
dugong in Surabaya Zoo, which has been in captivity
since 1985. Its food is harvested from Celengan-
Muncar, East Java, about 340 km from Surabaya. It
feeds mostly on Syringodium isoetifolium, which forms
95 percent of the dugong’s dietary intake. The con-
sumption rate of the captive dugong is approximately 30
kg wet weight/day“". Recently Sea World of Indonesia in
Ancol-Jakarta has acquired two male dugongs. One of
them was caught in seine nets in Banten Bay in 1998
and the other one was trapped in a sero [fish trap) on
the seagrass bed at Miskam Bay in 2001.

The degradation of seagrass beds in Indonesian
waters has been poorly documented from only limited
areas. The decline of seagrass beds at Banten Bay was
caused by converting agricultural areas and fish ponds
into an industrial estate, with a total loss of about 116
ha or 26 percent of seagrass mainly in the western part
of the bay'’. The decline of other seagrass beds has
been caused by reclamation activities. Less damaging
than the reclamation was the uprooting of seagrasses
by fishing boats using seine nets to catch shrimp and
fish”. In Kuta and Gerupuk the decline of seagrass was
caused by people collecting dead coral for building
material in the seagrass beds.

PRESENT COVERAGE

It is difficult to present accurate information about the
present coverage of Indonesian seagrass, since
observations on seagrass ecosystems in Indonesia vary
considerably in duration, location, method of sampling
and object of study, and many places in Indonesia have
not been studied yet. Table 16.6 summarizes existing
knowledge about the present coverage in Indonesia.
Based on this available information, and to the best of
our knowledge, we estimate that seagrass covers at
least 30000 km’ throughout the Indonesian
Archipelago.

Seagrasses in Indonesia are presently threatened
mainly by physical degradation such as mangrove
cutting and coral reef damage, and by marine pollution
from both land- and marine-based sources, and by
overexploitation of living marine resources such as fish,
mollusks and sea cucumbers. The alarming amount of
land reclamation is an increasing cause of seagrass
habitat loss in Indonesia.

POLICY

No specific regulation relating to seagrass is currently
available and so management is implemented through
general regulations pertaining to marine affairs,
environmental protection and management of living
resources. Of primary importance is the Act of the
Republic of Indonesia {RI} No. 5 1990, concerning the
conservation of living resources and their ecosystems,
together with Act of the RI No. 5 1994 on the ratification
of the Convention on Biodiversity and Act of the RI No.
23 1997 concerning the management of the living
environment. Apart from acts and statutes, there are
three other types of regulation which are hierarchically
lower than the former: they are government regulation,
presidential decree and ministerial decree.

To have a proper management system for
coastal ecosystems, appropriate laws and regulations
must be established. The Indonesian Seagrass Com-
mittee [ISC) has therefore prepared a draft Seagrass
Policy, Strategy and Action Plan to guide the manage-
ment of the seagrass ecosystem in Indonesia. It forms
an integral part of the activities of the South China Sea
Project, financed by UNEP-GEF [the United Nations
Environment Programme section of the Global
Environment Facility], and seeks to address the main
issues concerning the management of seagrasses.
The draft, scheduled to be completed in 2004, is
expected to become a reference document in the
formulation of official regulations by the government.

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Enhalus acoroides growing among living coral in Komodo National
Park, Indonesia

AUTHORS

T.E. Kuriandewa, W. Kiswara, M. Hutomo, S. Soemodihardjo, Research
Centre for Oceanography - Indonesian Institute of Sciences (LIPI),
Jalan Pasir Putih 1, Ancol Timur, Jakarta Utara 12190, Indonesia. Tel: +62
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Banten Bay. Scientific Report.

Hendrokusumo S, Sumitro S, Tas’ an [1979]. The distribution of the
dugong in Indonesian waters. In: Marsh H (ed) The Dugong.
Proceedings of a Seminar/Workshop held at James Cook
University 8-13 May 1979, North Queensland, Australia. pp 5-10.
Douven WJAM [1999]. Human Pressure on Marine Ecosystems in
the Teluk Banten Coastal Zone: Recent Situation and Future
Prospects. Teluk Banten Research Program. Report Series No. 3.
IHE-Delft, WOTRO.

Zainudin [2002]. Personal communication.

Regional map: Asia

SEA
OF
JAPAN

YELLOW
SEA

PACIFIC OCEAN

PHILIPPINE
SEA

Gulf
of
“Thailand

CELEBES
< SEA

coe)

ARAFURA
SEA

INDIAN OCEAN
: 0 300 600 900 1200 1500 km
[a

100° 115°

WORLD ATLAS OF SEAGRASSES

THE SEX LIFE OF SEAGRASSES

Photo: J.S. Bujang

Halophila decipiens female [right] and male (left)

flowers, Malaysia

Photo: J.S. Bujang

Enhalus acoroides in Malaysia and
Indonesia: female flowers [above]; pollen on
the water surface (right, top); fruit (right, Spadix of eelgrass, Zostera marina, with male

middle]; seed dispersal (right, bottom} flowers releasing pollen

Photo: J.S. Bu

Thalassia hemprichii fruit

The seagrasses of

The Philippines and Viet Nam

Philippine Archipelago. There are documented

sizeable beds offshore from western, north-
western and southern islands covering 978 km’ at 96
well-studied sites. Approximately one third of this area
has been mapped in detail using a combination of
remote sensing and field survey techniques. The
remainder is estimated. With many other areas not
surveyed for seagrasses, the total seagrass area is
likely to be many times greater.

The Philippines is reported to have 15 species of
seagrass. In addition to Ruppia maritima and
Halophila beccarii, Fortes lists a new variety of Halophila
minor”. Calumpong and Menez" consider Halophila
beccarii to have been extirpated from Philippine waters,
because the only specimens to be collected were in 1912
from Manila Bay”, now heavily impacted by the growth
of metropolitan Manila. Fortes disagrees, believing this
species still occurs in Manila Bay” and to be common in
Lingayen Gulf, northwestern Philippines.

Many plants and animals live in the seagrass
beds of the Philippines and Viet Nam, supporting
fisheries with their rich nutrient pool and the diversity
of physical structures protecting juveniles from
predators. Major commercial fisheries occur
immediately adjacent to seagrass beds". Fish and
shrimp are the most important elements of the
commercial fishery, although coastal villages derive
their sustenance from other components of the grass
beds. The major invertebrates found in the beds are
shrimps, sea cucumbers, sea urchins, crabs, scallops,
mussels and snails. Some endangered species of sea
turtles reported in seagrass beds include the green sea
turtle, the olive Ridley, the loggerhead and the flatback.
In the Philippines and Viet Nam the sea cow (Dugong
dugon), which is almost completely dependent on
seagrass, IS an endangered species.

Coral reefs and their associated seagrasses
potentially supply more than 20 percent of the fish

Gries are found extensively throughout the

catch in the Philippines. A total of 1384 individuals and
55 species from 25 fish families were identified from
five seagrass sites!”

Calumpong and Menez” describe two mixed
species associations, one of Syringodium (or
sometimes Thalassia) with Cymodocea and Halodule
spp., growing primarily on sandy sediment, the other of
Enhalus and Thalassia spp. on muddy substrates.
Monospecific seagrass beds are less common than
mixed populations in the Philippines and tend to occur
under certain conditions: Enhalus acoroides colonizes
turbid, quiet, protected areas such as bays and
estuaries and Thalassia hemprichii occurs as pure
stands in the tidepools of the most northerly islands in
the Philippines'"'. Halophila decipiens grows primarily
at depths of 11-23 m'”. Thalassodendron ciliatum and
Halophila spinulosa are found in deep, clear water”.
Thalassodendron ciliatum also grows in shallow waters
but only in conditions of low turbidity on coarse or rocky
substrates”. Cuyo Island is the northernmost limit of
Thalassodendron ciliatum in the Pacific’.

The vital role of seagrasses as nursery grounds
and food for fish and invertebrates in the Philippines
has been appreciated for some time!”. The rabbitfish,
Siganus canaliculatus, is a voracious herbivore and
particularly important as a food species. In Bais Bay,
Negros Oriental, the population of Siganus
canaliculatus consumes 0.64 metric tons per day from
a 52-ha Enhalus acoroides meadow'”. However, this
represents less than 1 percent of the daily organic
production of Enhalus acoroides. Rabbitfish are often
caught in seagrass beds using bamboo traps”,
representing a direct link between seagrass habitat and
human subsistence.

Seagrass beds in the Philippines are threatened
by eutrophication, siltation, pollution, dredging and
unsustainable fishing methods. Many thousands of
hectares of seagrass have been lost as a result of land
reclamation for housing, airports and shipping

184

Photo: M. Kochzius

WORLD ATLAS OF SEAGRASSES

Spear-fisher over a seagrass bed in the Philippines

facilities”. Some attempts have been made at

rehabilitating damaged seagrass beds _ using

transplanting techniques'™”’.

Puerto Galera, a quiet ecotourist destination
south of Manila, is the site of one of the first
SeagrassNet global monitoring locations. Quarterly
sampling of the seagrass habitat has been conducted
at reference and impacted seagrass sites monitored by
graduate students from the University of the
Philippines. Even in the early stages of monitoring the

REFERENCES

1 Mefiez EG, Phillips RC, Calumpong HP [1983]. Seagrasses from the
Philippines. Smithsonian Contributions to the Marine Sciences No.
21. pp 1-40.

2 Mefiez EG, Calumpong HP [1983]. Thalassodendron ciliatum: An
unreported seagrass from the Philippines. Micronesia 18: 103-111.

3 Menez EG, Calumpong HP [1985]. Halophila decipiens: An
unreported seagrass from the Philippines. Proceedings of the
Biological Society of Washington 98(1): 232-236.

4 Fortes MD [1990]. Seagrass resources in East Asia: Research
status, environmental issues and management perspectives. In:
ASEAMS/UNEP Proceedings of First ASEAMS Symposium on
Southeast Asian Marine and Environmental Protection. UNEP
Regional Seas Reports and Studies No. 116. pp 135-144.

5 Fortes MD [1986]. Taxonomy and Ecology of Philippine Seagrasses.
PhD dissertation, University of the Philippines, Diliman, Quezon
City. 245 pp.

6 Short FT, Coles RG (eds) [2001] Global Seagrass Research
Methods. Elsevier Science, Amsterdam.

7 Fortes MD [1989]. Seagrasses: A Resource unknown in the ASEAN
Region. ICLARM Education Series 5. 46 pp.

8 Calumpong HP, Mefiez EG [1997]. Field Guide to the Common
Mangroves, Seagrasses and Algae of the Philippines. Bookmark,
Makati City, Philippines. 197 pp.

SeagrassNet team has clearly shown the impacts of
eutrophication at the site adjacent to a coastal town.
Seagrass-Watch is now established in Puerto Galera.
This community-based seagrass monitoring program
is coordinating with SeagrassNet to provide a second
data stream, generated by volunteer members.

VIET NAM

There are 11 species of seagrass in Viet Nam distributed
along the coastline but mostly from the middle to the
southern sections. Their status is unknown though in
general the Viet Nam coastal zone has been heavily
impacted by sedimentation and domestic and
agricultural pollution. Viet Nam has at least 440 km? of
seagrasses determined from remote sensing and
ground-truth surveys. Viet Nam is at the overlap of
temperate and tropical seagrass species with Zostera
japonica growing intertidally in the north and mixing
with Halophila ovalis, while in the south the species
composition is similar to the Philippines and Malaysia.

AUTHORS

Miguel Fortes, Marine Science Institute CS, University of the Philippines,
Diliman, Quezon City 1101, Philippines. Tel: + 63 (0}2 9205301. Fax: +63
(0}2 9247678. E-mail: mdfortes138(@yahoo.com

Ed Green, UNEP World Conservation Monitoring Centre, 219 Huntingdon
Road, Cambridge CB3 ODL, UK.

Fred Short, University of New Hampshire, Jackson Estuarine Laboratory,
85 Adams Point Road, Durham, NH 03824, USA.

9 Merrill ED [1912]. A Flora of Manila. Philippine Islands Bureau of
Science Publication Number 5. Bureau of Printing, Manila. 490 pp.

10 Phillips RC, Mefiez EG [1988]. Seagrasses. Smithsonian
Contributions to the Marine Sciences No. 34. 104 pp.

11 Calumpong HP, Mefez EG, Phillips RC [1986]. Seagrasses in
Batanes Province, northern Philippines. Silliman Journal 33(1-4):
148-154.

12 Dolar MLL [1991]. A survey on the fish and crustacean fauna of the
seagrass beds in North Bais Bay, Negros Oriental, Philippines. In:
Proceedings of the Regional Symposium on Living Resources in
Coastal Areas. University of the Philippines Marine Science
Institute, Quezon City. pp 367-377.

13 Leptein MV [1992]. The gut passage rate and daily food
consumption of the rabbitfish Siganus canaliculatus {Park}. In:
Third ASEAN Science and Technology Week Conference
Proceedings Vol. 6. National University of Singapore and National
Science Technology Board, Singapore. pp. 327-336.

14 Calumpong HP, Phillips RC, Menez EG, Estacion JS, de Leon ROD,
Alava MNR [1993]. Performance of seagrass transplants in Negros
Island, central Philippines and its implications in mitigating
degraded shallow coastal areas. In: Proceedings of the 2nd RP-
USA Phycology Symposium/Workshop. Philippine Council for
Aquatic and Marine Research and Development, Los Banos,
Laguna. pp 295-313.

17 The seagrasses of

JAPAN

ate (Zosteraceae] species and nine tropical

species (Hydrocharitaceae and Cymodoceaceae},
occur on the coasts of Japan, about a quarter of the
total number of seagrass species in the world [Table
17.1). Species diversity is high not only for seagrasses
but also for algal flora, with about 1500 species of
algae occurring around Japan. Such a high species
diversity in Japanese marine flora is probably related to
complex hydrodynamic properties around the Japanese
coasts that are affected by several major ocean
currents such as the Oyashio cold current, and the
Kuroshio and Tsushima warm currents.

Among the 16 species of seagrasses in Japan,
nine belong to the families Hydrocharitaceae and
Cymodoceaceae and are tropical species commonly
found in tropical and subtropical areas of the Indo-West
Pacific region'”. In Japan, their distribution is restricted
to the southwestern islands (Ryukyu and Amami
Islands) except for Halophila ovalis. In contrast,
distribution of all the species of Zosteraceae Is limited
to the main island areas, except for Zostera japonica
which also occurs in the Ryukyu Islands. Thus, the
seagrass flora in Japan differ distinctly between the
subtropical southwestern islands and the temperate
coasts of the main islands. The southern limit of the
temperate species of Zosteraceae is determined by the
summer high seawater temperature of 28°C around
Kyushu, while the distribution of tropical seagrass
species is restricted by the winter seawater
temperature of 15°C”.

Along the temperate coasts of China, the Korean
Peninsula and the islands of Japan, species diversity of
Zosteraceae is high. In addition to Zostera marina, a
cosmopolitan species widespread in the northern
hemisphere in both the Pacific and Atlantic Oceans, six
species of the family Zosteraceae are present that are
considered to be endemic to the northwestern Pacific
(Japanese, Korean, Chinese and southeast Russian

S ixteen seagrass species, including seven temper-

Japan

K. Aioi
M. Nakaoka

waters], namely Zostera asiatica, Zostera caespitosa,
Zostera caulescens, Zostera japonica, Phyllospadix
iwatensis and Phyllospadix japonicus®“’. The region can
be regarded as a “hotspot” of seagrass floral diversity
within the temperate waters of the northern
hemisphere. Most of these species have limited
distribution in some localities along the northern part
of Japan (see below). The hemispheric distributions in
the western Pacific may reflect the speciation process
of Zosteraceae from its possible ancestral origins in
equatorial regions".

Despite the high species diversity of Japanese
seagrasses, there are relatively few ecological studies
of these species with the exception of Zostera marina.
After pioneer studies by Tomitaro Makino and Shigeru
Miki who described these species in the late 19th and
early 20th centuries, few seagrass studies were
conducted in Japan until the early 1970s. This is
especially true for the endemic species of Zosteraceae
for which information on distribution and ecology was
not available until recently, partly due to their
occurrence in deep water {see below).

Eelgrass, Zostera marina, is a cosmopolitan
species commonly found in temperate to subarctic
coasts in the northern hemisphere". In Japan, Zostera
marina occurs in numerous localities along the
coastlines of the main islands, i.e. Honshu, Hokkaido,
Kyushu and Shikoku“. The northernmost population of
Zostera marina in Japan is found near Soya Cape,
Hokkaido (45°30'N] and the southernmost population
in Satsuma Peninsula, Kyushu [(31°10'N)'”. Most
eelgrass populations in Japan are perennial and extend
their distribution both by clonal propagation of
rhizomes and by seed production, although an annual
form of Zostera marina is found in some localities such
as Hamana-ko, Okayama and Kagoshima®”.

Zostera japonica is a small seagrass that
generally inhabits intertidal and shallow subtidal
bottoms along the coast of East Asia, from Viet Nam to

185

186

WORLD ATLAS OF SEAGRASSES

Sakhalin and Kamchatka, Russia'’". In Japan, Zostera
japonica is found in various localities, such as Notsuke
Bay in the northeastern part of Hokkaido'", Toyama
Bay in the Sea of Japan'’*“, Sagami Bay on the Pacific
coast of central Honshu'’ and the Ryukyu Islands, in
the southwestern part of Japan'*"*.

Zostera asiatica was originally recorded by Miki
from southern Sakhalin (Russia), the northeastern and
southern parts of Hokkaido, in the central part of
Honshu facing the Sea of Japan, and on the eastern
coast of the Korean Peninsula”. In Japan, populations
of Zostera asiatica are currently known only in
Hamanaka and Akkeshi Bay, Hokkaido”, and in
Funakoshi Bay, on the northeastern coast of Honshu”.
Additionally, the stranded dead plants have been
collected at several beaches in Hokkaido and one site in
Toyama Bay".

Zostera caulescens was known from limited
localities along the central to northern coast of Honshu
and the southern coast of the Korean Peninsula when
Miki first described this species'’”". Some recent
papers report the existence of populations in Mutsu
Bay, northern Honshu", along the Sanriku coast,
northeastern Honshu'***", in Tokyo Bay and Sagami

Table 17.1
Seagrasses recorded in Japan

Species Distribution

Hydrocharitaceae
Enhalus acoroides
Thalassia hemprichii
Halophila decipiens
Halophila ovalis

Ryukyu Islands
Ryukyu Islands
Ryukyu Islands
From Ryukyu Islands to
central Honshu

Cymodoceaceae
Cymodocea rotundata
Cymodocea serrulata
Halodule pinifolia
Halodule uninervis
Syringodium isoetifolium

Ryukyu Islands
Ryukyu Islands
Ryukyu Islands
Ryukyu Islands
Ryukyu Islands

Zosteraceae
Phyllospadix iwatensis
Phyllospadix japonicus
Zostera asiatica
Zostera caespitosa
Zostera caulescens
Zostera japonica

North Honshu and Hokkaido
South Honshu

Hokkaido and north Honshu
Hokkaido and north Honshu
Central and north Honshu
From Ryukyu Islands to
Hokkaido

Zostera marina From Kyushu to Hokkaido

(2, 15, 24-26)
'

Bay, on the Pacific coast of central Honshu and

in Toyama Bay, on the Sea of Japan'™”’.

Zostera caespitosa was reported to occur in
Hokkaido, in the northern half of Honshu and on the
east of the Korean Peninsula’. Populations of this
species were recently reported from Notoro Lake and
Notsuke Bay in Hokkaido"®*”, Mutsu Bay, northern
Honshu”, Yamada Bay and Otsuchi Bay, northeastern
Honshu”, and Toyama Bay, in the Sea of Japan'™’.

Two Phyllospadix species, Phyllospadix iwatensis
and Phyllospadix japonicus, inhabit the intertidal and
subtidal rocky bottoms of temperate regions of Japan.
Distribution of Phyllospadix iwatensis ranges from
Hokkaido to the northern part of Honshu. Phyllospadix
japonicus occurs in the central part of the Pacific coast
of Honshu and the western part of the Sea of Japan
coast of Honshu’.

Among the nine tropical seagrass species
belonging to the families Hydrocharitaceae and
Cymodoceaceae, Halophila ovalis has the widest
distribution, occurring from the Yaeyama Islands to
Chiba Prefecture [Odawa Bay) and to Toyama Bay, on
the Sea of Japan'”. The distribution of the other eight
species is restricted to the Amami and Ryukyu Islands
(Table 17.1}. Detailed information on island-by-island
distribution of each species has been given!” *:*).

Geographical distribution of these species
overlaps widely, with multispecific seagrass habitats
commonly observed both in the temperate and tropical
regions of Japan. In Hokkaido, three species coexist in
a single bed in Notoro-ko (Zostera marina, Zostera
japonica and Zostera caespitosa) and in Akkeshi Bay
(Zostera marina, Zostera asiatica and Phyllospadix
iwatensis}. In Honshu, four seagrass species co-occur
in Odawa Bay (Zostera marina, Zostera japonica,
Zostera caulescens and Halophila ovalis)'“’ and in
Otsuchi Bay (Zostera marina, Zostera caespitosa,
Zostera caulescens and Phyllospadix iwatensis), and
three species co-occur in Funakoshi Bay (Zostera
marina, Zostera asiatica and Zostera caulescens) and
in lida Bay (Zostera marina, Zostera japonica and
Zostera caespitosa). In the Ryukyu Islands, nine
species were found in a single seagrass bed in Iriomote
Island (Enhalus acoroides, Thalassia hemprichii,
Halophila ovalis, Cymodocea rotundata, Cymodocea
serrulata, Halodule pinifolia, Halodule uninervis,
Syringodium isoetifolium and Zostera japonica)'”’; eight
species were found in some beds at Ishigaki Island,
Miyako Island and Okinawa Island"? ****,

BIOGEOGRAPHY

The depth range of seagrasses in Japan is reported for
some multispecific seagrass beds where two or more
species coexist in a single bed’. Generally, each
species in the mixed beds shows a different depth

distribution, forming some specific patterns of zonation
along depth gradients.

Among Zostera spp. in temperate multispecific
seagrass meadows, Zostera japonica |s always found in
the uppermost parts of the bed, as its main habitat is
intertidal flats. Zostera marina occurs in the shallowest
parts of subtidal beds, mostly between 1 and 5 m deep,
but in some places down to 10 m. Zostera asiatica
occurs between the intertidal zone and a depth of 5 m.
Two other species generally occur in deeper habitats
than Zostera marina: Zostera caespitosa, between 1
and 20 m, and Zostera caulescens, between 3 and 17m.
In most of the mixed seagrass beds, the plants’ depth
ranges overlap to some degree with Zostera marina.
Depth zonation in Zostera asiatica, Zostera caespitosa
and Zostera caulescens cannot be described since
these species do not generally co-occur.

In multispecific seagrass beds in the Ryukyu
Islands, Halodule pinifolia, Cymodocea rotundata and
Thalassia hemprichii are dominant in the intertidal to
upper subtidal zone, while Cymodocea serrulata and
Enhalus acoroides are more abundant in the deeper
subtidal zone'**". The observed depth distribution of
these species generally agrees with those reported in
other parts of the tropical Indo-West Pacific region”.

Quantitative studies on biomass, shoot density,
shoot size and productivity have been conducted in
about 30 seagrass beds in Japan. Biomass, shoot
density and shoot size of Zostera marina vary greatly
among and within populations. Within populations,
biomass, shoot density and shoot size have sometimes
varied more than twofold, with greater biomass
generally observed in shallower parts of seagrass
beds’”“". Biomass as high as 500 g dry weight/m’ was
recorded in some areas such as Notsuke Bay, Otsuchi
Bay, Ushimado and Maizuru Bay, whereas maximum
biomass was less than 200 g dry weight/m’ for
populations in Odawa Bay, Yanai Bay and Toyama
Bay’. Estimates for above-ground net production were
available for several Zostera marina populations, and
varied between less than 1 g to 13 g dry weight/m’/day
at different sites, depths and seasons. Between-site
variation in these parameters did not appear to be
correlated with variations in latitude or geographical
distances.

Quantitative information on abundance and
productivity is very sparse for other species of Zostera,
and for the tropical seagrass species, in Japan.
Biomass of Zostera japonica varies greatly with season;
a maximum biomass of 270 g dry weight/m? was
recorded in July and a minimum of 30 g dry weight/m*
from December to January at Mikawa Bay, the Pacific
side of central Honshu". For Zostera caespitosa,
maximum above-ground biomass of 60 g dry weight/m’
was recorded for the population in lida Bay, Noto

Japan

140°
RUSSIAN 3 E
FEDERATION Soya Cape.

Notsuke Bay
Hokkaido “ee
Hamanaka

“Akkeshi Bay
4— Mutsu Bay .
~~ DPR E SEA OF JAPAN e Yamada Bay
“KOREA * Tope Bay Funakoshi Bay
he Tie Bae) Otsuchi Bay
4 Ly; Maizuru Bay > Honshu
YELLOW @REROF \\/ Tokyog . JAPAN
SEA ~
5 oe dl Okavertecz 3 Odawa Buy
> of \ Sagumi Bay
Kyichut iliag Shikoku Iamana-ko
Kagoshima > Seto Inland Sea
EAST oh
CIIINA *
SEA PACIFIC OCEAN
*
. Amami ls
Ryukyu Is.
?
Okinawa Island 0 200 400 600 Kilometers
@ **Yaeyama Is
Map 17.1
Japan

Peninsula (the Sea of Japan coast)”. For Zostera

asiatica at Akkeshi Bay, Hokkaido, biomass (427 g dry
weight/m’] was twice that of Zostera marina, whereas
the shoot density (134 shoots/m’) was about half of
Zostera marina when comparing monospecific stands
at the same depth, reflecting the larger shoot size of
the former”. The above-ground net production of
Zostera asiatica was estimated to be 3-5 g dry
weight/m’/day.

Information on the flowering and fruiting seasons
of Zostera marina and other Zostera species is
available from some localities in Japan’. In Zostera
marina, seasons for flowering and fruiting vary by 2-4
months across the region, with early flowering and
fruiting observed at lower latitudes. Seed germination
of Zostera marina was generally observed during the
winter in southern populations and during spring in
northern populations. For other Zostera species,
flowering and fruiting seasons have been reported only
from limited localities, and vary greatly among

\.
pS hes
aS
“|
>

Photo: K. Aioi

187

188

WORLD ATLAS OF SEAGRASSES

localities. For Zostera asiatica and Zostera caulescens,
the flowering and fruiting seasons are generally the
same as those of coexisting Zostera marina, whereas
Zostera caespitosa flowers and fruits about one month

earlier than sympatric Zostera marina™’.

HISTORICAL PERSPECTIVES

Although seagrasses have been very familiar to, and
traditionally utilized by, Japanese people living in
coastal areas, very little information is available about

Table 17.2
Traditional uses of seagrasses in Japan

Traditional use Species Locality
Rope for gill net Phyllospadix iwatensis Hokkaido
Cushions for horse Zostera marina Sanriku
saddles (Miyagi Pre.]
Fishermen's skirts Phyllospadix iwatensis Sanriku

and Zostera marina _|wate Pre.)
Cushions for train Zostera marina Tokyo Bay area
seats
Seto Inland Sea
Miura Peninsula
(Kanagawa Pre.)
Hamana-ko

Tatami mats Zostera marina
Agricultural compost Algae and
Zostera marina
Agricultural compost Algae and Zostera
marina (Shizuoka Pre.)
Agricultural compost Zostera marina Mikawa Bay
Agricultural compost Zostera marina Seto Inland Sea
(Okayama Pre.]
Nakaumi
(Shimane Pre.)

Agricultural compost Zostera marina and
freshwater plants

Note: Pre. = Prefecture.

Table 17.3

Estimates of total areas of algal and seagrass beds in
Japan in 1978 and 1991, and the percent area lost during
the period

Area of macrophyte Arealost %
beds (km’] (km?) lost
1978 1991
Algal beds* 2748 2664 83 3.0
Seagrass beds 515 495 21 4.0
Total 3263 3159 104 3.2

Note: * Algal beds consisted of Ulva, Enteromorpha,
Sargassum, Laminaria, Eisenia and Gelidium..

Source: As reported by the Japanese Environment Agency in 1994.

the historical distribution of seagrass beds. In Tokyo
Bay, an old chart issued in 1908 shows the distribution
of Zostera marina and Zostera japonica in the early
20th century. Extensive seagrass meadows of
approximately 3-5 km’ in area were located in shallow
waters (<3 m] in some localities such as Yokohama,
Tokyo, Funabashi and Chiba’. Unfortunately, all these
seagrass beds were destroyed in land reclamation
(filling and hardening of the shoreline] projects during
industrialization in the mid-20th century.

Traditional uses of seagrasses in Japan include
direct use as fiber for rope or padding (e.g. cushions
and tatami mats] or use as agricultural compost (Table
17.2). Besides those listed, there may well be further
traditional uses. For example, eelgrass was named
moshiogusa in Japanese, which means salt grass, and
might have been used to produce salt.

ESTIMATES OF HISTORICAL LOSS AND PRESENT
COVERAGE

The area of seagrass beds, especially those consisting
of eelgrass Zostera marina, has declined since the
1960s, mainly because of land reclamation. During
these last decades, the Japanese economy has
developed rapidly. The Environment Agency of Japan
surveyed the status of algal and seagrass beds along
most of the coastal areas of Japan in 1978 and again in
1991, from which the loss during this period was
estimated (Table 17.3]. The total area of algal and
seagrass beds together was 3262 km’ in 1978 and
3 159 km? in 1991. For seagrass beds, the total area
declined from 515 km* to 495 km’ during the period, i.e.
about 4 percent of Japan's total seagrass resource was
lost in 13 years. In particular, more than 30 percent of
Zostera marina beds disappeared in localities such as
Ariake Bay, Kagoshima Bay and Hyuga-nada in Kyushu
during this period”. In the Seto Inland Sea, more than
70 percent of Zostera marina beds have been lost since
1977, a loss which has seriously affected coastal
fisheries“.

For regionally endemic species of Zostera, the
situation may be more serious than for Zostera marina,
because populations are now known to exist in only a
few localities around Japan. In fact, Zostera asiatica and
Zostera caulescens are now ranked as VU [vulnerable
stage] in the Red Data Book of threatened Japanese
plant species. Among tropical seagrass species,
Enhalus acoroides and Halophila decipiens are found
only in limited localities in the Ryukyu Islands, and they
are also listed as VU in the Red Data Book.

PRESENT THREATS

As described above, seagrasses have been
disappearing rapidly due to industrial development in
the coastal regions of Japan. Major threats for further

Case Study 17.1
AKKESHI, EASTERN HOKKAIDO

In Hokkaido, the northernmost island of Japan,
some healthy Zostera marina beds remain. At
Akkeshi [(42°50'N, 144°50'E), located in eastern
Hokkaido, extensive seagrass meadows occur in
Akkeshi-ko (a brackish lagoon) adjacent to Akkeshi
Bay. In Akkeshi-ko, the dominant seagrass is
Zostera marina with minor amounts of Zostera
Japonica. A large-scale study was recently initiated
here to examine the interactions between terrestrial
and coastal ecosystems. It was found that
considerable amounts of nutrients of terrestrial
origin flow into this lagoon and these are important
for the productivity of Zostera marina and associated
communities. Studies on food web dynamics in the
Zostera marina bed have revealed that the major
consumer of Zostera marina was the whooper swan
(Cygnus cygnus) which overwinters in the lagoon,
and that mysids are the most dominant herbivores
grazing on epiphytic algae on eelgrass”. Both the
biomass and the diversity of mysids are high, and
this supports high productivity of commercially
important fish and shellfish species such as
epifaunal shrimps and several species of fish®”.

decline in present seagrass coverage include land
reclamation, environmental deterioration such as
reduced water quality, and rise in water temperature
and water level due to global warming.

The loss of seagrass vegetation over the last two
decades along the Japanese coast is mostly attributed
to land reclamation’. Many land reclamation projects
are still ongoing or at the planning stage, and will
probably further accelerate the loss of seagrass beds.
For example, the coastline has been damaged by land
reclamation and port construction in the Ryukyu
Islands where large economic investments have been
made toward rapid modernization. The natural
ecosystems of coral reefs and lagoons were greatly
impacted, especially along the coasts of Okinawa
Island. Dugongs inhabit several seagrass beds in the
northeastern coast of Okinawa Island, which is the
northern limit of global distribution of this threatened
marine mammal. Nevertheless, a large-scale land
reclamation project is now planned in the center of the
seagrass beds (Henoko coral lagoon) to build an
offshore runway for the US air base. Such construction
would almost certainly be fatal to the lagoon ecosystem
and directly destroy seagrass habitats for dugongs. The
Environment Agency of Japan decided to make a
general survey of the northernmost dugongs and their

Japan

Photo: C. Hily

Zostera marina leaves coated with epiphytes

habitats in February 2002. Scientists and non-
governmental organizations in Japan must support and
collaborate in these surveys to save the dugongs and
conserve their habitats.

Some seagrass beds have been declining rapidly
even in areas where no major land reclamation has
occurred, such as the Seto Inland Sea. In these areas,
water pollution and disturbance of habitats by fish
trawling are major causes of decline in seagrass beds.

In the case of multispecific seagrass meadows,
changes in environmental conditions due to human
activities have effects not only on overall seagrass
distribution and abundance but also on the species
composition of the seagrass beds. In Odawa Bay near
the Tokyo metropolitan area, for example, reduced light
condition due to eutrophication over the past 20 years
caused a decrease in areas of Zostera marina in
shallow habitats, but possibly favored the deeper-living
Zostera caulescens to expand its populations into
shallower depths'. However, due to lack of species-
by-species data in past literature, it is not possible to
determine whether Zostera caulescens truly increased
in recent years. Long-term field surveys of seagrass
beds using a unified approach are necessary in order to
monitor future changes in seagrasses in relation to
changes in environmental conditions.

189

190

WORLD ATLAS OF SEAGRASSES

Photo: K. Aioi

Case Study 17.2
RIAS COAST IN IWATE PREFECTURE, NORTHEASTERN HONSHU

Five temperate seagrass species, Zostera marina,
Zostera caulescens, Zostera caespitosa, Zostera
Japonica and Phyllospadix iwatensis, occur in the
three bays along the Rias Coast facing the
northeastern Pacific, namely Yamada Bay,
Funakoshi Bay and Otsuchi Bay, in lwate Prefecture.
The species composition of seagrasses varies
among the bays. In Yamada Bay, Zostera caespitosa
is the most abundant, with Zostera marina co-
occurring. The dominant species in the seagrass
bed in Funakoshi Bay is Zostera caulescens with
small patches of Zostera marina and Zostera
asjatica occurring at the shallower part of the bed.
Zostera caulescens, Zostera marina and Zostera
caespitosa are found to coexist in several seagrass
beds in Otsuchi Bay.

A large-scale census of these seagrass beds
has been undertaken using an acoustic sounding

The world’s longest seagrass, Zostera caulescens, at 10 m
deep in Funakoshi Bay.

technique to estimate overall distribution and
abundance of seagrasses®. The survey in
Funakoshi Bay has shown that the areal extent of the
seagrass bed was approximately 0.5 km? with the
depth distribution extending from 2 to 17 m.
Variation in canopy height of Zostera caulescens by
depth was also analyzed from the echo-trace of the
sounder. The same technique has been utilized to
estimate the abundance of Zostera caespitosa in
Yamada Bay and to monitor long-term changes in
patch dynamics of a seagrass bed at a river mouth
on Otsuchi Bay.

In the seagrass bed at Funakoshi Bay, Zostera
caulescens develops a high canopy at the deeper
parts of the bed (>10 m) by extending long flowering
shoots. A maximum shoot height of 6.8 m was
recorded in 1998, known as the world’s record
longest among all seagrasses”. In July 2000, an
even longer shoot (7.8 m] was found at the same
site. Studies of the dynamics and production of the
Zostera caulescens population revealed that most of
the flowering shoots emerge in winter and grow
rapidly, reaching an average height of 5 m in late
summer, Annual above-ground net production per
area was estimated to be 426 g dry weight/m’/year,
similar to estimates for other Zostera species that
live in intertidal and shallow subtidal beds {<1 m
deep). Thus, the productivity of Zostera caulescens
iS quite high despite its distribution in deep water [4-
6 m) with poor light conditions. Comparative
morphological and phenological studies of Zostera
caulescens between Iwate and Sangami Bay {near
Tokyo] showed that the large differences in shoot
height and seasonal dynamics are probably related
to differences in environmental factors such as
temperature”).

In these seagrass beds, the abundance and
dynamics of associated communities have been
investigated for epiphytic algae, sessile
epifauna'™, mobile epifauna®*****' and benthic
infauna®”. The dynamics of these organisms are
greatly influenced by spatial and temporal variations
in seagrass abundance. Most interestingly, a species
of tanaid crustacean (Zeuxo sp.) was found to feed
on predispersal seeds of Zostera marina and
Zostera caulescens™. The crustacean consumes up
to 30 percent of the seeds, which may have a large
negative impact on the seed abundance of the
seagrasses.

The global circulation of ocean currents is

important not only for land vegetation but also for
marine plants, as distributions of temperate and
tropical seagrass species are restricted by seawater
temperature in summer and winter, respectively, along
the Japanese archipelago. Most physicists and meteor-
ologists believe that the seas have warmed from 2°C to
5°C over the past 50 years due to global warming.
Global warming is predicted to affect the photosynthetic
activities of marine plants in Japan. A further warming
of 2 or 3°C in the seawater temperature may prove fatal
to seagrass beds in shallower areas”. Shallow water
vegetation such as seagrass and algae along the coasts
of Japan is also at risk of accelerated loss due to water
level rise caused by global warming.

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ACKNOWLEDGMENTS
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photographs of Japanese seagrasses, and N. Kouchi and F.T. Short for

reviewing the manuscript.

AUTHORS

Keiko Aioi, Aoyama Gakuin Women’s Junior College, Shibuya 4-4-25,
Shibuya, Tokyo 150-8366, Japan. Tel/fax: +81 (0]3 3313 1296. E-mail:
ai0i357(agalaxy.ocn.ne.jp

Masahiro Nakaoka, Graduate School of Science and Technology, Chiba
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18 The seagrasses of

The Republic of Korea

THE REPUBLIC OF KOREA

of the Eurasian continent, lies between 33°N and

43°N. The total coastline of the peninsula,
including the coastlines of the islands, reaches
17000 km. About 3400 islands are distributed along the
coasts of the Republic of Korea. Since each coast shows
very distinct characteristics, seagrass habitat
properties also vary. The west and the south coasts
have highly complex and indented coastlines, while the
east coast has a simple and linear one. Sand dunes are
well developed, and several lagoons are formed on the
east coast of the peninsula. Tidal flats are located at
several places on the south coast. Tidal range is 1-4 m
on the south coast and higher along the west part of the
coastline. About 2000 islands are distributed in the
western part of the south coast. Although the linear
distance of the west coast is some 650 km, the actual
length of the coastline is about 4700 km. Tidal range is
extremely high on the west coast of the Korean
peninsula; maximum tidal range is about 10 m on this
coast. Very large tidal flats are formed because of the
flat sea bottom and high tidal range.

Eight temperate seagrass species, five Zostera,
two Phyllospadix and Ruppia maritima, are distributed
on the coasts of the Korean peninsula’. Although
seagrasses are relatively abundant, few studies have
reported on their physiology and ecology in this area
and most of these reports were written in the Korean
language. In this paper, we review the status, habitat
characteristics and ecology of seagrasses on the coasts
of the Republic of Korea.

The Korean peninsula is enclosed by the Yellow
Sea (to the west of Korea], the South Sea and the East
Sea, which have considerably different characteristics
(Table 18.1]. The coastline of the Yellow Sea [the west
coast] shows a heavily indented coast with maximum
tidal range of about 10 m. The hydrographic properties
and circulation characteristics of the Yellow Sea are
strongly influenced by climatic conditions. The South

Ty: Korean peninsula, located at the eastern end

K.-S. Lee
S.Y. Lee

Sea is connected to the East China Sea and the
Tsushima current, a branch of Kuroshio, flows towards
the East Sea through the South Sea. The coastline of
the South Sea is also heavily indented. Tidal ranges on
the south coast vary from about 1.0 m in the east part
of the coast to about 4.0 m in the west part. The East
Sea is deeper than the Yellow Sea or the South Sea, and
the eastern coastline is very simple and linear. Tidal
range Is usually less than 0.3 m.

PRESENT SEAGRASS DISTRIBUTION

Eight temperate seagrass species are distributed on
the coasts of the Korean peninsula. Zostera marina is
the most abundant seagrass species, widely distributed
throughout all coastal areas (Table 18.2) in relatively
large meadows. Zostera asiatica is mostly distributed
in the cold and temperate coasts of northeastern Asia.
In the Republic of Korea Zostera asiatica occurs on the
east coast; the distribution of this species on the west
and the south coasts of the Korean peninsula is not
clear. Zostera caespitosa, Zostera caulescens and
Zostera japonica are found on all the Republic of
Korea's coasts (Table 18.2).

Two Phyllospadix species, Phyllospadix iwatensis
and Phyllospadix japonicus, are found on Korean
coasts”. Phyllospadix japonicus occurs on all coasts of
the peninsula, while Phyllospadix iwatensis occurs on
the east and west coasts. On the east coast,
Phyllospadix iwatensis usually appears in the northern
parts of the coast, while Phyllospadix japonicus is
distributed in the southern parts. Distribution of Ruppia
maritima in the Republic of Korea has been reported
from limited areas on the west and south coasts"””.

BIOGEOGRAPHY OF THE REGION

Seagrasses are distributed in numerous locations
along the coast of the Korean peninsula with habitat
types varying among the different coasts (Table 18.3).
Seagrasses are widely distributed throughout the south

194

WORLD ATLAS OF SEAGRASSES

Table 18.1
Physical characteristics of seagrass beds on the west, south and east coasts of the Republic of Korea

Characteristics West coast
Wave energy Low

Sediment Muddy sand
Tidal range (m) 3-10

Coastline Heavily indented
Seagrass habitat Bays, islands

coast, while on the east coast, where the wave energy is
high, the distribution of seagrasses is limited to
lagoons, ports and barrier reefs. On the west coast,
seagrasses are mainly distributed in the intertidal and
subtidal zones of islands. Seagrasses usually form
small patches on the east coast, while large seagrass
meadows occasionally occur on the west and the south
coasts of the Republic of Korea.

Zostera marina appears at the intertidal and
subtidal zones, where the water depth is usually less
than 5 m, and forms relatively large meadows. Zostera
marina can be observed in both muddy and sandy
sediments". Zostera asiatica is distributed in relatively
deep water (9-15 m] in bays or along open shores, and
forms small patches. Zostera asiatica is usually
observed in sandy sediments along the east coast.
Zostera caespitosa also usually forms small patches
and is distributed in deeper water (3-8 m] than Zostera
marina. Zostera caespitosa occurs on all coasts of the
Korean peninsula, but is limited to a few areas with
mixed sediments of sand and gravel. Zostera
caulescens is distributed on both sandy and muddy
bottoms. As a result of its height, Zostera caulescens
usually occurs in deep water (6-12 m). Zostera japonica

Table 18.2

Seagrass species distributed on the coasts of the Republic of Korea

Species
West coast
Genus Zostera
Zostera marina
Zostera asiatica
Zostera caespitosa
Zostera caulescens
Zostera japonica
Genus Phyllospadix
Phyllospadix iwatensis
Phyllospadix japonicus
Genus Ruppia
Ruppia maritima

South coast East coast
Low High

Muddy sand Sand

1-4 0.1-1

Heavily indented Simple linear
Bays, islands Lagoons, bays

is mainly distributed in the intertidal zone around
islands.

Both Phyllospadix species, Phyllospadix iwa-
tensis and Phyllospadix japonicus, occur mainly on
rocky substrata along the east coast of the Korean
peninsula. Although Phyllospadix species are observed
in both sheltered and open shores, they usually grow in
high-energy environments. Distribution of Ruppia
maritima has been reported from a few estuaries on
the west and the south coasts. However, the Ruppia
maritima habitats have been severely disturbed
recently, so the present distribution of this species
should be investigated. Although a few mixed beds with
Zostera marina and Zostera japonica occur on the west
coast, different seagrass species do not usually coexist
in the Republic of Korea.

The vegetative shoot height of Zostera marina in
the Republic of Korea ranges from 30 cm to 210 cm
(Table 18.4], and varies significantly among habitats.
Reproductive shoots, which are usually taller than
vegetative shoots, range from 50 cm to 350 cm. The leaf
width of Zostera marina also shows significant
variation according to environment. Some plants from
eelgrass beds on the east and the south coasts have

Distribution

South coast East coast

The Republic of Korea 195

very wide leaves (about 15 mm). Zostera marina in the ; 0 30 60 90 Kilometers
; ; DEMOCRATIC PEOPLE'S =
Republic of Korea has 5-11 leaf veins. REPUBLIC OF KOREA
The shoot heights of Zostera asiatica are 50-90 cm ;
for vegetative shoots and 60-80 cm for reproductive

shoots. Leaf widths range from 11 to 15 mm, and the

leaves have 9-11 veins (Table 18.4]. The shoot height of & “SEA OF
Zostera caespitosa for both vegetative and reproductive JAnAN)
shoots ranges from 50 cm to 170 cm. Zostera caespitosa eh esi

has relatively narrow leaves (5-8 mm wide], and usually YELLOW OF KOREA

5 leaf veins. Zostera caulescens is a very tall seagrass SEA, 6°
species; the height of its reproductive shoot reaches
7-8 m. Zostera caulescens has wide leaves (10-16 mm]
and 9-11 leaf veins. Zostera japonica is a very small

= x Kwangyang Bay
seagrass species, usually less than 30 cm tall, with 3 leaf | :
veins. The leaf width of Zostera japonica is 1-2 mm. So ad tet Kaduk |
Phyllospadix iwatensis and Phyllospadix ; orks Faustina

japonicus show several morphological differences. The : : a (JAPAN)
shoot heights of both Phyllospadix species range from Korea Sinai
20 cm to 100 cm. Phyllospadix iwatensis has 5 veins in
the lower portion of the leaf, but only 3 veins in the
apical portion”. Phyllospadix japonicus has 3 leaf veins.
The leaf width of Phyllospadix japonicus ranges from
1.5 mm to 2.5 mm, while the width of Phyllospadix Map 18.1
iwatensis ranges from 2.0 mm to 4.5 mm. Republic of Korea

SOUTH SEA

Table 18.3
Habitat characteristics of seagrass species in the Republic of Korea

Species Sediment type Wave energy Water depth (m) Location

Zostera marina Muddy, sandy Low 0-5 Bay, lagoon
Zostera asiatica Sandy Intermediate 9-15 Bay, open shore
Zostera caespitosa Gravelly Low 3-8 Bay

Zostera caulescens Muddy, sandy Low 6-12 Bay

Zostera japonica Muddy, sandy Low Intertidal zone Bay
Phyllospadix iwatensis Rocky High 0-3 Open shore
Phyllospadix japonicus Rocky High 0-3 Open shore
Ruppia maritima Muddy, sandy Low 0-2 Estuary

Table 18.4
Morphological characteristics of seagrasses distributed in the Republic of Korea

Species Shoot height (cm) Leaf width (mm) Number of leaf veins
Vegetative Reproductive

Zostera marina 30-210 50-350 5-15 5-11

Zostera asiatica 50-90 60-80 11-15 9-11

Zostera caespitosa 50-170 50-170 5-8 5-7)

Zostera caulescens 90-200 150-800 10-16 9-11

Zostera japonica 15-40 10-20 1-2 3
Phyllospadix iwatensis 20-100 = 2-4.5 5
Phyllospadix japonicus 20-100 - 1.5-2.5 3

nit

196

WORLD ATLAS OF SEAGRASSES

Case Study 18.1
RECENT RESEARCH ON
SEAGRASSES

Few biological and ecological studies have been
conducted on seagrasses of the Korean peninsula.
Recently, the Government of the Republic of Korea
began to realize the ecological and economic
importance of seagrasses in coastal and estuarine
ecosystems. There is now an effort to preserve
seagrass habitats and to restore disturbed and
destroyed habitats. Since there Is little physiological
and ecological information on seagrasses in the
Republic of Korea, basic research on seagrass
biology and ecology is necessary for efficient
management and restoration of seagrass habitats
on the Korean coast.

Most seagrass research in the Republic of
Korea, except for taxonomic studies, has been
conducted during the past few years. Current
seagrass research projects are as follows: Dr Choi
{Ajou University], Dr Shin (Soonchunhyang

Few studies on seagrass ecology have been
reported from the Korean peninsula. Therefore, few
data exist concerning seagrass biomass or productivity.
The density, biomass and productivity of seagrasses
change significantly with environmental conditions
such as water temperature, underwater irradiance and
nutrient concentration. Since water temperature along
the coasts of the Korean peninsula shows obvious
seasonal variation, being less than 10°C during winter
and about 25°C during summer, seagrass biomass and
productivity also show significant seasonal variations.
The shoot density of Zostera marina varies from about
50 shoots/m*? to 300 shoots/m? depending on
environmental conditions. Shoot densities of Zostera
caulescens and Zostera japonica are about 120
shoots/m* and about 8000 shoots/m’, respectively,
during the summer months on the south coast”.
Biomass of both Zostera marina and Zostera
caulescens on the south coast is about 500 g dry
weight/m’ during summer months, while Zostera
japonica has about 200 g dry weight/m’. Leaf
productivity is about 2 g dry weight/m?/day for Zostera
marina and Zostera caulescens, and about 5 g dry
weight/m’/day for Zostera japonica during summer
months. The small seagrass species Zostera japonica
has higher leaf productivity because of its much higher
shoot density.

More than 60 fish species can be observed in
seagrass beds in the Republic of Korea; fish collected
in seagrass beds are primarily small fish species or

University], Dr Oh (Kyungsang National University)
and Drs Choi and Lee (Hanyang University) are
conducting taxonomic studies. Drs Choi and Lee
have conducted a molecular phylogenetic study to
examine the phylogeny of the Zostera species in the
Republic of Korea. The sequences of the internal
transcribed spacer (ITS) regions in nuclear
ribosomal DNA have been determined for five
Zostera species in the Republic of Korea. From the
study, Zostera marina and Zostera caespitosa were
the most closely related species, and Zostera
Japonica was the most distinctive Zostera species.

Dr Hong [Inha University) is investigating
benthos in seagrass beds on the south and west
coasts of the Korean peninsula. Dr Huh (Pukyung
National University] and Dr Kim (Chonnam National
University) are studying fish populations and
phytoplankton communities in seagrass beds. Dr K.
Lee (Pusan National University) is conducting basic
physiological and ecological studies on seagrass in
the Republic of Korea, and research into carbon and
nutrient dynamics in seagrass beds.

juveniles of big fish species. Fish species abundant in
seagrass beds include Sgnathynus schlegeli, Pholis
sp., Pseudoblennius cottoides, Sebastes inermis and
Acanthogobius flavimanus®”. Juveniles of economi-
cally valuable fish species such as Sebastes inermis,
Platycephalus indicus and Limanda yokohamae,
Acanthopagrus schlegeli and Lateolabrax japonicus
grow in seagrass beds. In seagrass beds on the south
coast, Acanthopagrus schlegeli were not observed
during winter and spring. However, many small-size
juveniles (less than 3 cm body length) of Acanthopagrus
schlegeli were found in July; then they were seen
infrequently in October when their body length reaches
about 6 cm'". Sebastes inermis, which is a very
valuable fish species in the Republic of Korea, also
migrates into seagrass beds when its body size is about
2 cm and spends its juvenile stage in seagrass beds.

There are seasonal variations in the species
composition and abundance of fish populations in
seagrass meadows. A peak of fish abundance occurs
during spring, with a secondary peak during the fall.
The peaks are probably caused by increased larval
recruitment. Seasonal variation in fish species
composition is closely related to standing crops of
seagrasses",

A peak of shrimp abundance occurs in the late
winter and spring”. Shrimp species in seagrass beds
were most diverse during the late summer, and least
diverse during the late fall. Crab species in seagrass
beds were most abundant during summer, and most

diverse during spring and summer”. The dominant
group of benthic macrofauna in seagrass beds was
polychaete worms". About 15 epiphytic algae species
on seagrass leaf tissues have been reported from
seagrass beds in the Republic of Korea. The dominant
epiphyte species are Callophyllis rhynchocarpa and
Champia sp. during spring and summer, and
Polysiphonia japonica and Lomentaria hakodatensis
during fall and winter. Epiphyte biomass is lowest during
summer, and highest during winter. Epiphytic algae
account for approximately 15 to 20 percent of total plant

standing crop of the seagrass beds in Kwangyang Bay'”’.

USES OF SEAGRASSES

Seagrasses are rarely used either directly or indirectly
in the Republic of Korea. Seagrasses have been
considered as useless weeds around ports and boat
channels and in shallow fishing grounds; fishermen cut
off seagrasses to have a better waterway. However,
fishermen and the Government now realize the
ecological and economical importance of seagrasses
for fisheries and coastal ecosystems in the Republic of
Korea. We are trying to use seagrass for conservation
and restoration of coastal ecosystems. The coasts of
the Korean peninsula have been highly disturbed and
polluted as a consequence of industrial development
since the 1970s. Additionally, an expanse of tidal flats
and seagrass habitats has been reclaimed for factory
sites or residential districts. These coastal distur-
bances have led to a reduction in spawning grounds and
nursery areas for economically valuable fish, and
consequently led to decreases in coastal fish
production. Concrete constructs have been added to
coastal waters in the Republic of Korea for artificial
fish-breeding reefs. Most artificial fish reefs were
constructed in deep water, so few types of seaweed can
grow on the construct, and the construct provides
habitat for only adult fish. However, seagrass beds can
provide a good fish spawning ground and nursery area
for juvenile fish, so we are now trying to restore
seagrass habitats on Korean coasts. Seagrasses will
also be used as a nutrient filter to reduce algal blooms,
especially red tide, which damage coastal fisheries in
the Republic of Korea almost every year.

Seagrass leaf detritus piled up on the beach is
collected in some coastal areas to make compost,
which is used for fertilizing agricultural land. In earlier
times, children in the coastal zones chewed seagrass
rhizomes for their sweet taste.

ESTIMATES OF HISTORICAL LOSSES AND PRESENT
DISTRIBUTION

There are no studies of seagrass areas in the Republic
of Korea. Therefore, we must estimate historical losses
and present seagrass coverage using personal

The Republic of Korea

observation and verbal information obtained from
fishermen. Most large seagrass beds in the Republic of
Korea were located in the bays of the south coast. Many
of these bay areas are now urbanized, so bay water is
highly over-enriched by anthropogenic nutrients. Most
seagrass has disappeared from these eutrophic bays.
Numerous former tidal flats and seagrass habitats on
the south and west coasts of the Republic of Korea have
been reclaimed for factory sites, residential districts or
agricultural land. Large areas of seagrass have been
lost due to reclamation, particularly from the west and
south coasts. For example, a large Zostera marina bed
(13.6 km’) existed in front of Kaduk Island, on the south
coast of the Republic of Korea, until the late 1980s".
However, this eelgrass bed disappeared after
reclamation of the adjacent mud flats during the
early 1990s.

Many oyster and seaweed farms are located in
shallow coastal waters, where seagrasses exist. Lots of
seagrass beds were destroyed by the construction and
maintenance of these farms. Seagrass areas in the
Republic of Korea also have been lost to boat traffic,
trawling and clamming. From the estimates of

Table 18.5
The estimated areas of seagrasses distributed on the coasts
of the Republic of Korea

Species Area (km’)
Zostera marina 50-60
Zostera asiatica <1.0
Zostera caespitosa 1.0
Zostera caulescens 1.0-5.0
Zostera japonica 1.0
Phyllospadix iwatensis <1.0
Phyllospadix japonicus 1.0-2.0
Ruppia maritima <1.0
Total 55-70

potential seagrass area and present seagrass
coverage, and verbal information from fishermen, we
believe that more than 50 percent (and maybe as much
as 70 or 80 percent) of the seagrass area in the
Republic of Korea has been lost since the beginning of
industrial development during the 1970s.

Most of the seagrass area in the Republic of
Korea is located on the south coast, and Zostera marina
beds account for about 90 percent of total seagrass
coverage in the Republic of Korea. Our estimated area
of Zostera marina on the coasts of the Korean
peninsula is about 50 to 60 km? (Table 18.5]. The
estimated area for Zostera caulescens is 1 to 5 km’.
Most Zostera asiatica and Phyllospadix iwatensis beds

197

198

“Sits

WORLD ATLAS OF SEAGRASSES

are found on the east coast; the estimated area for both
species is less than 1 km’. Most Phyllospadix japonicus
beds are also found on the east coast, and the bed area
is estimated at 1 to 2 km*. The estimated area for
Zostera caespitosa and Zostera japonica is about 1 km?
{Table 18.5). There is no information on the area of
Ruppia maritima in the Republic of Korea, but it is
probably less than 1 km’.

PRESENT THREATS

Seagrasses in the Republic of Korea have been severely
impacted by coastal eutrophication, land reclamation,
aquaculture and fishing activities, and these threats
still exist. Estuaries and coastal ecosystems in the
Republic of Korea are receiving extraordinary amounts
of nutrients as a consequence of anthropogenic
loading, as well as through industrial pollutants.
Nutrient over-enrichment and pollutant discharge
widely affect estuarine and coastal ecosystems and
damage seagrass habitats. On the west and south
coasts of the Korean peninsula land reclamation is a
major contributor to loss of seagrass habitats. Since
1945, more than 62 km* of tidal flats have been
reclaimed’. Reclamation of tidal flats caused loss of
adjacent seagrass beds, and many seagrass beds have
disappeared due to reclamation over the last decades.
Many land reclamation projects, which did not consider
the ecological and economical values of tidal flats and
seagrass beds, are still being constructed by the
Government of the Republic of Korea. Oyster and

REFERENCES

1 Chung YH, Choi HK [1985]. Distributional abundance and standing
crop of the hydrophytes in the estuary of the Nadong River. Nature
Conservation 49: 37-42 lin Korean).

2 Shin H, Choi HK, Oh YS [1993]. Taxonomic examination of Korean
seagrasses: Morphology and distribution of the genus Phyllospadix
(Zosteraceae]. Korean Journal of Plant Taxonomy 23: 189-199.

3 Shin H, Choi HK [1998]. Taxonomy and distribution of Zostera
(Zosteraceae] in eastern Asia, with special reference to Korea.
Aquatic Botany 60: 49-66.

4 Lee SY [2001]. A Study on the Ecological and Taxonomical
Characteristics of Zostera (Zosteraceae] in Korea. PhD thesis,
Hanyang University, Seoul. 165 pp {in Korean).

5 Choi HK [2000]. Aquatic Vascular Plants. Korea Research Institute
of Bioscience and Biotechnology.

6 Lee SY, Kwon CJ, Choi Cl [2000]. Sediment characteristics from the
beds of Zostera marina and Z. asiatica. Journal of Natural Science
& Technology, Hangyang University 2: 25-29 {in Korean).

7 Lee K-S, Lee SY [2001]. Status and restoration of seagrass habitat
on the south coast of the Korean peninsula. Nature Conservation
116: 15-20 {in Korean).

8 Huh SH [1986]. Species composition and seasonal variations in
abundance of fishes in eelgrass meadows. Bulletin of the Korean
Fisheries Society 19: 509-517 lin Korean).

9 Huh SH, Kwak SN [1997]. Species composition and seasonal
variations of fishes in eelgrass (Zostera marina) bed in Kwangyang
Bay. Korean Journal of Ichthyology 9: 202-220 {in Korean).

seaweed farming, and fishing activities such as
clamming and trawling, are also serious threats to
Korean seagrasses.

POLICY

There is no policy which directly serves to protect
seagrasses in the Republic of Korea. However, several
coastal areas are protected as Environmental
Conservation Areas or Special Coastal Management
Areas, and many seagrass beds are located in the
protected areas. There are critical problems associated
with the management of estuaries and designated
protected areas. There is no long-term management
plan for effective management and protection of
estuarine and coastal ecosystems in the Republic of
Korea. Punishment for illegal activities in the protected
areas, such as illegal fishing activities or illegal
dumping, is very weak, so protection of Korean coastal
ecosystems by the law is not effective. Additionally,
economic advantages are usually given priority over
ecological conservation or environmental preservation.
Therefore, even protected areas can be developed or
reclaimed for industrial facilities in the Republic of
Korea based on economic considerations.

AUTHORS

Kun-Seop Lee and Sang Yong Lee, Department of Biology, Pusan
National University, Pusan 609-735, Republic of Korea. Tel: +82 (0)51 510
2255. Fax: +82 (0)51 581 2962. E-mail: klee(@hyowon.cc.pusan.ac.kr

10 Huh SH, Kwak SN [1998]. Feeding habits of juvenile Acanthopagrus
schlegeli in the eelgrass (Zostera marina] bed in Kwangyang Bay.
Korean Journal of Ichthyology 10: 168-175 (in Korean].

11 Lee TW, Moon HT, Hwang HB, Huh SH, Kim DJ [2000]. Seasonal
variation in species composition of fishes in the eelgrass beds in
Angol Bay of the southern coast of Korea. Journal of the Korean
Fisheries Society 33: 439-447 lin Korean).

12 Huh SH, An Y-R [1997]. Seasonal variation of shrimp (Crustacea:
Decapoda) community in the eelgrass (Zostera marina] bed in
Kwangyang Bay, Korea. Journal of the Korean Fisheries Society 30:
532-542 lin Korean).

13 Huh SH, An Y-R [1998]. Seasonal variation of crab (Crustacea:
Decapoda) community in the eelgrass (Zostera marina) bed in
Kwangyang Bay, Korea. Journal of the Korean Fisheries Society 31:
535-544 (in Korean).

14 Yun SG, Huh SH, Kwak SN [1997]. Species composition and
seasonal variations of benthic macrofauna in eelgrass, Zostera
marina, bed. Journal of the Korean Fisheries Society 30: 744-752.

15 Huh SH, Kwak SN, Nam KW [1998]. Seasonal variations of eelgrass
(Zostera marina] and epiphytic algae in eelgrass beds in
Kwangyang Bay. Journal of the Korean Fisheries Society 31: 56-62
(in Korean).

16 Koh C-H [ed] [2001]. The Korean Tidal Flat: Environment, Biology
and Human. Seoul National University Press, Seoul.

19 The seagrasses of

The Pacific coast of North America

THE PACIFIC COAST OF NORTH

AMERICA

extending from the Baja Peninsula in Mexico

through Alaska includes a wide variety of
ecosystems ranging from subtropical through arctic in
a northerly transect. Given the nature of the leading
edge coast and the resultant paucity of large regions
where soft sediments can accumulate, one would
expect a rather limited diversity of marine angiosperms
or seagrasses. However, a reasonably large number of
species exist in this region for a number of reasons,
related in part to the ability of members of the genus
Phyllospadix to colonize rocky shores. Eight seagrass
species are recognized: Halodule wrightii, Ruppia
maritima, Zostera marina, Zostera japonica, Zostera
asiatica, Phyllospadix scouleri, Phyllospadix serrulatus
and Phyllospadix torreyi'“'. Four of them, Zostera
marina, Phyllospadix scouleri, Phyllospadix serrulatus
and Phyllospadix torreyi, have probably been growing in
the region since the Pliocene”; one, Zostera japonica,
is a recent addition to the northeast Pacific flora, being
introduced as a result of oyster enhancement
programs"; and little is known about the phyto-
geographic history of the three other species (Zostera
asiatica, Ruppia maritima and Halodule wrightii).

In terms of ecosystems, members of the genus
Phyllospadix (the surfgrasses) dominate the rocky
subtidal and intertidal zones, where their condensed
rhizomes allow them to colonize hard substrates. The
three species in the genus Phyllospadix (Phyllospadix
serrulatus, Phyllospadix scouleri and Phyllospadix
torreyi) are endemic to the Northeast Pacific’. Both
Phyllospadix torreyi and Phyllospadix scouleri were
widely used in the region by indigenous people before
European contact’. For example the flowers of
Phyllospadix torreyi were sucked for sweetness by
children of the Makah people who live on the Olympic
Peninsula of Washington state, and leaves of the same
plant were woven into pouches by the coastal Chumash
in the Channel Islands of California.

T° region along the Pacific coast of North America

S. Wyllie-Echeverria
J.D. Ackerman

In contrast, soft-bottom habitats in the subtidal
and intertidal zones and estuaries are more commonly
associated with plants in the genus Zostera, which can
form large monotypic stands in the Northeast Pacific
estuaries, and mixed stand populations of Zostera
marina and Zostera japonica, and sometimes Ruppia
maritima, in estuaries from southern British Columbia,
Canada, to Coos Bay, Oregon” ”!. Zostera marina
provides important habitat for migrating waterfowl,
juvenile salmon, resident forage fish, invertebrates and
wading birds”, and Zostera japonica is commonly eaten
by resident and migratory waterfowl’. Noteworthy is
the use of Zostera marina as substrate for the laying of
Pacific herring {Clupea harengus pallasi) roe; the roe is
also used by humans”.

Whereas little is known about the primary
production rates for Zostera japonica, Zostera marina
productivity can be quite high on an annual basis (84-
480 g carbon/m’/year) and standing stocks may cover
many hectares of seafloor”. For example, the large
populations at Izembek Lagoon, Alaska, United States
{160 ha) and Laguna Ojo de Liebre, Baja California,
Mexico [175 ha], which are the primary staging
grounds for migratory waterfowl, may be the largest
Zostera marina ecosystems in the world! *". In
addition, pre-contact First Nations peoples recognized
Zostera marina and its ecosystems as valuable
cultural and food resources. In British Columbia a
number of First Nations people (Nuu-chah-nulth,
Haida and Kwakwaka'wakw) ate fresh rhizomes and
leaf bases or dried them into cakes for winter food'™”’.
Moreover, the Seri Indians living on the Gulf of
California in Sonora, Mexico, used the Zostera marina
seeds to make flour’.

Ruppia maritima grows in many of the brackish
water coastal lagoons from Alaska south to Mexico”.
Interestingly, Ruppia maritima was recognized as a
separate species (from Zostera marina) by the Seri
elders but was not used by them'™.

200

WORLD ATLAS OF SEAGRASSES

The last two species, namely Zostera asiatica
and Halodule wrightii, have rarely been the focus of
biogeographic investigation within this region.
Zostera asiatica was found recently at three sites
in southern California” and, leaving aside some
regional studies documenting the presence of
Halodule wrightii in the Gulf of California”, there are
no studies that discuss the habitat value or
autecology of these plants in the Northeast Pacific
region.

Case Study 19.1

BIOGEOGRAPHY

Zostera marina lor eelgrass) is the dominant species in

terms of biomass and habitats on the Pacific coast of

North America, where it grows in:

fo) the shallow waters of the continental shelf;

() the Gulf of California (Sea of Cortez);

(o) coastal lagoons such as San Quintin, Baja
California, Mexico, and Izembek Lagoon, Alaska'"";

fo) estuaries formed by tectonic processes like San
Francisco Bay;

THE LINK BETWEEN SEAGRASS AND MIGRATING BLACK BRANT ALONG THE

PACIFIC FLYWAY

Black brant lor sea goose, Branta bernicla nigricans)
forage on seagrass flats (primarily Zostera marina)
from Alaska to Mexico. In late August, after raising
young in the Yukon-Kuskokwim Delta (61°N, 165°W),
flocks gather at Izembek Lagoon [55°N, 163°W} to
graze on one of the largest intertidal stands of
Zostera marina in the world [see photograph below

Photos: D, Ward

Black brant grazing on the Zostera marina bed in Izembek
Lagoon, United States

left). In the fall, most of the population moves on a
non-stop, three-day transoceanic flight to Zostera
marina and Ruppia maritima beds in Baja California
at Bahia San Quintin (30°N, 116°W; see photograph
below right}, Laguna Ojo de Liebre (27°N, 114°W)
and Laguna San Ignacio [26°N, 113°W).

Spring migration coincides with midday
maximum low water events, which allow brant day-
light opportunities to graze on the extensive
seagrass resources growing on the tide flats at
locations like Morro Bay and Humboldt Bay,
California; South Slough and Yaquina Bay, Oregon;
Willapa Bay and Padilla Bay, Washington; and
Boundary Bay, British Columbia, Canada.
International conservation efforts by the United
States, Canada and Mexico are under way at
wintering and migration stopover sites along the
eastern Pacific Flyway to protect seagrass habitats
in coastal embayments and estuaries.

In collaboration with David Ward (US Geological Survey, Anchorage]
and Dr Silvia Ibarra-Obando (Centro de Investigaciones Cientifica y de
Educacion Superior de Ensenada, Baja California, Mexico).

= ee =
Black brant on the Zostera marina and Ruppia maritima beds in
Bahia San Quintin, Mexico.

) coastal fjords similar to Puget Sound,
Washington”.

It is found along the coast of British Columbia
including the coasts of Vancouver Island and Queen
Charlotte Islands (Haida Gwaii] in sheltered bays and
coves including Bamfield Harbour and Sooke Basin“.
The species also extends well into Alaskan waters to the
Arctic Circle". In the intertidal zone Zostera marina can
co-mingle with Zostera japonica in the Pacific Northwest
and Ruppia maritima in Baja California® ™.
Whereas the majority of Zostera marina
populations are perennial, annual populations [e.g.
Bahia Kino, Gulf of California, Mexico; Yaquina Bay,
Oregon, United States) in which 100 percent of the
population are generative shoots that recruit from
seeds each year have been reported’. The
appearance of branched reproductive shoots, a
dimorphic expression quite distinct from the ribbon-
shaped leaves of the vegetative shoots, begins to occur
as water temperatures warm in the spring. In the
Northeast Pacific, reproductive shoots are visible in
February at southern sites such as Baja California,
Mexico and southern California; in late March or early
April in Puget Sound, Washington; and as late as June in
northern sites like Izembek Lagoon, Alaska. Flowering
phenology is protogynous and the emergence of
stigmas and then anthers effect the release, transport
and capture of pollen, which rotate in the shear around
stigmas'”. Zostera marina is monoecious; however the
release of pollen and its stigmatic capture is separated
in time to promote an outcrossing breeding system'”"".
In a region-wide analysis of population
structure’”, Alberte and colleagues found that:
fo) there was high genetic diversity among Zostera
marina populations in the region;
to) gene flow restriction existed for populations that
were near each other;

) intertidal plants in disturbed environments were
less diverse genetically than those in undisturbed
sites.

In a subsequent study, focused on San Diego,
California, and Baja California, Mexico, Williams and
Davis discovered that transplanted Zostera marina
populations were less diverse genetically than naturally
occurring populations”.

Although Zostera japonica is typically smaller
than Zostera marina, it can be confused with the
intertidal growing habit of Zostera marina (var.
typica\"". However Zostera japonica commonly grows
higher in the intertidal zone and has an open [as
opposed to tubular) leaf sheath characteristic of its
subgenus Zosterella”. It is a possible invader to the
region coming by way of the oyster trade with Japan in

The Pacific coast of North America

BERING Yukon
SEA Delta

Izembek
Lagoon

—

“=?

Gulf of Alaska

} ~]
ms
yi
AZ British
Columbia

Graham Island.

Queen Wy
Charlotte §
Islands §

a
o

b.
¢

Vancouver

Island % yes Cove
+ tb

ae 9
Olympic Peninsula~—¢ “A Boundary Bay
; t =| Padilla Bay
Willapa Bay rf
* Puget Sound

‘
Yaquina Bay

Coos Bay bd
Laguna San Ignacio a Oregon

PACIFIC OCEAN

*
*
.

San Francisco Bay -—#
°
Monterey California

: Morro Bay
Channel 5*
Islands Bs
San Diego A
.

San Quintin? exico
+, Sonora
bs Bahia
20° N Laguna Ojo de Liebre ie i . ok
Humboldt Bay,
Gulf of cm — fe
California 5

0 200 400 600 800 1000 Kilometers Baja California
a — | .
120° W Z f

Map 19.1
The Pacific coast of North America

the early part of the 1900s". At several sites from
southern British Columbia, Canada, to southern
Oregon, Zostera japonica co-mingles with Zostera
marina (and occasionally Ruppia maritima’) in the
intertidal region of many estuaries”. Zostera japonica
is restricted in its northerly extent to the region near
the city of Vancouver including Boundary Bay and
Tsawwassen, where it is found primarily in the upper
intertidal zones in muddy or silty areas”. Some
unconfirmed reports also exist of the species further

201

202

WORLD ATLAS OF SEAGRASSES

Case Study 19.2 .
THE LINK BETWEEN THE SEAGRASS ZOSTERA MARINA (TS’ATS’AYEM) AND
THE KWAKWAKA'WAKW NATION, VANCOUVER ISLAND, CANADA

Photo: K. Recalma-Clutesi

3 a = ~, ~
Chief Adam Dick twisting the seagrass (Zostera marina] for
dipping in eulachon (Thaleichthys pacificus] grease. Plants were
harvested at Deep Bay on the east coast of Vancouver Island on
28 July 2002

north in the Strait of Georgia’. Large stands are
present in Boundary Bay, southern British Columbia,
Canada, and Padilla Bay and Willapa Bay,
Washington'”’. The sediments and fauna within Zostera
Japonica beds were found to be largely similar to those
found in Zostera marina beds in Oregon, although
some differences in sediment grain size and organic
constituents were observed”. Zostera japonica has
been shown to be important to resident and migratory
waterfowl in Boundary Bay'”, and is used as habitat by
epibenthic crustaceans in Padilla Bay. To the best of our
knowledge, there are no other studies linking Zostera
Japonica to secondary consumers either as a food or
habitat in North America.

The three species of the genus Phyllospadix are
found on exposed rocky coasts in the surf zone and in
tide pools in the intertidal zone where their condensed
rhizome allows them to attach to hard substrates. Three
of the five species in this North Pacific genus are found
on the west coast of North America. Turner and Lucas”

Chief Adam Dick (Kwaxsistala) and Kim Recalma-
Clutesi {(OqwiloGwa] are members of the
Kwakwaka'wakw Nation on the northeast coast of
Vancouver Island, British Columbia, Canada. Both
are keenly aware of the value of Zostera marina or
ts ‘ats ayem from oral tradition of their nation.

They recall that at Grassy Point or wawasalth,
ts ‘ats ayem is collected with a long thin pole or
k'elpawi that is stuck into the substrate, rotated to
entwine the leaves of ts‘ats‘ayem, and pulled from
the bottom to reveal leaves, rhizomes and roots. On
removal the plants are peeled exposing the tender
soft tissue of the leaf base. The leaves are then
wrapped around the rhizome, dipped in klina
{eulachon [Thaleichthys pacificus] grease) and eaten
as a ceremonial food

Whereas Grassy Point has both cultural and
ecological value, Chief Dick, Kim Recalma-Clutesi
and others of the Kwakwakawakw Nation have
concern about regional and global practices that
threaten the survival of ts ‘ats ayem.

In collaboration with Chief Adam Dick and Kim Recalma-Clutesi
(Kwakwaka'wakw Nation) and Dr Nancy J. Turner (University of
Victoria, Victoria, Canada]

and Phillips and Menez” describe the habitat and
regional distribution of the three species. Phyllospadix
serrulatus grows in the upper intertidal zone (+1.5 m to
mean lower low water) on the outer coasts of Alaska,
British Columbia, Washington and Oregon. Its
distribution is often confused with Phyllospadix
scouleri, which inhabits the lower intertidal and shallow
subtidal zone. It can be locally quite common, as on
Graham Island (Haida Gwaii]", and has a distribution
that extends from southeast Alaska to Baja California,
although it is reported to be more abundant north of
Monterey, California” “. Phyllospadix torreyi grows at
greater depths and is generally more abundant on the
exposed parts of the coast and even in tidal pools with
sandy bottoms, which are typically devoid of the other
two Phyllospadix species. The distribution of
Phyllospadix torreyi nearly overlaps Phyllospadix
scouleri, but it is more abundant south of Monterey,
California. The lack of information on its distribution
may be related to the difficulty of making collections in

energetic habitats where Phyllospadix torreyi is found’.
Whereas little is known about the biogeography of these
species, studies have revealed aspects of their
autecology and life history such as the adaptations of
seeds and roots to cling to surfaces in the rocky
intertidal zone”. Phyllospadix spp. form patches of
various sizes in the surf zones, except Phyllospadix
serrulatus, which is often found in more protected
environments”. Plants in the genus Phyllospadix are
largely clonal, and can be of a single sex due to the
dioecious nature of the genus in this region.

Few studies have documented the habitat value of
Phyllospadix; however, infaunal polychaetes are known
to live in the rhizome mats of Phyllospadix scouleri and
Phyllospadix torreyi. Surfgrass wrack, identified as
Phyllospadix torreyi, has also been found in the
macrophyte detritus layers in submarine canyons, in
southern and central California’. This decomposing
vegetation provides food and habitat for deep-sea
benthic fauna. In terms of commercially important
species, researchers in southern California found that
in their larval pelagic stage, spiny lobsters, Panulirus
interruptus, were attracted to experimental treatments
containing Phyllospadix torreyi.

Ruppia maritima is a variable plant with a number
of named varieties with characteristic features, and is
found in both freshwater and marine habitats. Ruppia
maritima var. spiralis occurs along the southern coast
of Alaska including the Alaska Peninsula, in British
Columbia and in California’. Varieties longipes and

Case Study 19.3
THE LINK BETWEEN SEAGRASSES AND HUMANS IN PICNIC COVE, SHAW
ISLAND, WASHINGTON, UNITED STATES

Picnic Cove is a sheltered embayment on the
southeast corner of Shaw Island, which is centrally
located in the San Juan Archipelago in the Pacific
Northwest (see photograph; 48°35'N 122°57'W).

It contains a Zostera marina meadow of
ca 0.05 km?! and a very small patch of Zostera
Japonica, in addition to multi-layered shell middens
on the low bank at the head of the cove, which
indicate historical use by coastal Salish people.

After European contact, Picnic Cove became a
favorite picnic spot.

It is now the site of a long-term monitoring
station for Washington State Department of Natural
Resources’ Submerged Vegetation Monitoring
Project, and is the location of quadrat-based
investigations by S. Wyllie-Echeverria, University of
Washington.

The Pacific coast of North America

maritima occur in coastal lagoons and estuaries
throughout British Columbia including the Haida
Gwaii". Further south Ruppia maritima occurs at many
sites influenced by saline water in Washington, Oregon,
California and northern Mexico'''. The leaves,
rhizomes and seeds of this plant are eaten by resident
and migratory waterfowl.

Halodule wrightii is a subtropical species that
occurs in the Gulf of California off the coast of
mainland Mexico'’”, and Zostera asiatica is known to
occur in three subtidal regions in central California,
United States, where it forms underwater forests
ca 3 m tall. More work is necessary to elucidate the
life history traits and habitat value of these species in
this region.

HISTORICAL PERSPECTIVES

Potential changes in the standing crop and areal
extent of Zostera marina have concerned natural
resource managers in the Northeast Pacific for more
than two decades® *!. This concern is primarily a
function of the habitat value provided by the large
ecosystems created by these plants. Changes in the
distribution of Zostera japonica have received less
attention. This species is an exotic but provides
valuable waterfowl habitat'”. Given this, and the fact
that Zostera japonica has not yet been shown to
negatively impact the indigenous Zostera marina,
prompts some to argue for detailed resource
inventories. Information about changes in the local or

Photos: S. Wyllie-Echeverria

The San Juan Archipelago with
insert of Picnic Cove on Shaw
Island, Washington, United
States.

203

204

WORLD ATLAS OF SEAGRASSES

Table 19.1
Zostera marina and Zostera japonica basal area cover in the
Northeast Pacific

Country —- Region Area (km’)
USA Port Clarence, AK'*:**! 42
USA Safety Lagoon, AK'*: 7! 91
USA Izembek Lagoon, AK'*”” 159.5
USA Kinzarof Lagoon, AK®: “7! 8.7
USA East Prince William Sound, AK") 4.4
Canada Roberts Bank, BC! 4
Canada Boundary Bay, BC!” 56°
USA Puget Sound, WA‘! 200
Sites within Puget Sound, WA

Padilla Bay’!

King County'**!
USA Grays Harbor, WA
USA Willapa Bay, WA’
USA Netarts Bay, OR”
USA Yaquina Bay, OR!
USA Tillamook Bay, OR'*’!
USA Coos Bay, OR!
USA Humboldt Bay, CA\“”!
USA Tomales Bay'“"!
USA San Francisco Bay
USA San Diego Bay’
Mexico Bahia San Quintin
Mexico Laguna Ojo de Liebre
Mexico Laguna San Ignacio'””

(42)

(30)

Note: * Includes both Zostera marina and Zostera japonica.

Source: Various sources - see individual references by regions.

regional abundance of the other seagrass species in
the Northeast Pacific remains largely unknown”.

Direct use of seagrasses by humans for food,
technology and medicine in the Northeast Pacific was
widespread before European contact”'™. However,
use now is quite localized and involves the weaving of
Phyllospadix spp. as a decorative element in small
personal baskets and the collection of Zostera marina
plants for green mulch or the protection of culturally
significant sites [see Case Study 19.2]. The United
States Department of Agriculture investigated the
potential use of Zostera marina as a cultivar in coastal
desert ecosystems during the 1980s, but we are
unaware of any projects to further this goal.

It is difficult to ascertain the extent of seagrass
losses due to coastal development and population
expansion since the beginning of the 20th century, as
no baseline data exist prior to the onset of these
changes. Any attempt to do so would be conjecture.

However, there is anecdotal information to suggest that
losses of Zostera marina have occurred in the two
largest estuaries on the west coast of the continental
United States - Puget Sound and San Francisco Bay”
— and we suspect losses have occurred at other sites as
well. Widespread efforts to monitor and map this
species in this region should help to determine if local
and regional losses continue in the 21st century. More
effort is needed to develop a programmatic response
for comprehensive resource inventories of the other
seven seagrass species”.

SEAGRASS COVERAGE

Whereas an estimate of the seagrass cover is
marginally possible for Zostera marina, it is not
possible for the other seven species. The conservative
estimate for Zostera marina is approximately 1000 km?
and is based on studies cited in Table 19.1 and our
personal knowledge of sites not yet mapped.

THREATS

The following discussion of the present and potential
threats to seagrasses is based on some information
documented by Phillips’, Wyllie-Echeverria and
Thom”! and studies therein, as well as a degree of
unpublished observation and conjecture.

Coastal modifications and overwater structures in
the form of ferry terminals, commercial docks, and
smaller residential docks and floats threaten the
survival of species that could be shaded in either soft-
bottom or rocky littoral zones. Shoreline armoring,
which can alter the trajectory of reflected wave energy,
may also displace seagrasses. The direct removal of
seagrasses through maintenance dredging is a rare
occurrence in the Northeast Pacific, but resuspension
of sediment associated with activity outside the
seagrass zone may reduce transmission of light and/or
bury plant populations. The deposition of upland soils
into the littoral zone as a result of industrial, com-
mercial and residential development may smother
and/or kill seagrass. Moreover, modifications to the
coastline projection may alter longshore current
patterns resulting in changes to water clarity.

Recreational watercraft (powerboats, jet skis,
etc.) may scar seagrasses in soft-bottom environments
resulting in the fragmentation of populations and the
subsequent loss of wildlife habitat. Whereas larger
vessels (ferries, freighters, tankers, etc.) rarely venture
into shallow waters, accelerated currents associated
with propeller wash connected with landing and getting
under way may displace seagrasses and affect current
flow during pollen and seed release. The swing of
anchor chains, and chains and lines connected to
permanent buoys, can uproot plants and leave
permanent scars in populations.

Rack and rope culture techniques used
in commercial shellfish culture may shade the
bottom and alter nutrient regimes and current flow,
which may result in the loss of seagrass cover in
localized areas. Human trampling associated with the
harvest of market-sized oysters from stakes used to
set and grow oyster spat can also result in reductions
in seagrass cover. Moreover, recreational clam
removal using shovels can destroy meters of
seagrass cover.

Spills associated with oil production from
offshore oil platforms such as those located on the
continental shelf of southern California or the
transport by oceanic tankers from Alaska to southern
ports in Washington and California may result in the
death of seagrasses in the littoral zone depending on
the intensity and duration of the spill. Proposals for
offshore oil development in Canada, the United States
and Mexico are most problematic in this regard.

Episodic events such as ENSO (El Niftio Southern
Oscillation) and interdecadinal variation have the
potential to alter ocean temperature and rainfall
regimes, which may affect local populations and may
also operate on the regional scale. However, a
preliminary investigation in Puget Sound found that
both biomass and productivity of a subtidal Zostera
marina population increased during an El Nino year
(1991-92) demonstrating the need for time-series
data collection to evaluate the status and trend of
seagrass ecosystems. Subduction associated with the
nearshore plate tectonic activity may alter the shape
and size of the littoral zone, reducing or eliminating
the seagrass cover, as in the case of the 1964 Alaska
earthquake.

The fragmentation of populations caused by
natural or anthropogenic disturbance can also provide
habitat for introduced species such as the mussel,
Musculista senhousia, which can in turn prevent
regrowth into fragmented areas, potentially leading toa
more widespread decline in seagrass cover.

POLICY OPTIONS AND SEAGRASS PROTECTION

It is not clear that federal, provincial or state, or local
administrative laws and ordinances recognize the
eight seagrass species in the Northeast Pacific.
However, in the United States, Canada and Mexico,
protection is afforded to Zostera marina because the
ecosystems provided by this plant are valuable habitat
for commercially and recreationally important species
such as Pacific salmon (Oncorhynchus spp.], Pacific
herring (Clupea harengus pallasi) and black brant
(Branta bernicla nigricans)’. In Washington state,
Zostera japonica is also protected, but to the best of
our knowledge no other seagrasses are protected by
administrative code in the Northeast Pacific.

coast of North America

The Pacific

Small net bag or flexible basket woven from the leaves of
Phyllospadix torreyi , found at Santa Rosa Island, California, and
dated 1100-1500 in the Common Era

Zostera marina prairie adjacent to the ferry terminal on Whidbey
Island in central Puget Sound. Prairie density is influenced by both
the overwater structure and ferry propwash

AUTHORS
Sandy Wyllie-Echeverria, School of Marine Affairs, Box 355685,
University of Washington, Seattle, WA, USA, 98105-6715.

Tel: +1 360 468 4619; 293 0939. Fax: +1 206 543 1417. E-mail:
zmseed(du.washington.edu

Josef Daniel Ackerman, Physical Ecology Laboratory, University of
Northern British Columbia, Prince George, BC, Canada, V2N 429.

Photo: W.B. Dewey, courtesy of the Santa Barbara Museum of

Photo: T. Wyllie-Echeverria

31.60-4E-1)

A
J

Natural History (cat. no. NA-CA-1

205

206 WORLD ATLAS OF SEAGRASSES

en ee SS

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20 The seagrasses of

The western North Atlantic

THE WESTERN NORTH ATLANTIC

dominant seagrass in coastal and estuarine areas
of the western North Atlantic, a region considered
here as the Atlantic coast from Quebec (Canada) at
approximately 60°N to New Jersey (United States) at
39°N''' 7. Eelgrass meadows provide a wide array of
ecological functions important for maintaining healthy
estuarine and coastal ecosystems", creating essential
habitat and forming a basis of primary production that
supports ecologically and economically important
species in the region“. The importance of eelgrass to
estuarine and coastal productivity was highlighted in the
1930s, when a large-scale die-off of eelgrass occurred
on both sides of the Atlantic due to wasting disease”.
The wasting disease has since been shown to be caused
by a pathogenic slime mold, Labyrinthula zosterae” and
has been reported in several species of Zostera". The
disease resulted in the loss of over 90 percent of the
North Atlantic eelgrass population, and this loss had a
catastrophic effect on estuarine productivity including
the disappearance of the scallop (Argopecten irradians}
fishery and drastic reduction in brant (Branta bernicla)
populations". After 30-40 years, eelgrass largely
recovered from the 1930s’ wasting disease, although in
some areas it has not regained its previous distribution”.
A second seagrass found in the region is widgeon
grass (Ruppia maritima); it occurs sporadically, mainly
in low-salinity, brackish and freshwater areas, marsh
pools and some tidal rivers. Relatively little is known
about the distribution and ecology of widgeon grass; in
most areas it is much less common than eelgrass.
Throughout the western North Atlantic region,
large meadows of eelgrass are found from Canada
through New Jersey. Despite fluctuations in some areas
due to recent episodes of wasting disease and recovery,
the trend over the past 30 years has been a steady
decrease in eelgrass distribution and abundance due to
anthropogenic impacts. In the few areas of this region
where habitat change analysis has been carried out,

Ever (Zostera marina} is the overwhelmingly

F.T. Short
C.A. Short

dramatic declines in eelgrass populations have been
documented'”'”. Despite some laws that recognize the
habitat value of eelgrass, there is no direct protection of
seagrasses in Canada or the United States.

In Canada, eelgrass is found on the east coast
south of the Arctic Circle, where it occupies vast inter-
tidal and subtidal areas. Eelgrass is found in Hudson
Bay, in the harbors of Newfoundland’s rocky shoreline
and in large meadows in the Northumberland Strait off
Prince Edward Island. Eelgrass beds circumscribe much
of Nova Scotia, though absent from the northern coast-
line of the Bay of Fundy.

In Maine, the northernmost US state on the east
coast, extensive eelgrass beds occupy the full range of
eelgrass habitat conditions. In northern Maine, with the
highest tidal ranges in the world (more than 8 ml,
eelgrass occurs mostly in protected bays and harbors, as
well as tidal rivers. In mid-coast Maine, eelgrass Is also
found on exposed coasts and around islands, for
instance in Penobscot and Casco Bays. Eelgrass
distribution in southern Maine ranges from sheltered
areas to exposed coasts, but eelgrass occurs less
frequently, due to the coastal geomorphology which is
dominated by salt marshes; widgeon grass is found in
many salt marsh ponds and tidepools.

New Hampshire, south of Maine, has a coastline
of only 27 km, and a drowned river valley estuary
consisting of the Piscataqua River and Great and Little
Bays’. Eelgrass meadows occur at the mouth of the
river in Portsmouth Harbor (see Case Study 20.1}, both
intertidally and to a depth of 12 m below mean sea level,
in small patches along the sides of the deeper river
channels, sparsely in Little Bay and in a large
monospecific expanse within Great Bay. Along the rest
of the New Hampshire coastline, eelgrass is found in
deep meadows along the exposed coast and in smaller
patches in sheltered areas and harbors. Widgeon grass
occurs in salt marsh ponds and, to a limited extent, in
upper Great Bay'®"*. Further south, the state of

207

+ ‘Sp “i a

208

WORLD ATLAS OF SEAGRASSES

Massachusetts has extensive eelgrass meadows in the
physically protected areas of Cape Cod, the offshore
islands and along its glacially striated southern
shoreline. In Boston Harbor, north of Cape Cod,
eelgrass beds are slowly recovering due to improved
water clarity from installation of an offshore sewage
discharge. South of Cape Cod, in Buzzards Bay and

Case Study 20.1
PORTSMOUTH HARBOR, NEW HAMPSHIRE AND MAINE

The western North Atlantic exhibits a range of
environmental conditions supporting eelgrass, from
pristine to highly developed and from intertidal to
deep subtidal. Cold winters produce conditions of ice
scour while summer heat can desiccate intertidal
eelgrass. Portsmouth Harbor, the mouth of the
Great Bay Estuary on the border of Maine and New
Hampshire, typifies many of these conditions. Within
the harbor, eelgrass flourishes in large intertidal
flats, often exposed for several hours around low
tide and, at high tide, submerged by over 3 m of
water. Eelgrass plants on these flats are small and
thin bladed, typically with leaves less than 30 cm
long. Across the channel in water about 3 m mean
sea level, exceptionally long-leaved (2 m) eelgrass
grows in a protected area behind a US Coast Guard
pier; the bed is subject to frequent boat activity and
mooring impacts.

Upstream from the Coast Guard station in the
highly developed commercial harbor, some eelgrass
thrives despite the nearby sewage discharge for the
city of Portsmouth, because high tidal volumes
deliver clear ocean water. However, adjacent to these
beds, dredge spoil illegally dumped in a shallow
subtidal zone buries former eelgrass habitat, while
across the channel the hardened shoreline of the
Portsmouth Naval Shipyard has virtually eliminated
eelgrass and the possibility of its recovery. In less
heavily developed areas upstream in the Piscataqua
River eelgrass has been transplanted as mitigation
for port expansion, replacing beds lost in the early
1980s to an outbreak of wasting disease®”. Some of
the transplants expanded into beds which continue to
thrive eight years after transplanting; others died
soon after transplanting due primarily to biotur-
bation’. Further up-estuary, the Piscataqua River
connects to Little Bay and then Great Bay with its
extensive intertidal eelgrass meadows.

At the mouth of Portsmouth Harbor and along
the open New Hampshire coast, eelgrass beds thrive
in the clear Gulf of Maine waters to a depth of 12 m
mean Sea level. Here, at depths below most human

Vineyard Sound, eelgrass is disappearing due to
anthropogenic impacts'”’. No known intertidal eelgrass
occurs in Massachusetts or further south. Widgeon
grass occurs in some salt marshes and brackish ponds.

Rhode Island is the smallest state in the United
States, with a long shoreline for its size. Heavily develop-
ed Narragansett Bay, a water body dominating the state,

impacts, eelgrass forms a lush green expanse only
rarely disturbed by lobster pots or fishing activity.

The mix of habitats in which eelgrass grows in
Portsmouth Harbor is representative of many of the
eelgrass habitats found throughout the western
North Atlantic. North of Portsmouth Harbor, in
Maine and Canada, eelgrass may grow in vast inter-
tidal meadows in areas of extreme tidal fluctuation.
South of Portsmouth Harbor, eelgrass is rarely found
intertidally, but often forms shallow meadows in
back barrier lagoons or salt ponds. However, the
eelgrass habitats in Portsmouth Harbor capture
many of the conditions affecting its distribution
throughout the western North Atlantic, including
large tidal variation, temperature extremes, ice, both
significant human impacts and restoration efforts,
and ongoing wasting disease episodes.

22
3.0 1.5(m0 1.5 3.0 4.5 11
Above sea level_Below sea level

Eelgrass distribu

Eelgrass distribution by depth in Portsmouth Harbor, Great Bay
Estuary, on the border of New Hampshire and Maine, United States.

Notes: Depths plotted as mean low water, with an average tidal range
of 2.7 meters. Data from 1996; eelgrass polygons were determined
from image analysis and ground-truthing of aerial photography using
the C-CAP protocol”. USCG United States Coast Guard station; PNS
Portsmouth Naval Shipyard.

has only a few remaining small eelgrass beds. More
extensive eelgrass occurs in sheltered coastal ponds be-
hind barrier beaches on the south shore of Rhode Island
but losses are occurring [see Case Study 20.2]. Widgeon
grass is found in the salt ponds in areas of groundwater
intrusion and in some freshwater ponds. Connecticut, on
Long Island Sound, has eelgrass in subtidal habitats of
some protected bays, with offshore beds in the shelter of
Fishers Island. All eelgrass beds in Connecticut occur in
the eastern third of the coastline due to poor water
quality in the western part of Long Island Sound.
Widgeon grass occurs in some salt marshes. New York
State has eelgrass only around Long Island with no
known beds on the north shore of the island, but
substantial meadows in some bays and inlets of the east
and south shores, including the Peconic Estuary.
Widgeon grass is found in the upper brackish portions of
some bays and salt marshes. New Jersey, the
southernmost state in the region, has extensive eelgrass
beds in the southern bays with Barnegat Bay having the
best-documented populations. In New Jersey, eelgrass
is predominantly found in shallow, open lagoons, while
widgeon grass occurs in brackish water areas.

Within the western North Atlantic region, eelgrass
restoration has been undertaken sporadically; consider-
able research has taken place on both transplanting and
seed planting. New transplanting methods have been
developed which simplify the transplanting process and
increase its level of success; projects have transplanted
up to 2.62 hectares of eelgrass”. These relatively small
and expensive projects also demonstrate that pres-
ervation of seagrass is vastly preferable to, and less
costly than, restoring lost habitat.

BIOGEOGRAPHY

In the western North Atlantic, eelgrass is found in both
intertidal and subtidal areas, from a depth of +2 m to
-12 m mean sea level’. Depth distribution is limited by
water clarity and the large tidal range along the North
Atlantic coastline. Eelgrass distribution ranges from
the protected low-salinity (5 psu) waters of inner
estuaries and coastal ponds to high-energy locations
fully exposed to the Gulf of Maine and the North Atlantic
with salinity of 36 psu. Eelgrass inhabits a range of
sediment conditions from soft, highly organic muds to
coarse sand and partial cobble". In a comparative study
of eelgrass populations from Maine to North Carolina,
some general patterns of variation with latitude were
found". In summary, eelgrass shoot density decreases
(1275 to 339 shoots/m’) with increasing latitude [south
to north], while leaf biomass (from 106 to 249 g dry
weight/m’] and plant size (35 cm to 125 cm average leaf
length) increase with increasing latitude". Additionally,
eelgrass leaf growth showed a significant increase
from south to north over this geographic range, froma

The western North Atlantic

Hudson LABRADOR
Bay SEA

Gulf of
St Lawrence *
St Lawrence River. ey
¥ Prince Edward Island
New .
Brunswick ~ 4
Bay of Fundy ~
ME % \
Penobscot Bay___. ps «
Maquoit Bay — Po
bi cell vy
NH Casco Bay

=~ Northumberland
Strait

ny
Boston Harbor. *
ea Sat Portsmouth Harbor

ct Ph 4x Cape Cod
©) \ >> Waquoit Bay
Narragansett Bay Se AQs
J Ninigret Pond ATL A NT IG
Long Island Sound OCEAN
Barnegat Bay

yy oe

0 200 400 600 800 1000 Kilometers
aS

Map 20.1
The western North Atlantic

low of 0.7 to a high of 19.1 g dry weight/m7/day. At the
southern end of its western North Atlantic range,
eelgrass distribution is limited by high summer
temperatures, the relatively small tidal range, and the
generally low-organic, sandy sediments of the back
barrier island lagoons. North of Cape Cod, eelgrass
grows most commonly in estuarine environments or
along the open coast where the cooler water
temperatures, higher tidal ranges, and fine-grained
organic sediments create conditions that support
larger plants and greater biomass.

Eelgrass in the western North Atlantic provides
habitat for numerous commercially important fish
and shellfish species'”. Young winter flounder
(Pseudopleuronectes americanus) concentrate in
eelgrass beds'®'; juvenile lobsters (Homarus
americanus) likewise favor eelgrass habitat and have
been shown to overwinter in burrows within eelgrass
beds'”*"; Atlantic cod {Gadus morhua] is documented
as using eelgrass beds as nursery habitat in Canada”.
Other commercially and recreationally important
species that use eelgrass habitat include smelt
(Osmerus mordax), which spends time in eelgrass as
part of its migratory cycle’, and striped bass (Morone
saxatilis) which have been tracked moving into eelgrass
beds to feed'*. Shellfish, including bay scallops
(Argopecten irradians) and blue mussels (Mytilus

209

210 WORLD ATLAS OF SEAGRASSES

COE OOO TSS 3 ess ———

edulis), have been shown to utilize eelgrass beds,
sometimes for settlement of juvenile phases and
sometimes as adults”**".

While some species associated with eelgrass
habitat are in decline, such as flounder, cod and
scallops, no species are officially designated as threat-
ened. The eelgrass limpet, Lottia alveus, became extinct
after the 1930s’ wasting disease”. The brant goose
(Branta bernicla), a species dependent on eelgrass as a
primary food source, was abundant before the 1930s
and has only partially recovered. Ducks, swans and
other species of goose use eelgrass as food and are
known to stop in eelgrass areas during migration.

HISTORICAL PERSPECTIVES

Major losses of eelgrass area in the western North
Atlantic occurred before any documentation of
distribution was accomplished. Areas such as Boston
Harbor {Massachusetts} and the Providence River
(Rhode Island) have experienced human modification
and impact for the last 400 years; sites within these
harbors which probably supported eelgrass are now
filled or degraded. Historical reports and anecdotal
information from fishermen, as well as early navigation
charts, all indicate that eelgrass extent was previously
much greater than it is today. For example, in
Narragansett Bay, Rhode Island, S. Nixon has found
charts dating to the 1700s showing eelgrass well up
into the Providence River in the upper estuary. Today,
the small amount of eelgrass in Narragansett Bay
extends only two thirds of the way up the bay”.
Quantitative studies of seagrass loss in the western
North Atlantic have occurred only in the past decade or
so, and in only a few locations.

The wasting disease of the 1930s almost
eliminated eelgrass from much of the area reported
here. This decline had major ecological impacts". The
human use of eelgrass wrack for insulation, bedding,
stuffing and as mulch, which constituted a commercial
effort in Canada and northern New England states,
dropped off during the 1930s and 1940s and never
revived". Today only a few home gardeners collect
eelgrass wrack for mulch.

AN ESTIMATE OF HISTORICAL LOSSES

Since the arrival of Europeans in the region, the western
North Atlantic has lost eelgrass populations in virtually
all areas of intense human settlement. Today, most of
these areas remain devoid of eelgrass although, with
improved sewage treatment and environmental controls
of discharge, some industrialized areas (Boston Harbor
and New Bedford Harbor, Massachusetts] are beginning
to show eelgrass recovery or are now Suitable for
restoration. Dredging, filling, marina development, boat
activity, fishing practices, hardening of the shoreline

and anthropogenic nutrient and sediment discharge all
continue to impact eelgrass habitat and areas where it
could return. The loss of eelgrass has not been
quantified in the region but certainly differs in two areas
of the coast. North of Cape Cod, Massachusetts,
eelgrass loss since settlement is estimated to be in the
order of 20 percent, while south of Cape Cod, which is
more heavily populated and industrialized, we estimate
that 65 percent of eelgrass distribution has been lost.

Two locations in New’ England have
documentation of the rapid decline of eelgrass
populations resulting from anthropogenic nutrient
loading by way of contaminated groundwater
discharge: Waquoit Bay, Massachusetts, and Ninigret
Pond, Rhode Island. In Waquoit Bay, the decline in
eelgrass associated with nitrogen loading rates was
documented in a space-for-time substitution of seven
sub-estuaries having varying degrees of housing
development'”’. The greatest eelgrass loss occurred in
the sub-estuaries with most development; overall, 60
percent of the eelgrass was lost from this estuary in
five years. In Ninigret Pond, eelgrass distributions were
compared over a 32-year period using historical and
recent maps; areal distribution of eelgrass declined by
41 percent'™”! (see Case Study 20.2).

In New Jersey’s Little Egg Harbor and Barnegat
Bay, eelgrass beds were mapped through the 1970s
and 1980s, and again in 1999°". Throughout the period,
20 km’ of eelgrass were lost. Little Egg Harbor and the
adjacent Barnegat Bay are the only two areas in New
Jersey that still support eelgrass to any extent. Other
areas in New Jersey which supported eelgrass
historically have declined and show no recovery.

Maquoit Bay in Maine (northern Casco Bay) has
been impacted by mussel dragging, a fishery practice in
which a weighted steel frame and net are dragged
through eelgrass beds to harvest blue mussels” (see
Case Study 20.3). Dragging for mussels in 1999 created
a 28.3-hectare bare area in the center of a large
eelgrass meadow”.

Great Bay, New Hampshire, experienced a
recurrence of the wasting disease in the 1980s.
Eelgrass populations went from 824 hectares in 1986 to
130 hectares in 1989. This loss, accounting for 80
percent of the eelgrass in Great Bay, was reversed by
rapid recruitment from seed production and a recovery
of eelgrass to 1015 hectares by 1996.

Changes in the physical environment that may
result from eelgrass loss include seafloor subsidence
and loss of fine particle sediments and organic
matter”, increase in sediment transport and
decrease in sediment deposition®’, and short-term
water quality degradation caused by resuspended
sediment :*”. Biological changes may include a shift
in the benthic infauna from a _ predominantly

Case Study 20.2
NINIGRET POND, RHODE ISLAND

Loss of eelgrass is a problem in shallow nutrient-
enriched estuaries of the urban and urbanizing
northeastern United States. From 1960 to 1992 there
was a Clear relationship between increased housing
density and decreased eelgrass area in Ninigret
Pond, Rhode Island, a shallow estuarine embayment
behind a barrier beach’. With increased housing
density, and corresponding increased nutrient
loading via enriched groundwater which produced
macroalgal blooms, eelgrass area in Ninigret Pond
decreased rapidly between 1974 and 1992, primarily

No
)

0.8
0,4

ww
=
=
=
Ss
S
5
5
is
&
2
a)
a
B
co
ge
on

20.50 05 1.0 1.5 20

Above sea level Below sea level

[grass distribution (km?)
Oo

[3 0.5(m0 0.5 1.0 1.5 2.0
Above sea level Below sea level

500 1000 Meters

1992

Eelgrass distribution in Ninigret Pond, Rhode Island (United
States) plotted by depth for 1974 and 1992.

Notes: Data from image analysis of aerial photography and ground-
truthing'”.

The western North Atlantic

in shallow areas of the pond [see figures). The major
loss of eelgrass in the pond occurred in shallow
areas where macroalgae and groundwater enrich-
ment had the greatest impact; eelgrass in the
deeper areas showed little change.

Maps of eelgrass distribution were compared
with the number of houses in the watershed, and a
significant linear trend of eelgrass area loss with
increased housing over time was demonstrated (see
figure]'"*!. Over the 32-year period examined, housing
in the watershed quadrupled, while eelgrass areal
distribution declined 41 percent.

In shallow estuarine systems, such as Ninigret
Pond, throughout the northeastern United States",
especially within watersheds dominated by highly
permeable sand/gravel glacial outwash aquifers,
groundwater is a dominant source of freshwater and
associated nitrate contamination'*” There is
minimal removal of nitrate as groundwater
discharges from highly permeable and low-organic
soils into estuarine shorelines. In Ninigret Pond,
groundwater discharge entering the pond was
clearly visible in thermal infrared photographs,
ultimately contributing to eelgrass loss, mostly in
shallow areas and due to macroalgal smothering’.
Subsequently, eelgrass has continued to decline in
Ninigret Pond.

@ 1974

1980 @ 1992

Eelgrass distribution (km?)

500 1000 1500 2000 2500 3000
Houses in watershed

Change in eelgrass area in Ninigret Pond, Rhode Island
(United States) plotted against increasing number of houses in
the watershed’).

211

deposit-feeding community to a suspension-feeding
community” and a reduction in epifaunal species
abundance’. These types of physical and biological

changes reduce estuarine productivity and can prevent
natural recolonization of eelgrass even when water
quality becomes adequate.

212

WORLD ATLAS OF SEAGRASSES

Table 20.1
The area of eelgrass, Zostera marina, in the western North
Atlantic

Location Area (km’} Year Method
Maine 128.10 1992-97 C-CAP
New Hampshire 11.88 996 C-CAP
Massachusetts 158.94 995 C-CAP
Rhode Island and C-CAP
a0 992 C-CAP
Connecticut 2.56 Diver survey
New York 8.50 994, Ground
(data for Peconic Estuary only) survey
New Jersey 60.83 999 Aerial photo
(data for Barnegat Bay and Little Egg Harbor only)
Total 374.37 1990s

Notes: Year indicates the date of sampling. C-CAP is the US
National Oceanic and Atmospheric Administration's Coastal

Change Analysis Program, which includes a protocol for
assessing seagrass from aerial photography’! The estimated
area of eelgrass was obtained from comprehensive surveys
within each location, except for New York and New Jersey,
where more cursory information was available. No quantitative

data were available for Canada.

Sources: Maine: S. Barker, Maine Department of Marine
Resources; New Hampshire: F.T. Short, University of New
Hampshire; Massachusetts: C. Costello, Massachusetts
Department of Environmental Protection; Rhode Island:
Narragansett Bay Estuary Program and Short et al.'"*!;
Connecticut: R. Rozsa, Connecticut Department of
Environmental Protection; New York: Peconic Estuary Program,
NY; New Jersey: Center for Remote Sensing and Spatial
Analysis, Rutgers University and Lathrop et al."

AN ESTIMATE OF PRESENT COVERAGE
Eelgrass in Canada was mapped in the early 1980s but
never digitized. The primary known areas of eelgrass
distribution in eastern Canada are summarized here.
There is eelgrass in James Bay, Quebec, part of Hudson
Bay’. Extensive eelgrass meadows are reported in the
Northumberland Strait between New Brunswick and
Prince Edward Island. Eelgrass beds are found in parts
of the St Lawrence River’. In Nova Scotia, on the
Atlantic coast, eelgrass grows in coves, tidepools and on
the exposed coast". There is probably more eelgrass in
eastern Canada than in the US states of the western
North Atlantic region combined, but no quantitative data
are available for Canada.

In the United States, current distribution by
state ranges from 250 hectares in Connecticut to over
15000 hectares in neighboring Massachusetts (Table

20.1}. The majority of eelgrass area occurs north of
Cape Cod. There are no known areal estimates for
widgeon grass.

Potential seagrass habitat is difficult to measure
because the depth distribution of eelgrass in most areas
of the northeastern United States varies depending on
water clarity. Methods have been developed for
determining potential seagrass habitat’, but have not
been comprehensively applied to the region.

A DESCRIPTION OF PRESENT THREATS
Over the last decade, eelgrass populations have
declined in some parts of New England and elsewhere
due to pollution associated with increased human
populations'*“” and episodic recurrences of the
wasting disease“, as well as other human-induced
and natural disturbances“.

Seagrass is often impacted by direct damage
from boating activities such as actual cutting by
propellers, propeller wash and boat hulls dragging
through vegetated bottom'”“". Other activities relating
to boat operation and storage that impact eelgrass
include docks which can shade the tide flat and prohibit
light penetration’, moorings which create holes
within meadows from the swing of the anchor chain”,
and channel and marina dredging".

Certain fishing and aquaculture practices also
impact eelgrass’. For example, harvesting mussels by
trawling or dragging through Zostera marina meadows
can eliminate areas of eelgrass or reduce shoot density
and plant biomass’ (see Case Study 20.3). Clam
digging can disturb eelgrass either by direct removal or
increased turbidity.

The following threats to eelgrass in the western
North Atlantic are listed roughly in order of magnitude,
except for the last three where the level of threat is
difficult to quantify. The impact of brown tide can be
severe in localized areas, occurs frequently in part of
the region (Long Island) and is unknown in others’.
The relative impacts to eelgrass health and distribution
from both climate change and sea-level rise are
presently unknown’. Wasting disease has the
potential for very great impact, as seen in the 1930s,
but most recent outbreaks of the wasting disease have
been followed by rapid recovery.

) Point and non-point source nutrient loading:
Anthropogenic inputs of nutrients from land
development, sewage disposal, agriculture and the
increase in impervious surfaces all contribute,
resulting in overenrichment which promotes algal
blooms’. In many places, nutrient-contaminated
groundwater discharge to bays and coastal ponds
is a major contributor to eelgrass loss!” *.

fe) Sediment runoff: Land disturbance and defor-
estation produce increased loads of sediment to

coastal waters, increasing and
decreasing light levels.

) Dredging: Despite laws regulating dredge and fill,
routine dredging is permitted in bays and harbors
for channel maintenance, deepening of mooring
fields, and improved boat access. All these
activities often cause direct and _ indirect
destruction of eelgrass.

) Fisheries and shellfisheries harvest practices:
Net dragging for fish and shellfish in parts of the
region can have severe local impacts, uprooting
eelgrass over large areas of the bottom. Dragging
scars persist in eelgrass beds for many years.

) Hardening of the shoreline: Creation of bulkheads
and sea walls, as well as elimination of shoreline
vegetation, increase sediment input to coastal
waters and exacerbate sediment resuspension.

) Filling: Historically, filling had a large impact on
eelgrass, but now regulations limit fill activity in
coastal waters.

0) Boating, including boat docks and moorings:
Boating activities in shallow waters resuspend
sediments and create propeller scars, damaging
eelgrass beds. Docks shade eelgrass to the point
of elimination and bed fragmentation. Moorings
create holes in eelgrass beds as the long mooring
chains, needed for the high tidal ranges in the
region, drag across the bottom.

fo) Aquaculture pens and rafts: The rapid expansion
of Atlantic salmon aquaculture in Maine and
Canada has led to deployment of pens within
sheltered estuarine areas. High nutrient loads
resulting from excess feed and fish waste create
local eutrophication conditions. Blue mussel rafts
shade the bottom and promote macroalgal
growth that causes eelgrass loss.

fo) Brown tide: Algal blooms shade and eliminate
eelgrass.

0) Climate change and sea-level rise: The potential
impacts of these changes are great".

) Wasting disease: Historically, the wasting disease
severely impacted eelgrass distribution;
currently, the disease impacts populations at less
severe levels. The conditions that led to the
widespread disease outbreak of the 1930s are not
known, but there is the potential for recurrence.

turbidity

POLICY

In Canada, seagrass receives no specific legal
protection. In the United States, seagrass is protected
under the Clean Water Act as a “special aquatic site”
and falls within Essential Fish Habitat as a “habitat area
of particular concern” under the Magnuson-Stevens
Fishery Conservation and Management Act. Neither of
these laws provides complete or direct protection of

The western North Atlantic

eelgrass, but eelgrass habitat may be given special
consideration in permit review processes.

There are no marine protected areas having
eelgrass in the western North Atlantic region. There are
five National Estuarine Research Reserve (NERR] sites

Case Study 20.3
MAQUOIT BAY, MAINE

Maquoit Bay, Maine (United States} is the
location of a vast eelgrass bed representing one
of the more extensive stands of intertidal
seagrass in the western North Atlantic.
The plants range from small, thin-bladed
eelgrass with extensive flowering in the shallow
intertidal to robust, densely growing large plants
{more than 2 m] at the lower extent of the
intertidal. This estuary in mid-coast Maine has a
tidal range of 5 m, resulting in the twice daily
exposure of much of the eelgrass; subtidal beds
extend to a depth of 10 m in the clear waters of
the outer bay. The bay is harvested for wild blue
mussels (Mytilus edulis), soft-shell clams (Mya
arenaria) and clam worms (Nereis virens}.
Fishing practices include dragging for mussels,
which has destroyed up to 0.3 km? of eelgrass in
a season (see photograph). Such uprooted areas
in the eelgrass meadow are predicted to require
10-17 years to recover via a combination of seed
recruitment and rhizome elongation’. In
contrast, the local practice of digging for clams
and clam worms with a shovel or rake results in
partial disturbance to the inshore edge of the
eelgrass meadow; the beds recover after two

Photo: J. Sowles

Maquoit Bay, Maine (United States], showing scars in the
eelgrass bed caused by mussel dragging.

Note: Below the scrape marks, the round areas of disturbance
to the bed are caused by the mussel draggers discharging
debris from their nets as they return for another pass.

213

214

Photo: F.T. Short

WORLD ATLAS OF SEAGRASSES

Students sampling intertidal Zostera marina at a SeagrassNet
monitoring site in Portsmouth Harbor, New Hampshire.

which contain eelgrass. While these reserves afford no
legal or direct protection to eelgrass, they are managed
for research purposes and knowledge of eelgrass
distribution within these reserves has been established.
Most NERR sites have programs that include public
awareness and outreach education.

There is some increasing scientific, policy and
public awareness and interest in seagrass within the
region. A group of scientists and managers meets
annually under the auspices of the US Environmental
Protection Agency to discuss eelgrass and receive an
update on research activities. A multimillion dollar port
development project in Maine was denied a construction

REFERENCES

1 Roman CT, Jaworski N, Short FT, Findlay S, Warren RS [2000].
Estuaries of the Northeastern United States: Habitat and land use
signatures. Estuaries 23(6): 743-764.

2 Short FT, Davis RC, Kopp BS, Short CA, Burdick DM [2002 in press).
Site selection model for optimal restoration of eelgrass, Zostera
marina L. Marine Ecology Progress Series.

3. Short FT, Burdick DM, Short CA, Davis RC, Morgan PA [2000].
Developing success criteria for restored eelgrass, salt marsh and
mud flat habitats. Ecological Engineering 15: 239-252.

4 Thayer GW, Kenworthy WJ, Fonseca MS [1984]. The Ecology of
Eelgrass Meadows of the Atlantic Coast: A Community Profile. US
Fish and Wildlife Service FWS/OBS-84/24. 85 pp.

5 Short FT, Burdick DM, Wolf J, Jones GE [1993]. Eelgrass in
Estuarine Research Reserves along the East Coast, USA, Part I:
Declines from Pollution and Disease and Part |: Management of
Eelgrass Meadows. Jackson Estuarine Laboratory, University of
New Hampshire, Durham, NH. 107 pp.

6 Heck KL Jr, Able KW, Roman CT, Fahay MP [1995]. Composition,
abundance, biomass and production of macrofauna in a New
England estuary: Comparisons among eelgrass meadows and
other nursery habitats. Estuaries 18(2): 379-389.

7 Rasmussen E [1977]. The wasting disease of eelgrass (Zostera
marina] and its effects on environmental factors and fauna. In:
McRoy CP, Helfferich C (eds] Seagrass Ecosystems: A Scientific
Perspective. Marcel Dekker, New York. pp 1-52.

8 Muehlstein LK, Porter D, Short FT [1991]. Labyrinthula zosterae sp.
nov., the causative agent of wasting disease of eelgrass, Zostera
marina. Mycologia 83(2): 180-191.

9 Short FT, Muehlstein LK, Porter D [1987]. Eelgrass wasting

permit in the mid-1990s based largely on its potential
impact on eelgrass habitat. The US Army Corps of
Engineers, the agency primarily responsible for dredge,
fill and other construction activities in coastal waters of
the United States, has an increasing awareness of the
importance of eelgrass habitat, and has recently
undertaken mitigation for some routine mooring area
dredge activities that impacted an eelgrass bed. Clearly,
more specific protection of seagrass habitat is needed in
the western North Atlantic.

ACKNOWLEDGMENTS

We thank the University of New Hampshire Agricultural Experiment Station
for support. Thanks to Jamie Adams for GIS contributions. Eelgrass dis-
tribution coverages and data were provided by Seth Barker, Maine
Department of Marine Resources; Charles Costello, Massachusetts
Department of Environmental Protection; the Narragansett Bay Estuary
Program, Rhode Island; Ron Rozsa, Connecticut Department of Environ-
mental Protection; the Peconic Estuary Program, New York; Richard
Lathrop, Grant F. Walton Center for Remote Sensing and Spatial Analysis,
Rutgers University, New Jersey. This is Jackson Estuarine Laboratory
contribution number 392 and AES scientific contribution number 2144.

AUTHORS

Frederick T. Short and Catherine A. Short, University of New Hampshire,
Jackson Estuarine Laboratory, 85 Adams Point Road, Durham, NH 03824,
USA. Tel: +1 603 862 2175. Fax: +1 603 862 1101. E-mail:
fred.short(@unh.edu

disease: Cause and recurrence of a marine epidemic. Biology

Bulletin 173; 557-562.

Muehlstein LK, Porter D, Short FT [1988]. Labyrinthula sp., a

marine slime mold producing the symptoms of wasting disease in

eelgrass, Zostera marina. Marine Biology 99: 465-472.

Milne LJ, Milne MJ [1951]. The eelgrass catastrophe. Scientific

American 184: 52-55.

Short FT, Burdick DM [1996]. Quantifying eelgrass habitat loss in

relation to housing development and nitrogen loading in Waquoit

Bay, Massachusetts. Estuaries 19(3): 730-739.

Short FT, Burdick DM, Granger S, Nixon SW [1996]. Long-term

decline in eelgrass, Zostera marina L., linked to increased housing

development. In: Kuo J, Phillips RC, Walker DI, Kirkman H [eds]

Seagrass Biology: Proceedings of an International Workshop,

Rottnest Island, Western Australia, 25-29 January 1996. University

of Western Australia, Nedlands, Western Australia. pp 291-298.

14 Short FT ed] [1992]. The Ecology of the Great Bay Estuary, New
Hampshire and Maine: An Estuarine Profile and Bibliography.
Jackson Estuarine Laboratory, University of New Hampshire,
Durham, NH. 222 pp.

15 Richardson FD [1980]. Ecology of Ruppia maritima L. in New
Hampshire [USA] tidal marshes. Rhodora 82: 403-439.

16 Richardson FD [1983]. Variation, Adaptation, and Reproductive
Biology in Ruppia maritima L. Populations from New Hampshire
Coastal and Estuarine Tidal Marshes. PhD dissertation, University
of New Hampshire, Durham. 147 pp.

17 Kurland JM [1994]. Seagrass habitat conservation: An increasing
challenge of coastal resource management in the Gulf of Maine. In:
Wells PG, Ricketts PJ (eds) Coastal Zone Canada 94: Cooperation
in the Coastal Zone: Conference Proceedings. Vol. 3. Coastal Zone

ro)

ARCTIC
OCEAN

PACIFIC OCEAN

0. 300 600 900 1200 1500 km
a

Regional map: North America

Gulf of

Mexico

Xll

WORLD ATLAS OF SEAGRASSES

DIVERSITY OF SEAGRASS HABITATS

s of Zostera marina in the Netherlands

Enhalus acoroides and Cymodocea rotundata in Puerto

Galera, Philippines

Halophila tricostata in the Great Barrier Reef,

ja hemprichii on a high energy shore of Kosrae, Federated

Queensland, Australia

Intertidal Thalass

States of Micronesia

id rock with kelp in Ensenada, Mexico

Phyllospadix torreyi, growing on sol

Canada Association, Bedford Institute of Oceanography, Dartmouth,
Nova Scotia.

Armstrong MP [1995]. A Comparative Study of the Ecology of
Smooth Flounder, Pleuronectes putnami, and Winter Flounder,
Pleuronectes americanus, from Great Bay Estuary, New
Hampshire. PhD dissertation, University of New Hampshire. 147 pp.
Short FT, Burdick DM, Bosworth W, Grizzle RE, Davis RC [1998].
New Hampshire Port Authority Mitigation Project Progress Report,
June 1998. Prepared for the New Hampshire Port Authority and the
New Hampshire Dept. of Transportation. 59 pp.

Karnofsky EB, Atema J, Elgin RH [1989]. Natural dynamics of
population structure and habitat use of the lobster, Homarus
americanus, in a shallow cove. Biological Bulletin 176: 247-256.
Short FT, Matso K, Hoven H, Whitten J, Burdick DM, Short CA
[2001]. Lobster use of eelgrass habitat in the Piscataqua River on
the New Hampshire/Maine Border, USA. Estuaries 24: 249-256.
Gotceltas V, Fraser S, Brown JA [1997]. Use of eelgrass beds
(Zostera marina) by juvenile Atlantic cod (Godus morhua). Canadian
Journal of Fisheries and Aquatic Sciences 54: 1306-1319.
Normadeau Associates [1979]. Piscataqua River Ecological Studies,
1978 Monitoring Studies, Report No. 9 for Public Service Company
of New Hampshire. Volume |: Physical/chemical Studies, Biological
Studies. Normadeau Associates, Inc., Bedford, NH. 479 pp.

Short FT [1988]. Eelgrass-scallop Research in the Niantic River.
Waterford-East Lyme, Connecticut Shellfish Commission, Final
Report. 12 pp.

Newell CR, Hidu H, McAlice BJ, Podniesinski G, Short F, Kindblom
L [1991]. Recruitment and commercial seed procurement of the
blue mussel Mytilus edulis in Maine. Journal of the World
Aquaculture Society 22: 134-152.

Grizzle RE, Short FT, Newell CR, Hoven H, Kindblom L [1996].
Hydrodynamically induced synchronous waving of seagrasses:
“Monami” and its possible effects on larval mussel settlement.
Journal of Experimental Marine Biology and Ecology 206: 165-177.
Carlton JT, Vermeij GJ, Lindberg DR, Carlton DA, Dudley EC [1991].
The first historical extinction of a marine invertebrate in an ocean
basin: The demise of the eelgrass limpet Lottia alveus. Biological
Bulletin 180: 72-80.

Nixon SW, Personal communication.

Wyllie-Echeverria S, Cox PA [1999]. The seagrass [Zostera marina,
[ZOSTERACEAE]] industry of Nova Scotia (1907-1960). Economic
Botany 53: 419-426.

Wyllie-Echeverria S, Arzel P, Cox PA [2000]. Seagrass conservation:
Lessons from ethnobotany. Pacific Conservation Biology 5: 329-
335.

Lathrop RG, Styles RM, Seitzinger SP, Bognar JA [2001]. Using GIS
modeling approaches to examine the spatial distribution of
seagrasses in Barnegat Bay, New Jersey. Estuaries 24: 904-916.
Neckles HA, Short FT, Barker S, Kopp B [2001]. Evaluation of
Commercial Fishing Impacts to Eelgrass in New England.
Abstract. Estuarine Research Federation Conference, Nov. 3-8, St
Petersburg, FL.

Barker S, Marine Department of Marine Resources. Personal
commmunication.

Christiansen C, Christoffersen H, Dalsgaard J, Nornberg P [1981].
Coastal and nearshore changes correlated with die-back in
eelgrass (Zostera marina]. Sedimentary Geology 28: 168-178.

Hine AC, Evans MW, Davis RA, Belknap DA [1987]. Depositional
response to seagrass mortality along a low-energy, barrier-island
coast: West-central Florida. Journal of Sedimentary Petrology
573): 431-439.

Duarte CM [1995]. Submerged aquatic vegetation in relation to
different nutrient regimes. Ophelia 41: 87-112.

Olesen B [1996]. Regulation of light attenuation and eelgrass
Zostera marina depth distribution in a Danish embayment. Marine
Ecology Progress Series 134: 187-194.

The western North Atlantic

215

Connolly RM [1995]. Effects of removal of seagrass canopy on
assemblages of small, motile invertebrates. Marine Ecology
Progress Series 118: 129-194.

Lalumiere R, Messier D, Fournier JJ, McRoy CP [1994]. Eelgrass
meadows in a low arctic environment, the northeast coast of James
Bay, Quebec. Aquatic Botany 47: 303-315.

Wyllie-Echeverria S. Personal commmunication.

Robertson Al, Mann KH [1984]. Disturbance by ice and life history
adaptations of the seagrass, Zostera marina. Marine Biology 80:
131-142.

Dobson JE, Bright EA, Ferguson RL, Field DW, Wood LL, Haddad
KD, Iredale H, Jensen JR [1995]. NOAA Coastal Change Analysis
Program (C-CAP]: Guidance for Regional Implementation. NOAA
Technical Report NMFS 123. US Dept. of Commerce, Seattle,
Washington. 92 pp.

Kemp WM, Boyton WR, Stevenson JC, Twilley RR, Means JC [1983].
The decline of submerged vascular plants in the upper Chesapeake
Bay: A summary of results concerning possible causes. Marine
Technology Society Journal 7: 78-89.

Short FT, Mathieson AC, Nelson JI [1986]. Recurrence of the
eelgrass wasting disease at the border of New Hampshire and
Maine, USA. Marine Ecology Progress Series 29: 89-92.

den Hartog C [1994]. The dieback of Zostera marina in the 1930s in
the Wadden Sea: An eye witness account by van der Werff A.
Netherlands Journal of Aquatic Ecology 28: 51-54.

Short FT, Wyllie-Echeverria S [1996]. Natural and human-induced
disturbance of seagrasses. Environmental Conservation 23(1):
17-27.

Zieman J [1976]. The ecological effects of physical damage from
motorboats on turtle grass beds in southern Florida. Aquatic
Botany 2: 127-139.

Walker DI, Lukatelich RJ, Bastyan G, McComb AJ [1989]. Effect of
boat moorings on seagrass beds near Perth, Western Australia.
Aquatic Botany 36: 69-77.

Burdick DM, Short FT [1998]. Dock Design with the Environment in
Mind: Minimizing Dock Impacts to Eelgrass Habitat. UNH Media
Services, Durham, NH. CD-ROM.

Burdick DM, Short FT [1999]. The effects of boat docks on eelgrass
beds in coastal waters of Massachusetts. Environmental
Management 23: 231-240.

Short FT, Jones GE, Burdick DM [1991]. Seagrass decline:
Problems and solutions. Proceedings of Seventh Symposium on
Coastal and Ocean Management/ASCE. Long Beach, CA

ASMFC [1999]. Evaluating Fishing Gear Impacts to Submerged
Aquatic Vegetation and Determining Mitigation Strategies. Atlantic
States Marine Fisheries Commission, Washington, DC.

Dennison WC, Marshall GJ, Wigand C [1989]. Effect of “brown tide”
shading on eelgrass (Zostera marina L.} distributions. Coastal and
Estuarine Studies 35: 675-692.

Short FT, Neckles H [1999]. The effects of global climate change on
seagrasses. Aquatic Botany 63: 169-196.

Short FT, Burdick DM, Kaldy JE [1995]. Mesocosm experiments
quantify the effects of eutrophication on eelgrass, Zostera marina
L. Limnology and Oceanography 40: 740-749.

Deegan LA, Wright A, Ayvazian SG, Finn JT, Golden H, Merson RR,
Harrison J [2002]. Nitrogen loading alters seagrass ecosystem
structure and support of higher trophic levels. Aquatic
Conservation 12(2): 193-212.

Burdick DM, Short FT, Wolf J [1993]. An index to assess and
monitor the progression of the wasting disease in eelgrass, Zostera
marina. Marine Ecology Progress Series 94: 83-90.

Davis R, Short FT [1997]. An improved method for transplanting
eelgrass, Zostera marina L. Aquatic Botany 59: 1-16.

Valiela |, Costa J, Foreman K, Teal JM, Howes B, Aubrey D [1990].
Transport of groundwater-borne nutrients from wastelands and
their effects on coastal waters. Biogeochemistry 10: 177-197.

216

WORLD ATLAS OF SEAGRASSES

21 The seagrasses of

THE MID-ATLANTIC COAST OF
THE UNITED STATES

includes four states: Delaware, Maryland, Virginia

and North Carolina. It is characterized by
numerous estuaries and barrier-island coastal lagoons
with expansive salt marshes and seagrass beds in most
shallow-water areas". There are no rocky shores. Hard
substrates are either man-made [rock jetties and
riprap or wood pilings) or biogenically generated
(oyster and worm reefs}. Sediments are predominantly
quartz sand in shallow exposed areas with finer grain
sediments in deeper or well-protected areas. Marsh
peat outcroppings or cohesive sediments are
sometimes found in the subtidal areas adjacent to
eroding marshes. Climatic variations are large with air
temperatures ranging from -10°C to 40°C and water
temperatures ranging from O°C to 30°C. Tides are
equal and semi-diurnal but relatively small in range
(maximum of 1.3 m during spring tides).

The largest estuary in the country, the
Chesapeake Bay {18130 km/’}, occurs in this area. Its
watershed covers 165760 km’, drains from six states
and is inhabited by more than 15 million people.
Additionally, the estuarine system of the state of North
Carolina is the third largest in the country,
encompassing more than 8000 km’ with a watershed of
more than 63000 km’. Other estuaries in the mid-
Atlantic include the Delaware Bay and a series of
barrier-island coastal lagoons.

Flowering aquatic plants are common in the
estuaries of the mid-Atlantic region. They are often
referred to as submersed aquatic vegetation [SAV]. This
term includes all flowering aquatic plants from
freshwater to marine habitats. The term “seagrass” is
used exclusively for species that occur in the higher
salinity zones (>10 psu)”. Only three seagrass species
are found in the mid-Atlantic region: Halodule wrightii
{shoal grass), Ruppia maritima (widgeon grass) and
Zostera marina (eelgrass). The northernmost area of
the mid-Atlantic (Delaware estuaries and bays) is

Ts mid-Atlantic region of the United States

E.W. Koch
R.J. Orth

presently unvegetated. In contrast, the middle and
southern areas are colonized by monospecific stands or
by intermixed beds of seagrass (usually two species).
The beds can vary from small and patchy to quite
extensive. The largest seagrass bed in the Chesapeake
Bay is composed of a mixture of Zostera marina and
Ruppia maritima and covers 13.6 km’.

Seagrass habitat provides food and refuge from
predators for a wide variety of species, some of which
have recreational and commercial significance. The
invertebrate production in just one seagrass bed in the
lower Chesapeake Bay was estimated to be 0.4 metric
tons per year’. Seagrass beds in Chesapeake Bay are
reported to be important nursery areas for the blue
crab, Callinectes sapidus, whose commercial harvest
can yield close to 45000 metric tons in a good year.
The bay scallop (Argopecten irradians) fishery is also
closely tied to seagrass abundance because the larval
stage attaches its byssal thread to seagrass leaves.
The decline of seagrasses in Virginia's coastal bays in
the 1930s led to the complete disappearance of the bay
scallop, and loss of a substantial commercial fishery.
Seagrasses have not returned to this region, nor have
bay scallops. Other important local fisheries
sometimes (but not always) associated with seagrasses
include hard clams (Mercenaria mercenaria) and fish
of commercial and recreational importance, e.g.
striped bass (Morone saxatalis], spotted sea trout
(Cynoscion nebulosus}, spot (Leiostomus xanthurus)
and gag grouper (Mycteroperca microlepis)".

BIOGEOGRAPHY

The state of North Carolina is an interesting
biogeographical boundary for seagrasses in the North
Atlantic. On the east coast of the United States it is the
southernmost limit for the distribution of the
temperate seagrass Zostera marina and the
northernmost limit for the distribution of the tropical
seagrass Halodule wrighti/*'. Due to their existence at

The mid-Atlantic coast of the United States

the limits of their thermal tolerance, the seagrasses
found in this boundary zone are expected to show early
effects of global warming in this area. Ruppia maritima
is able to tolerate a broad range of temperatures and is
found throughout the mid-Atlantic region and possibly
along the coasts of South Carolina and Georgia.

Seagrasses in the mid-Atlantic region occur in
wave-protected habitats. The extensive lagoon system
(from Delaware to North Carolina) is delimited to the
east by long barrier islands. These islands provide
shelter from oceanic waves, making the lagoons ideal
habitats for Zostera marina, Ruppia maritima and
Halodule wrightii. No seagrasses (but seagrass wrack,
including reproductive shoots with viable seeds) have
been reported for the exposed shores of the Atlantic
Ocean. The seagrasses in the mid-Atlantic region also
colonize areas covering a wide range of salinities: from
full-strength seawater (30-32 psu] near the mouths of
the estuaries to mesohaline zones (10-20 psu) in the
middle portion of the estuaries. Due to its ability to
tolerate relatively low salinities, Ruppia maritima is
usually the seagrass that extends farthest into the
estuaries.

The distribution of seagrasses in the mid-Atlantic
region is restricted to shallow waters because of the
high suspended sediment and nutrient loadings leading
to relatively turbid waters in seagrass habitats [light
attenuation coefficients higher than 1 per m’ are quite
common). In relatively pristine areas (North Carolina
sounds adjacent to barrier islands and Chincoteague
Bay], the maximum depth to which seagrasses grow
can be as great as 2 m, while in habitats associated with
the mainland and eutrophic [i.e. nutrient enriched)
conditions (Chesapeake Bay, North Carolina sounds
near the mainland), the maximum vertical distribution
only reaches depths of 0.5 to 1.0 m”®!. In other areas,
such as the Delaware coastal bays, seagrasses are
almost completely absent due to high water turbidity.

HISTORICAL PERSPECTIVES
No record exists of the extent of the vegetation prior to
the 1930s, but anecdotal evidence of historical changes
in eelgrass” suggest that seagrasses occurred in the
Chesapeake Bay region in the mid- to late 1800s'"". In
the pre-colonial period (1800s), seagrasses are
believed to have formed extensive beds in estuaries and
lagoons in the mid-Atlantic region covering the coastal
bays in their entirety. It is not known to what depths
seagrasses used to grow in the estuaries, but it may
have been as deep as 4 m. When Zostera marina beds
were extensive, the seagrass was used for packing and
upholstery stuffing. It was also used for insulation of
buildings due to its low flammability and excellent
insulating properties.

A massive decline of seagrasses in the mid-

Delaware
Bay

Delaware »— ~ Rehoboth Bay

Assateague Island
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Chincoteague aN
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ye
Chesapeak ?
esapeake
iq Bay ¢

sa ~~ Currituck Sound
Virginia a
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anc
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5

Albee
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, a

Pamlico
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: af Raleigh Bay

‘ Core Sound
a” ve" Cape
ys Lookout

0 10 20 30 40 50 Kilometers az
_ Sneads Ferry

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Map 21.1
The mid-Atlantic coast of the United States

Atlantic region occurred in the 1930s as Zostera marina
was affected, and in many locations eliminated, by
wasting disease'”'”. The loss of eelgrass was reported
throughout the northern Atlantic. In some areas in the
mid-Atlantic (Chesapeake Bay, Chincoteague Bay,
North Carolina sounds), eelgrass beds slowly
recovered. In the Delaware coastal bays [Indian River
and Rehoboth Bays], recovery of eelgrass through the
1950s ended, apparently due to eutrophication. In the
coastal bays of the lower eastern shore of Virginia,
eelgrass was completely eliminated and never

217

218

WORLD ATLAS OF SEAGRASSES

Figure 21.1

Seagrass distribution (mainly Zostera marina and Ruppia maritima
but possibly also a few hectares of other SAV species} in
Chesapeake Bay

nN
a
oO

nN
So
r—

a
oO

1986 86 88 9 92 9% %%6 98 2000

Source: Based on data from the Virginia Institute of Marine Science SAV
mapping program

Figure 21.2

Changes in seagrass (Zostera marina and Halodule wrightil)
distribution in the Cape Lookout area (southern Core Sound,
North Carolina) between 1985 and 1988

Note: Areas of seagrass coverage that did not change between the two

years are shown in green cross-hatch; areas of gain are shown by the
vertical white hatching and areas of loss are shown by the horizontal white
hatching

Source: Poster produced by the Beaufort Lab entitled SAV Habitat in 1985

Ferguson, Lisa Wood and Brian Pawlak

recovered. The decline in the 1930s was complicated by
a hurricane of unprecedented proportions in August
1933. There is no evidence of eelgrass ever being
present in Delaware Bay.

PRESENT DISTRIBUTION

Although rare, sparse and small eelgrass beds are
present in the coastal bays of Delaware (a result of
restoration efforts). They are too small to map and also
ephemeral in nature. There is very little seagrass in the
state of Delaware.

Unprecedented changes to eelgrass populations
in Chesapeake Bay occurred following Tropical Storm
Agnes in June 1972. Eelgrass beds in the upper
portions of Chesapeake Bay were the most influenced
by the effects of the runoff [low salinities and high
turbidity], which occurred during the peak growth
period for eelgrass. While the distribution of
seagrasses in Chesapeake Bay (Maryland and Virginia]
had been partially documented in 1971 and 1974, the
first baywide survey was conducted in 1978, and annual
surveys began in 1984. Based on these data, seagrass
distribution in Chesapeake Bay was observed to
increase 63 percent between 1985 and 1993, but
distribution then declined 27 percent between 1993 and
2000 (Figure 21.1). In contrast, from 1986 to 2000,
seagrass distribution in the coastal bays of Maryland
and Virginia increased 238 percent [see Case Study
21.1). Presently, the seagrasses in Chesapeake Bay
show declines in some areas while recovering in
others. There is great interannual variation, making it
difficult to estimate the area of seagrass.

In North Carolina, where the seagrass habitats
are dominated by shallow areas protected by extensive
barrier islands, seagrass distribution has only recently
been mapped. Core Sound was mapped in 1988 and
inside of Cape Hatteras in 1990. The area south of Cape
Lookout has not yet been mapped but it is known that
no seagrasses are found south of Sneads Ferry (80 km
north of the city of Wilmington)". The lack of
seagrasses in Albermarle Sound is believed to be the
result of the high water turbidity in this area. The
western portion of Pamlico Sound is also mostly
unvegetated due to the long fetch and consequent high
turbidity during strong wind events. Although there has
not been a sustained effort to map seagrasses in North
Carolina, researchers have been investigating aspects
of seagrass ecology and report no noticeable changes
in species composition or distribution since the
1970s'". One quantitative effort (Figure 21.2) confirms
this. In the Core Sound area [between Drum Inlet and
Cape Lookout) seagrass distribution was generally
consistent between the two years in which it was
mapped. In 1985 there were 7 km? of seagrass and in
1988 there were 6.6 km’, only a 5.7 percent loss. There

were 151 beds in 1985 and 149 in 1988. Two
anthropogenic impacts on seagrasses were noted
between 1985 and 1988: a clam harvesting operation
dug up seagrasses, while in another area dredge spoil
was deposited on a seagrass bed"! In North Carolina,
seagrass beds have been relatively stable since the
1970s at approximately 80 km*. It is not clear if
seagrass beds in North Carolina also suffered the
declines observed in the Chesapeake Bay before
researchers began to work in these habitats in the
1970s. Zostera marina was affected by the wasting
disease of the 1930s in North Carolina, but recovered,
as in Chincoteague Bay.

PRESENT THREATS

The main threats to seagrasses in the mid-Atlantic
region today are eutrophication and high turbidity from
poor land-management practices. As the coastal zone
continues to be developed, nutrient loads and
suspended sediments in the water column tend to
increase”. These nutrients may come from well-
defined sources such as a sewage treatment plant, a
pig farm or a golf course, but a large amount of
nutrients also comes from non-point sources such as
farmland and groundwater nutrient enrichment by
septic systems. As a result of increased nutrient
loading, epiphytic algae may grow directly on the
seagrass leaves while blooms of phytoplankton or
macroalgae may occur in the water column. These
processes decrease the amount of light that reaches
the seagrasses and cause their decline or death. Most
water bodies in the mid-Atlantic are now
phytoplankton dominated, and the few pristine lagoons
are showing signs of deterioration resulting from
blooms of nuisance macroalgae such as
Chaetomorpha linum and Ulva lactuca {mats up to 1.5
m thick]. These algal blooms have adversely impacted
healthy seagrass beds (see Case Study 21.1] as well as
recent eelgrass restoration efforts in the Delaware
coastal bays.

Seagrass beds are vulnerable to disruption by
commercial fishing practices, especially clam and
scallop dredging. Hydraulic clam dredging digs deep
trenches or circles into the sediments [see Case Study
21.1). If these are vegetated by seagrasses, the plants
are lost and the recovery is relatively slow'®. Clam
dredging also has a negative impact on other fisheries.
The trenches caused by hydraulic clamming in
seagrass beds prevent crabbers from pulling their
scrapes through the seagrass beds (a practice that
causes relatively little damage to the plants], directly
threatening their livelihood.

As coastal areas become more heavily populated,
more individuals also want to enjoy water-related
activities. Boat-generated waves and turbulence have a

The mid-Atlantic coast of the United States

negative impact on seagrasses and their habitats!”
There is also no doubt that propeller scars have a
detrimental effect on seagrasses’. The effect is
similar to that described for clam dredging although
the scars are narrower. This problem is most severe in
North Carolina but has also been documented in
Maryland and Virginia.

Dredging and maintenance dredging of channels
is a threat to seagrasses in all mid-Atlantic states. This
operation increases the turbidity of the water, may bury
seagrasses and may increase the nutrient
concentration in the water column. Regulations in
North Carolina suggest [but do not require) that
damage to seagrasses be minimized during dredging
activities. Maryland is currently re-evaluating its
dredging regulations.

Sea-level rise has the potential to pose a threat to
seagrasses in the mid-Atlantic. The vulnerability of
coastal zones to sea-level rise has been classified as
very high in this region, the highest risk on the east
coast of the United States. Unfortunately, our
understanding of how sea-level rise affects seagrasses
is in its infancy. It is known that sea-level rise leads to
marsh erosion”! and the eroded sediments are then
transported to coastal waters where seagrass beds
may occur. This may lower the light available to
seagrasses and may lead to their decline or loss.
The loss of the seagrasses could then lead to further
coastal erosion due to the loss of wave attenuation
previously provided by the seagrasses.

Although a natural event, a storm can be
detrimental to seagrasses. Hurricanes are quite
common in the mid-Atlantic, especially in the state of
North Carolina, and have shown to be detrimental to
seagrasses by removing the plants, eroding the
sediment, burying seagrass beds and/or increasing
turbidity of the water”. It is expected that with global
warming hurricane frequency and intensity will
increase. With that, the threat to seagrasses is also
expected to increase. However, little quantitative data
exist on the effects of hurricanes on long-term stability
of seagrass beds in this region. Hurricanes are more
frequent in the fall period (September and October) and
itis possible that water quality effects may be marginal
as temperatures are lower and growth is generally less
than in the spring.

POLICIES AND REGULATIONS

No state or federal marine parks exist in the mid-
Atlantic region, but several protected islands include
the adjacent waters in their jurisdiction. The national
estuarine research reserves in Maryland and North
Carolina include seagrass habitats, although no
protection is afforded by this designation. The
Assateague Island National Seashore Park protects its

219

220 WORLD ATLAS OF SEAGRASSES

adjacent seagrasses. The state of Delaware currently
has no protection for seagrasses in its regulatory
framework. The total area of protected seagrass beds
has not been identified for the mid-Atlantic.

At the federal level, seagrasses are afforded
some protection under Section 404 of the Clean Water
Act (33 USC 1341-1987] and Section 10 of the Rivers
and Harbors Act {33 USC 403}, which regulate the
discharge of dredged or fill material into US waters.
Authority for administering the Clean Water Act rests
with the US Environmental Protection Agency.
Seagrass protection under the Act is provided by a
federal permit program that is delegated to and
administered by the US Army Corps of Engineers.
Potential impacts on “special aquatic sites”, such as
seagrass beds, are considered in the permit review

Case Study 21.1

Chincoteague Bay is one of the most pristine water
bodies in the mid-Atlantic. It is a relatively shallow
coastal lagoon {average depth 1.2 m) with limited
freshwater input and long residence times (flushing
of 7.5 percent per day). Salinities are close to those
of seawater (26-31 psu] and nutrient levels are
relatively low (<10 uM total nitrogen, <4 pM
phosphate”). The western shore of Chincoteague
Bay is characterized by extensive salt marshes and
isolated, small towns representing an area of low
developmental pressure [less than 0.04 person per
hectare). The eastern shore is located adjacent to an
unpopulated [but accessible to tourists) barrier
island (Assateague Island National Seashore) with

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o
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o
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o
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aD
oO
o

Recovery and recent decline of seagrass (Zostera marina and
Ruppia maritima) distribution in Chincoteague Bay.

process. Section 10 of the Rivers and Harbors Act, also
administered by the Army Corps, regulates all activities
in navigable waters including dredging and placement
of structures.

On a regional basis, considerable and cooperative
efforts by scientists, politicians, federal and state
resource managers, and the general public have
developed policies and plans to protect, preserve and
enhance the seagrass populations of Chesapeake
Bay’. The foundation for the success of these
management efforts has been the recognition of the
habitat value of seagrasses to many fish and shellfish,
and the elucidation of linkages between seagrass
habitat health and water quality conditions. Because of
these linkages, the distribution of seagrasses in
Chesapeake Bay and its tidal tributaries is being used

SEAGRASSES IN CHINCOTEAGUE BAY: A DELICATE BALANCE BETWEEN
DISEASE, NUTRIENT LOADING AND FISHING GEAR IMPACTS

an extensive dune system along the Atlantic coast
and marshes along the Chincoteague Bay shoreline.

Seagrasses in Chincoteague Bay are found
almost exclusively on the eastern shores. Due to its
relatively shallow depth, it is believed that the entire
bay used to be colonized by Zostera marina. In the
1930s, Zostera marina disappeared as a result of
wasting disease after which it slowly began to
recolonize the eastern shore. The recovery of the
seagrasses in Chincoteague Bay has been well
documented since 1986 (see figure, left]. Although
there was a 40 percent increase in the human
population on the western shore of Chincoteague
Bay between 1980 and 2000, the total nitrogen and
phosphorus loadings declined between 1987 and
1998 [in some areas as much as 50 percent). This is
believed to be due to the construction of sewage
treatment plants and the reduction of the amount of
fertilizers used on the farms west of Chincoteague
Bay. As a result, phytoplankton concentration is low
and light penetration relatively deep. Seagrasses
flourished during this period showing a 238 percent
increase in distribution between 1986 and 1999. In
1996, seagrasses even began colonizing the
western shore which had remained unvegetated
since the 1930s.

One of the first threats to seagrass in
Chincoteague Bay since its decimation in the 1930s
came from a fisheries practice’. In 1997, severe
damage to the seagrass beds was noted and
attributed to two types of hard clam fishing gear:
hydraulic dredges and modified oyster dredges (see

The mid-Atlantic coast of the United States

as an initial measure of progress in the restoration of
living resources and water quality. Restoration targets
and goals have been established to link demonstrable
improvements in water quality to increases in seagrass
abundance”. The states of Maryland and Virginia each
have separate regulatory agencies to oversee activities
that could be injurious to seagrass populations. Both
states are committed to protecting seagrass habitat
while maintaining viable commercial fisheries and
aquaculture operations.

Maryland State Code COMAR 4-213 specifically
prohibits damage to seagrasses for any reason except
for commercial fishing activities and certain specific
situations such as clearing seagrasses from docks,
piers and navigable waters. If seagrasses will be
adversely affected, the Maryland Department of the

photograph, right]. The seagrass area affected by
hydraulic dredging increased from 0.53 km? in 1996
to 5.08 km? in 1997, while modified oyster dredge
scars increased from 10 in 1995 to 218 scars in 1997.
Analysis of the recovery from both types of scarring
showed that some scars require more than three
years to revegetate to undisturbed levels. Once
notified of these impacts, resource managers in
Maryland and Virginia responded within several
months to protect seagrasses through law and
regulation preventing clam dredging within seagrass
beds. In Virginia, the new regulation was successful
in reducing scarring, but required later revisions for
successful enforcement. In Maryland, however,
procedural requirements to fully implement the law
required additional time, during which scarring
increased to 12.57 km* in 1999. This issue has
demonstrated the importance of close linkages
between the scientific research community, poli-
ticlans, management agencies, law enforcement
agencies and the public, as well as the importance
of sanctuaries or protection zones to prevent
damage to critical seagrass habitats.

Over the last three years, seagrasses in
Chincoteague Bay have been exposed to another
stress: the blooms of the nuisance macroalga
Chaetomorpha linum, suggesting that this formerly
pristine area may be experiencing eutrophication.
Indeed, nutrient data shows a renewed increase in
total nitrogen and phosphorus loads in 1999 and
2000. While pristine systems are dominated by
seagrasses, systems in the early and late stages of
eutrophication are dominated by macroalgae and/or
phytoplankton, respectively®”. The macroalgal mats
observed in Chincoteague Bay over the last two
years can be as thick as 1.5 m, killing the

Environment and the Maryland Department of Natural
Resources are responsible for issuing a permit, which
includes a plan showing the site at which the activity is
proposed, a dated map of current seagrass distribution
and the extent of seagrass to be removed. Maryland
does prohibit one type of commercial fishing activity,
hydraulic clam dredging, in specific regions of its state
waters. Hydraulic clam dredging is prohibited both
within a specified distance from shore, which varies by
political boundaries (NRA 4-1038], and in existing
seagrass beds [NR 4-1006.1), as determined by annual
aerial mapping surveys.

In Virginia, permits to use state-owned
submerged lands now include seagrass presence as a
factor to be considered in the application process (Code
28.2-1205 (A), amended in 1996). On-bottom shellfish

seagrasses beneath and leaving long scars visible
via aerial photography. Managers are currently
attempting to determine the source of the nutrients
fueling these macroalgal blooms and threatening
the seagrasses of Chincoteague Bay.

Photo: B. Orth

Aerial photograph taken in 1998 of a portion of Chincoteague
Bay, Virginia, seagrass bed showing damage to the bed from a
modified oyster dredge.

Notes: Arrows point to circular "donut-shaped” scars created by
the dredge being pulled by a boat in a circular manner. The light
areas in each circle represent areas that had vegetation that
was uprooted and are now unvegetated. The dark spot within
each circle is seagrass that was not removed. The long, light-
colored streaks emanating from some of the scars are
sediment plumes created by the digging activities of sting rays.

221

222

Ta,

WORLD ATLAS OF SEAGRASSES

aquaculture activities requiring structures are now
prohibited from being placed on existing seagrass beds
(4-VAC 20 335-10, effective January 1998). In 1999, the
Virginia Marine Resources Commission was directed
(Code 28.2-1204.1} to develop guidelines with criteria to
define existing beds and to delineate potential
restoration areas. Dredging for clams (hard and soft) in
Virginia is prohibited in waters less than 1.2 m where
seagrasses are likely to occur. A special regulation was
passed for seagrasses in the Virginia portion of
Chincoteague Bay (4-VAC 20-1010) where clam and
crab dredging is prohibited within 200 m of seagrass
beds. Because of enforcement issues, the Virginia
regulation has recently been modified (4-VAC 20-70-10
seq.) to include permanent markers with signs
delineating the protected seagrass”.

In the state of North Carolina, regulations
involving seagrasses are not as strong as in Virginia
and Maryland. North Carolina protects seagrass beds
along underdeveloped areas. These areas are to be
used mainly for education and research although some
recreational activities are permitted. The dredging of
channels is regulated such that seagrass beds must be
avoided. Damage to seagrasses is also to be

REFERENCES

1 Orth R, Heck JKL Jr, Diaz RJ [1991]. Littoral and intertidal
systems in the mid-Atlantic coast of the United States. In:
Mathieson AC, Nienhuis PH (eds) Ecosystems of the World 24:
Intertidal and Littoral Ecosystems of the World. Elsevier,
Amsterdam. pp 193-214.

2 Orth R [1976]. The demise and recovery of eelgrass, Zostera
marina, in the Chesapeake Bay, Virginia. Aquatic Botany 2: 141-
159.

3 Moore KA, Wilcox DJ, Orth RJ [2000]. Analysis of the abundance of
submersed aquatic vegetation communities in the Chesapeake Bay.
Estuaries 23: 115-127.

4 Fredette TJ, Diaz RJ, van Montfrans J, Orth RJ [1990]. Secondary
production within a seagrass bed (Zostera marina and Ruppia
maritima] in lower Chesapeake Bay. Estuaries 13: 431-440.

5 Ross SW, Moser ML [1995]. Life history of juvenile gag,
Mycteroperca microlepis, in North Carolina estuaries. Bulletin of
Marine Science 56: 222-237.

6 Ferguson RL, Pawlak BT, Wood LL [1993]. Flowering of the
seagrass Halodule wrightii in North Carolina, USA. Aquatic Botany
46: 91-98.

7 Dennison WC, Orth RJ, Moore KA, Stevenson JC, Carter V,

Kollar S, Bergstrom P, Batiuk RA [1993]. Assessing water
quality with submersed aquatic vegetation. Bioscience 43:
86-94.

8 Ferguson RL, Korfmacher K [1997]. Remote sensing and GIS
analysis of seagrass meadows in North Carolina, USA. Aquatic
Botany 58: 241-258.

9 Cottam C [1934]. Past periods of eelgrass scarcity. Rhodora 36:

261-264.

Cottam C [1935]. Further notes on past periods of eelgrass

scarcity. Rhodora 37: 269-271.

11 Orth RJ, Moore KA [1984]. Distribution and abundance of
submersed aquatic vegetation in Chesapeake Bay: An historical
perspective. Estuaries 7: 531-540.

—

minimized when docks, piers, bulkheads, boat ramps,
groins, breakwaters, culverts and bridges are
constructed.

ACKNOWLEDGMENTS

Mark Finkbeiner, Ben Anderson and Brian Glazer are thanked for their
help and for sharing their data. Mike Durako and Mark Fonseca
contributed valuable information. Lisa Wood and Randolph Ferguson
developed the seagrass vectors in Figure 21.2. Mike Naylor and several of
the above listed colleagues provided comments on the report. Melissa
Wood and Dave Wilcox provided technical support. This is contribution
number 3613 from Horn Point Laboratory, University of Maryland Center
for Environmental Science and contribution number 2491 from the
Virginia Institute of Marine Science, College of William and Mary,
Gloucester Point, Virginia.

AUTHORS

Evamaria W. Koch, Horn Point Laboratory, University of Maryland Center
for Environmental Science, P.0. Box 775, Cambridge, MD 21613, USA.
Tel: +1 410 221 8418. Fax: +1 410 221 8490. E-mail: koch{dhpl.umces.edu

Robert J. Orth, Virginia Institute of Marine Science, School of Marine
Science, College of William and Mary, Gloucester Point, VA 23062, USA.

12 Renn CE [1934]. Wasting disease of Zostera in American waters.
Nature 134: 416.

13 Tutin TG [1938]. The autecology of Zostera marina in relation to its
wasting disease. New Phytology 37: 50-71.

14 Durako. Personal communication.

15 Fonseca MS. Personal communication.

16 Finkbeiner. Personal communication.

17 Kemp WM, Twilley RT, Stevenson JC, Boynton WR, Means JC
[1983]. The decline of submerged vascular plants in Upper
Chesapeake Bay: Summary of results concerning possible causes.
Marine Technology Society Journal 17: 78-89.

18 Stephan CD, Peuser RL, Fonseca MS [2000]. Evaluating Fishing
Gear Impacts to Submerged Aquatic Vegetation and Determining
Mitigation Strategies. Atlantic States Marine Fisheries Commission
Habitat Management Series 5. 35 pp.

19 Koch EW [2002]. The impact of boat-generated waves on a
seagrass habitat. Journal of Coastal Research 37: 66-74.

20 Clark PA [1995]. Evaluation and management of propeller damage
to seagrass beds in Tampa Bay, Florida. Florida Scientist 58:
193-196.

21 Dawes CJ, Andorfer J, Rose C, Uranowski C, Ehringer N [1997].
Regrowth of the seagrass Thalassia testudinum into propeller
scars. Aquatic Botany 59: 139-155.

22 Kearney MS, Stevenson JC, Ward LG [1994]. Spatial and temporal
changes in marsh vertical accretion rates at Monie Bay:
Implications for sea-level rise. Journal of Coastal Research 10:
1010-1020.

23 Ward LG, Kearney MS, Stevenson JC [1998]. Variations in
sedimentary environments and accretionary patterns in estuarine
marshes undergoing rapid submergence, Chesapeake Bay. Marine
Geology 151: 111-134.

24 Rooth JE, Stevenson JC [2000]. Sediment deposition patterns in
Phragmites australis communities: Implications for coastal areas
threatened by rising sea-level. Wetlands Ecology and Management
8: 173-183.

Fonseca MS, Kenworthy WJ, Whitfield PE [2000]. Temporal
dynamics of seagrass landscapes: A preliminary comparison of
chronic and extreme disturbance events. In: Pergent G, Pergent-
Martini C, Buia MC, Gambi MC [eds] Proceedings 4th International

Seagrass Biology Workshop, Sept. 25-Oct. 2, 2000, Corsica, France.

pp 373-376.

Orth RJ, Batiuk RA, Bergstrom PW, Moore KA [2002a, in

press]. A perspective on two decades of policies and

regulations influencing the protection and restoration of
submerged aquatic vegetation in Chesapeake Bay, USA. Bulletin
of Marine Science.

Batiuk RA, Orth RJ, Moore KA, Dennison WC, Stevenson JC,
Staver LW, Carter V, Rybicki NB, Hickman RE, Kollar S, Bieber S,
Heasly P [1992]. Chesapeake Bay Submerged Aquatic Vegetation
Habitat Requirements and Restoration Targets: A Technical
Synthesis. Chesapeake Bay Program, Annapolis, MD, CBP/TRS
83/92. 248 pp.

The mid-Atlantic coast of the United States

Orth RJ, Fishman JR, Wilcox DW, Moore KA [2002]. Identification
and management of fishing gear impacts in a recovering seagrass
system in the coastal bays of the Delmarva Peninsula, USA.
Journal of Coastal Research 37: 111-119.

Boynton WR, Murray L, Hagy JD, Stokes C, Kemp WM [1996]. A
comparative analysis of eutrophication patterns in a temperate
coastal lagoon. Estuaries 19: 408-421.

Valiela |, McClelland J, Hauxwell J, Behr PJ, Hersh D, Foreman K
[1997]. Macroalgal blooms in shallow estuaries: Controls and
ecophysiological and ecosystem consequences. Limnology and
Oceanography 42: 1105-1118.

223

224

WORLD ATLAS OF SEAGRASSES

22 The seagrasses of

THE GULF OF MEXICO

spanning 12° of latitude, from 18° to 30°N, and

17° of longitude, from 81° to 98°W. It is bisected
by the Tropic of Cancer and is largely subtropical;
however, along the northern edge, up to five days with
freezing temperatures are probable on an annual basis.
The coastal fringe is moist, with annual precipitation in
excess of 1000 mm, except for southern Texas and
northern Mexico. Precipitation is concentrated in the
summer period, most pronounced along the coast of
Mexico and least pronounced along the coast of
Louisiana. Most of the Gulf of Mexico is fringed by a
broad coastal plain, except for northwestern Cuba and
sections of the Mexican coast near Veracruz. The inner
continental shelf to a depth of 20 m is broad off the
western side of the Yucatan Peninsula, along the coast
of Louisiana and along the western side of Florida,
extending as much as 80 km offshore to the tip of
Florida. Elsewhere, the inner shelf is relatively narrow.
Most of the rivers draining into the Gulf of Mexico have
restricted catchments, except along the north shore,
most obviously the Mississippi River, and parts of the
western gulf, including the Rios Bravo (Grande],
Panuco, Grijalva and Usumacinta. Barrier islands and
spits are prominent features along much of the coast,
and coral reefs shelter the large expanse of water off
the southern tip of Florida and off the coasts of
Veracruz, Campeche, Yucatan and northwestern Cuba.
Lunar spring tides are less than 1 m throughout
the region.

T= Gulf of Mexico is a vast basin of water,

CUBA

No recent assessment has been performed of the
seagrass resources on Cuba’s coast bordering the Gulf
of Mexico". Therefore, we must resort to an extensive
report of a survey of the northwestern Cuban shelf
conducted in 1972-73". Fortuitously, this region from
22 to 23°N and 83 to 85°W is essentially all of the Cuban
coast that borders the Gulf of Mexico. At that time,

C.P. Onuf

R.C. Phillips

C.A. Moncreiff

A. Raz-Guzman

J.A. Herrera-Silveira

seagrasses covered 75 percent of the 2740 km’ area of
the northwestern Cuban shelf. Seagrasses were limited
to the part of the shelf shoreward of a fringing reef. A
total of four species were found at 282 stations:
Thalassia testudinum was found to a depth of 14 m
and accounted for 97.5 percent of total angiosperm bio-
mass (190g/m‘), Syringodium filiforme to 16.5m
and 3.5g/m’, Halophila engelmanni to 14.4 m and
0.25g/m’, and Halophila decipiens to 24.3m
and 0.14g/m’.

UNITED STATES

Florida

In 1995, there were 9888 km’ of seagrasses along the
Gulf of Mexico coast of Florida’. This includes the
seagrass beds of Monroe County off the Florida Keys
but does not include the seagrasses in Card Sound of
Biscayne Bay in Dade County. Nor does it include the
large sparse offshore beds of Halophila decipiens from
the Florida Keys to the Big Bend area.

The southern tip of the Florida Peninsula
bordering on the Gulf of Mexico (Monroe and Collier
Counties) contained 5901 km* of seagrasses. Monroe
County alone, mostly in Florida Bay and the Florida
Keys, contained 54.6 percent of the state's seagrasses.
The middle section of the Florida Peninsula’s Gulf of
Mexico coast (Lee County to Pinellas County) contained
446 km’ of seagrasses. The Big Bend region (Pasco
County to Wakulla County) contained 3346 km’ while
the Florida Panhandle (Franklin to Escambia Counties)
contained 195 km’ of seagrasses”.

Florida Bay and the Florida Keys are relatively
shallow and, because of the tourism in the area, the
seagrasses have been particularly subject to damage
from boat traffic and sewage pollution from greatly
expanded residential and hotel development, and
marina and boat usage. As much as 17.3 percent of
seagrass meadow in Monroe County had been scarred
by boat propellers, and 32 percent of the 17.3 percent

had been severely scarred”. This scarring often leads
to a loss of seagrass because of erosion and blow-outs.
In addition, Florida Bay suffered a massive die-off of
Thalassia testudinum beginning in 1987 that continued
at least through 1994. Researchers have hypothesized
the involvement of several factors in the initiation of the
die-off, but few have been investigated adequately’.
Beginning in 1991, algal blooms and persistent high
turbidity were widespread, accounting for further
deterioration of seagrass meadows, such that between
1984 and 1994 Thalassia testudinum biomass declined
by 28 percent, Syringodium filiforme by 88 percent and
Halodule wrightii by 92 percent”.

The seagrasses in the Big Bend of Florida (31
percent of all seagrasses in Florida) have experienced
relatively little impact from poor water quality
problems or scarring from boat usage. This is due to
their remoteness from population centers and the
relatively low population density of the area. However,
the area is on the brink of a huge development effort. It
can only be hoped that the state and local jurisdictions
will demand proper sewage disposal (not septic tanks]
and will not engage in the dredge and fill activities that
occurred in Tampa Bay and Sarasota Bay in the 1950s
and 1960s.

Historical analysis is limited to only a few bay
systems along the west coast of Florida. Charlotte
Harbor lost approximately 30 percent of its seagrasses
prior to the 1980s". There was a further harbor-wide
decline of 3.3 percent (2.43 km’) between 1988 and
1992. In 1992, the Southwest Florida Water Manage-
ment District initiated a biennial mapping project to
assess trends in Charlotte Harbor. Data from these
studies will be used to assess the effectiveness of
pollutant load reduction strategies on water quality.
Between 1992 and 1994, a 4 percent (2.91 km’) increase
was observed in the seagrass beds of the harbor,
followed by an additional 3.6 percent increase (2.74
km’) between 1994 and 1996.

Prior to the 1980s, seagrass losses in Sarasota
Bay were estimated to total approximately 30 percent.
However, changes in seagrass coverage in Sarasota
Bay have been dramatic since 1988. Between 1989 and
1990, nitrogen loads to the bay from wastewater
treatment plants diminished by as much as 25 percent.
Water transparency off the city of Sarasota and
Manatee County increased from a mean Secchi disc
depth of 1.1 m to 1.5 m, often deeper. Between 1988 and
1994, seagrass coverage in Manatee County increased
6.4 percent (1.42 km’) and another 7.8 percent (1.85
km?] between 1994 and 1996. In Sarasota County,
seagrass coverage increased 10.1 percent (0.78 km’)
between 1988 and 1994, and 22.7 percent (1.93 km’)
between 1994 and 1996. Most of these increases were
along the deep [>1.0 m) edges of existing seagrass

The Gulf of Mexico

3 MS 5
Lake Pe Org artrain perdido Bay ee
Mobile Bay, Big Bend

\ Biloxiy J le ~
1A £9 + Mississippi Sound
a 5? | Tampa Bay-@ FL

#S Galveston Bay Chandeleur
93" Matagorda Bay Islands
# San Antonio Bay
> Corpus Christi Bay

\ Baffin Bay

Laguna Madre

USA

Lake Calcasieu

Sarasota Bay
Charlotte Harbor \

Biscayne Bay @
llorida Bay

Gulf of Mexico

Tamaulipas » Alacranes

Quintana Roo

Laguna de Términos Banco

Laguna de Alvarado), “hinc
2% Chinchorro

0 100 200 300 Kilometers
= laa

Map 22.1
The Gulf of Mexico

beds". These observed increases are believed to be
directly linked to improving water quality and light
penetration resulting from reductions in point-source
pollutant loads.

Alabama

Alabama has only 90 km of exposure to the Gulf of
Mexico, and much of that is encompassed by Mobile
Bay which receives river discharge volumes second
only to the Mississippi River along the US portion of the
Gulf of Mexico. Consequently, there is little opportunity
for the establishment of true seagrass beds. A few
small patches of Halodule wrightii have been reported
at the south end of Mobile Bay along the western shore,
and 2.5 km’ are present in Perdido Bay, shared with
Florida, down from 4.9 km? in 1940-41". At the west
end of the Alabama coast and shared with Mississippi,
ephemeral beds of Ruppia maritima cover ca 2 km? in
Grand Bay during the late spring and early summer,
and Halodule wrightii has also been documented in this
area.

Mississippi
Historically, populations of Halodule wrightti, Halophila
engelmanni, Ruppia maritima, Syringodium filiforme
and Thalassia testudinum were present and abundant
along the northern shores of Mississippi's barrier
islands'“:*""" Overall, Mississippi has lost most of the
seagrass cover that was present in 1967-69, and only
one marine species, Halodule wrightii, still exists in
measurable quantities in Mississippi Sound. Ruppia
maritima (widgeon grass) occurs in isolated but well-
developed patches along the immediate coastline, and
as an occasional component in Halodule wrightii beds
along the barrier islands in Mississippi Sound.

Some well-established populations of Halodule

225

226

WORLD ATLAS OF SEAGRASSES

wrightii, Halophila engelmanni, Ruppia maritima,
Syringodium filiforme and Thalassia testudinum exist
along the western shorelines and in the small internal
bayou systems of the Chandeleur Islands, in south-
eastern Louisiana. These islands begin 37 km due south
of Biloxi, and are a likely source of vegetative propagules
and possibly seeds supplementing or repopulating
seagrass beds in some areas of the Mississippi coast.
Seagrass distributions from a 1967-69 Gulf of

Case Study 22.1
TAMPA BAY

Based on the available habitat at that time,
Tampa Bay is estimated to have supported
309.6 km? of seagrasses in 1879". By 1981, only
57.5 km? remained. The most dramatic decrease
occurred between 1950 and 1963, when approxi-
mately 50 percent of the total seagrass cover
disappeared. During this period, Hillsborough
Bay lost 94 percent of its grass beds, Old Tampa
Bay lost 45 percent and Tampa Bay proper lost
35 percent®”

The losses up to the 1950s were due to
poorly treated wastewater discharges and
industrial wastes from phosphate mines, citrus
canneries and other industrial sources", as well
as extensive dredging, and dredge and fill
activities that changed water circulation patterns
and caused extensive turbidity in the waters!"

Recent work has shown that the trend of
seagrass loss in Tampa Bay has been reversed.
In 1988, 93.1 km? of seagrass were present [this
was the first year of monitoring conducted by
the Southwest Florida Water Management
District)’. In 1990, this coverage increased
to 99.3 km’, and increased again in 1994 to
105.7 km’. The bay-wide seagrass coverage
in 1997 was estimated at 109.3 km?" In
Hillsborough Bay, seagrass increased from near
zero in 1984 to about 0.57 km’ in 1998.

This expansion apparently started in
response to water quality improvements from
the late 1970s to the mid-1980s. These
improvements followed a nearly 50 percent
reduction in the early 1980s in external nitrogen
loading from domestic and industrial point
sources, primarily discharging to Hillsborough
Bay. A slight decline in seagrass coverage
occurred in Tampa Bay in the late 1990s,
presumably a result of high rainfall during 1995,
1996 and the 1997-98 El Nino event, all of which
increased nitrogen loading to the bay'”!.

Mexico estuarine inventory’ were used as a historical

baseline, while data from a 1992 US Geological Survey
aerial imagery study'’’ were ground-truthed to
document recent distribution patterns. Potential
seagrass habitat was also Identified using a 2 m critical
depth limit which had been previously established in a
National Park Service seagrass monitoring project".

Seagrasses and potential seagrass habitat in
Mississippi Sound lie mainly along the northern
shorelines of the offshore islands. From east to west,
Petit Bois Island supported 6.8 km’ of seagrass
meadow according to the 1969 survey, down to 1.5 km*
in 1992; Horn Island seagrass cover decreased from
22.5 km? to 2.2 km’ over the same period; Dog Keys
Pass beds from 8.4 km’ to none; Ship Island from 6.2
km? to 1.0 km’; and Cat Island from 2.4 km’ to 0.7 km’.
Only on T-shaped Cat Island do seagrass beds occur in
protected areas along its southwest shoreline as well
as along its north side. Ruppia maritima occurs at two
locations at opposite ends of the mainland shore: Point
aux Chenes Bay at the Alabama border - 5.3 km? in
1969 down to 0.5 km’ in 1992, and Buccaneer State
Park, 10 km from the Louisiana border - 0.8 km? in
1969 down to 0.2 km? in 1992.

State-wide in 1969 submersed aquatic vascular
plants covered an estimated 55.2 km’ of coastal waters,
mostly true seagrasses on the north sides of offshore
islands. In 1992, only 8.1 km? of submersed vascular
plants were found, 2.1 km’? of which were from areas
not included in the 1967-69 survey'“!. Almost all of the
2.1 km’ were located in Grand Bay and are shared with
Alabama, as noted in the Alabama section. Therefore,
seagrasses in Mississippi suffered a decline of between
85 and 89 percent over 23 years. Information from the
early survey'’ indicated that 67.6 percent of potential
seagrass habitat was vegetated, in comparison to only
13.4 percent in 1992. Physical loss of seagrass habitat
is assumed for areas where 1969 coverage exceeds
current estimates of seagrass habitat. This total is
estimated to be 19.6 percent. Since the discrimination
of seagrasses from macroalgae in the 1967-69 survey
was less precise than in the 1992 assessment, losses
may be somewhat overestimated.

In Mississippi Sound, seagrasses appear to be
threatened by the cumulative effects of both natural
events and anthropogenic activities in the coastal
marine environment. The primary vector for the
disappearance of seagrasses is presently thought to be
an overall decline in water quality. Development may be
a major factor, as it often results in elevated nutrient
levels, higher sediment loads, and the introduction of
contaminants, which lead to a loss of water quality.
Cyclic shifts in precipitation patterns that affect both
salinity and turbidity, and extreme events, especially
hurricanes, are also involved. Areas of seagrass habitat

loss coincide with areas where rapid coastal erosion'”
and massive long-term movement of sand have been
documented”. Physical loss of habitat and decreased
light availability in combination with declining water
quality are the most visible features that directly affect
seagrass communities.

Louisiana

The coast of Louisiana features a wide band of fresh to
brackish marsh, with some large lakes. Extensive beds
of submersed aquatic vascular plants occur there, but
the salinity is generally too low for seagrasses to thrive.
Since the mid-1950s, seagrasses have been lost from
Lake Pontchartrain and White, Calcasieu and Sabine
Lakes and from behind the south coast barrier
islands". Small amounts of Halodule wrightii have
reappeared on sand flats along the north shore, and
still smaller amounts along the southeastern shore of
Lake Pontchartrain in the 1990s. However, most of
Louisiana's seagrasses are confined to the mixed
species beds along the western shore of the
Chandeleur Islands. The beds are relatively stable, at
least by regional standards, only decreasing from
64.1km/ in 1978 to 56.6 km’ in 1989 despite the passage
of two hurricanes in that period. Apparently, the islands
provide a protected shallow-water environment far
enough removed from the plume of the Mississippi
River and other influences of developed coastlines for
seagrasses to thrive in the middle of an otherwise
inhospitable shore.

Texas
Based on a recent compilation of surveys from the late
1980s and 1990s'"', the coast of Texas supports 951 km?
of seagrass meadow. Unlike Florida, seagrasses in
Texas do not occur seaward of the barrier islands and
along the open coast. Rather, they are confined to the
more protected waters of the bays behind the barrier
islands, especially in the lagoonal segments extending
away from river mouths. Seagrasses are limited in
occurrence along the upper Texas coast to 16.6 km? in
Galveston and Matagorda Bays, covering less than 1
percent of the bottom. Along the middle Texas coast,
including the San Antonio, Aransas-Copano and Corpus
Christi Bay systems, cover by seagrasses increases by
an order of magnitude (174.8 km? and 12 percent of bay
bottom}. Along the lower Texas coast, encompassing
upper and lower Laguna Madre and Baffin Bay,
seagrasses define the ecosystem, covering 751.9 km?
and 50 percent of bay bottom. In Laguna Madre proper,
seagrasses carpet more than 70 percent of bay bottom.
Halodule wrightii is the dominant seagrass and
Halophila engelmanni and Ruppia maritima are at least
sporadically present in all bay systems along the Texas
coast. Ruppia maritima can dominate some beds in the

The Gulf of Mexico

north. Thalassia testudinum is present at one location
at the extreme west end of the Galveston Bay system
and then is next seen 200 km to the southwest, where,
within 10 km of the gulf outlet at Aransas Pass, it is the
dominant species over a quarter of the vegetated
bottom. The association of Thalassia testudinum with a
natural gulf outlet is even stronger in Laguna Madre.
Within 20 km of Brazos Santiago Pass at the south end
of the lagoon, Thalassia testudinum is the dominant
species over 90 percent of the seagrass meadow.
Farther from the outlet, Thalassia testudinum is
uncommon. Syringodium filiforme occurs only south
from Aransas Bay near Aransas Pass and is uncommon
in Aransas and Corpus Christi Bays. It is the dominant
species over 7 percent of the vegetated bottom in upper
Laguna Madre and 30 percent of vegetated bottom in
lower Laguna Madre.

Precipitation, inflow of freshwater and bathy-
metry are the most influential environmental
determinants of the gradient of increasing seagrass
abundance from northeast to southwest along the
Texas coast. The much higher precipitation and inflow
of the upper Texas coast ensure that its estuaries
receive higher loads of sediments and nutrients and
greater freshening of bay waters than do estuaries of
the middle or lower Texas coast. This tends to result in
higher turbidity and a reduced area of suitable salinity
for seagrass growth. In addition Laguna Madre is the
shallowest Texas bay so that sufficient light to support
seagrass growth reaches much more of the bottom
than in other bays.

The Galveston Bay system supported more than
20 km* of submersed aquatic vegetation in 1956, but by
1987 only 4.5 km? remained’. Seagrasses were
limited to West Bay and its tributary embayment,
Christmas Bay, which is furthest removed from riverine
influences. In West Bay, seagrass beds declined from
4.6 km’ in 1956 to 1.3 km* in 1965 and were absent in
1987. In Christmas Bay the 5.0 km? of seagrasses in
1971-72 declined to 1.1 km? in 1987. Losses are
attributed to shorefront development and lower water
quality associated with the urbanization of the area,
including discharges of six sewage treatment plants,
two of which have been discharging since the early
1960s. In the main stem of Galveston Bay extensive
beds of Ruppia maritima present along the western
shore in 1956 were destroyed by Hurricane Carla in
1961 and have not recovered, whereas beds in Trinity
Bay have changed little. Reduced water clarity and
subsidence resulting from excessive groundwater
withdrawal coupled with bulkheading of the western
shore of Galveston Bay may be responsible for the
failure of submersed vegetation to re-establish. The
appearance of some patches of Halophila engelmanni
in West Bay since 2000 may be an early indication that

227

228

WORLD ATLAS OF SEAGRASSES

Case Study 22.2
LAGUNA MADRE

Laguna Madre accounts for 75 percent of seagrass
cover in the state of Texas, while making up only 20
percent of the state’s embayment area. Seagrasses
are the foundation of the Laguna Madre ecosystem.
As a result of the high-quality nursery habitat pro-
vided by large expanses of continuous meadow,
Laguna Madre supports more than 50 percent of the
Texas inshore finfish catch. Together with its sister
lagoon, the Laguna Madre of Tamaulipas, which lies
across the delta of the Rio Grande in Mexico, the
area is even more important for the redhead duck,
Aythya americana, providing wintering habitat for
more than 75 percent of the world population.

As a result of the importance of Laguna Madre
as a natural resource, whole system seagrass surveys
have been conducted at approximately decade
intervals since the mid-1960s. Although seagrasses
strongly dominate the Laguna Madre ecosystem, they
have been undergoing profound change. In lower
Laguna Madre seagrasses covered almost the entire
bottom in 1965, but between 1965 and 1974 large
tracts of deep bottom went bare and, with small
adjustments in configuration, have remained bare to
the present day. Shifts in species composition have
been even more far reaching, with Halodule wrightil
dominant over 89 percent of the seagrass meadow in
1965 and only 41 percent in 1998-99, being replaced
by other species from the south. Syringodium
filiforme achieved maximal coverage in the 1988
survey but already was being replaced in the south by
Thalassia testudinum. By the 1998-99 survey this
displacement was much farther advanced. Halophila
engelmanni is a transient in this system, occupying a
considerable area at the outer edge in the 1988 survey
but not dominant at any other time. In upper Laguna
Madre, between 1967 (see figure, opposite) and 1988
(not shown], cover of Halodule wrightii increased from
118 to 249 km? and was continuous from shore to
shore over the northern third of the lagoon. However,
by 1998-99 Halodule wrightii cover had decreased to
214 km?, with a central deep area in the north
reverting to bare bottom and a large patch of
Syringodium filiforme taking over at the north end.

From the mid-1960s to the present, for the
lagoon as a whole, the area of bare bottom has
increased by 10 percent. The area of Thalassia
testudinum has increased from barely present to
dominating some 11 percent of lagoon bottom.
Syringodium filiforme increased from 7 to 17
percent, and then fell back to 15 percent, all at the

expense of Halodule wrightii which covered 67
percent of lagoon bottom in the earliest survey, and
then declined to 41 percent at present. The loss of
Halodule wrightii may have serious consequences
because it is almost the sole food source for 400 000-
600000 wintering redhead ducks.

WATERWAY’S PROMINENT ROLE

The Gulf Intracoastal Waterway plays a prominent
role in most of the radical change seen in Laguna
Madre’s seagrass meadows over the last 35 years.
The loss of seagrass cover in deep parts of lower
Laguna Madre between 1965 and 1974, and its failure
to revegetate since, is probably due to maintenance
dredging of the Gulf Intracoastal Waterway. Intensive
monitoring of the light regime before, during, and up
to 15 months after maintenance dredging in 1988
documented significantly increased light attenuation
to the end of the study in the region where sea-
grasses had been lost. Laguna Madre is a notoriously
windy location and frequent episodes in which
sediment from the mounds of unconsolidated, fine-
textured dredge deposits is resuspended and dis-
persed by currents account for the propagation of
dredging effects over large areas and long periods of
time. Since dredging frequency is in the order of two
years, the light reduction is chronic”.

The Gulf Intracoastal Waterway is also
implicated in the other big change in seagrasses in
lower Laguna Madre, the displacement of Halodule
wrightii by more euhaline [adapted narrowly to
marine salinity] species moving north over time. Prior
to completion of the Gulf Intracoastal Waterway in
1949, there was no permanent water connection
between upper Laguna Madre and lower Laguna
Madre. A 30 km reach of seldom flooded sand flats
prevented this. Before 1949, salinities in excess of 60
psu, or about twice the salt content of the adjacent
Gulf of Mexico, were not uncommon in lower Laguna
Madre, and in the southern extremity of upper Laguna
Madre salinities in excess of 100 psu were measured
several times. The breaching of the sand flat barrier
at the midpoint of the lagoon greatly enhanced
exchange within the lagoon and between the lagoon
and the Gulf of Mexico. Prevailing southeasterly winds
now drive lagoon water north across Corpus Christi
Bay and ultimately out into the gulf, with inflow from
the gulf at the south end replenishing the system. The
net result was a moderation of hypersaline conditions
within the lagoon. Now, salinities seldom reach
50 psu anywhere in the lagoon.

Halodule wrightii is the only species that can
tolerate salinities greater than 60 psu and is a

ve ee

superior colonizer compared to Syringodium filiforme
or Thalassia testudinum. Consequently, Halodule
wrightii was probably widespread before construction
of the waterway, although there are only incidental
reports from a few locations for that period, and it is
not surprising that according to the first systematic
survey of seagrass cover in the mid-1960s it
dominated the lower Laguna Madre overwhelmingly.
Gradual displacement from the south by Syringodium
filiforme, in its turn later displaced by Thalassia
testudinum, is consistent with what we know of the
relative salinity tolerances of the species, and their
colonizing and competitive abilities under conditions
of moderate salinity. The euhaline species had been
confined to the immediate vicinity of the natural gulf
outlet at the extreme south end of the lagoon until
moderation of the salinity regime. Thereafter, life
history and competitive characteristics of the plants
set the time course of change”.

THE UPPER LAGUNA MADRE

Presumably, upper Laguna Madre has experienced
the same system shift as lower Laguna Madre, yet
its trajectory of seagrass change has been very
different. Halodule wrightii increased rather than
decreased through 1988 and Syringodium filiforme
was not evident until 1998-99. Changes in upper
Laguna Madre seem to lag those in lower Laguna
Madre by 20 or 30 years. Almost certainly, the reason
for the lag is the extreme hypersalinity of the
southern section of upper Laguna Madre before
completion of the waterway. Even Halodule wrightii
cannot tolerate 100 psu salinity and must have been
absent from most of upper Laguna Madre, except
close to Corpus Christi Bay. The much greater
distance to source populations probably accounts for
expansion of Halodule wrightii meadows through
1988 in the upper Laguna Madre, whereas it was
already at a maximum in the lower Laguna Madre by
1965. Similarly, the possible sources of Syringodium
filiforme for the colonization of upper Laguna Madre
are the lower Laguna Madre or across Corpus
Christi Bay, near the closest gulf outlet to the north.
Not surprisingly, establishment in upper Laguna
Madre was long delayed compared to lower Laguna
Madre, where it was present from the outset.

The last large historical change is the loss of
vegetation from deep parts of upper Laguna Madre
between 1988 and the present. Through 1990,
Laguna Madre was renowned for its crystal clear
water. However, in June 1990, a phytoplankton
bloom was first noted that was dense and long-lived
enough to earn it its own name, the “Texas brown

The Gulf of Mexico

tide". The bloom varied in intensity but was
continually present from 1990 to 1997 and has flared
up sporadically since. Light intensity at 1 m depth
was reduced by half over large areas, and gradually
Halodule wrightii died back in deep areas. Although
a suite of factors played a role in the initiation and
unprecedented persistence of the brown tide,
nutrients regenerated from the gradual die-back of
the seagrass meadow were almost certainly involved
in sustaining the bloom, until steady state was
reached between seagrass distribution and the
brown tide-influenced light regime. A disturbing
aspect of this perturbation is that as yet there is little
sign of recovery. Apparently because of the loss of
seagrass cover, the bottom is much more prone to
sediment resuspension. Because new recruits have
no reserves to tide them over episodes of low light,

establishment has not occurred?”

mid-1960s

Upper
Laguna
Madre

Lower

Laguna
Madre

Seagrass cover in the Laguna Madre of Texas

Notes: Halodule wrightii (green), Syringodium filiforme (grey),
Thalassia testudinum (black), bare/no seagrass (white).

229

230

WORLD ATLAS OF SEAGRASSES

management efforts are resulting in improved water
quality in the bay.

Little net change in seagrass cover is evident
along the middle Texas coast’. The dredging of
navigation channels, boating activities and nutrient
enrichment from non-point sources are the suspected
causes of a loss of 3.3 km’ of Thalassia near Aransas
Pass, while in the same general area, subsidence has
led to inundation of previously emergent flats and
colonization of 8.7 km’ by Halodule wrightii. Thus, in the
absence of bulkheading in this part of Corpus Christi,
the effect of subsidence on submersed vegetation is the
opposite of what it was with bulkheading in Galveston
Bay. A growing management concern along this part of
the coast is that large areas of shallow seagrass
meadow close to population centers show moderate to

heavy propeller scarring”.

MEXICO

The southwestern coast of the Gulf of Mexico has
approximately 15 estuarine systems. The largest
include Laguna Madre (2000 km’) in the state of
Tamaulipas, Laguna de Tamiahua (880 km’} and
Laguna de Alvarado (118.3 km’) in the state of Veracruz,
and Laguna de Términos (1700 km’) in the state of
Campeche. The study of seagrasses and their
distribution in Mexico dates from the 1950s. In the
southwestern Gulf of Mexico there are five genera of
seagrasses: Thalassia, Syringodium, Halodule, Halo-
phila and Ruppia, of which Thalassia has the widest
distribution. It is found from Tamaulipas in the north to
Quintana Roo in the south as well as in various reef
systems”.

Tamaulipas

The seagrass species reported for this coast include
Thalassia testudinum, Syringodium filiforme, Halodule
wrightii and Halophila engelmanni. Laguna Madre has
four inlets that change position over time. As a result of
its location in a semi-arid area, its restricted
communication with the sea and a minimum river
runoff from the San Fernando river, this lagoon is
hypersaline, with marine conditions restricted to the
areas of tidal influence near the inlets. The western
margin has extensive beds of macroalgae, while
Halodule wrightii is established along both the eastern
and western margins of the lagoon and covers
357.4 km’ or 18 percent of the lagoon area. Associated
macrofauna includes 76 species of mollusks, 42 of
crustaceans and 105 of fish’””.

Veracruz

The system of coral reefs in front of the port of Veracruz
boasts five seagrass species: Halodule wrightii,
Thalassia testudinum, Syringodium filiforme, Halophila

engelmanni and Halophila decipiens. Halodule wrightii
is found in the shallower areas where it tolerates
changes in temperature and salinity, and Halophila
decipiens is found in the deeper parts down to 10 m.
Other species associated with the Thalassia
testudinum here include green, brown and red
macroalgae, foraminifers, sponges, anemones, corals,
polychaetes, mollusks, crustaceans, sea urchins, sea
stars and fish”. First identified in 1977 and
continuing largely unchanged to the present, the main
environmental problems in this area are caused by
local fisheries as well as by the great loads of sediment,
fertilizers, insecticides and herbicides that are
transported along the coastal rivers to the coral reefs
and seagrass beds, only to be resuspended during
winter storm seasons.

The waters of Laguna de Tamiahua are
predominantly euhaline because the lagoon has only
two small sea inlets at the north and south ends and
freshwater inflow is limited to several very small
creeks. The western margin has extensive beds of
macroalgae while Halodule wrightii is established
along the eastern margin of the lagoon and covers
106.2 km? or 12 percent of the lagoon area. Associated
macrofauna includes 67 species of mollusks, 32 of
crustaceans and 129 of fish”.

By contrast Laguna de Alvarado has two sea
inlets, one of which is a narrow channel, and four
rivers, one of which carries a great volume of water.
Consequently, the lagoon is oligo-mesohaline with
salinities below 18 psu throughout the greater part of
the year. Ruppia maritima covers 3.2 km’ or 3 percent
of the lagoon area. This is the only species of seagrass
in Alvarado where it forms dense beds along the inner
margin of the sand barrier. Associated macrofauna
includes 49 species of mollusks, 26 of crustaceans and
106 of fish'*”.

Tabasco

Very little is known about seagrasses in the state of
Tabasco. Only Halodule wrightii and Ruppia maritima
have been recorded for the coastal lagoons with a cover
of 8.1 km’. The scarcity of seagrasses along the coast is
the result of the large sediment load and high turbidity
delivered by the Grijalva-Usumacinta river system and
transported west along the coast.

Yucatan Peninsula

The Yucatan Peninsula is located in the southeastern
Gulf of Mexico, includes the states of Campeche,
Yucatan and Quintana Roo, and encompasses
approximately 1800 km of coastline, including islands.
The karstic nature of the peninsula is responsible for
non-point groundwater discharges through springs
directly into coastal lagoons, the broad continental

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PACIFIC
OCEAN

ATLANTIC
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900

1200 1500 km

25°

shelf and the open sea. Based on satellite images and
field observations during 2000-01, there are 5911 km?
of seagrasses'" in the coastal lagoons, the coastal sea
and the coral reef lagoons of Chinchorro and
Alacranes.

Seagrasses along the coasts of the peninsula
include the six species present in the southwestern
Gulf of Mexico. The most widespread species are
Thalassia testudinum, Syringodium filiforme and
Halodule wrightii, with this last species also found in
the hypersaline Ria Lagartos, Yucatan. Halophila
engelmanni and Halophila decipiens are found in
small areas while Ruppia maritima is found in the
shallow brackish coastal lagoons of Términos,
Celestun, Chelem, Dzilam, Ria Lagartos, Nichupte,
Ascension and Chetumal’. Beds of Thalassia

Case Study 22.3 |
LAGUNA DE TERMINOS

Laguna de Términos is the best studied coastal
lagoon in the Mexican Gulf of Mexico. It is located at
the transition area between a western terrigenous
region and an eastern calcareous region and Is also
characterized by a marked north-south salinity
gradient, established by the tides that enter through
two sea inlets and the freshwater provided by three
rivers“. The seagrasses Thalassia testudinum,
Syringodium filiforme and Halodule wrightii cover
496.4 km? or 29 percent of the lagoon area.

Thalassia testudinum covers extensive areas
along the northern, eastern and southeastern
margins where salinity is high and the water is
relatively clear, creating an ideal environment for
this tropical, polyeuhaline species“. Syringodium
filiforme is restricted to the northeastern region
where salinity is high and the sediment is biogenic,
sandy and calcareous. This species favors calcar-
eous substrates and is found forming dense
seagrass beds along the eastern Caribbean coast of
Mexico. Halodule wrightii is found along the north-
ern and western margins of the lagoon, the first with
high salinity, clear water and sandy substrates, and
the second with low salinity, turbid water and muddy
substrates, where the great Grijalva-Usumacinta
river system drains into the lagoon. Its distribution
shows it is a tropical euryhaline, pioneering and
adaptable species that tolerates a variety of
environmental characteristics. Ruppia maritima has
also been observed in the low-salinity areas of the
southwest of the lagoon.

In this lagoon, all seagrass beds, but mainly
those of Thalassia testudinum, play an important

The Gulf of Mexico

testudinum and Syringodium filiforme have also been
sighted around the reefs of Alacranes and Cayo Arcas,
Campeche.

Thalassia testudinum is dominant in open waters,
especially in the coral reef lagoons. The maximum total
biomass and shoot density recorded are 2000 g/m’ and
1222 shoots/m? '**“. Halodule wrightii is the most
widely distributed species in the peninsula. It is found in
mixed and monospecific stands, in shallow waters
{<1 m), around freshwater springs and at salinities
between 20 and 57 psu. The maximum total biomass
and shoot density recorded are 700 g/m? and 14872
shoots/m’"**!. Syringodium filiforme has been obser-
ved mainly in open waters mixed with Halodule wrightii
and Thalassia testudinum, dominating in regions where
strong currents are observed. The maximum total

part as nursery, feeding and protection areas for the
larvae and juveniles of commercially important
species, such as the shrimp Litopenaeus setiferus,
Farfantepenaeus aztecus and Farfantepenaeus
duorarum, and the fish Caranx hippos, Lutjanus
analis, Bagre marinus, Centropomus undecimalis
and Archosargus rhomboidalis, that migrate
through the lagoon during their life cycles and con-
stitute offshore fisheries of great economic value,
among which the shrimp fishery is particularly
noteworthy.

Associated macrofauna include 174 species of
mollusks, 60 of crustaceans and 214 of fish,
establishing Laguna de Términos as the most
species rich [448] of Mexico’s four large lagoons
along the Gulf of Mexico, supporting almost twice as
many species as the other lagoons (181 species in
Laguna de Alvarado, 228 species in Laguna de
Tamiahua and 223 species in Laguna Madre). The
environmental heterogeneity and complexity of
Laguna de Términos arise from the presence and
distribution of the four seagrass species, macro-
algae, mangrove forests and the marked salinity
gradient, all of which favor the recruitment of a great
number of stenohaline and euryhaline estuarine
species, and some marine species. These establish
communities with different trophic structures!
subdividing the lagoon according to their
preferences for different habitat types”.

No long-term data on seagrass coverage have
been recorded for Laguna de Términos. However,
the extent of the seagrass beds, as well as shoot
density, along the inner margin of the barrier island
were markedly reduced when Hurricane Roxanne
passed over the lagoon twice in October 1996.
Recovery occurred within three years.

231

232

Photo: A. Raz-Guzman

WORLD ATLAS OF SEAGRASSES

biomass and shoot density recorded are 1000 g/m’ and
7140 shoots/m?*'*. Halophila decipiens and Halophila
engelmanni can be observed in small patches mixed
with other seagrasses and macroalgae in Yucatan and
Quintana Roo, mainly on shallow {<1-5m) sandy
bottoms. Ruppia maritima has been observed growing
in mixed stands with Halodule wrightii in polyhaline (18
psu) waters, and in monospecific stands in mesohaline
(5-18 psu) waters with a biomass of 1000 g/m’.

The seagrasses of the peninsula have been
affected by trawling and eutrophication in Campeche, by
trawling, tourism, eutrophication and port development
in Yucatan, and by tourism and eutrophication in
Quintana Roo, all suggesting that water quality is a
major concern for the seagrasses in this region.

Historical analysis is limited. Observations from
1985 to 2001 in Progreso, Yucatan, show a loss of 95
percent of seagrass cover and a replacement by green
macroalgae (Caulerpa spp.}, with eutrophication again
the main cause’. However not all decline has proved
permanent. Following the construction of port
infrastructure in the north of Yucatan the hydrology of
the Chelem Lagoon changed and the seagrass
community was negatively impacted. Four years later

Ray on low-density Syringodium filiforme, Mexican Caribbean.

REFERENCES

1 Beatriz Martinez, Instituto de Oceanologia, Habana, Cuba. Personal
communication.

2 Buesa RJ [1975]. Population biomass and metabolic rates of
marine angiosperms on the northwestern Cuban shelf. Aquatic
Botany 1: 11-23.

3 Sargent FJ, Leary TJ, Crewz DW, Kruer CR [1995]. Scarring of
Florida's Seagrasses: Assessment and Management Options. FMRI
Technical Report TR-1. Florida Marine Research Institute, St
Petersburg, FL.

4 Fourqurean JW, Robblee MB [1999]. Florida Bay: A history of recent
ecological changes. Estuaries 22: 345-357.

hydrological restoration took place and the seagrass
community recovered’. Natural events such as
hurricanes have significant effects on seagrass
communities. However, these have shown an important
recovery capacity. For example, during Hurricane
Gilbert in 1988, Halodule wrightii beds in the coastal
lagoon of Celestun, Yucatan, lost 93 percent of their
area. Within three years, they had recovered to their
initial condition”. A similar pattern of recovery was
observed for Thalassia testudinum in Cancun”.

CONCLUSION

The Gulf of Mexico is a globally important seagrass
area. Extensive beds cover about 19000 km’ from Cuba
and the southern tip of Florida through Texas to the
Yucatan Peninsula of Mexico. In many places impacts
appear to be low and seagrass beds healthy; however,
some recent perturbations are disturbing because of
their magnitude and our inadequate understanding of
causation. Most worrisome are the persistent and
recurring algal blooms, high turbidity and changes in
species composition afflicting seagrass meadows of
Florida Bay on the east side and Laguna Madre on the
west side of the Gulf of Mexico.

AUTHORS

Christopher P. Onuf, US Geological Survey, National Wetlands Research
Center, Campus Box 339, 6300 Ocean Drive, Corpus Christi, Texas, USA.
Tel: +1 361 985 6266. Fax: +1 361 985 6268. E-mail: chris_onuffdusgs.gov

Ronald C. Phillips, 3100 South Kinney Road #77, Tucson, Arizona 85713,
USA.

Cynthia A. Moncreiff, Gulf Coast Research Lab, P.0. Box 7000, 703 East
Beach Drive, Ocean Springs, Mississippi, USA.

Andrea Raz-Guzman, Instituto de Investigaciones sobre los Recursos
Naturales, Universidad Michoacana de San Nicolas de Hidalgo, Avenida
San Juanito s/n, San Juanito Itzicuaro, Morelia 58330, Michoacan, Mexico.

Jorge A. Herrera-Silveira, CINVESTAV-IPN, Merida, Carr. Ant. Progreso
km 6, Merida 97310, Yucatan, Mexico.

5 Hall MO, Durako MJ, Fourqurean JW, Zieman JC [1999]. Decadal
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[2000]. Recent trends in seagrass distributions in southwest Florida
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pp 157-166.

7 Lewis RR Ill, Durako MJ, Moffler MD, Phillips RC [1985]. Seagrass
meadows of Tampa Bay: A review. In: Treat SF, Simon JL, Lewis RR
Ill, Whitman RL (eds) Proceedings, Tampa Bay Area Scientific
Information Symposium. Burgess Pub. Co., Minneapolis, MN.

Johansson JOR, Ries TF [1997]. Seagrass in Tampa Bay: Historic
trends and future expectations. In: Treat SF, Clark PA leds)
Proceedings, Tampa Bay Scientific Information Symposium 3.
Tampa, FL. pp 139-150.

Lewis RR Ill, Clark PA, Fehring WK, Greening HS, Johansson RO,
Paul RT [1998]. The rehabilitation of the Tampa Bay estuary,
Florida, USA, as an example of successful integrated coastal
management. Marine Pollution Bulletin 37: 468-473.

Johansson JOR, Lewis RR Ill [1991]. Recent improvements in water
quality and biological indicators in Hillsborough Bay, Florida. In:
Treat SF, Clark PA (eds) Proceedings, Tampa Bay Scientific
Information Symposium 2. Tampa, FL. pp 1199-1215.

Lewis RR Ill, Estevez ED [1988]. The Ecology of Tampa Bay, Florida:
An Estuarine Profile. US Fish and Wildlife Service Biological Report
85(7.18).

Johansson JOR, Greening H [2000]. Seagrass restoration in Tampa
Bay: A resource-based approach to estuarine management. In:
Bortone SA (ed) Seagrasses: Monitoring, Ecology, Physiology and
Management. CRC Press, Boca Raton, FL. pp 279-293.

Handley LR [1995]. Seagrass distributions in the northern Gulf of
Mexico. In: LaRoe ET, Farris GS, Puckett CE, Doran PD, Mac MJ
{eds} Our Living Resources: A Report to the Nation on the
Distribution, Abundance, and Health of U.S. Plants, Animals, and
Ecosystems. US Department of the Interior, National Biological
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Eleuterius LN [1973]. The distribution of certain submerged plants
in Mississippi Sound and adjacent waters. In: Christmas JY (ed)
Cooperative Gulf of Mexico Estuarine Inventory and Study,
Mississippi, Phase IV: Biology. State of Mississippi, Gulf Coast
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Eleuterius LN, Miller GJ [1976]. Observations on seagrasses and
seaweeds in Mississippi Sound since Hurricane Camille. Journal of
the Mississippi Academy of Sciences 21: 58-63.

Sullivan MJ [1979]. Epiphytic diatoms of three seagrass species in
Mississippi Sound. Bulletin of Marine Science 29: 459-464.

US Geological Survey [1992]. Draft maps: Isle au Pitre, LA-MS, Cat
Island, MS-LA, Ship Island, Dog Keys Pass, MS, Horn Island West,
MS, Horn Island East, MS, Petit Bois Island, MS, Grand Bay SW,
MS-AL, Kreole, MS-AL. Scale 1:24 000. National Wetlands
Research Center, Lafayette, LA.

Heck KL, Sullivan MJ, Zande JM, Moncreiff CA [1996]. An Ecological
Analysis of Seagrass Meadows of the Gulf Islands National
Seashore, Years One, Two, and Three: Seasonal assessment and
inventory, interaction studies and continuing assessment/inventory,
August 1996. Final Report to the National Park Service.

Oivanki SM [1994]. Belle Fontaine, Jackson County, Mississippi:
Human history, geology, and shoreline erosion. Mississippi
Department of Environmental Quality, Office of Geology, Bulletin
No. 130.

Otvos EG [1981]. Barrier island formation through nearshore
aggradation: Stratigraphic and field evidence. Marine Geology 43:
195-243.

Pulich W Jr [1999]. Introduction. In: Seagrass Conservation Plan for
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Pulich W Jr, White WA [1991]. Decline of submerged vegetation in
the Galveston Bay system: Chronology and relationships to physical
processes. Journal of Coastal Research 7: 1125-1138.

Adair SE, Moore JL, Onuf CP [1994]. Distribution and status of
submerged vegetation in estuaries of the upper Texas coast.
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Dunton KH, Schonberg SV [2002]. Assessment of propeller scarring
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Research Special Issue No. 37: 100-110.

Onuf CP [1994]. Seagrasses, dredging and light in Laguna Madre,
Texas, USA. Estuarine Coastal and Shelf Science 39: 75-91.

fos}

ie)

The Gulf of Mexico 233

Quammen ML, Onuf CP [1993]. Laguna Madre: Seagrass

changes continue decades after salinity reduction. Estuaries 16:
303-311.

Onuf CP [2000]. Seagrass responses to and recovery (?] from seven
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Lot A [1977]. General status of research on seagrass

ecosystems in Mexico. In: McRoy CP, Helfferich C [eds] Seagrass
Ecosystems. A Scientific Perspective. Marcel Dekker Inc, NY.

pp 233-245.

Raz-Guzman A, Reguero M, Huidobro L, Corona A [2001]. Estuarine
community composition in Mexican Gulf of Mexico coastal lagoons.
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Conference Abstracts. p 114.

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de Veracruz, Ver. Anales del Instituto de Biologia Seria Botanica
UNAM 42: 1-48.

http://www.dumac.org.mx

Espinoza J [1996]. Distribution of seagrasses in the Yucatan
Peninsula, Mexico. Bulletin of Marine Science 59: 449-454.
Gallegos ME, Merino M, Marba N, Duarte CM [1993]. Biomass and
dynamics of Thalassia testudinum in the Mexican Caribbean:
Elucidating rhizome growth. Marine Ecology Progress Series 95:
185-192.

Van Tussenbroek BI, Hermus K, Tahey T [1996]. Biomass and
growth of the turtle grass Thalassia testudinum (Banks and Konig)
in a shallow tropical lagoon system in relation to tourist
development. Caribbean Journal of Science 32: 357-364.
Herrera-Silveira JA [1994]. Phytoplankton productivity and
submerged macrophyte biomass variation in a tropical coastal
lagoon with groundwater discharge. Vie Milieu 44: 257-266.
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Marba N, Gallegos ME, Merino M, Duarte CM [1994]. Vertical
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Crustacean Biology 17: 609-620.

=e =

234 WORLD ATLAS OF SEAGRASSES

23 The seagrasses of

THE CARIBBEAN

sub-regions’: western Caribbean [Mexico,

Belize, Guatemala and Honduras), southern
Caribbean (Nicaragua, Costa Rica and Panama, and
South American Colombia], the Lesser Antilles
(Venezuela, and the islands Aruba, Curacao, Bonaire,
Trinidad and Tobago, Barbados, Grenada, St Vincent
and the Grenadines, St Lucia, Martinique, Dominica,
Guadeloupe, Antigua and Barbuda, Montserrat, St
Kitts and Nevis, St Martin (Sint Maarten), St Eustarius,
Saba, Anguilla, the British Virgin Islands, Turks and
Caicos Islands, and the US Virgin Islands) and the
Greater Antilles (Puerto Rico, Hispaniola, Jamaica, the
Cayman Islands and Cuba). In the wider Caribbean
context, here we also consider the Guyanas (Guyana,
Suriname and French Guiana], the Bahamas and the
east coast of Florida.

The coastlines of the mainlands and islands
under consideration stretch from about 26°N to 4°S
and from 88°W to 52°W, and are influenced by the Gulf
of Mexico, the Caribbean Sea and the Atlantic Ocean.
They stretch from the Tropic of Cancer (only the north-
ern Bahamian islands and Florida are subtropical) to
just north of the equator.

In a review of seagrass ecosystems and resources
of Latin America in 1992, Phillips' stated that “the
most basic research is needed in almost every place”.
During the subsequent decade, the number of
published reports and surveys on the biology and
ecology of the seagrasses of Central and South
America has increased. The seagrass communities of
some of the islands of the Bahamas, and the Greater
and Lesser Antilles, have also been quite well studied,
but both quantitative and qualitative information on the
status of seagrasses is highly variable, reflecting the
large number of countries and territories which make
up the region and their individual political and
economic approaches to research, as well as
exploitation and protection of coastal marine

T: Caribbean region includes the following

J.C. Creed
R.C. Phillips
B.I. Van Tussenbroek

resources. Substantial research is still needed in order
to provide a comprehensive assessment of Caribbean
seagrasses.

Seagrasses are found throughout the Caribbean.
They grow in the reef lagoons between the beaches and
coral reefs or form extensive meadows in more
protected bays and estuaries. Seven seagrass species
are recognized. Turtle grass, Thalassia testudinum, is
the most abundant seagrass in the region, but is not
known south of Venezuela. Plants are erect, leaves
generally varying from 5 to 15 mm wide and from 10 to
50 cm long, but can reach up to 1 m. This seagrass
forms dense rhizome mats below the sediment
creating extensive meadows on shallow sand or mud
substrates from the lower intertidal to a maximum 10-
12 m depth, but has also been reported below 20 m.
Manatee grass, Syringodium filiforme, has a similar
geographical distribution, with cylindrical, narrow
leaves which form canopies up to 45 cm high. It usually
grows intermixed with Thalassia testudinum, but can
grow in monospecific areas, beds or patches from the
upper sublittoral down to more than 20 m.

Shoal grass, Halodule wrightii, is found
throughout the wider Caribbean region. It has small,
supple, grass-like leaves varying in width between 2
and 5 mm and in length between 4 and 10 cm, but
sometimes reaching more than 50 cm in length. It is
found growing on sand and mud from the intertidal
down to 5 m. Ruppia maritima, widgeon grass, is also
found throughout the Caribbean and, like Halodule
wrightii, has small grass-like leaves. It is a shallow-
water species found in the brackish waters of bays and
estuaries between 0 and 2.5 m deep. The three sea vine
species belonging to the genus Halophila - Halophila
baillonii, Halophila engelmanni and Halophila
decipiens - are small and delicate. Their leaves are
paddle shaped, are less “grass-like” than the other
species and lack a basal sheath. Halophila decipiens Is
found in deep water [to 30 ml), while Halophila

305.N 0200 400 600 Kilometers
az

Gulf of

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Biscayne Bay —~

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~ Indian River Lagoon
° — Sebastian Inlet
=,
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a? BAHAMAS

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Calabash Cay r
ai South Water Cay JAMAICA

CARIBBEAN SEA

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fone >

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.

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Map 23.1
The Caribbean

engelmanni is found only down to 5 m and is restricted
to the Bahamas, Florida, the Greater Antilles and the
western Caribbean. Halophila baillonii is only found in
the Lesser Antilles”.

ECOSYSTEM DESCRIPTION

The coastlines of the Caribbean are characterized by
three ecosystems: seagrasses, coral reefs and
mangroves, with numerous linkages and trophic
interactions existing between these ecosystems".
Seagrasses are considered to be open systems,
exporting leaves and other components of primary
production in the form of organic material to other
habitats. At Galeta Point, Caribbean Panama, a
0.01-km* seagrass bed has been estimated to export
37-294 kg/month of Thalassia testudinum leaves, and
3-171 and 3-74 kg/month, respectively, of the
associated macroalgae Laurencia and Acanthophora
spp. Seagrass and its associated algal material can
even end up as offshore foodfalls, which have been
shown to be a significant pathway by which energy
enters the deep sea‘. Seagrasses, by stabilizing
sediments in their extensive systems of roots and
rhizomes, prevent abrasion and burial by sediments of
the adjacent corals during storms.

Migratory movements of various animals such as
fish, spiny lobsters, prawns and sea urchins enhance
the links between the seagrasses, reefs and
mangroves. These migratory movements can occur on
a daily basis (e.g. foraging in the seagrass beds during
the day and sheltering from predation in the reefs
during the night) or seasonally, when juvenile stages of
species migrate from mangroves or seagrasses to the
reefs when reaching adulthood”.

Thalassia testudinum typically dominates
seagrass vegetation in the reef lagoons where it often

The Caribbean

coexists with Syringodium filiforme, Halodule wrightii
and calcareous rhizophytic green algae belonging to
the order Caulerpales, amongst which Halimeda spp.
are the most conspicuous members, and play an
important role in production of sediments. Calcium
carbonate sand production of Halimeda spp. in
seagrass beds can exceed 2 kg/m*/year”. Other non-
calcified rhizophytic algae of the same order such as
Caulerpa spp. and Avrainvillea spp. are also found in
these beds. Drifting or free-floating masses of algae
(e.g. Laurencia spp., Lobophora sp., Euchema sp.,
Hypnea sp. and Acanthophora sp.) may be abundant
locally. Thalassia testudinum-dominated communities
in reef environments are usually preceded on the beach
side by a small fringe of Halodule wrightii. In deeper
waters, other seagrasses such as Syringodium
filiforme and Halophila decipiens replace Thalassia
testudinum.

In more protected areas, such as estuarine
environments, or zones influenced by mangroves, and
depending on prevailing salinity, nutrient conditions,
light and sediment conditions, seagrass vegetation
consists of virtually monospecific beds or alternating
monospecific patches of Thalassia testudinum and
Halodule wrightii with rhizophytic Caulerpa spp. and
loosely attached green algae, many of which belong to
the order Dasycladales (e.g. Batophora sp.,
Acetabularia spp.). Drifting mats, when occurring, are
typically formed of filamentous red and green algae in
these areas. Ruppia maritima is found in brackish
waters in bays and estuaries, sometimes with Halodule
wrightii. Halodule wrightii forms monospecific stands
in lagoons with high salinity fluctuations. Halophila
spp. grow in finer sands and sediments, forming
monospecific or mixed species beds with the above-
mentioned seagrasses. Halophila spp. require less
light than the other seagrass species, and can be found
in very deep waters or in very shallow areas with turbid
conditions.

Seagrasses are colonized by calcareous and
filamentous epiphytes. In classic models of Caribbean
seagrass succession, rooted vegetation starts with
rhizophytic algae followed by Halodule wrightii (and
sometimes Syringodium filiforme) which are con-
sidered to be pioneer species, with a Thalassia
testudinum-dominated vegetation as climax" ””.

An enormous diversity of fauna is associated with
the Caribbean seagrasses. Groups that contribute most
to the richness of seagrass systems in the Caribbean
are fish, echinoderms, decapods, gastropods, mollusks
and sponges. Foraminifera, polychaetes, oligochaetes,
nematodes, coelenterates, amphipods, isopods,
hydrozoans and bryozoans are important mesofaunal
groups. The Caribbean seagrasses have distinct
demersal fish assemblages. Fish assemblages in the

235

236

WORLD ATLAS OF SEAGRASSES

seagrasses vary depending on their affinity with
mangrove and coral reef communities. At Martinique,
French West Indies, 65 species of fishes belonging to 28
families were collected in Thalassia testudinum beds.
In Belize barrier reef lagoons, the fish community Is
dominated numerically and in biomass by grunts,
apogonids and tetraodontiforms. Most fishes are either
juveniles of species that occur as adults on the reef, or
are small species that reside in the lagoon. In Panama
and the Virgin Islands, juvenile snappers, scorpion
fishes, grunts and goatfishes in seagrass meadows
feed predominantly on decapod crustaceans and other
fishes.

Macroinvertebrate diversity in seagrass beds is
high; for example, in Venezuela, 127 macroinvertebrate
species are associated with the seagrass beds at
Mochimba Bay'!. Throughout the Caribbean, sea
urchins such as Lytechinus variegatus and Tripneustes
ventricosus are also major herbivores of seagrass

Case Study 23.1
FLORIDA'S EAST COAST

The seagrasses of Florida’s east coast, from
Mosquito Lagoon [29°N] in the north to lower
Biscayne Bay [25°N] south of Miami, occur in the
shallow lagoonal coastal river systems typical of this
area. [The seagrasses of the Florida Keys are
covered in Chapter 22.) Approximately 2800 km? of
seagrass habitat is found along the east coast of
Florida, much of it in the Indian River Lagoon, 250
km long and encompassing population centers and
many canal-side and marina-oriented housing
developments. Estimates of seagrass decline in-
clude a loss of about 30 percent from the Indian
River and, since 1950, a 43 percent loss from the
northern and urbanized section of Biscayne Bay.
However, Indian River seagrasses showed some
increase during the years 1994-987.

In the Indian River, dredge spoil islands
vegetated with mangroves and Australian pines dot
the intercoastal waterway; bridges and supported
highways cross the river to provide access to the
coastal beaches. The east coast of Florida is subject
to hurricanes. Manatee live in the Indian River,
eating seagrass; many manatee are killed or
scarred by boat propellers. In the cooler winter
months, manatees cluster in the warm water at the
outlets of electric plants, deep boat basins and
other large facilities.

Seven species of seagrass are found along

blades, consuming 0.155 (Jamaica) and 1.4 (St Croix,
US Virgin Islands) g dry weight/individual/day,
respectively, of Thalassia testudinum. Diadema
antillarum is another important herbivorous urchin in
some places. Leaves of seagrasses are used as a
substratum by invertebrates such as hydroids and
sponges. Foraminiforans play a large role in the
production of calcareous sediments.

Two potentially important mesofaunal top-down
regulators in Thalassia testudinum beds are the
isopod Limnoria simulata, which bores into the live
tissue of Thalassia testudinum”, and the small green
snail Smaragdia viridens, which grazes on the
chloroplast-containing epidermis. Macroalgae in sea-
grass beds can provide food and shelter for associated
fauna. The inconspicuous epiphytes are a major food
source to members of the mesofauna. The seagrass-
associated alga Batophora sp. is a preferred source of
food for the queen conch, and Laurencia spp. are the

Florida's east coast, usually in mixed beds
rather than pure stands: Thalassia testudinum,
Syringodium filiforme, Halodule wrightil, Halophila
decipiens, Halophila engelmanni, Ruppia maritima
and Halophila johnsonii. The first six are also found
throughout the Caribbean. Similar to its growth habit
in other areas, Thalassia testudinum is a climax
species, slow growing, long lived and requiring high
light levels. Thalassia testudinum is more abundant
in the south, reaching its northern limit in the mid-
Indian River Lagoon; beds often persist for decades.
Shoal grass, Halodule wrightii, is the most abundant
seagrass in the main part of the Indian River Lagoon,
an early colonizer, and grows in both shallow and
mid-depths (to 2 m). Syringodium filiforme is known
as "Manatee grass” and is habitat and food for the
manatee and the second-most commonly occurring
species in the Indian River Lagoon, although in
Mosquito Lagoon, a sub-estuary of the Indian River
Lagoon, Ruppia maritima is more common than
Syringodium filiforme. Elsewhere in the Indian River,
Ruppia maritima is common and grows in both salt
and fresh environments. The Halophila species in
Florida include the cosmopolitan Halophila decipiens
and Halophila engelmanni, and the rare and fragile
Halophila johnsonii, a seagrass found only along the
southeast coast of Florida between Sebastian Inlet
(27°51'N) and Virginia Key (25°45'N), primarily in the
Indian River.

Halophila johnsonii was given threatened
species status in 1998 by the National Marine

principal settling substrate for the recruitment of the
spiny lobster.

Seagrass beds have been recognized as
productive fishery areas in the Caribbean'”. Soft-
bottom demersal fisheries exploit scianeids, mullets,
snappers, groupers, grunts, sharks, penaeid shrimp,
loliginid squid and octopods over seagrass beds. Other
resources are free-living macroalgae Eucheuma and
Hydropuntia, which are collected and used to make
seamoss drinks in the Lesser Antilles and seamoss
porridge in Belize. The queen conch and the spiny
lobster are major fisheries resources. The queen
conch Strombus gigas is associated with Thalassia
testudinum beds and is now seriously threatened by
overfishing. The spiny lobster Panulirus argus is also a
very important resource fished in the seagrass beds
and on the nearby reefs. Though its abundance has
decreased due to overfishing, present restrictions in
fisheries aim to protect this resource in various

Fisheries Service under the Federal Endangered
Species Act. It has one of the most limited
geographical distributions of any seagrass in the
world, although it is currently under genetic study to
investigate the possibility that it may be an
introduced species*™, Beds of Halophila johnsonii
are highly transient and the plants are quick
growing, with individual plants reaching mature size
in about two weeks and beds often persisting no
longer than a few months. Beds are often
discontinuous and patchy. Neither male flowers of
Halophila johnsonii nor seeds or seedlings have
been found, and it is speculated that the plant's
populations are maintained by vegetative growth
alone™!. The St Johns River Water Management
District has been monitoring seagrass in the Indian
River since 1994. The monitoring program has
documented large changes in the distribution of
some seagrasses, with Halophila johnsonii and
other Halophila species increasing more than 500
percent in four years at some locations.

Grouper, snapper, sea trout and flounder use
seagrass habitat as nursery on the Florida east
coast. Bay scallops, shrimp and blue crabs also
depend on seagrasses. Controls on dredge and fill
activities set standards for turbidity, water color and
other physical parameters. There are guidelines to
protect manatee habitat and to preserve indigenous
life forms, including seagrasses, on State of Florida
submerged lands. Removal or destruction of
seagrasses in state parks Is forbidden, and some

The Caribbean

countries. In Belize, spiny lobster and queen conch
contribute most of the total value of exported seafood,
estimated at US$10.4 million in 1995. Spiny lobster
fishing alone is worth over US$23 million per year in
Nicaragua.

The Caribbean is exposed to three types of
natural hazard: hurricanes, volcanic eruptions and
earthquakes. Hurricane activity may result in loss of
seagrass vegetation because of sediment erosion or
sediment deposition on the seagrass beds. In 1989
Hurricane Hugo, with squalls exceeding 160 knots,
was the most violent of the century to pass over
Guadeloupe and Puerto Rico. It had a more
destructive impact on Syringodium filiforme beds
than on Thalassia testudinum. Hugo eroded
nearshore areas, and tens of square kilometers of
highly productive seagrass meadows were destroyed
by the formation of large sediment “blow-outs”, holes
in otherwise continuous seagrass meadows. Such

areas limit boats with engines in order to decrease
propeller scarring of the grass beds. Educational
efforts aimed at sports fishers and boaters are
attempting to decrease human impacts on sea-
grasses, though the impacts from land-based
human development are probably of greater concern.

Photo: FT. Short

237

238

Photo: E. Green

WORLD ATLAS OF SEAGRASSES

A “blow-out” in the Turks and Caicos Islands.

blow-outs can migrate and expand, taking many years
to recover".

However, in many cases, either hurricanes had no
visible effects at all® '’’ or recovery was relatively fast,
which was the case for Thalassia testudinum in a
Mexican Caribbean reef lagoon in 1988 after the
passage of Hurricane Gilbert, a class 5 hurricane with
the lowest atmospheric pressure (888 mb) ever
reported in the area’. In Costa Rica, the Limon
earthquake of 1991 resulted in a 0.5 m uplift of a lagoon
and Thalassia testudinum completely overgrew it,
although the following year there was an equivalent
reduction in seagrass area”. Perez and Galindo’
reported mass defoliation of Thalassia testudinum in
Parque Nacional Morrocoy, Venezuela, due to
hyposalinity after torrential rains, but recovery was fast
(several months] as the apical-shoot meristems did not
die and shortly after the event formed leaves again.
These reports indicate that overall, under natural
conditions, Caribbean seagrass beds seem to be fairly
resistant or resilient to major natural disturbances.

PRESENT DISTRIBUTION
The only data available on area coverage of seagrasses
are from specific studies in which seagrasses have
been mapped at a very local scale. The following
estimates are compiled from various sources: Mexico
500 km’; Belize 1500 km’; Guatemala (one site] 20 km’;
Nicaragua (Great Corn Island) 2.4 km’; Costa Rica
(Parque Nacional Cahuita) 0.2 km’; Venezuela (Cariaco
Gulf] 500 km’; Curacao 8 km’; Bonaire 2 km’; Tobago
0.64 km’; Martinique 41.4 km’; Guadeloupe 82.2 km’;
Antigua [Seatons Harbour] 1 km’; Puerto Rico (La
Parguera, Guayanilla Bay) 27.68 km?; Jamaica
(Discovery Bay] 0.5 km’; Cuba (Cayo Coco, Sabana-
Camagtey Archipelago] 75 km’; Grand Cayman 25 km’.
More extensive mapping may have been carried
out but area estimates not published; further mapping
and distribution studies in the Caribbean are badly

needed. Distribution data are required in order to
assess the real or potential threats to seagrass and
losses. Determining the distribution of Caribbean
seagrasses is a problem because mapping of coastal
marine resources using remote-sensing techniques
has only recently been refined to be able to differentiate
seagrass communities, and most countries in the
Caribbean have neither the infrastructure nor the
funding to execute projects of this nature.

HISTORICAL PERSPECTIVES

There are few historical reports on permanent losses of
seagrass beds in the Caribbean. Barbados and
Carriacou in the Grenadine Island chain lost
seagrasses between 1969 and 1994. In Trinidad and
Tobago seagrass beds once found in Scotland Bay,
Grand Fond Bay (Monos Island], Five Islands, Cocorite
(near the mouth of the Diego Martin River] and
Speyside in Tobago have disappeared.

In the past, grazing by the green turtles and
manatees must have had an enormous impact on the
seagrass beds. The common names “turtle grass” and
“manatee grass” are a testament to the importance of
seagrasses in the diet of the green turtle Chelonia
mydas and the West Indian manatee Trichechus
manatus. The manatee and the green turtle are
threatened throughout the Caribbean because of
overfishing and, in the case of the turtle, the collection
of eggs for food. Although both animals have received
considerable conservation status, they are still hunted.
We can only speculate about their past impact on the
seagrass communities and how these communities
have changed since populations of these large
herbivores have diminished or disappeared.

PRESENT THREATS
The vast expanses of the seagrass beds in the
Caribbean, together with their relatively high resistance
or resilience to major natural disturbances, may give a
false sense of security and lead to the perception that
they are immune to human impacts. Socio-
economically, the Caribbean region includes high
proportions of urban human populations and rapidly
expanding agricultural and tourist-industrial frontiers.
The population growth of the Caribbean over the last 20
years has been estimated to be 58 percent", which has
led to increasing pressure on the adjacent coastlines
and their seagrasses. Additionally, an estimated
12 million tourists per year visit the Caribbean region.
The number of tourists who visited the Belize Barrier
Reef Complex in 1994 was 128000, generating an
estimated US$75 million.

On local scales, seagrasses are being destroyed
or removed by the construction of coastal develop-
ments associated with tourism or other coastal

activities. Tourist developments are accompanied by
the construction of harbors and docks, channel
dredging and recreational moorings. In Venezuela,
houses were constructed over seagrass beds'”. At La
Parguera, Puerto Rico, increased traffic of ships and
recreational vessels are causes of anchor damage,
littering, trampling, propeller scarring, fuel impacts,
detrimental shading of the seagrasses by marinas and
piers, and damage of the beds by dredging. Seagrass
beds in front of hotel beaches are often removed, for
example in Pointe Sable National Park on St Lucia, in
Venezuela and in Mexico. At other sites, seagrasses
have been removed to make way for salt production and
mariculture; seagrass beds were used for the
cultivation of seamoss (Gracilaria spp.) in St Lucia. In
Guatemala 95 km’ were lost between 1965 and 1984 to
shrimp and salt production. In St Lucia, dynamite
fishing has destroyed seagrass areas. Damage of
seagrasses through illegal sand mining from beaches
is widespread, particularly in the smaller islands. Sand
mining suspends sediments and alters local
hydrodynamics. The seagrasses at Ambergris Cay,
Belize, have been damaged by dredging (sand
extraction and deposition], and Belize has suffered
coastal erosion because of sand land seagrass]
removal.

Pollution from land-based sources varies from
country to country. The greatest threats are from

Case Study 23.2 é
PARQUE NATURAL TAYRONA, BAHIA DE CHENGUE, COLOMBIA

The small bay (3.3 km’) of Bahia de Chengue is
situated on the Caribbean coast of Colombia in the
Parque Natural Tayrona’”. The bay contains
sedimentary beaches, rocky shores, small lagoons
and small rivers. Mangroves, coral reefs and
seagrass beds consisting mainly of Thalassia
testudinum occur in the bay. Four other seagrass
species (Syringodium filiforme, Halodule wrightii,
Halophila baillonii and Halophila decipiens) are also
found in the bay. Syringodium filiforme can form
monospecific patches.

Corals of the genera Manicina, Siderastrea,
Millepora, Diaporia, Porites and Cladocora grow
within the Thalassia testudinum beds. Sea urchins
and seaweeds, such as Halimeda opuntia, are
common within the beds.

Biological diversity is considered to be high at
Parque Natural Tayrona because of the range of
habitats. For example 372 fish species have been
reported for this area. Thalassia testudinum
biomass has been estimated as between 631 and

The Caribbean

eutrophication (sewage and agricultural fertilizers),
hydrocarbons, pesticides and other toxic wastes'”.
Eutrophication is characterized according to type of
effluent discharge, being diffused through freshwater
surface runoff (for example, rivers], distinct point
sources [effluents from sewage treatment plants] or
multiple point sources (such as submarine springs
connected to the aquifers that are contaminated by
land-based human activities]. The detrimental effects
of diffuse river loads are exacerbated by erosion of
watersheds caused by deforestation, urbanization and
agricultural activities. Throughout the Caribbean, the
impact of moderate eutrophication on seagrass
ecosystems results in changes in community structure
or species composition and higher productivity of
epiphytes on seagrass leaves. As nutrient loads
increase, epiphytes or drifting algal masses become
more abundant, resulting in a decline in seagrass shoot
density, leaf area and biomass.

Rapidly increasing development throughout the
Caribbean will result in an ever-increasing load of
wastewater nutrients into coastal marine environ-
ments; such loading has already been particularly
damaging to seagrasses at Curacao, at Antigua and
Barbuda and in Jamaica. Oil is drilled in the southern
region of the Caribbean with Venezuela and Trinidad
and Tobago being the principal producing countries!”
In 1986, 8 million liters of crude oil spilled onto

1831 g dry weight/m/ with green leaves representing
less than 10 percent of that weight. Productivity has
been estimated as 1.71-5.36 g dry weight/m?/day.
Twenty-six shrimp species have been identified
within the Thalassia testudinum beds.

The importance of the site lies in its proximity
to Santa Marta and the Instituto de Investigaciones
Marinas y Costeras [INVEMAR) and because it is
relatively well preserved. Only one family lives on
the bay and there is no road, so tourists are rare.
There is fishing and small-scale salt mining in the
bay, and fishermen sometimes use dynamite to
fish. Gill nets and beach seines are extended across
the seagrass beds.

Bahia de Chengue is a CARICOMP site and is
thus regularly monitored. Such programs usually
attract future studies to the regions where they are
initiated. This seagrass site is representative of
the region, although it is relatively protected
from human impacts and receives special attention
from scientists.

239

240

WORLD ATLAS OF SEAGRASSES

Case Study 23.3
PUERTO MORELOS REEF NATIONAL
PARK

Puerto Morelos Reef National Park (Parque
Nacional Arrecifes Puerto Morelos] is situated at
21°00'00" and 20°48 °33"N, and 86°46 °39"W and has
an area of ca 90 km’. It extends along the northern
part of an extensive barrier-fringing reef complex
that runs from Belize to the Yucatan Strait [Mexico],
the second largest barrier-fringing reef complex in
the world. In this park, three seagrass species and
264 macroalgal species have been reported,
together with 649 species of marine invertebrate and
vertebrate fauna”. The dominant ecosystems are
coral reefs, seagrass beds and the inland
mangroves which are separated from the marine
environment by sand berms 2-3 m high. During
periods of exceptionally heavy rains, overflow of
mangrove wetlands exports brackish tannin-colored
waters into the lagoon. The Yucatan limestone is
extremely karstic, and rainwater rapidly infiltrates
into the aquifer, resulting in the absence of surface
drainage or rivers. Rainfall varies between 1.1 and
1.3 m per year, and the water passes through an
immense network of underground caves and
channels to vent into marine coastal areas through
submarine springs (ojos del agua) and fissures.
Thus, the lagoon environment is_ principally
governed by marine conditions. The water in the
lagoon is oligotrophic: low mean nitrite (0.06 uM),
nitrate (13.9 uM) and phosphate (0.46 pM)
concentrations were recorded during 1982 and 1983.
Salinity varies little throughout the year, generally
fluctuating between 35.8 and 36.2 psu. Surface
water temperature varies seasonally, from ca 26°C
in the winter [extreme minimum of 12.5°C) to 31°C
in the summer [extreme maximum 34.5°C]. The
vegetation in the lagoon largely consists of Thalassia
testudinum, accompanied by Syringodium filiforme
{occasionally Halodule wrightii) and rhizophytic and
calcareous algae growing on coarse carbonate sand.
Halodule wrightii forms very narrow fringing zones
near the beach. During 1990-91, total biomass of
Thalassia testudinum in Puerto Morelos reef lagoon
attained annual mean values of 573 g dry weight/m?
in a back-reef station, 774 g dry weight/m? in a
coastal fringe area and 811 g dry weight/m’ in a lush
bed in a mid-lagoon station: leaf biomass
constituted between 4.8 and 8.6 percent of total
biomass”. Total biomass of Syringodium filiforme
or Halodule wrightii is usually small when growing

intermixed with Thalassia testudinum [between ca
20 and 250 g dry weight/m’), but can attain high
values (>500 g dry weight/m?) in small monospecific
patches or fringes”.

The Mexican Caribbean coast of the Yucatan
Peninsula has undergone immense growth over the
last four decades. It is now one of the premier
destinations for resort tourism within the Caribbean.
Amongst the major attractions are the crystal-clear
seas, the white-sand beaches and the reef
ecosystems. The reefs of Puerto Morelos received
the status of National Park through presidential
declaration in February 1998. The effects of
increased population pressure throughout the
region have been substantial. Puerto Morelos has
changed from a tiny fishing village to a rapidly
growing community of approximately 3000 residents
and 2500 hotel rooms”! Several significant
potential sources of nutrients occur in the region:
hotels, intensive farming, rubbish disposal and
residences.

Although the Puerto Morelos Reef National
Park lagoon is relatively pristine, the increasing
pressure of human development is starting to be
noticeable. The village of Puerto Morelos is not yet
equipped with a central sewer system, and wastes
are discharged into septic tanks or directly, without
any treatment, into holes in the ground. These land
sources of nutrients can enter the water table and
flow through to the reef lagoon kilometers away.
Reefs in the coastal seas thrive under low natural
nutrient concentrations [also the reason why the
waters are so clear], which implies that any
increase in nutrient input into these areas may
cause drastic changes in the coastal ecosystems in
the near future.

Thalassia testudinum shoot with a female flower.

Photo: F.T. Short

The Caribbean 241
— DDO AN KT

seagrasses at Bahia Las Minas, Panama’. Thalassia

testudinum initially suffered blade damage and
browning but eventually recovered, except for a 20-90
cm wide shoreward margin where the seagrass died
off. Syringodium filiforme, which proved to be more
sensitive, still had lower biomass two to three years
after the event. The density of seagrass infauna was
reduced by a factor of three at oiled sites. Additionally,
effluent from bauxite mining has been reported to
damage seagrass beds in Jamaica, Suriname, Guyana,
the Dominican Republic and Haiti'"”.

Often different factors of human impact act
synergistically and together they are responsible for
severe seagrass loss. For example, overfishing of
wrasses and triggerfish off the coast of Haiti and the US
Virgin Islands caused an explosion in sea urchins which
then destroyed the seagrass beds by overgrazing. In
Jamaica, urban and industrial pollution, dredging of
canals, landfilling, bauxite mining, oil spills,
channelization, urban runoff, urban sewage,
construction of river bulkheads and docks, artificial
beach nourishment, thermal effluents and cement
tailings all degrade seagrass ecosystems'”. Other
seagrass beds near industrial areas are also highly
impacted, such as those at Lake Maracaibo
{Venezuela}, the "El Mamonal" industrial complex
(Cartagena Bay, Colombia], the west coast of Trinidad
and Havana Bay in Cuba’. The replanting of
seagrasses has successfully mitigated a fraction of
these impacts.

As seagrasses actively form and maintain
extensive subtidal flat structures in the Caribbean,
there is concern about the effects of global warming
and sea-level rise on seagrasses. Models of global
climate change predict considerable changes for the
coastal environments of the Caribbean, including rising
sea level, increasing water temperature and more
frequent hurricanes. Seagrasses should be able to
maintain vertical rates of habitat accretion in pace with
predicted rises in sea level until at least the middle of
this century, and a rise in sea level is not expected to
seriously affect the predominant species unless a
general deterioration of the habitat occurs”.

POLICY, REGULATION, PROTECTION

In the Caribbean, two major intergovernmental efforts
to protect the environment can be singled out: the
Caribbean Environment Programme of the United
Nations Environment Programme (CEP-UNEP) and the
Meso American Barrier Reef Project [Sistemas
Arrecifales Mesoamericanos) which forms part of the
Corredor Bioldgico Mesoamericano (CBM). Both
include countries of the Caribbean which have
recognized the desirability of managing marine coastal
areas; seagrasses are included, but not singled out for

Sand dunes adjacent to Halodule wrightii and Thalassia testudinum
beds, Florida, USA

specific environmental legislation. Most countries are
formulating or have formulated marine management
system plans. Systems of marine protected areas vary
from country to country, but most include seagrasses.
Of the 31 fully managed marine protected areas of the
Caribbean, 24 (74 percent] include seagrasses'”".

The CARICOMP network (Caribbean Coastal
Marine Productivity network] was set up to monitor
coral reefs, mangroves and seagrasses”. In this
network, associated marine laboratories and conser-
vation units work together, using standardized tech-
niques to measure the target ecosystems. CARICOMP
was established in 1985, the associated network in 1990
and operation of the network was initiated at the end of
1992. The stated aims of CARICOMP are “to determine
the dominant influences on coastal productivity, to
monitor for ecosystem change, and ultimately to
discriminate human disturbance from long-term
natural variation in coastal systems over the range of
their distribution". To these ends, CARICOMP is
coordinated through a Data Management Centre at the
University of the West Indies in Jamaica. Seagrass
parameters such as biomass, areal productivity and
turnover, shoot density, leaf width and length, and leaf
area indices are measured twice yearly. CARICOMP
involves 27 institutions in 17 countries where
seagrasses are being, or will be, monitored”.

ACKNOWLEDGMENTS
We would like to acknowledge the help and information provided by
Phanor Montoya-Maya, Eduardo Klein, Daisy Pérez and Ricardo Bitter-

hoto: C.A. Moncreiff

242

WORLD ATLAS OF SEAGRASSES

Soto, The first author was supported by fellowships from CNPq and UERJ
(Prociéncia) during the preparation of this chapter. The third author is
grateful to Tracy Blanchon for critically reviewing the manuscript.

AUTHORS

Joel C. Creed, Laboratorio de Ecologia Marinha Bentica, Departamento
de Ecologia, Instituto de Biologia Roberto Alcantara Gomes, Universidade
do Estado do Rio de Janeiro - UERJ, PHLC Sala 220, Rua Sao Francisco

REFERENCES

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America. In: Seeliger U (ed) Coastal Plant Communities of Latin
America. Academic Press, San Diego, California. pp 107-121.

2 Littler DS, Littler MS [2000]. Caribbean Reef Plants. Offshore
Graphics, Washington.

3 UNESCO [1983]. Coral Reefs, Seagrass Beds and Mangroves: Their
Interaction in the Coastal Zones of the Caribbean. UNESCO Reports
in Marine Science 23.

4 Kilar JA, Norris JN [1988]. Composition, export, and import of drift
vegetation on a tropical, plant-dominated, fringing-reef platform
(Caribbean, Panama]. Coral Reefs 7: 93-103.

5 -Freile D, Hillis L [1997]. Carbonate productivity by Halimeda
incrassata in a land proximal lagoon, Pici Feo, San Blas, Panama.
Proceedings of 8th International Coral Reef Symposium 1: 767-772.

6 Patriquin DG [1975]. “Migration” of blowouts in seagrass beds at
Barbados and Carriacou, West Indies, and its ecological and
geological implications. Aquatic Botany 1: 163-189.

7 UNESCO [1998]. CARICOMP - Caribbean Coral Reef, Seagrass and
Mangrove Sites. Coastal Region and Small Island Papers 3.

8 Williams SL [1990]. Experimental studies of Caribbean seagrass
development. Ecological Monographs 60: 449-469.

9 Van Tussenbroek BI, Brearley A [1998]. Isopod burrowing in leaves

of turtle grass, Thalassia testudinum, in a Mexican Caribbean reef

lagoon. Marine and Freshwater Research 49: 525-531.

Sturm MG de L [1991]. The living resources of the Caribbean Sea

and adjacent regions. Caribbean Marine Studies 2: 18-44.

Rodriguez RW, Webb RMT, Bush DM [1994]. Another look at the

impact of Hurricane Hugo on the shelf and coastal resources of

Puerto Rico, USA. Journal of Coastal Research 10: 278-296.

Glynn PW, Almodovar LR, Gonzalez JG [1964]. Effects of hurricane

Edith on marine life in La Parguera, Puerto Rico. Caribbean

Journal of Science 4: 335-345,

Van Tussenbroek BI [1994]. The impact of Hurricane Gilbert on the

vegetative development of Thalassia testudinum in Puerto Morelos

reef lagoon, Mexico: A retrospective study. Botanica Marina 37:

421-428.

Perez D, Galindo L [2000]. Effects of hyposalinity in Thalassia

testudinum (Hydrocharitaceae] from Parque Nacional Morrocoy,

Venezuela. Revista Biologia Tropical 48: (Supplement) 243-249.

UNEP [1997]. Global Environment Outlook. Oxford University

Press, New York.

Vera B [1992]. Seagrasses of the Venezuelan coast: Distribution and

community components. In: Seeliger U (ed) Coastal Plant

Communities of Latin America. Academic Press, San Diego,

California. pp 135-140.

oOo

Xavier 524, CEP 20559-900, Rio de Janeiro RJ, Brazil. Tel: +55 (021 2587
7328. Fax: +55 (0)21 2587 7655. E-mail: jcreed(dopenlink.com.br

Ron C. Phillips, 3100 So. Kinney Road #77, Tucson , Arizona 85713, USA.

Brigitta |. Van Tussenbroek, Unidad Acdemica Puerto Morelos, Instituto
de Ciencias del Mar y Limnologia, Universidad Nacional Autonoma de
Mexico, Apdo. Postal 1152, Cancun, 77500, Quintana Roo, Mexico.

17 UNEP [1994]. Regional Overview of Land-based Sources of
Pollution in the Wider Caribbean Region. CEP Technical Report
No. 33.

18 Marshall MJ, Batista V, Matias D [1993]. Effects of the 1986 Bahia
Las Minas, Panama, oil spill on plants and animals in seagrass
communities. In: Keller BD, Jackson JBC [eds] Long-term
Assessment of the Oil Spill at Bahia Las Minas, Panama Synthesis
Report. US Department of the Interior Minerals Management
Service OCS Study MMS 93-0048.

19 Thorhaug A, Miller B, Jupp B, Bookers F [1985]. Effects of a variety
of impacts on seagrass restoration in Jamaica. Marine Pollution
Bulletin 16: 355-360.

20 UNEP [1993]. Ecosystem and Socioeconomic Response to Future

Climatic Conditions in the Marine and Coastal Regions of the

Caribbean Sea, Gulf of Mexico, Bahamas, and the Northeast Coast

of South America. CEP Technical Report No. 22.

Kelleher G, Bleakley C, Wells S [1995]. A Globa! Representative

System of Marine Protected Areas. Vol. 4. Environment

Department, The World Bank, Washington.

22 Morris LJ, Virnstein RW, Miller JD, Hall LM [1999]. Monitoring
seagrass changes in Indian River Lagoon, Florida using fixed
transects. In: Bortone SA (ed) Seagrasses: Monitoring, Ecology,
Physiology, and Management. CRC Press, Boca Raton. pp 167-176.

23 Waycott, M. Personal communication.

24 Heidelbaugh WS, Hall LM, Kenworthy WJ, Whitfield P, Virnstein
RW, Morris LJ, Hanisak MD [1999]. Reciprocal transplanting of the
threatened seagrass Halophila johnsonii (Johnson's seagrass) in
the Indian River Lagoon, Florida. In: Bortone SA (ed) Seagrasses:
Monitoring, Ecology, Physiology, and Management. CRC Press,
Boca Raton. pp 197-210.

25 INE (Instituto Nacional de Ecologia, Comunidad de Puerto Morelos,
Quintana Roo) [2000]. Programa de manejo del Parque Nacional
Arrecife de Puerto Morelos. Instituto Nacional de Ecologia, México,
DF. 222 pp.

26 Van Tussenbroek BI [1998]. Above- and below-ground biomass and
production of Thalassia testudinum in a tropical reef lagoon.
Aquatic Botany 61: 69-82.

27 Gallegos ME, Merino M, Rodriguez A, Marba N, Duarte CM [1994].
Growth patterns and demography of pioneer Caribbean seagrasses
Halodule wrightii and Syringodium filiforme. Marine Ecology
Progress Series 109: 99-104.

24 The seagrasses of

South America: Brazil, Argentina and Chile

SOUTH AMERICA: BRAZIL,
ARGENTINA AND CHILE

coastlines and islands of the following countries:

Brazil, Uruguay, Argentina, Chile, Peru and
Ecuador. These coastlines stretch from about 5°N to
57°S and from 82°W to 34°W; thus they are influenced
by both the Pacific and Atlantic Oceans.

Phillips"! stated in 1992 in a review of seagrass
ecosystems and resources of Latin America that “the
most basic research is needed in almost every place”.
During the subsequent decade, the number of
published reports of surveys, biology and ecology of the
seagrasses of South America has increased somewhat.
However, despite the fact that some progress has been
made with respect to Phillips's comment, it must be
recognized that much important information remains
unavailable as gray literature or, as is often the case, no
information has been collected.

Te: geographical region considered includes the

ECOSYSTEM DESCRIPTION

Although South America’s seagrasses are the subject
of some taxonomic debate, at least six seagrass
species have been reported for the region; nearly all
are restricted to the Atlantic coast. In the southwest
Atlantic, seagrasses are common but rarely form very
extensive meadows. Remarkably, the only seagrasses
known on the Pacific coast of South America are
a couple of small populations of Heterozostera
tasmanica (now Zostera tasmanica] in northern Chile at
Coquimbo™!. Intriguingly, this species is otherwise
known only from Australia; it has been suggested that
these are remnants of formerly widely distributed
Chilean populations". No seagrasses are known for
Peru or Ecuador.

Shoalgrass (Halodule wrightii) and sea vines
(Halophila decipiens) have a tropical-subtropical
distribution in the southwest Atlantic, stretching from
the Caribbean to the Brazilian states of Parana and Rio
de Janeiro, respectively. Surprisingly, Syringodium
filiforme and Thalassia testudinum, which one might

J.C. Creed

also expect to find, are restricted to the Caribbean and
are not found in the southwest Atlantic. Consequently,
in the northeast of Brazil Halodule wrightii is able to
form large monospecific beds, such as those found at
Itamaraca Island.

In Brazil, Halodule wrightii is the seagrass that
most frequently occurs and has the widest distribution.
Halophila baillonii, which is also found widely in the
Caribbean, has been reported twice [in 1888 and in the
1980s, though not since} at Itamaraca Island, in the
northeast of Brazil. Large extents of the Brazilian
coastline have no recorded seagrasses, either because
seagrasses have not yet been found or because they are
not present. The continental shelf is sometimes as
narrow as 15 km, and for this and other reasons
extensive reefs have not developed in Brazil.
Consequently, along most of the coast Halodule
wrightii is restricted to estuaries, bays and other
protected ecosystems.

Where the continental platform widens, such as
in the Abrolhos region of Brazil, the formation of
extensive reefs allows the establishment of
seagrasses, which thrive in these protected areas.
Here, beds of Halodule wrightii (2-7 m] and Halophila
decipiens (5-22 m) become more common. Halophila
decipiens reaches its southernmost limit in the
Atlantic Ocean in Guanabara Bay at Rio de Janeiro,
right under the famous Sugarloaf Mountain. Because
it can occupy deeper waters, Halophila decipiens may
be of greater ecological importance than has
previously been thought, but its distribution is still
not very well known. As these species reach the
southeast of Brazil they form smaller and more
isolated populations.

Halodule emarginata is a species endemic to
Brazil, and forms small populations from northeast to
southeast Brazil. However, there is no agreement as to
whether Halodule emarginata should be maintained
as a distinct species from Halodule wrightii. Leaf-tip

243

244

WORLD ATLAS OF SEAGRASSES

characteristics are used to distinguish the species,
which rarely flower or fruit.

Ruppia maritima is found sporadically from
Brazil down to Argentina, where it forms the
southernmost populations of seagrass in the world, at
the Magellan Straits’. Such records reflect the
species’ wide latitudinal distribution and tolerance to
variable environmental conditions, as it can be found
growing in coastal lagoons and estuaries with
salinities from 0 to 39 psu. At the Patos Estuarine
Lagoon in southern Brazil, a large {about 120 km’) area
of Ruppia maritima dominates the benthos and local
primary productivity.

An unattached leaf of what was reported as
Zostera has been found at Montevideo, Uruguay.
Phillips" commented that the leaf tip resembled that of

Case Study 24.1
ITAMARACA ISLAND, NORTHEAST BRAZIL

The regional importance of the populations of
seagrasses at Itamaraca Island, Pernambuco State
(7245'S, 34°50'W) has been recognized for some
time". At ltamaraca there are large expanses of
Halodule wrightii on the eastern side of the island in
shallow-water flats protected from the open sea by
reefs. Locally, Halodule is known as capim agulha
which means needlegrass. In 1967, Halodule
stretched approximately 1.2 km seaward in a mapped
portion 1.2 km wide (1.4 km’], although the total area
is greater but unknown". Halophila baillonii, only
found at Itamaraca in Brazil, is known from
collections in the Santa Cruz Channel made in 1888

(9)

and in the 1980s, and has not been found since”.

ECOLOGICAL INTERACTIONS

There are ecological interactions between the
seagrasses and the local mangrove, estuarine and
reef systems. The fauna is taxonomically diverse:
over 100 macrofaunal and 46 epiphyte floral taxa
have been identified in or on Halodule at
ltamaraca”. Amongst the Halodule beds at
Itamaraca are clams, shrimp, lobsters, stone and
blue crabs, and common and ballyhoo halfbeaks, all
of which are fished recreationally and commercially.
The region’s seagrass beds are feeding grounds for
the West Indian manatee. About 12 metric tons a
year of Halodule wrightii are collected for fodder for
captive-reared manatees at the Centro de Pesquisas
do Peixe-boi Marinho {National Manatee Research
Centre] run by the Instituto Brasileiro do Meio-
Ambiente e Recursos Naturais Renovaveis IBAMA,
which is located on the island.

Heterozostera tasmanica but that it was unlikely that it
came from so far away as Chile.

The dearth of studies dealing with seagrasses in
South America can be exemplified by the Brazilian
experience, although Brazil has the most studies
available. After a pioneering study of the biota
associated with Halodule wrightii by Kempf’, few
studies were carried out until the 1980s. From 1980
until the present, an average of 22 additional
companion species a year have been reported
associated with the Brazilian seagrasses and the trend
suggests that this rate will continue”, demonstrating
that seagrass habitats are attracting research effort
(Figure 24.1}. However only one or two research
papers relating to seagrasses of the region are
published each year.

The area of Itamaraca is one of the most
productive fisheries in the state of Pernambuco, and
the seagrasses contribute as a nursery and foraging
area. Local inhabitants have reported regression in
the areal coverage of Halodule at |tamaraca.
Furthermore, the local fishermen report that a
reduction in the area of Halodule has resulted in a
drop in fisheries production, especially of prawn and
halfbeaks. It has been suggested that coastal
development, bad landuse practices, landfill,
pollution and an increase in tourism are responsible.
Local researchers have recommended that environ-
mental education programs be implemented to help
preserve and manage the ecosystem.

Three basic research needs have been
highlighted at Itamaraca Island:

Oo the realization of a survey of the distribution of
the seagrass meadows and their associated
flora and fauna;
the identification of impacting anthropogenic
agents;
the development of research programs which
identify the regional ecological importance of
seagrasses”.

The ltamaraca area stands out because:

o there is a co-occurrence of seagrass species;

fo) Halodule wrightii, a known pioneer in the
Caribbean seagrass succession, here is the
climax dominant;
the seagrass beds are of commercial
importance and may be suffering die-back due
to human activities.

=
So
i)

wo
So
So

nD
So
—)

a
2
3
a
a
2
w
a
oa
c
—
a
=
a
=>
=
&
Sa
E
|
oO

1980 1990 2000

Year reported

1960 1970

Figure 24.1
Cumulative number of companion species to the Brazilian
seagrasses reported since 1960”

BIOGEOGRAPHY

South American seagrasses are often found near to, or
closely trophically linked with, other marine and
coastal ecosystems and habitats, and this juxtaposition
results in heightened diversity. For example, recent
studies which have compared the macrofauna
associated with Halodule wrightii and Halophila
decipiens beds with nearby areas devoid of vegetation
have shown that total density, richness and the
diversity of the infauna is enhanced by the presence of
seagrasses. Coral reefs extend from the Caribbean to
Abrolhos, Brazil, and mangroves to Santa Catarina
State, Brazil, where they are replaced by salt marshes
and mud flats.

Halodule is associated with shallow habitats
without much freshwater input, such as reefs, algal
beds, coastal lagoons, rocky shores, sand beaches and
unvegetated soft-bottom areas and nearby mangroves
without too much salinity fluctuation. Halophila is
associated with deeper reefs, algal and marl beds, and
deeper soft-bottom vegetated areas. Ruppia maritima
can be found in low-salinity (coastal lagoon, estuary,
fishpond, mangrove, salt marsh and soft-bottom
unvegetated) and high-salinity [coastal lagoon, salt
pond, soft-bottom unvegetated) habitats.

Seagrass beds in South America are known to be
important habitat for a wide variety of plants and
animals. About 540 taxa [to genus or species level) of
organisms associated with the Brazilian seagrasses
have been compiled by Creed”. The groups that
contributed most to species diversity are polychaetes,
fish, amphipods, decapods, foraminifera, gastropod
and bivalve mollusks, macroalgae and diatoms.

Two threatened species which feed directly on

South America: Brazil, Argentina and Chile

Femando ae
Noronha

had
Ttamaraca Island }

”

a
2
-

Abrolhos Bank and__ =
Marine National Park ~te

Rio de Janeiro
Sao Pauloe
’

Guanabara Bay

? Coquimbo
\Patos Estuarine Lagoon
URUGUAY

ARGENTINA

{TLANTIC OCEAN

Magellan Straits

0 400 800 1200 1600 2000 Kilometers
ea ==

Map 24.1
South America

seagrasses from the Caribbean to Brazil are the green
turtle Chelonia mydas” and the West Indian manatee
Trichechus manatus"'. Both have benefited from
specific conservation action sponsored privately and by
the Brazilian environmental agency IBAMA (green
turtles by the Projeto TAMAR and manatees by the
Projeto Peixe-Boi Marinho]. The black-necked swan
Cygnus melancoryphus and the red-gartered coot
Fucila armillata also feed directly on Ruppia maritima
in southern Brazil and Argentina but are not
endangered”. Recently, the semi-aquatic capybara
Hydrochaeris hydrochaeris, which is the world’s
largest rodent, was observed feeding on Ruppia
maritima near Rio de Janeiro. Amongst the fauna
which use seagrasses as a habitat are two corals,
Meandrina brasiliensis and Siderastrea stellata. They
grow unattached in Halodule wrightii beds and are sold
as souvenirs locally.

While the seagrasses of South America
contribute to coastal protection and local productivity,
and thus fisheries, there is hardly any information
available about the value of seagrasses to the local
economy. Economically important fish species such as
the bluewing searobin (Prionotus punctatus),
whitemouth croaker (Micropogonias furnieri) and
mullet (Mugil platanus) are found and fished in
Brazilian seagrass beds. Local fisheries exploit
commercially important crustaceans such as blue

245

246

o
=
oO

WORLD ATLAS OF SEAGRASSES

Siderastrea stellata, a coral that occurs in a wide range of shallow
habitats and is common in seagrass beds

Ruppia maritima is found sporadically from Brazil down to Argentina

crabs [(Callinectes sapidus), stone crab (Menippe
nodifrons}, lobster (Panulirus argus and Panulirus
laevicauda) and shrimp (Penaeus brasiliensis and
Penaeus paulensis), all associated with seagrass beds.
Other shellfish which are commercially collected from
seagrass beds are clams (Anomalocardia brasiliana,
Tagelus plebeius, Tivela mactroides), volutes (Voluta

ebraea), rockshells (Thais haemastoma), oysters
(Ostrea puelchana) and cockles [(Trachycardium
muricatum)"”. In Chile, the Chilean scallop (Argopecten
purpuratus] preferentially settles in Zostera tasmanica
beds”.

HISTORICAL PERSPECTIVES

As no detailed seagrass mapping work has been
carried out in South America, there is little anecdotal or
factual information about changes in seagrass dis-
tribution and abundance. It is thought that the Zostera
tasmanica beds in Chile are historically remnant
populations of much larger meadows'". Researchers
from the Universidade Federal Rural of Pernambuco
are currently mapping Halodule wrightii beds at
Itamaraca Island, Brazil. This should allow some
measure of loss over the last 40 years to be estimated,
as the area was partially mapped before, in the 1960s.
For now, the only quantified seagrass loss is of
Halodule wrightii beds at Rio de Janeiro. These were
listed by Oliveira et al.’ and were revisited ten years
later”. Seagrass was no longer found at 16 percent of
these sites. Losses are not due to direct use of
seagrasses, as the only known use of Halodule wrightii
is to feed captive-reared manatees.

PRESENT DISTRIBUTION

Estimating the real area of seagrass cover in South
America is at present almost impossible because of
the dearth of studies. The little data available allow
only an educated “best guess”. Brazil probably has
about 200 km’ of seagrasses, Chile 2 km’ and
Argentina about 1 km’.

PRESENT THREATS

As Phillips" pointed out, all seagrasses found from
Mexico to southern Brazil are species characteristic of
the western tropical Atlantic Ocean, so management
problems concerning them should be relatively similar.
In fact, some general observations of threats to marine
coastal ecosystems are pertinent. The population of
Latin America continues to grow, from 179 million to
481 million between 1950 and 1995''". The concen-
tration of population growth in urban areas and
marginal agricultural lands is the main factor respons-
ible for pressures exerted by human population on the
environment’. In South America, this pressure is
concentrated in the coastal cities. The continent has
several large urban centers: Sao Paulo, Brazil,
population in 2000 27.9 million {second largest city in
the world]; Buenos Aires, Argentina, 11.4 million (12th);
Rio de Janeiro, Brazil, 10.2 million (16th]'”. By 2020,
over 80 percent of the population of South America is
expected to live in urban areas'". Such concentrations
put incredible stresses on the coastal marine

environment. Human activity affects the environment in
three major ways: landuse and landcover change, the
extraction and depletion of natural resources, and the
production of wastes.

It is necessary at least to know the distribution of
seagrasses in order to assess potential or real threats
to them. This is a problem when considering the
seagrasses of South America. Direct reports of impacts
on seagrasses on the continent are few. However,
pollution by heavy metals from sporadic mining and

Case Study 24.2
ABROLHOS BANK, BAHIA STATE, NORTHEAST BRAZIL

The Abrothos Bank is formed by a widening of the
continental shelf at the extreme south of the state of
Bahia [18°S, 38°W]. The area consists of an inner
line of reef banks, a small archipelago of five islands
with embryonic fringing reefs, and outer reef
banks". The Abrolhos Marine National Park
protects the archipelago, surrounding waters and an
inshore reef system. Peculiar to the area are reef
columns called chapeiroes which typically extend
from a depth of about 20 m to the surface.
Nearshore areas are subjected to higher turbidity
because of local river inputs but offshore areas are
characterized by less turbid waters.

Despite the considerable research interest
invested in the national park, until recently"*
seagrasses were overlooked and not reported. In
fact, Halodule wrightii and especially Halophila
decipiens are more common than previously
believed. Halodule wrightii is found in shallow sandy
areas interspersed with coastal reefs and around the
Abrolhos Archipelago, while Halophila decipiens is
found down to at least 22 m. The suspicion that
Halophila decipiens may be very abundant on the
Abrolthos Bank was confirmed in a recent rapid
assessment protocol of biodiversity carried out in
the region'!. Of the 45 reef edge/soft-bottom sites
selected, Halophila was present at 18 (40 percent).
Although no total area quantification was made,
these sites were distributed over a study area of
about 6000 km?, so the potential importance of
Halophila decipiens in the region, especially in
terms of primary productivity, could be enormous.
Very little is known about the biology or ecology of
Halophila decipiens in Brazil.

The Abrolhos Bank has important reef-based
and open-sea fisheries. In Abrolhos, there are
trophic interactions between seagrass beds and
reefs across distinct grazing halos. Large
vertebrates, such as sea chub, parrotfish and

South America: Brazil, Argentina and Chile

metalworking activities, by polychlorinated biphenyl
congeners and organochlorine compounds, and by
nutrients from agricultural runoff and sewage
discharge have all been reported. Effects of physical
damage by anchors and trampling on seagrass and
associated macroalgae have also been identified. Loss
of water area, because of sediments produced after
erosion due to deforestation, infilling for construction
and dredging activities, has also reduced the area
occupied by South America’s seagrasses. Ruppia

surgeonfish [seagrass stomach contents: Kyphosus
spp. 12 percent; Acanthurus chirurgus 8 percent;
Sparisoma and Scarus 0.5-5 percent'”) and green
turtles (Chelonia mydas which has been observed
taking 32 bites of Halodule wrightii per minute in
situ) heavily graze the seagrass and 56 associated
seaweed species. Predatory fish of commercial
importance hunt over the seagrass beds and juvenile
yellowtailed snapper and angelfish live in the
seagrass. The Abrolhos Archipelago receives about
900 tourist boat visits per year and is an important
ecotourist destination". Despite being protected
within the national park, the seagrass beds have lost
0.5 percent per year because of anchor damage,
showing reduced seagrass density and a change in
the community structure which can take more than
a year to recover after a single impact". Buoys were
installed recently which should alleviate the
problem, but despite its desirability no trans-
plantation has been carried out to mitigate the
losses suffered so far.

Photo: J.C. Creed

Redonda Island, Abrolhos Archipelago, Brazil.

247

248 WORLD ATLAS OF SEAGRASSES

I, a a

maritima has suffered from reduced freshwater inputs criteria, 100 percent of Chilean and Argentine, and
because of rice irrigation, population growth and lock 40 percent of Brazilian seagrasses are “highly
construction. threatened”. Thirty-six percent of Brazil's seagrasses

Acknowledging that there are intrinsic human- are “moderately threatened” and 24 percent are in “low
related pressures on the coastal zone, and that these threat” areas.

have been quantified for the South American continent,

the superimposition of known threat potential onto the POLICY, REGULATION, PROTECTION

known seagrass distribution can provide a measure of Seagrasses are not specifically protected by legislation
the threat to South American seagrasses. Using these in Brazil, Chile or Argentina but are covered by resource

Case Study 24.3

RUPPIA MARITIMA IN THE PATOS LAGOON SYSTEM

The Ruppia maritima meadows in the Patos Lagoon,
near the city of Rio Grande, Rio Grande do Sul [32°S,
52°W) have received more research attention than
any other seagrass system in South America. The
Patos Lagoon consists of shallow bays with mean
annual water depths of 20-70 cm. The Ruppia
maritima meadows occupy an area of about 120 km?
of the estuary system. Considerable scientific
knowledge has been accumulated about these
seagrass beds during the last 25 years, and has
recently been summarized". Ruppia forms
extensive beds in these shallow marginal bays with
both annual and perennial populations, depending
on local environmental factors, interspecific (algal)
shading and epiphyte fouling". When compared
with other seagrass habitats worldwide, light
attenuation in the waters of the Patos Lagoon is
relatively high, and consequently Ruppia is restricted
to relatively shallow water”. This imposes seasonal
influences on primary productivity; net annual
primary productivity of Ruppia maritima has been
estimated as 39.6-43.2 g carbon/m*/year”.

The Ruppia meadows interface with sandy
shorelines, unvegetated tidal flats and salt marsh
habitats. The large areas of Ruppia meadows serve
as complex habitats for a local fishery by providing
substrate, refuge, nursery and feeding grounds.
Associated drift algae can also be locally abundant
alternative habitats. Pink shrimp {ca 2800 metric
tons landed annually in the region) and the blue crab
{ca 1400 tons}, found foraging in the seagrass, are
important local artisanal fishery resources.
Whitemouth croaker (ca 7500 tons) and mullet [ca
2300 tons) also use the Ruppia beds as nursery or
foraging grounds. The stout razorclam [Tagelus
plebius) is another commercially important species.
Predators such as the bottlenose dolphin are
common (31-100 individuals within the lagoon
system] in the Patos Lagoon and feed principally on
whitemouthed croaker which is found in the Ruppia

beds. Eleven percent of the water area has been lost
since the 1700s and this includes substantial areas
of Ruppia meadow; many anthropogenically filled
areas were previously inhabited by seagrasses.
Areas of preservation, conservation and develop-
ment have been proposed for the region. Ruppia
beds would be partially protected under such a
proposal. However, “management efforts of the
Patos Lagoon estuary are hampered by technical
and legal problems”. The Ruppia beds continue to
be studied as part of the Brazilian Long Term
Ecological Research Program [(PELD]. Locally
Ruppia maritima is called lixo-capim which means
weedgrass.

fe
S
Cc
Ss
=
(s)
s
o
2
a

management and conservation legislation. Brazil has
comprehensive environmental legislation. The Federal
Constitution of 1988 dedicates a chapter exclusively to
the environment. The federal government has amongst
other items the responsibility to “preserve and restore
essential ecological processes and promote the
ecological management of species and ecosystems ...
preserve the diversity and integrity of genetic resources
... protect the flora and fauna”. The coastal zone is
recognized as a national resource by this constitution.
In 1998, Congress approved the Environmental Crimes
Law. It regulates crimes against the natural environ-
ment. Although algal beds, coral reefs and mollusk
beds are specifically mentioned, seagrasses are not.

Brazil has a complex management system based
on the creation of conservation units at federal, state
and municipal government levels. Approximately 290
conservation units are recognized in the coastal zone,
which represent about 21 million hectares that have
specific legislation. Of these, seagrasses are found in
both Marine National Parks (Abrolhos and Fernando de
Noronha} as well as numerous ecological stations,
state parks, biological reserves and environmental
protected areas.

ACKNOWLEDGMENTS

| would like to acknowledge the help and information provided by the
following colleagues: Alejandro Bortolus [from Argentina], Carlos
Eduardo Leite Ferreira, Eduardo Texeira da Silva, Erminda da Conceicao
Guerreiro Couto, Karine Magalhaes, Marcia Abreu de Oliveira Figueiredo
and Ulrich Seeliger (from Brazil], and Evamaria W. Koch and Ronald
Phillips (from the USA). The author was supported by fellowships from
CNPq and UERJ (Prociéncia] during the preparation of this chapter.

AUTHOR

Joel C. Creed, Laboratorio de Ecologia Marinha Béntica, Departamento
de Ecologia, Instituto de Biologia Roberto Alcantara Gomes, Universidade
do Estado do Rio de Janeiro - UERJ, PHLC Sala 220, Rua Sao Francisco
Xavier 624, CEP 20559-900, Rio de Janeiro RJ, Brazil.
Tel: +55 (0)21 2587 7328. Fax: +55 (0)21 2587 7655. E-mail:
jcreed(dopenlink.com.br

REFERENCES

1 Phillips RC [1992]. The seagrass ecosystem and resources in Latin
America. In: Seeliger U (ed) Coastal Plant Communities of Latin
America. Academic Press, San Diego, California. pp 107-121.

2 Gonzalez SA, Edding ME [1990]. Extension of the range of
Heterozostera tasmanica (Martens ex Aschers] den Hartog in Chile.
Aquatic Botany 38: 391-395.

3 Short FT, Coles RG (eds} [2001]. Global Seagrass Research
Methods. Elsevier Science, Amsterdam.

4 Kempf M [1967/9]. Nota preliminar sobre os fundos costeiros da
regiao de Itamaraca (Norte do Estado de Pernambuco, Brasil).
Trabalhos do Instituto do Oceanografico da Universidade do Recife
9/11: 95-110.

South America: Brazil, Argentina and Chile

me i

FANS

The Brazilian 2 real banknote
depicts a turtle, corals, algae
and seagrass. A closer look
inset], however, reveals the
artist's mistake - the seagrass
is probably Thalassia, a genus
that is not found in Brazil

5 Creed JC [2000]. The biodiversity of Brazil's seagrass and
seagrass habitats: A first analysis. Biologia Marina Mediterranea
7: 207-210.

6 Barros HM, Eskinazi-Leca E, Macedo SJ, Lima T leds} (2000).
Gerenciamento participativo de estuarios e manguezais.
Universitaria da UFPE, Recife.

7 Seeliger U, Odebrecht C, Castello JP {eds} [1997]. Subtropical
Convergence Environments: The Coast and Sea of the
Scuthwestern Atlantic. Springer-Verlag, Berlin.

8 Aguilar M, Stotz WB [2000]. Settlement of juvenile scallops
Argopecten purpuratus (Lamarck, 1819) in the subtidal zone at
Puerto Aldea, Tongoy Bay, Chile. Journal of Shellfish Research 19:
749-755.

249

250

WORLD ATLAS OF SEAGRASSES

10
1

Oliveira EC de, Pirani JR, Giulietti AM [1983]. The Brazilian
seagrasses. Aquatic Botany 16: 251-267.

Creed JC. Personal observations.

UNEP [1997]. Global Environment Outlook. Oxford University Press,
New York.

UNEP [1994]. Regional Overview of Land-based Sources of
Pollution in the Wider Caribbean Region. CEP Technical Report
No. 33.

den Hartog C [1972]. The seagrasses of Brazil. Acta Botanica
Neerlandica 21: 512-516.

Leao ZMAN, Kikuchi RKP [2001]. The Abrolhos reefs of Brazil. In:
Seeliger U, Kjerfve B {eds} Coastal Marine Ecosystems of Latin
America. Springer-Verlag, Berlin. pp 83-96.

Creed JC, Amado Filho GM [1999]. Disturbance and recovery

of the macroflora of a seagrass (Halodule wrightii

Ascherson] meadow in the Abrolhos Marine National Park,
Brazil: An experimental evaluation of anchor damage.

Journal of Experimental Marine Biology and Ecology 235:
285-306.

Figueiredo MAO [in press]. Diversity of macrophytes in the Abrolhos
Bank, Brazil. Conservation International, Washington, DC.

Ferreira CEL. Unpublished data.

Seeliger U [2001]. The Patos Lagoon Estuary, Brazil. In: Seliger U,
Kjerfve B (eds) Coastal Marine Ecosystems of Latin America.
Springer-Verlag, Berlin. pp 167-184.

Costa CSB, Seeliger U [1989]. Vertical distribution and resource
allocation of Ruppia maritima L. in a southern Brazilian estuary.
Aquatic Botany 33: 123-129.

Creed JC. Unpublished data.

Appendix 1 251
$$$ AN ssessssSssSssSssSSSSSSs Ap pO MGIX 251

Appendix 1: Seagrass species, by country or territory

and Barbuda
British Indian
Ocean Territory
Brunei

NINN OSNISA8 Australia

Algeria
Angola
Anguilla
Antigua
Azerbaijan
Bahamas
Bahrain
Bangladesh
Barbados
Belize
Bermuda
Brazil
Bulgaria
Cambodia
Canada
Cayman
Islands
Chile
China
Colombia
Comoros
Costa Rica
Croatia
Cuba
Cyprus
Denmark
Dominican
Republic

SPECIES

Amphibolis antarctica
Amphibolis griffithii
Cymodocea angustata
Cymodocea nodosa
Cymodocea rotundata
Cymodocea serrulata
Enhalus acoroides
Halodule beaudettei
Halodule bermudensis
Halodule emarginata
Halodule pinifolia
Halodule uninervis
Halodule wrightil
Halophila australis
Halophila baillonii
Halophila beccarii
Halophila capricorni
Halophila decipiens
Halophila engelmanni
Halophila hawaiiana
Halophila johnsonii
Halophila minor
Halophila ovalis
Halophila ovata
Halophila spinulosa
Halophila stipulacea
Halophila tricostata
Phyllospadix iwatensis
Phyllospadix japonicus
Phyllospadix scouleri
Phyllospadix serrulatus
Phyllospadix torreyi
Posidonia angustifolia
Posidonia australis
Posidonia coriacea
Posidonia denhartogii
Posidonia kirkmanii
Posidonia oceanica
Posidonia ostenfeldii
Posidonia robertsoniae *
Posidonia sinuosa
Syringodium filiforme
Syringodium isoetifolium
Thalassia hemprichii
Thalassia testudinum
Thalassodendron ciliatum
Thalassodendron pachyrhizum
Zostera asiatica
Zostera caespitosa
Zostera capensis
Zostera capricorni
Zostera caulescens
Zostera japonica
Zostera marina
Zostera mucronata*
Zostera muelleri*
Zostera noltii v
Zostera novazelandica*

Zostera tasmanica v

TOTAL SOT SEs Oy Sea 21125643 5 32

NS
N\
SSS OSS SSIS, ISIGESISSESS

N\
SN

Notes: 7 indicates presence of a species; 0 indicates a species name no longer used.
" Posidonia robertsoniae is conspecific with Posidonia coriacea. * Species that are now considered to be conspecific with Zostera capricorni.
Not including Ruppia spp. Heterozostera tasmanica is now designated Zostera tasmanica.

252 WORLD ATLAS OF SEAGRASSES

EES SS Oe eeeeeSeSeSeSeSeSeSeSeSeSeSeSeSeSsS—SstsSse. COCO TLL TC

SPECIES
Amphibolis antarctica
Amphibolis griffithi

New Caledonia

French

=|
0
wn
a)
a
0
o
&
=)
oO

Egypt
Eritrea
Estonia
France -
Guadaloupe
France -
Martinique
France -
Polynesia
Germany
Greece
Greenland
Grenada
Guadeloupe
Guatemala
reland
srael

taly
Jamaica
Japan
Jordan

Cymodocea angustata
Cymodocea nodosa

Cymodocea rotundata
Cymodocea serrulata

SNN

Enhalus acoroides

NINN
NINN
NINN
NINN

Halodule beaudette/
Halodule bermudensis
Halodule emarginata
Halodule pinifolia
Halodule uninervis
Halodule wrightii

Halophila australis
Halophila baillonii
Halophila beccarii
Halophila capricorni
Halophila decipiens
Halophila engelmanni
Halophila hawaiiana
Halophila johnsonii
Halophila minor
Halophila ovalis
Halophila ovata
Halophila spinulosa
Halophila stipulacea
Halophila tricostata

N\
SQN
Ss
SN

Phyllospadix iwatensis
Phyllospadix japonicus
Phyllospadix scouleri
Phyllospadix serrulatus
Phyllospadix torreyi

Posidonia angustifolia
Posidonia australis
Posidonia coriacea
Posidonia denhartogii
Posidonia kirkmanii
Posidonia oceanica
Posidonia ostenfeldii
Posidonia robertsoniae *
Posidonia sinuosa

Syringodium filiforme
Syringodium isoetifolium

Thalassia hemprichii
Thalassia testudinum

NIN
NIN

VVV~a

Thalassodendron ciliatum
Thalassodendron pachyrhizum

Zostera asiatica
Zostera caespitosa
Zostera capensis
Zostera capricorni
Zostera caulescens
Zostera japonica
Zostera marina
Zostera mucronata*
Zostera muelleri*
Zostera noltii
Zostera novazelandica*
Zostera tasmanica

VIS v Yev

v vv vd

TOTAL

VASMIEOMIN 11

Notes: ¥ indicates presence of a species; 0 indicates a species name no longer used.
* Posidonia robertsoniae is conspecific with Posidonia coriacea. * Species that are now considered to be conspecific with Zostera capricorni.
Not including Ruppia spp. Heterozostera tasmanica is now designated Zostera tasmanica.

Kazakhstan

22512521321 1461216 5 4164 1

Appendix 1 253
AP PONGIX 1 253

Korea, Rep.
Libyan Arab
Jamahiriya
Martinique
Mauritania
Mauritius
Micronesia
Morocco
Netherlands
Netherlands
Antilles
Nicaragua
Norway
Oman

Kenya
Kiribati
Korea, DPR
Kuwait
Latvia
Lebanon
Lithuania
Madagascar
Malaysia
Maldives
Marshall
Islands
Mayotte
Mexico
Mozambique
Myanmar
New Zealand
Palau
Panama

SPECIES

Amphibolis antarctica

Amphibolis griffithii

Cymodocea angustata

Cymodocea nodosa YJ v v

Cymodocea rotundata

Cymodocea serrulata

Enhalus acoroides

Halodule beaudettei

Halodule bermudensis

Halodule emarginata

Halodule pinifolia v v v

Halodule uninervis v v v

Halodule wrightii v

Halophila australis

Halophila baillonii v v

Halophila beccarii v v

Halophila capricorni

Halophila decipiens v vv v v v

Halophila engelmanni v

Halophila hawaiiana

Halophila johnsonii

Halophila minor v v 4 v¢ v

Halophila ovalis v v VJ v arn Ar A VJ

Halophila ovata

Halophila spinulosa v

Halophila stipulacea v v v v v

Halophila tricostata

Phyllospadix iwatensis vv

Phyllospadix japonicus v

Phyllospadix scouleri v

Phyllospadix serrulatus

Phyllospadix torreyi v

Posidonia angustifolia

Posidonia australis

Posidonia coriacea

Posidonia denhartogii

Posidonia kirkmanii

Posidonia oceanica v v

Posidonia ostenfeldii

Posidonia robertsoniae *

Posidonia sinuosa

Syringodium filiforme v v vv v

Syringodium isoetifolium A v

Thalassia hemprichii ars v
v

NSN

NINN
NINN
NS

NINN
NISIN SSN
NINN

NIN
NS

Thalassia testudinum

Thalassodendron ciliatum /
Thalassodendron pachyrhizum

Zostera asiatica Vv
Zostera caespitosa ars
Zostera capensis v v v

Zostera capricorni v
Zostera caulescens

Zostera japonica v
Zostera marina v
Zostera mucronata*

Zostera muelleri*

Zostera noltii v v v v
Zostera novazelandica* 0
Zostera tasmanica

TOTAL

WEI WAP SS 22373 8104125 2 513° 2:4 105

Notes: ¥ indicates presence of a species; 0 indicates a species name no longer used.
" Posidonia robertsoniae is conspecific with Posidonia coriacea. * Species that are now considered to be conspecific with Zostera capricorni.
Not including Ruppia spp. Heterozostera tasmanica is now designated Zostera tasmanica.

254 WORLD ATLAS OF SEAGRASSES

Saudi Arabia
St Vincent &
the Grenadines

Sao Tomé and
Senegal
Sierra Leone
Singapore
Solomon
Islands

Principe
St Kitts and

South Africa
Nevis

Papua

New Guinea
Philippines
Poland
Portugal
Puerto Rico
Qatar
Romania
Russian
Federation
Samoa
Seychelles
Somalia
Spain

Sri Lanka
St Lucia

SPECIES

Amphibolis antarctica
Amphibolis griffithii
Cymodocea angustata
Cymodocea nodosa
Cymodocea rotundata
Cymodocea serrulata
Enhalus acoroides
Halodule beaudettei
Halodule bermudensis
Halodule emarginata
Halodule pinifolia
Halodule uninervis
Halodule wrightii
Halophila australis
Halophila baillonii
Halophila beccarii
Halophila capricorni
Halophila decipiens
Halophila engelmanni
Halophila hawaliana
Halophila johnsonii
Halophila minor
Halophila ovalis
Halophila ovata
Halophila spinulosa
Halophila stipulacea
Halophila tricostata
Phyllospadix iwatensis
Phyllospadix japonicus
Phyllospadix scouleri
Phyllospadix serrulatus
Phyllospadix torreyi
Posidonia angustifolia
Posidonia australis
Posidonia coriacea
Posidonia denhartogii
Posidonia kirkmanii
Posidonia oceanica
Posidonia ostenfeldii
Posidonia robertsoniae *
Posidonia sinuosa
Syringodium filiforme
Syringodium isoetifolium
Thalassia hemprichii
Thalassia testudinum
Thalassodendron ciliatum
Thalassodendron pachyrhizum
Zostera asiatica
Zostera caespitosa
Zostera capensis
Zostera capricorni
Zostera caulescens
Zostera japonica
Zostera marina

Zostera mucronata*
Zostera muelleri*
Zostera noltii J v
Zostera novazelandica*

Zostera tasmanica

TOTAL ANAT TE SE GESEZ 6 3 UO SPS

Notes: v indicates presence of a species; 0 indicates a species name no longer used.
Posidonia robertsoniae is conspecific with Posidonia coriacea. * Species that are now considered to be conspecific with Zostera capricorni.
Not including Ruppia spp. Heterozostera tasmanica is now designated Zostera tasmanica.

Appendix 1 255

Syrian Arab
Republic
Tanzania
Thailand
Tonga
Trinidad and
Tobago
Tunisia
Turkey
Turkmenistan
Turks and
Caicos Islands
Ukraine
United Arab
Emirates
USA - total
USA - Pacific
Islands

US Virgin
Islands

Vanuatu
Venezuela
Viet Nam
Western
Samoa
Yemen

SPECIES

Amphibolis antarctica
Amphibolis griffithit
Cymodocea angustata
Cymodocea nodosa
Cymodocea rotundata
Cymodocea serrulata
Enhalus acoroides
Halodule beaudettei
Halodule bermudensis
Halodule emarginata
Halodule pinifolia
Halodule uninervis
Halodule wrightii
Halophila australis
Halophila baillonii
Halophila beccarii
Halophila capricorni
Halophila decipiens
Halophila engelmanni
Halophila hawaliana
Halophila johnsonii
Halophila minor
Halophila ovalis
Halophila ovata
Halophila spinulosa
Halophila stipulacea
Halophila tricostata
Phyllospadix iwatensis
Phyllospadix japonicus
Phyllospadix scouleri
Phyllospadix serrulatus
Phyllospadix torreyi
Posidonia angustifolia
Posidonia australis
Posidonia coriacea
Posidonia denhartogii
Posidonia kirkmanil
Posidonia oceanica
Posidonia ostenfeldii
Posidonia robertsoniae *
Posidonia sinuosa
Syringodium filiforme
Syringodium isoetifolium
Thalassia hemprichii
Thalassia testudinum
Thalassodendron ciliatum
Thalassodendron pachyrhizum

Zostera asiatica

Zostera caespitosa

Zostera capensis

Zostera capricorni

Zostera caulescens

Zostera japonica

Zostera marina

Zostera mucronata*

Zostera muelleri*

Zostera noltii v
Zostera novazelandica*

Zostera tasmanica

TOTAL 4 1211 3 445 1 4 2 126 11

Notes: / indicates presence of a species; 0 indicates a species name no longer used.
* Posidonia robertsoniae is conspecific with Posidonia coriacea. * Species that are now considered to be conspecific with Zostera capricorn.
Not including Ruppia spp. Heterozostera tasmanica is now designated Zostera tasmanica.

256 WORLD ATLAS OF SEAGRASSES

Appendix 2: Marine protected areas known to include seagrass beds, by country or territory

Few of these sites are managed directly to support seagrass protection, and in many cases they do not protect the most important areas of seagrass
in a region. Total protected area is given in hectares but this is not indicative of the area of seagrass.

Summary of IUCN management categories - more detailed information at: http://www.unep-wcmc.org/protected_areas/categories/ index.html
la: Strict Nature Reserve: protected area managed mainly for science

lb: Wilderness Area: protected area managed mainly for wilderness protection

Il: National Park: protected area managed mainly for ecosystem protection and recreation

Ill: Natural Monument: protected area managed mainly for conservation of specific natural features

IV: Habitat/Species Management Area: protected area managed mainly for conservation through management intervention

V: Protected Landscape/Seascape: protected area managed mainly for landscape/seascape conservation and for recreation

VI: Managed Resource Protected Area: protected area managed mainly for the sustainable use of natural ecosystems

u/a Unavailable

IUCN management category does not always equate with management effectiveness.

Country Area name Designate Size (ha) IUCN cat. Year

Anguilla Crocus Bay Marine Park
Sombrero Island Marine Park -
Antigua and Barbuda Cades Bay Marine Reserve =
Australia Ashmore Reef National Nature Reserve 58 300
Corner Inlet Marine and Coastal Park 18 000
Great Barrier Reef Commonwealth Marine Park 34 480 000
Hinchinbrook Island National Park 39 900
Marmion Marine Park 9 500
Ningaloo Marine Park 225 564
Ningaloo Reef Commonwealth Marine Park 232 600
Rowley Shoals Marine Park 23 250
Shark Bay Marine Park 748 735
Shoalwater Islands Marine Park 6 545
Wilsons Promontory National Park 49 000
Bahamas Union Creek Managed Nature Reserve 1813
Bahrain Hawar Islands Other area -
Belize Half Moon Cay National Monument 3925
Hol Chan Marine Reserve 411
Port Honduras Marine Reserve 84 700
South Water Cay Marine Reserve 29 800
Brazil Abrolhos Marine National Park 91 300
Fernando de Noronha Marine National Park 11 270
Saltinho State Forest Reserve 2
British Indian Ocean Diego Garcia Restricted Area
Territory
Cambodia Ream National Park
Canada Race Rocks Ecological Reserve
Cayman Islands Little Sound (Grand Cayman) Environmental Zone
North Sound (Grand Cayman) Replenishment Zone
South Sound (Grand Cayman) Replenishment Zone
Spott Bay (Cayman Brac] Replenishment Zone
Shan Kou Nature Reserve

Appendix 2

Country Area name Designate Size (hal IUCN cat. Year
Colombia Corales del Rosario y de Natural National Park 120 000 Il 1977
San Bernardo
Old Providence McBean Natural National Park 995 ll 1996
Lagoon
Tayrona Natural National Park 15 000 ll 1964
Costa Rica Cahuita National Park 14 022 ll 1970
Gandoca-Manzanillo National Wildlife Refuge 9449 V 1985
Croatia Briuni National Park 4 660 V 1983
Cuba Punta Francé+D225s - Parque Nacional Marino 17 424 ll 1985
Punta Pederales
Cyprus Lara-Toxeftra Marine Reserve 650 IV 1989
Dominica Cabrits National Park 531 ll 1986
Dominican Republic Del Este National Park 80 800 ll 1975
Jaragua National Park 137 400 ll 1983
Los Haitises National Park 154 300 ll 1976
Montecristi National Park 130 950 Il 1983
France Cote Bleue Marine Park 3070 Vl 1982
Golfe du Morbihan Nature Reserve (by Decree] 1500 u/a
Scandola Nature Reserve (by Decree] 1 669 \V 1975
French Polynesia Scilly (Manuae} Territorial Reserve 11 300 \V 1992
Germany Strelasund Sound/Greifswald Wetland Zone of National Importance - V 1980
Lagoon/Isle Greifswald
Wismar Bight/Salzhaff area Wetland Zone of National Importance - V 1980
Guadeloupe Grand Cul de Sac Marin Nature Reserve 3 736 \V 1987
Guam Guam Territorial Seashore Park 6 135 VI 1978
Guatemala Punta de Manabique/ Wildlife Refuge 38 400 u/a
Bahia La Graciosa
Honduras Guanaja Marine Reserve 28 000 u/a
Jeanette Kawas National Park 78 162 Il 1988
Punta Izopo Wildlife Refuge 11 200 V 1992
India Gulf of Kutch Marine National Park 16 289 ll 1980
Gulf of Kutch Marine Sanctuary 29 303 V 1980
Gulf of Mannar Marine National Park 623 Il 1986
Gulf of Mannar Biosphere Reserve (National) 1 050 000 Vl 1989
Wandur Marine National Park 28 150 Il 1983
Indonesia Arakan Wowontulap Nature Reserve 13 800 la 1986
Bali Barat National Park 77727 ll 1982
Kepulauan Karimata Nature Reserve 77 000 la 1985
Kepulauan Togian Nature Reserve 100 000 u/a 1989
Pulau Bokor Nature Reserve 15 la 1921
Pulau Rambut Nature Reserve 18 la 1939
Ujung Kulon National Park 122 956 Il 1992
Israel Elat Coral Reserve 50 IV
Italy Archipelago Toscano Zona di Tutela Biologica Marina (Italy) - \V 1982
Cinque Terre Zona di Tutela Biologica Marina (Italy) - \V 1982
Golfo di Portofino Zona di Tutela Biologica Marina (Italy) = V 1982
Miramare Zona di Tutela Biologica Marina (Italy) 27 \V 1986
Portofino Regional/Provincial Nature Park 4 660 u/a
Jamaica Discovery Bay Marine Park - u/a
Montego Bay Marine Park 1530 ll 1991
Negril Marine Park - u/a 1998

257

258 WORLD ATLAS OF SEAGRASSES

Country Area name Designate Size [ha] IUCN cat. Year

Jamaica Negril Bay/Bloody Bay- Fisheries Sanctuary
Hanover FIS
Ocho Rios Protected Area
Palisadoes-Port Royal Cays National Park
Kiunga Marine National Reserve
Malindi Marine National Park
Malindi-Watamu Marine National Reserve
Mpunguti Marine National Reserve
Watamu Marine National Park
Korea, Republic of Nakdong River Mouth Natural Ecological System
Preservation Area
Madagascar Grand Recif Marine National Park
Mananara Marine National Park 1 000
Malaysia Pulau Besar Marine Park 8414
Pulau Perhentian Besar Marine Park 9121
Pulau Perhentian Kecil Marine Park 8 107
Pulau Redang Marine Park 12750
Pulau Sibu Marine Park 4260
Pulau Sipadan Marine Reserve 710
Pulau Tengah Marine Park 5149
Pulau Tiga Park 15 864
Pulau Tinggi Marine Park 10 180
Pulau Tioman Marine Park 25 115
Talang-Satang National Park 19 414
Tunku Abdul Rahman Park 4929
Turtle Islands Heritage Protected Area 136 844
Martinique Caravelle Nature Reserve 422
Mauritania Banc d'Arguin National Park 1173 000
Mauritius Baie de l'Arsenal Marine Marine National Park
National Park
Balaclava Marine Park
Flacq Fishing Reserve
Port Louis Fishing Reserve
Trou d'Eau Douce Fir Fishing Reserve
Mexico Arrecifes de Puerto Morelos National Park 10 828
Banco Chinchorro Biosphere Reserve [National] 144 360
El Vizcaino Biosphere Reserve [National] 2546 790
La Blanquilla Other area 66 868
Ria Lagartos Other area 47 840
Sistema Arrecifal Veracruzano National Marine Park 52 239
Monaco Larvotto Marine Reserve 50
Mozambique Bazaruto National Park 15 000
Ilhas da Inhaca e dos Faunal Reserve 2 000
Portugueses
Maputo Game Reserve 90 000
Marromeu Game Reserve 1 000 000
Nacala-Mossuril Marine National Park -
Pomene Game Reserve 10 000
Primeira and Segunda Islands National Park -
Zambezi Wildlife Utilization Area 1 000 000

Appendix 2 259

Country Area name Designate Size [ha] IUCN cat. Year

Netherlands Antilles Bonaire Marine Park 2600 u/a 1979
5 Saba Marine Park 820 1987
Nicaragua Cayos Miskitos Marine Reserve 50 000 1991
Palau Ngerukewid Islands Designation unknown 1 200 1956
Panama Comarca Kuna Yala (San Blas} Indigenous Commarc 320 000 1938
Papua New Guinea Kamiali Wildlife Management Area 47 413 1996
Lou Island Wildlife Management Area -
Maza [I] Wildlife Management Area 184 230 1978
Motupore Island Wildlife Management Area
Nanuk Island Provincial Park 12 1973
Talele Islands Provincial Park 40 1973
Philippines St Paul Subterranean River National Park 5 753 1971
Tubbataha Reefs National Marine Park 33 200 1988
Marine Park
Puerto Rico Boqueron Wildlife Refuge (Refugio de Vida Silvestre) 237 1964
Cayos de la Cordillera Nature Reserve 88 1980
Estuarina Nacional Bahia Jobos Hunting Reserve 1 133 1981
Isla Caja de Muerto Nature Reserve 188 1988
Jobos Bay National Estuarine Research Reserve 1 168 1981
La Parguera Nature Reserve 4973 1979
Reunion Cap la Houssaye-Ravine Fishing Reserve - 1978
Trois Bassins
Iles Glorieuses Nature Reserve 1975
llot d'Europa Nature Reserve 1975
Pointe de Bretagne-Pointe Fishing Reserve 1978
de l'Etang Sale
Ravine Trois Bassins-Pointe Fishing Reserve 978
de Bretagne
Russian Federation Astrakhansky Zapovednik
Dalnevostochny Morskoy Zapovednik
Kedrovaya Pad Zapovednik
St Lucia Maria Islands Nature Reserve
Pigeon Island Other area
Soufriere Marine Management Area
St Vincent and Tobago Cays Marine Reserve 3 885
the Grenadines
Saudi Arabia Dawhat Ad Dafi, Dawhat Al- Other area 210 000
Musallamiyah & Coral Islands
Farasan Islands Protected Area 69 600
Seychelles Aldabra Special Nature Reserve 35 000
Port Launay Marine National Park 158
St Anne Marine National Park 1 423
Singapore Southern Islands Marine Nature Area
Slovenia Strunjan Landscape Park
South Africa Agulhas National Park
Cape Peninsula National Park
Greater St Lucia Wetland Park 258 686
Knysna Other area 15 000
Dofiana National Park (State Network] 50 720
Illa de Tabarca Marine Nature Reserve (Spain) 1 463
Illes Medes Submarine Nature Reserve

260 WORLD ATLAS OF SEAGRASSES

Country Area name Designate Size (ha) IUCN cat. Year

Tanzania Bongoyo Island Marine Reserve 1975
Chumbe Island Coral Park Marine Sanctuary 1994
(CHICOP}
Fungu Yasini Marine Reserve 1975
Mafia Island Marine Park 1995
Maziwi Island Marine Reserve 1981
Mbudya Marine Reserve 1975
Menai Bay Conservation Area 1997
Misali Island Conservation Area 1998
Mnemba Conservation Area 1997
Pangavini Marine Reserve 1975
Thailand Haad Chao Mai National Park 1981
Mu Ko Libong Non-hunting Area 1979
Tonga Fanga'uta and Fanga Kakau Marine Reserve 1974
Lagoons
Pangaimotu Reef Reserve 1979
“Trinidad and Tobago —_Buccoo Reef Nature Reserve 1973
Tunisia Ichkeul National Park 1980
Turks and Caicos West Caicos Marine National Park 1992
Islands
Ukraine Arabats kiy State Zakaznik
Karadagskiy Nature Zapovednik [Ukraine]
Karkinits'ka zatoka State Zakaznik
Kazantypskyi Nature Zapovednik (Ukraine]
Molochniy liman State Zakaznik
Mys Martiyan Nature Zapovednik [Ukraine]
United Kingdom Helford River Voluntary Reserve [UK]
Isles of Scilly Area of Outstanding Natural Beauty (UK) 1 600
Skomer National Nature Reserve (UK] 307
Skomer Marine Nature Reserve (UK) 1500
United States Acadia National Park 15 590
Apalachicola National Estuarine Research Reserve 99 630
Assateague Island National Seashore 16 038
Bahia Honda State Park 212
Biscayne National Park 72.900
Breton National Wildlife Refuge 3 661
Cape Cod National Seashore 18 018
Channel Islands National Park 100 987
Channel Islands National Marine Sanctuary 428 466
Chesapeake Bay (MD] National Estuarine Research Reserve 2374
Chesapeake Bay [VA] National Estuarine Research Reserve 1796
Dry Tortugas National Park 26 203
Everglades National Park 606 688
Fire Island National Seashore 7 834
Florida Keys Wilderness [Fish and Wildlife Service) 2508
Galveston Island State Park 786
Grand Bay National Estuarine Research Reserve 7 452
Great Bay National Estuarine Research Reserve 2 138
Gulf Islands [Florida] National Seashore 54 928
Hawaiian Islands [8 sites) National Wildlife Refuge 102 960
\zembek National Wildlife Refuge 122 660

Appendix 2 261

Country Area name Designate Size (ha] IUCN cat. Year

United States John Pennekamp Coral Reef State Park 22 684 1959
(continued) Merritt Island National Wildlife Refuge 55 953 1963
Narragansett Bay National Estuarine Research Reserve 1 286 1980
Padilla Bay National Estuarine Research Reserve 4 455 1980
Pinellas National Wildlife Refuge 159 1956
Rookery Bay National Estuarine Research Reserve 5 062 1978
South Slough National Estuarine Research Reserve 1 903 1974
St Marks National Wildlife Refuge 26 467 1931
Waquoit Bay National Estuarine Research Reserve 1013 1988
Wells National Estuarine Research Reserve 648 1984
United States Baker Island National Wildlife Refuge 12 843 1974
minor outlying island
Venezuela Archipiélago Los Roques National Park 221 120 1972
Ci Wildlife Refuge 25 723
Cuare Wildlife Refuge 11 825 1972
Laguna de la Restinga National Park 18 862 1974
Laguna de Tacarigua National Park 39 100 1974
Médanos de Coro National Park 91 280 1974
Mochima National Park 94935 1973
Morrocoy National Park 32 090 1974
San Esteban National Park 43 500 1987
Viet Nam Con Dao National Park 15 043 1982
Virgin Islands (British) Little Jost Van Dyke Natural Monument
Norman Island National Park
North Sound National Park
The Dogs Protected Area
Wreck of the Rhone Marine Park
Virgin Islands (US) Green Cay National Wildlife Refuge
Salt River Submarine Protected Area
Canyon NHS
Sandy Point National Wildlife Refuge
St James Marine Reserve and Wildlife Sanctuary
Virgin Islands National Park

262

WORLD ATLAS OF SEAGRASSES

Appendix 3: Species range maps

The range maps have been created to establish a guide to where individual
seagrass species might be expected to occur. Range boundaries were
drawn to encompass all points where there was sufficient documentation
to determine the occurrence of a seagrass species in a location. It is
possible that seagrass species occur beyond the ranges shown since not
all areas have been adequately surveyed. In some instances, isolated
observations of species occurrence were marked as distinct entries.
Range maps were not prepared for Ruppia species as the existing data
were deemed insufficient. The species range maps update earlier work by
den Hartog'” and by Phillips and Menez”. Estimates of species range area
are given with each map.

Morphological differences in seagrass plants have led to some
confusion regarding species designation, and several species are now
being revised based on genetic and morphometric research. Two recent
species revisions have been made which combine identified conspecific
species [see Halophila ovalis and Zostera capricorni, below); revised
species range maps have been included. The species range maps for
species formerly accepted have also been included to make a connection
with the literature documenting these species distributions. Several
other species designations remain a matter of debate and are currently
under genetic and morphometric investigation. Closely linked species
that may actually be conspecific have often been grouped together in a
complex while additional research is undertaken. These species do not
have adjusted range maps, but descriptions of the Posidonia ostenfeldii
complex and the Halodule spp. complexes are included below.

Halophila ovalis revision

A group of Halophila species found around the world have recently
received detailed genetic evaluation. Four species, Halophila johnsonii
Eiseman from the east coast of Florida, Halophila hawaiiana Doty and
Stone from Hawaii, Halophila ovata Gaudichaud from the Indo-Pacific and
Halophila minor (Zollinger) den Hartog, were all determined to be
morphological variations of, and therefore conspecific with, Halophila
ovalis (R. Brown} Hooker f.". Range maps are presented for each former
species individually as well as for the newly redefined Halophila ovalis.

Zostera capricorni revision

Zostera novazelandica Setchell and Zostera capricorni Ascherson in New
Zealand are conspecific, based on detailed genetic and morphometric
analysis’, From the same analysis, the Australian species Zostera muelleri
Irmisch ex. Aschers. and Zostera mucronata den Hartog are also
considered to be conspecific with Zostera capricorni. We have included
Zostera novazelandica and Zostera capricorni on the same range map.
Zostera muelleri and Zostera mucronata are displayed separately. Range
maps are presented for former species individually as well as for the newly
redefined Zostera capricorni",

Posidonia ostenfeldii complex

In the case of the Posidonia ostenfeldii complex, new genetic testing
suggests that some of the species are conspecific. The complex consists
of five species: Posidonia ostenfeldii den Hartog, Posidonia denhartogii
Kuo & Cambridge, Posidonia robertsoniae Kuo & Cambridge, Posidonia

coriacea Cambridge & Kuo and Posidonia kirkmanii Kuo & Cambridge”.

However, published results of genetic testing and analysis of
morphological characteristics shared by species within the complex have
shown that Posidonia coriacea and Posidonia robertsoniae are not
separate species”: they are treated as Posidonia coriacea here. More
genetic research is needed in order to re-evaluate and define the complex
as a whole”, Without publication of conclusive information, we have
continued to view the species separately but realize that the complex is

likely to contain conspecific species.

Halodule spp. complexes

The most recent genetic analysis indicates that two major groups of
Halodule exist”. The Atlantic Halodule spp. complex consists of Halodule
wrightii Ascherson, Halodule beaudettei (den Hartog) den Hartog and
Halodule bermudensis den Hartog. The three species are distinguished
by leaf tip morphology. However, some researchers have suggested that
leaf tip morphology changes under different environmental conditions”.
Further genetic studies and/or common garden experiments are needed.
The Indo-Pacific Halodule species, consisting of Halodule uninervis
(Forsskal] Ascherson and Halodule pinifolia (Miki) den Hartog, are
suggested to be conspecific in unpublished genetic studies. These results
indicate that Halodule uninervis is the only Halodule species in the Pacific
and Indian Oceans, except in eastern Africa and India where Halodule
wrightii is also found. Without conclusive published information, we
present the Halodule species separately but realize that both complexes
are likely to contain conspecific species.

References

1 den Hartog C [1970]. The Sea-Grasses of the World. North Holland
Publishing Co., Amsterdam. 275 pp.

2 Phillips RC, Menez EG [1988]. Seagrasses. Smithsonian
Contributions to the Marine Sciences 34. Smithsonian Institution
Press, Washington DC.

3 Waycott M, Freshwater DW, York RA, Calladine A, Kenworthy, WJ [2002].
Evolutionary trends in the seagrass genus Halophila (Thouars): insights
from molecular phylogeny. Bulletin of Marine Science.

4 Les DH, Moody ML, Jacobs SWL, Bayer RJ [2002]. Systematics of
seagrasses (Zosteraceae] in Australia and New Zealand. J Sys
Botany 27: 468-484.

5 Kuo J, Cambridge ML [1984]. A taxonomic study of the Posidonia
ostenfeldii complex (Posidoniaceae) with description of four new
Australian seagrasses. Aquatic Botany 20: 267-295.

6 Campey ML, Waycott M, Kendrick GA [2000]. Re-evaluating species
boundaries among members of the Posidonia ostenfeldii species
complex (Posidoniaceae) - morphological and genetic variation.
Aquatic Botany 66: 41-56.

7 Waycott M. Personal communication.

8 McMillan C, Williams SC, Escobar L, Zapata 0 [1981]. Isozyymes,
secondary compounds and experimental cultures of Australian
seagrasses in Halophila, Halodule, Amphibolis, and Posidonia. Aust
J Bot 29: 247-260.

In the maps below, * indicates species designations that are a matter of
debate and currently under genetic and morphometric investigation.

Appendix 3 263

Family
Hydrocharitaceae
(3 genera)

Genus Enhalus L.C. Richard (1 species)

Dioecious robust perennial with creeping, coarse unbranched or sparsely monopodially branched rhizomes with
short internodes. Fleshy thick roots are unbranched. Male inflorescence has a short stalk and a 2-bladed spathe
surrounding many flowers that break off and release pollen to float on the surface of the water. There are 3 sepals,
3 petals and 3 stamens. Female inflorescence with a long stalk and a 2-bladed spathe containing 1 large flower.
There are 3 sepals and 3 petals. The ovary is rostrate, composed of 6 carpels and 6 styles, and is forked from the
base. The stalk of the female flower coils and contracts after anthesis. Fruits are fleshy. Leaves are distichously
arranged and sheathed at the base; persistent fibrous strands from previously decayed leaves enclose the stem.
Leaf apex rounded.

Enhalus acoroides

MAP 1: Enhalus acoroides (L.f.) Royle (Hydrocharitaceae)

Shaded area = 5 005 000 km’, actual species distribution is much less

Genus Halophila Thouars (14 species)

Monoecious and dioecious small, fragile plants with long internodes on rhizomes each bearing 2 scales and a
lateral shoot. Each node has 1 unbranched root. Single inflorescence covered by 2 spathal bracts. Male flowers have
short stalks, 3 tepals, 3 stamens, sessile anthers and pollen grains in ellipsoid chains. Female flowers are sessile,
have 3-6 styles, and ellipsoid to globular fruit that hold numerous globular seeds. Leaves are either distichously
arranged along upright shoot, in pairs on long petioles or as pseudo-whorls at top of lateral shoots. Leaves have
ovate, elliptic, lanceolate or linear blades with 1 mid-vein and intramarginal veins linked by cross-veins. Leaf
margins smooth or serrate, with leaf surface smooth or hairy.

Halophila australis, Halophila baillonii, Halophila beccarii, Halophila capricorni, Halophila decipiens, Halophila
engelmanni, Halophila hawaiiana, Halophila johnsonii, Halophila minor, Halophila ovalis, Halophila ovata,
Halophila spinulosa, Halophila stipulacea, Halophila tricostata

264

WORLD ATLAS OF SEAGRASSES

f YW

yan
aa

MAP 2: Halophila australis Doty & Stone (Hydrocharitaceae]
Shaded area = 424 000 km’, actual species distribution is much less

Halophila baillonii

MAP 3: Halophila baillonii Ascherson (Hydrocharitaceae)
Shaded area = 139 000 km’, actual species distribution is much less

MAP 4: Halophila beccarii Ascherson (Hydrocharitaceae)
Shaded area = 1511 000 km’, actual species distribution is much less

Appendix 3 265

Halophila capricorni

MAP 5: Halophila capricorni Larkum (Hydrocharitaceae)
Shaded area = 269 000 km’, actual species distribution is much less

Halophila decipiens

MAP 6: Halophila decipiens Ostenfeld (Hydrocharitaceae)
Shaded area = 7 702 000 km’, actual species distribution is much less

Halophila engelmanni

MAP 7: Halophila engelmanni Ascherson (Hydrocharitaceae]
Shaded area = 725 000 km’, actual species distribution is much less

266

WORLD ATLAS OF SEAGRASSES

Halophila hawaiiana

MAP 8: Halophila hawaiiana Doty & Stone (Hydrocharitaceae)
Shaded area = 7 000 km’, actual species distribution is much less
Note: Halophila hawaiiana is now conspecific with Halophila ovalis”

Halophila johnsonii

MAP 9: Halophila johnsonii Eiseman (Hydrocharitaceae)
Shaded area = 12 000 km’, actual species distribution is much less
Note: Halophila johnsonii is now conspecific with Halophila ovalis”.

Halophila minor

MAP 10: Halophila minor (Zollinger) den Hartog (Hydrocharitaceae)
Shaded area = 3 761 000 km’, actual species distribution is much less
Note: Halophila minor is now conspecific with Halophila ovalis”

Appendix 3 267

Halophila ovalis

MAP 11: Halophila ovalis (R. Brown) Hooker f. (Hydrocharitaceae}
Shaded area = 7 614 000 km’, actual species distribution is much less
Note: Map represents the range of the former Halophila ovalis, before its current revision. See Map 12

Halophila ovalis
revision

1cm

MAP 12: Halophila ovalis revision

Shaded area = 7 633 000 km’, actual species distribution is much less

Note: Halophila johnsonii, Halophila hawailana, Halophila minor and Halophila ovata are now considered to be
conspecific with Halophila ovalis"’. The range map presented here is for the newly redefined Halophila ovalis.

Halophila ovata

MAP 13: Halophila ovata Gaudichaud (Hydrocharitaceae)

Shaded area = 3 186 000 km’, actual species distribution is much less

Note: Halophila ovata is now conspecific with Halophila ovalis”.

268

WORLD ATLAS OF SEAGRASSES

Halophila spinulosa

MAP 14: Halophila spinulosa (R. Brown) Ascherson (Hydrocharitaceae)
Shaded area = 3 796 000 km’, actual species distribution is much less

Halophila stipulacea

MAP 15: Halophila stipulacea (Forsskal) Ascherson (Hydrocharitaceae)
Shaded area = 924 000 km’, actual species distribution is much less

Halophila tricostata

i a

MAP 16: Halophila tricostata Greenway (Hydrocharitaceae)
Shaded area = 415 000 km’, actual species distribution is much less

Se a—<« SS OO

Appendix 3 269

Genus Thalassia Banks ex Konig (2 species)

Dioecious perennial with creeping rhizomes that have many small internodes and 1 scale leaf at each node. At
intervals there are 1 or more unbranched roots and a short erect stem with 2-6 leaves. Male flowers have a short
stalk, 3 perianth sections, 3-12 light yellow stamens and globular pollen grains linked into chains. Female flowers
also have 3 perianth segments with 6-8 styles each split into 2 lengthy stigmata. Fruit is prickly and spherical with
a fleshy pericarp that splits into non-uniform valves, releasing pear-shaped seeds with membranous testa. Seeds
germinate immediately. The linear leaf blade, sometimes slightly bowed, has 9-17 longitudinal veins and a round,
finely serrulated apex. Tannin cells are present but stomata are not.

Thalassia hemprichii, Thalassia testudinum

Thalassia hemprichii

Thalassia testudinum

a
MAP 18: Thalassia testudinum Banks ex K6nig (Hydrocharitaceae)
Shaded area = 1 165 000 km’, actual species distribution is much less

270

WORLD ATLAS OF SEAGRASSES

Family
Cymodoceaceae
(5 genera)

Genus Amphibolis C. Agardh (2 species)

Dioecious perennial with woody sympodially branched rhizomes. 1-2 wiry but abundantly branched roots at each
node. Nodes may have long, thin abundantly branched stiff stems with crown leaves on each branch. The singular,
terminal flowers are enclosed by several leaves. Male flowers have 2 anthers connected at the same height to a
short stalk. Female flowers are sessile with 2 free ovaries, each with a short style spilt into 3 long stigmata with
pericarpic lobes at each ovary base. Seedlings are viviparous and have comb-shaped structures extending from
the pericarpic lobes that act as anchors. Leaf sheaths shed leaving circular scar on the erect stems. The linear
leaf blade has 8-21 longitudinal veins and a bidentate apex.

Amphibolis antarctica, Amphibolis griffithii

Amphibolis antarctica

MAP 19: Amphibolis antarctica (Labill.) Sonder et Ascherson
(Cymodoceaceae]
Shaded area = 535 000 km’, actual species distribution is much less

Amphibolis griffithii

3cm

MAP 20: Amphibolis griffithii (Black) den Hartog (Cymodoceaceae)
Shaded area = 330 000 km’, actual species distribution is much less

Appendix 3 271

To —————————

Genus Cymodocea Konig (4 species)

Dioecious perennial with creeping herbaceous monopodially branched rhizomes. 1 to several branched roots with
a short stiff stem bearing 2-7 leaves found at each node. Stalked male flower has 2 anthers connected at same
height on stalk. Female flowers are sessile with 2 free ovaries each with a short style that splits into 2 long
stigmata. Fruit are semi-circular to elliptical shaped with a solid pericarp. The linear leaf blade has 7-17
longitudinal veins and smooth margins. Apex rounded, sometimes notched or serrate. Leaf sheaths shed leaving
circular scar on erect stems.

Cymodocea angustata, Cymodocea nodosa, Cymodocea rotundata, Cymodocea serrulata

Cymodocea angustata

écm

MAP 21: Cymodocea angustata Ostenfeld (Cymodoceaceae)}
Shaded area = 160 000 km’, actual species distribution is much less

Cymodocea nodosa

MAP 22: Cymodocea nodosa (Ucria) Ascherson (Cymodoceaceae)
Shaded area = 610 000 km’, actual species distribution is much less

272

WORLD ATLAS OF SEAGRASSES

Cymodocea rotundata

2cm

MAP 23: Cymodocea rotundata Ehrenberg & Hemprich ex Ascherson
(Cymodoceaceae)
Shaded area = 5 323 000 km’, actual species distribution is much less

Cymodocea serrulata

MAP 24: Cymodocea serrulata (R. Brown) Ascherson (Cymodoceaceae)
Shaded area = 5 578 000 km’, actual species distribution is much less

Genus Halodule Endlinger (6 species)

Dioecious perennial with creeping herbaceous monopodially branched rhizomes. 1 or more unbranched roots and
a short erect stem with 1-4 leaves found at each node. The singular, terminal flowers are enclosed by a leaf.
Stalked male flower has 2 anthers connected at same height on stalk. Female flowers have 2 free ovaries each
with a long, continuous and undivided style. Fruit has stony, solid pericarp. Leaf sheaths shed leaving circular scar
on the stems. The linear leaf blade has 3 longitudinal veins and a variable apex shape. The genus has 2 species
in the Pacific and 4 species in the Atlantic, all largely distinguished by leaf tip morphology.

Halodule beaudettei, Halodule bermudensis, Halodule emarginata, Halodule pinifolia, Halodule uninervis,
Halodule wrightii

Appendix 3

Halodule beaudettei*

MAP 25: Halodule beaudettei* (den Hartog) den Hartog (Cymodoceaceae)
Shaded area = 74 000 km’, actual species distribution is much less

Halodule
bermudensis*

MAP 26: Halodule bermudensis* den Hartog (Cymodoceaceae)
Shaded area = 1000 km’, actual species distribution is much less

Halodule emarginata*

MAP 27: Halodule emarginata* den Hartog (Cymodoceaceae)
Shaded area = 141 000 km’, actual species distribution is much less

273

274 WORLD ATLAS OF SEAGRASSES

Halodule pinifolia*

MAP 28: Halodule pinifolia* (Miki) den Hartog (Cymodoceaceae]}

Shaded area = 5 580 000 km’, actual species distribution is much less

Halodule uninervis*

MAP 29: Halodule uninervis* (Forsskal) Ascherson (Cymodoceaceae]
Shaded area = 6 734 000 km’, actual species distribution is much less

Halodule wrightii

MAP 30: Halodule wrightii Ascherson (Cymodoceaceae)
Shaded area = 2 625 000 km’, actual species distribution is much less

Appendix 3 275
APE NAIX Bo 275

Genus Syringodium Kiitzing (2 species)

Dioecious perennial with creeping herbaceous monopodially or sympodially branched rhizomes. Rhizomes with
1-4 little branched roots and an erect shoot bearing 2-3 round leaves at each node. Inflorescence cymose, flowers
are encompassed by a reduced leaf. Stalked male flower has 2 anthers connected at same height on stalk. Female
flowers have 2 free ovaries each with a short style and 2 short stigmata. Fruit has stony, solid pericarp. Leaf
sheaths shed leaving circular scar on the rigid stems. Round leaf blades tapering to the tip.

Syringodium filiforme, Syringodium isoetifolium

Syringodium filiforme

MAP 31: Syringodium filiforme Kiitzing (Cymodoceaceae)
Shaded area = 1 174 000 km‘, actual species distribution is much less

Syringodium
isoetifolium

MAP 32: Syringodium isoetifolium (Ascherson) Dandy (Cymodoceaceae)
Shaded area = 5 919 000 km’, actual species distribution is much less

276

WORLD ATLAS OF SEAGRASSES

Genus Thalassodendron den Hartog (2 species)

Dioecious perennial with woody sympodially branched rhizomes. 1 or more robust, woody, little branched roots
occur at the nodes preceding the erect stem-bearing nodes. From every fourth node there are long, wiry
infrequently branched stems each bearing crown leaves. Single flowers grow at the end of the stem and are
enclosed by several bracts. Male flowers with 2 anthers connected at the same height to the stalk. Female flowers
are sessile with 2 free ovaries, each with a short style split into 2 stigmata. Seedlings are viviparous. Leaf sheaths
shed leaving circular scar on the erect stems. The linear leaf blade has 13-27 longitudinal veins and the margin
and rounded apex are finely denticulate.

Thalassodendron ciliatum, Thalassodendron pachyrhizum

Thalassodendron
ciliatum

MAP 33: Thalassodendron ciliatum (Forsskal) den Hartog (Cymodoceaceae)
Shaded area = 4 087 000 km’, actual species distribution is much less

Thalassodendron
pachyrhizum

4cm

MAP 34: Thalassodendron pachyrhizum den Hartog (Cymodoceaceae]
Shaded area = 114 000 km’, actual species distribution is much less

Appendix 3 277
ee SE AP BDENGUX B27

Family
Posidoniaceae
(1 genus)

Genus Posidonia Konig (8 species)

Monoecious perennial with creeping, monopodially branching rhizomes with 1-2 branched or unbranched roots
and a shoot. Inflorescence racemose with many barbs. Flowers are hermaphroditic, have 3 stamens but no
perianth, Stigma are disc-shaped with inconsistent lobe shapes. Stone fruit with fleshy pericarp. Pericarp splits to
release oblong seeds with membranous testa. Leaves are distichous, ligulate and auriculate with a distinct sheath
and blade. The leaf sheath is persistent and frequently breaks into fibrous strands covering rhizome internodes.
The leaf blade is either flat and biconvex or terete and linear with 5-21 longitudinal veins and apex obtuse or
truncate.

Posidonia angustifolia, Posidonia australis, Posidonia coriacea (includes conspecific Posidonia robertsoniael,
Posidonia denhartogii, Posidonia kirkmanii, Posidonia oceanica, Posidonia ostenfeldii, Posidonia sinuosa

Posidonia angustifolia

MAP 35: Posidonia angustifolia Cambridge & Kuo (Posidoniaceae)
Shaded area = 284 000 km’, actual species distribution is much less

Posidonia australis

2cm

—————

= =

MAP 36: Posidonia australis Hooker f. (Posidoniaceae)
Shaded area = 600 000 km’, actual species distribution is much less

278

Posidonia coriacea*

4cm

MAP 37: Posidonia coriacea* Cambridge & Kuo (Posidoniaceae)

Shaded area = 324 000 km’, actual species distribution is much less

Note: Posidonia robertsoniae has been combined with Posidonia coriacea as recent research! suggests they are
conspecific.

Posidonia denhartogii*

4cm
MAP 38: Posidonia denhartogii* Kuo & Cambridge (Posidoniaceae)
Shaded area = 137 000 km’, actual species distribution is much less
Posidonia kirkmanii*
4cm

MAP 39: Posidonia kirkmanii* Kuo & Cambridge (Posidoniaceae)
Shaded area = 66 000 km’, actual species distribution is much less

WORLD ATLAS OF SEAGRASSES

Fy Oe a? ae

pals

MAP 40: Posidonia oceanica (L.) Delile (Posidoniaceae)
Shaded area = 533 000 km’, actual species distribution is much less

MAP 41: Posidonia ostenfeldii* den Hartog (Posidoniaceae)
Shaded area = 66 000 km’, actual species distribution is much less

MAP 42: Posidonia sinuosa Cambridge & Kuo (Posidoniaceae)
Shaded area = 266 000 km’, actual species distribution is much less

Appendix 3 279

Posidonia oceanica

2cm

Posidonia ostenfeldii*

4cm

Posidonia sinuosa

4cm

280

WORLD ATLAS OF SEAGRASSES

Family
Zosteraceae
(2 genera)

Genus Zostera L. (9 species)

Monoecious perennial [sometimes annual] that has creeping herbaceous rhizomes with 1 to several roots and 1
shoot with 2-6 leaves. Tannin cells absent; stomata absent. The inflorescence shoots show sympodial branching;
the spathe is stalked and bears alternate male and female flowers in 2 rows on the spadix without perianth. The
retinacula can be present or absent. Pollination hydrophilous. The fruit is ovoid to ellipsoid. The leaf blade is
linear, flattened, with 3-11 longitudinal veins. The apex shape is variable and the sheath can be open or closed.
Zostera asiatica, Zostera caespitosa, Zostera capensis, Zostera capricorni lincludes the conspecific Zostera
mucronata, Zostera muelleri and Zostera novazelandica), Zostera caulescens, Zostera japonica, Zostera marina,
Zostera noltii, Zostera tasmanica {formerly Heterozostera tasmanica]

Zostera asiatica

MAP 43: Zostera asiatica Miki (Zosteraceae)
Shaded area = 1 311 000 km’, actual species distribution is much less

Zostera caespitosa

Scm

MAP 44: Zostera caespitosa Miki (Zosteraceae)
Shaded area = 445 000 km‘, actual species distribution is much less

Appendix 3 281

Zostera capensis

MAP 45: Zostera capensis Setchell (Zosteraceae)
Shaded area = 363 000 km’, actual species distribution is much less

MAP 46: Zostera capricorni Ascherson (Zosteraceae)

Shaded area = 543 000 km’, actual species distribution is much less

Notes: Zostera novazelandica Setchell is now considered to be conspecific with Zostera capricorni.. The two show
complete overlap of occurrence in New Zealand. Zostera muelleriand Zostera mucronata are also now considered
to be conspecific with Zostera capricornt“.

Zostera capricorni
revision

MAP 47: Zostera capricorni revision

Shaded area = 773 000 km’, actual species distribution is much less

Note: Zostera mucronata, Zostera muelleri and Zostera novazelandica are now considered to be conspecific with
Zostera capricorni"“!. The range map presented here is for the newly redefined Zostera capricorni

282 WORLD ATLAS OF SEAGRASSES

Zostera caulescens

MAP 48: Zostera caulescens Miki (Zosteraceae)
Shaded area = 442 000 km’, actual species distribution is much less

Zostera japonica

MAP 49: Zostera japonica Aschers. & Graebner (Zosteraceae)
Shaded area = 2819 000 km’, actual species distribution is much less

Zostera marina

MAP 50: Zostera marina Linnaeus (Zosteraceae)
Shaded area = 5 738 000 km’, actual species distribution is much less

Appendix 3

MAP 51: Zostera mucronata den Hartog (Zosteraceae)
Shaded area = 116 000 km’, actual species distribution is much less .
Note: Zostera mucronata is now considered to be conspecific with Zostera capricorni™.

Zostera muelleri

[ 1cm

MAP 52: Zostera muelleri Irmisch ex Aschers. (Zosteraceae)
Shaded area = 144 000 km’, actual species distribution is much less
Note: Zostera muelleri is now considered to be conspecific with Zostera capricorni

Zostera noltii

MAP 53: Zostera noltii Hornemann (Zosteraceae)
Shaded area = 1571 000 km’, actual species distribution is much less

283

284

WORLD ATLAS OF SEAGRASSES

Zostera tasmanica

MAP 54: Zostera tasmanica (Martens ex Aschers.) den Hartog (Zosteraceae)
Shaded area = 479 000 km’, actual species distribution is much less

Note: Formerly Heterozostera tasmanica’.

Genus Phyllospadix Hooker (5 species)

Dioecious perennial with creeping herbaceous rhizomes bearing 2 to several short unbranched roots and 1 leaf at
each node. The spathe is stalked and bears alternate male and female flowers in 2 rows on the spadix. The
retinacula is present. Fruit are crescent-shaped and have lateral arms with hard bristles. The leaf blade is linear,
flattened, subterete, sometimes leathery, sometimes rolled, with 3-7 longitudinal veins. The apex shape is
variable and the sheath is open.

Phyllospadix iwatensis, Phyllospadix japonicus, Phyllospadix scouleri, Phyllospadix serrulatus, Phyllospadix
torreyi

Phyllospadix iwatensis

MAP 55: Phyllospadix iwatensis Makino (Zosteraceae)
Shaded area = 722 000 km’, actual species distribution is much less

rT oes

Appendix 3 285

Phyllospadix japonicus

%
Scm

MAP 56: Phyllospadix japonicus Makino (Zosteraceae)

Shaded area = 248 000 km’, actual species distribution is much less

Phyllospadix scouleri
8 iY
MAP 57: Phyllospadix scouleri Hooker (Zosteraceae)
Shaded area = 263 000 km’, actual species distribution is much less
Phyllospadix
serrulatus

OE —_——

MAP 58: Phyllospadix serrulatus Ruprecht ex Aschers. (Zosteraceae)
Shaded area = 363 000 km’, actual species distribution is much less

286

WORLD ATLAS OF SEAGRASSES

MAP 59: Phyllospadix torreyi S. Watson (Zosteraceae)

Shaded area = 181 000 km’, actual species distribution is much less

Genus Ruppia (4 marine species)

Dioecious annual or perennial with monopodially branched rhizomes and 1-2 unbranched roots per node. Root
hairs abundant. Inflorescence a spike of 1-2 flowers on opposite faces of the axis, enclosed at first in the inflated
sheath. Peduncle short, stout, erect or elongating greatly before anthesis to a fine thread raising the flowers to
the water surface and becoming tightly spirally coiled, retracting the developing fruits. Pollination either on or
below the water surface. Fruit is a fleshy drupe on a long stalk. Leaves alternate (except the 2 immediately below
the flower which are sub-opposite], sheath open, edges overlapping. Blade narrow-linear to filiform, more or less
concavo-convex with a large air canal either side of an inconspicuous median vein. Tannin cells present in most
tissues.

Ruppia cirrhosa, Ruppia maritima, Ruppia megacarpa, Ruppia tuberosa

Range maps were not prepared for Ruppia species as the existing data were deemed insufficient,

Acknowledgement
We are grateful to the following sources for the information on genera taxonomy given in
this appendix:

Kuo J, den Hartog C [2001]. Seagrass taxonomy and identification key. In: Short FT, Coles RG {eds} Global
Seagrass Research Methods. Elsevier Science, Amsterdam. pp 31-58.

Womersley HBS [1984]. The Marine Benthic Flora of Southern Australia. Part 1. DJ Woolman, Government
Printer, South Australia. 329 pp.

den Hartog C [1970]. The Sea-Grasses of the World. North Holland Publishing Co., Amsterdam. 275 pp.

Family
Ruppiaceae
(1 genus)

Global Seagrass Workshop 287

THE GLOBAL SEAGRASS WORKSHOP including seagrass distribution and diversity maps based
The Global Seagrass Workshop was organized and on an extensive literature search, framed much of the
convened by UNEP-WCMC, with considerable assistance discussion at the workshop. Delegates debated the map
from the World Seagrass Association, in St Petersburg, results and marked corrections. A standard species list
Florida, USA on 9 November 2001. Twenty-three was agreed upon and information on economic value,
delegates [see photograph] from 15 countries prepared uses and threats, associated species and management
discussion papers for their areas of expertise, and a interventions was shared. The workshop ended with a
further five papers were received from people unable to discussion of global priorities for seagrass research and
attend (see map). policy and a commitment by all delegates to contribute a
A preliminary study prepared by UNEP-WCMC, regional chapter to this World Atlas.

Photo: J. Barnes

Delegates at the Global Seagrass Workshop. From left, front row: Caroline Ochieng, Mark Spalding, Fred Short, Michelle Taylor, Hitoshi
lizumi. Second row: Evamaria Koch, Chatcharee Supanwanid, Graeme Inglis, Joel Creed, Nataliya Milchakova, Salomao Bandeira. Third row:
Paul Erftemeijer, Rob Coles, Tanaji Japtap, Miguel Fortes, Diana Walker, Hugh Kirkman, Jorge Herrera-Silveira, Japar Sidik Bujang . Back
row: Kun-Seop Lee, Ron Phillips, Andrea Raz-Guzman, Sandy Wyllie-Echeverria.

Map showing the location of all delegates at the Global Seagrass Workshop (circles), and other regions for which papers were prepared
(triangles).

288

WORLD ATLAS OF SEAGRASSES

Index to

THE WORLD ATLAS OF SEAGRASSES

Page references in bold refer to
figures in the text; those in /talics
refer to tables or boxed material

Abrolhos Bank, Brazil 243, 247
Abu Dhabi Emirate 74, 78, 80
Acanthopagrus schlegeli 196
Acanthophora 235
adaptations of seagrasses 5
Adriatic Sea 50, 52
Aegean Sea 65, 67, 68, 71, 72
Africa see East Africa; South Africa;
West Africa
agriculture
as threat to seagrasses 99, 130
uses of seagrasses 61, 62, 188, 197
aircraft runways 164-5, 166
Akkeshi, Hokkaido 187, 789
Al Iskandariya (Alexandria) 66-7
Alabama 225
Aland Islands, Finland 29, 30
Alaska 199-204
Albermarle Sound, North Carolina
218
exandria 66-7
facs Bay, Spain 54
algae see epiphytic algae;
filamentous algae; macroalgae;
phytoplankton
geria 257
ien species 49-50, 114, 203-4, 205
macroalgae 55, 68, 69, 71, 155
seagrasses 114, 203-4
Amami Islands, Japan 186
Amblygobius albimaculatus 96
Ambon Bay, Indonesia 179
Ammonia 175
Amphibolis antarctica 113, 117, 122,
251-5, 270
Amphibolis griffithii 251-5, 270
Amphiroa fragilissima 155
Anambas Island, Indonesia 778
anchor damage 43, 204, 247
Andaman and Nicobar Islands 101,
102-3, 104, 105

rye

Andaman Sea 144-50
Angola 257
Anguilla 251, 256
Anguilla anguilla 33
animal fodder 61, 62
annual populations 121
antibiotics 114
antifouling compounds 114
Antigua and Barbuda 238, 251, 256
Antilles, Netherlands 253, 259
Aplysia punctata 40
Apseudes chilkensis 175
Aqaba (Elat], Gulf of 67, 68-9, 70-1, 74
aquaculture
fish 114, 154, 158, 213
seaweeds 87-8, 176, 197
shellfish 43, 154, 197, 205, 213
Arabian Gulf
biogeography 74-8
policy and management 80
seagrass distribution 78
threats and seagrass losses 78, 80
turtles and dugong 79
Arabian Sea 75
Aral Sea 59, 61, 63
Aransas Bay, Texas 227
Arenicola marina 44
Argentina 14, 246
Argopecten irradians 209-10, 216
Argopecten purpuratus 246
ark shell 97
Aru Islands, Indonesia 179
associated biota 10-12
Brazil 244, 245
Caribbean 235-6
East Africa 83, 85
endangered/threatened 72, 17, 40,
183
India 101-2, 105, 707
Indonesia 174-80
major taxonomic groups 77
Mediterranean 51
migratory movements 235
New Zealand 134-5, 140
north western Atlantic 209-10
Philippines and Viet Nam 183
Scandinavia 27, 28, 30
western Europe 40

Asterina pancerii 51

Atlantic Ocean see mid-Atlantic
region; North Atlantic

Australia
associated species 11
endemic species 12, 170, 117
Northern Territory 111
policies and protection 23
seagrass species 257
southern coast 9, 122, 128
see also Eastern Australia;
Western Australia

Austrovenus stutchburyi 135

Avon-Heathcote Estuary, New
Zealand 135, 137, 138, 139-40

Aythya americana 228

Azerbaijan 62, 257

Azov Sea 59, 61-2

Bagamoyo, Tanzania 87

Baguala Bay, Indonesia 179

Bahamas 257, 256

Bahia de Chengue, Colombia 239

Bahrain 74, 75, 78, 80, 257, 256
causeway 6, 76

Baja California 199, 201

Balearic Islands 53

Baltic Sea 28-30, 33, 34, 35

Bangka, Indonesia 178

Bangladesh 251

banknote, Brazilian 249

“banquette” 53

Banten Bay, Indonesia 175-6, 178,
180

Barbados 257

Barbatia fusca 97

Barnegat Bay, New Jersey 209,
210

bass, striped 209

Batophora 235-6

bay scallop 209-10, 216

beach cast material 86, 88-9

beach seines 148-9

Belitung, Indonesia 178

Belize 74, 236, 237, 239, 251, 256

Benoa Bay, Indonesia 178
Bermuda 257
biodiversity
centers of 9, 10, 185
in seagrass ecosystems 10-12, 17
seagrasses 9, 22
biogeographic patterns 9-10
biomass 16
Baltic Sea 28
below-ground 172
Gulf of Mexico 231-2
India 104
Indonesia 172-3
Japan 187
Zostera 196
birds 40, 141, 789, 199, 200, 210, 228,
245
Biscay, Bay of 45
bivalves
digging/dragging for 98, 99, 157,
158, 210, 212, 213
dredging for 43-4, 219, 220-1
East Africa 83, 85
endemic 140
Malaysia 157, 758
New Zealand 135, 140
protected 51
western Europe 40, 43-4

western north Atlantic 209-10, 212,

213

black brant 200

Black Sea 59-61

“plow-out” areas 18, 237-8

boating 18
Brazil 247
East Africa 86-7
mid-Atlantic region 219
North America 204, 212, 213
western Europe 42, 43
see also shipping

Bonaire 14, 238

Boston Harbor 208

Botany Bay 123

bottlenose dolphin 248

Boundary Bay, Canada 201-2

Branta bernicla (brant goose) 40, 210

Branta bernicla nigricans (black
brant) 200

Brazil
Abrolhos Bank 243, 247
biogeography 245-6
ecosystem description 243-4
Itamaraca Island 243, 244
Patos Estuarine Lagoon 244, 248
policy and protection 248-9, 256
seagrass losses and coverage 14,
246
seagrass species 257

Brest, Bay of 40

British Columbia 199-204

British Indian Ocean Territory 257,
256

Brunei 257

Buenos Aires 246

Bulgaria 257

“bullata” ecophene 66

Calcarina calcar 175
Callinectes sapidus 216, 245-6, 248
Callophyllis rhynchocarpa 197
Calotomus carolinus 85-6
Calotomus spinidens 96, 97
Cambodia 257, 256
Canada
Atlantic coast 207, 212
Hudson Bay 207, 212
marine protected areas 256
Pacific coast 199-204
seagrass species 2517
Cape Cod 208, 210
Cape Lookout, North Carolina 218
capybara 245
carbon cycle 17, 84, 85
carbon dioxide levels 85
Caribbean 9, 234-41
ecosystem description 235-8
historical perspectives 238
policy and protection 241
species and coverage 234-5, 238
threats to seagrasses 238-9, 241
see also named islands
Caribbean Coastal Marine
Productivity (CARICOMP) network
239, 241
CARICOMP network 239, 241
Carpentaria, Gulf of 119, 120, 125
Caspian Sea 61, 62-3
Caulerpa 232, 235
eastern Mediterranean 68, 69, 71
Malaysia 755, 156
western Mediterranean 52-3, 54,
55
Caulerpa cactoides 126
Caulerpa prolifera 66, 68,71, 155
Caulerpa racemosa 55, 68, 69, 71,
155
Caulerpa scalpelliformis 68
Caulerpa serrulata 70
Caulerpa taxifolia 55
causeway development
Bahrain 6, 76
Kosrae 164-5, 166, 167
Cayman Islands 257, 256
Ceramium 60, 61, 62
Cerithium tenellum 175
Chaetomorpha linum 219, 221
Champia sp. 197
Chandeleur Islands, Louisiana 226,
227
Chara 62
Charlotte Harbor, Florida 225
Charophyceae 63
Cheilio enermis 177
Chelonia mydas see green turtle
Chesapeake Bay, US 216, 218, 220-1
Chicoreus ramosus 98
chicoric acid 55
Chile 10, 14, 243, 246, 257
China 185, 257
Chinocoteague Bay 220

Index 289

Christchurch, New Zealand 137, 138
Christmas Bay, Texas 227
Chrysochromulina 31
Chwaka Bay, Tanzania 85, 86
Cladophora 60, 61
Cladophora glomerata 33
clam worms 213
clams 246
dredging for 43-4, 219, 220-1
hand digging 43, 212, 213
soft-shell 213
Clean Water Act (US) 220
climate change 167, 191, 241
potential response of seagrasses
17, 85
coastal development
Arabian region 76, 78, 80
Caribbean 238-9, 241
Japan 188-9
Malaysia 157
Mediterranean 55
northeastern United States 277
Pacific islands 161
South America 246-7
Western Australia 112
western Pacific islands 165, 166-7
see also land reclamation
coastal management
East Africa 89-90
rapid assessment technique 77
coastal protection 17, 86-7, 88-9,
116-17, 147
Cockburn Sound, Western Australia
Vi, A We
cockles 135, 246
cod, Atlantic 209
Colombia 239, 241, 251, 257
Comoros 95, 257
Connecticut, US 209, 212
Coorong Lakes, Australia 130
coot, red-gartered 245
coral reefs 2
East Africa 82, 84
Eastern Australia 120-1
“halo zone” 71
Malaysia 1, 153, 755, 157-8
Red Sea 69-70
South America 245, 246
Thailand 145-6
western Pacific 161-3
corals 245, 246
Core Sound, North Carolina 218
Corpus Christi Bay, Texas 227, 229
Corsica 57, 53, 55
Costa Rica 238, 251, 257
crabs 40, 83, 156, 196-7
blue 216, 245-6, 248
hermit 101
New Zealand endemic 135
Thailand 148
threatened species 12
croaker, whitemouth 248
Croatia 257, 257
crustaceans 40, 97-8, 156
Caribbean 236-7
Indonesia 175

WORLD ATLAS OF SEAGRASSES

seed consumption 190
South America 245-6
see also named groups and
species
Cuba 224, 238, 241, 251, 257
Curacao 14, 238
curio goods 85, 98
Curonian Spit, Lithuania 30, 33
Cuyo Island 783
Cygnus atratus 141
Cygnus cygnus 189
Cygnus melancoryphus 245
Cymodocea angustata 251-5, 271
Cymodocea nodosa
by country/territory 251-5
eastern Mediterranean 65-8
range map 271
western Mediterranean 48, 49, 50,
52-3, 54
Cymodocea rotundata
by country/territory 257-5
Eastern Australia 128
India 104, 105, 106-7
Indonesia 171, 172, 173-4, 178-9
Japan 187
Malaysia 156, 157
Mozambique 95, 96, 99
photosynthetic studies 85
range map 272
Red Sea 69-70, 71
Thailand 144, 146, 147, 148
western Pacific 168, 169
Cymodocea serrulata
by country/territory 251-5
India 104, 105
Indonesia 171, 172, 173-4, 178-9
Japan 187
Malaysia 153, 155
Mozambique 95, 96, 99
range map 272
Red Sea 68-9
Thailand 144, 145, 146, 147
western Pacific 163
Cymodoceaceae 6
Cypraea tigris 85
Cyprus 67, 68, 71, 251, 257

Dahlak Archipelago 69

Dar es Salaam 87

Dasycladales 235

David and Lucile Packard Foundation
168

Deception Bay, Queensland 123

decline, global 20

deepwater seagrasses 69, 70, 120-1,
123, 124-5, 130

definitions 5-7

deforestation 138-9

Delaware 216-22, 220-1

Denmark
policies and protection 34-5
seagrass distribution and losses
27-8, 31-2, 33

seagrass species 257
uses of seagrasses 30
depth distribution
Australia 120-1, 123, 124-5, 130
Denmark 27, 32, 33
Japan 186-7
Malaysia 154
Red Sea 69, 70
and water quality 27, 32, 33, 112-
13, 154
western Pacific 162
Zostera marina 27, 32, 33, 232
Derawan Islands, Indonesia 178
detritus
direct uses 55, 197
ecological value 40
see also beach cast
Diadema antillarum 236
Diadema savignyi 86
Diadema setosum 86, 98
Diani-Chale Lagoon, Kenya 86
diatoms 101
Dick, Chief Adam 202
die-back see wasting disease
Diogenes 175
direct habitat maps 7
distribution maps
calculating global areas 13-16
development 3, 7-8
geographic regions 9-10
limitations 13
seagrass habitat 7, 13
seagrass species 8-10, 262, 263-86
dolphin, bottlenose 248
Dominica 257
Dominican Republic 241, 251, 257
Donuzlav Salt Lake 60
dragging, net 213
dredging
Arabian Gulf 76, 78, 80
for bivalves 43-4, 219, 220-1
Malaysia 157
mid-Atlantic US 219
duck, redhead 228
dugong [Dugong dugon) 2, 183
Arabian Gulf 78, 79
captivity 180
East Africa 83, 88
Eastern Australia 119
feeding 147, 149
India 102, 105
Indonesia 180
Japan 189
Malaysia 154, 156
Thailand 145, 147, 148-9
western Pacific 164

earthquakes 238
East Africa 82-90
biogeography 82-5
policies and protection 88-90, 258,
260
seagrass coverage 87-8

seagrass productivity and value

85-7

threats to seagrasses 86-8
Eastern Australia 119-31

biogeography 120-2

physical characteristics 119

policies and protection 23, 130-1,

256

seagrass coverage 714, 125-8

seagrass losses 122-5, 126-7

threats to seagrasses 129-30

uses of seagrasses 122, 128-9

echinoderms 97-8, 176

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