CORDIO Status Report 2000

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Impacts of bleaching on coral communities on artificial reef structures in Maldives SUSAN CLARK Department of Marine Sciences & Coastal Management, University of Newcastle, U.K. ABSTRACT A research programme to evaluate the feasibility of using artificial reef structures (ARS) to rehabilitate degraded reefs was conducted in Maldives between 1990- 1994. Detailed monitoring and analysis of coral recruitment patterns on the ARS over a period of 3.5 years demonstrated that a diverse community of branching corals developed within three years with a similar composition to adjacent reef flats. A warm water anomaly of +3° C occurred in Maldives between late April and May 1998 resulting in extensive bleaching of corals and other zooxanthellate reef invertebrates. On the ARS bleaching was followed by full to partial mortality of certain corals within 4 - 6 weeks of the onset of bleaching. Branching species of the genera Acropora and Pocillopora were the most susceptible corals to bleaching. At the same time massive corals, such as Porites, Favites, Pavona and Favia spp. showed partial to full recovery on the ARS and on natural reefs Quantitative surveys in March 1999 recorded 205 recently settled coral recruits on the three concrete SHED areas. Although branching corals were the dominant colonisers (67%), there was a significant increase in the abundance of massive corals (33%) when compared with the taxonomic patterns recorded between 1990-1994, in which massive recruits represented less than 2% of the population. On natural reefs rates of recruitment were 23.2 colonies per m 2 . Settlement and subsequent growth of coral recruits with both branching and massive growth forms since the bleaching event indicates that a supply of viable coral larvae are available from reefs located upstream or from deeper areas of the same reef. Bioerosion and breakage of dead standing corals on the ARS was evident ten months after the bleaching event. As the reef framework breaks down the ultimate fate of the calcium carbonate fragments will have important consequences for the integrity of the reef framework, which provides natural protection for low lying islands against oceanic waves. INTRODUCTION In Maldives coral mining for the construction industry has resulted in widespread degradation of shallow reef flat areas (Brown & Dunne, 1988). The loss of vital coastal resources, the associated problems of coastal erosion and the slow rates of natural reef recovery have prompted interest in the potential of artificial reef structures to rehabilitate physically damaged reefs. With funding from the UK Department for International Development (DFID - formerly ODA) an experimental artificial reef programme was initiated in 1990 to determine the feasibility of using a bio-engineering approach to kick-start natural reef recovery. The main objectives were to: i) restore reef fish and coral biodiversity, ii) test the hypothesis that lack of reef recovery is due to the lack of stable surfaces for settlement of coral planulae, iii) investigate the biological and physical conditions conducive to reef recovery and iv) determine which rehabilitation techniques are cost effective. Ac- – 187 –
cordingly, 360 tonnes of concrete structures with varying levels of topographic complexity, stabilising effect and cost were deployed on a heavily mined study site close to the island upon which the capital Malé is situated. Recruitment and subsequent growth and mortality of corals on the Artificial Reef Structures (ARS) were monitored over 4 years (Clark & Edwards, 1994; 1995; 1999). By late 1994, substantial coral recruitment had occurred on the larger reef structures, which were each supporting circa. 500 colonies. The coral community that developed on the reef structures was dominated by acroporids (53%) and pocilloporids (45%), with very few massive colonies (2%) present. Given the slow recruitment and growth of massive species, which are crucial for reef framework construction, it was predicted that a further 5-10 years are required to attain a community structure similar to pristine adjacent reefs. Coral bleaching on artificial reef structures In May 1998, scientists attending a training workshop supported by the South-east Asia Global Coral Reef Monitoring Network (GCRMN) visited the ARS at Galu Falhu and observed almost 100% bleaching of Plate 1. In May 1998, virtually all corals on the ARS at Galu Falhu exhibited bleaching. – 188 –
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CORAL REEF DEGRADATION IN THE INDIA
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Foreword The temperatures of the wo
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Address by the Global Coral Reef Mo
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Table of contents FORWARD 3 ADDRESS
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Executive Summary The World Conserv
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to date. Working group discussions
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Biophysical Generally, region-wide
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species exhibit different tolerance
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er-term, “shifting baselines” i
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flow diagram presented below. CORDI
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SECTION I Status Reports - 21 -
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East Africa - Summary DAVID OBURA C
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Kenya, reef status and ecology DAVI
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BENTHIC COMMUNITIES Benthic communi
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Figure 2. Three strategies for blea
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% cover % cover 16 14 12 10 8 6 4 2
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Table 3: Population densities and s
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Assessment of coral reef degradatio
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Table 1. Reef stations surveyed in
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live coral cover for Mbudya Marine
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Table 5. Some environmental paramet
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Coral reef monitoring and managemen
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L impopo Maputo Sa ve River Riv er
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category) and size classes (total n
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The status of South African coral r
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South Asia - Summary DAN WILHELMSSO
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SRI LANKA Most shallow coral reef h
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corals in Sri Lanka is relatively h
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Figure 1. Distribution of coral ree
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Kandakuliya Most of the nearshore r
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shallow water (0 m - 3 m) on the re
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Rajasuriya, A & De Silva, M.W.R.N.
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In each of these regions three reef
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Table 4. Summary data from transect
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The status of the coral reefs of In
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Relative importance in total landin
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Small pelagics Large pelagics Demer
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Indian Ocean Islands - Summary SUSI
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The reefs of the granitic islands o
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onies damaged was recorded using th
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FAMILY GENUS SPECIES DEAD SURVIVING
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FAMILY GENUS SPECIES DEAD SURVIVING
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Figure 10. Recruit on consolidated
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Reef systems of the islands of the
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Figure 2. Coral condition by locati
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At the Bank’s northern and southe
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chelles (Turner et al., this volume
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the shallow bays of Balaclava Marin
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Development of a geographical infor
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2 1,8 1,6 Mean Bleaching Score 1,4
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Meteorological data from the period
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Figure 16. Total sunshine (hrs) per
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solar irradiance. In Thailand, loca
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Harriott, V.J. 1985. Mortality rate
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Table 1. Location of CORDIO monitor
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Figure 1. Recovery from settlement
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that due to its low impact, dead co
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Map of the Western Indian Ocean wit
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In April 1998, close to the peak of
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Pachyseris, Turbinaria spp.) and en
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Partial mortality of Favites flexuo
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REFERENCES Barnes, J., Bellamy, D.J
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SECTION II Environmental Monitoring
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Sea surface temperature in the west
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Temperature and water exchange in a
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Figure 2a. Time series temperature
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ACKNOWLEDGEMENTS I would like to th
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Figure 2. Settlement plates for cor
Page 138 and 139: REFERENCES CARICOMP. 1994. Manual o
Page 140 and 141: Figure 2. Two possible recoveries f
Page 142 and 143: SECTION III Thematic/Research Repor
Page 144 and 145: Socio-economic assessment of the im
Page 146 and 147: to escape predation (Williams, 1991
Page 148 and 149: Table 4 Demersal fish landings in 1
Page 150 and 151: mersal species have not been heavil
Page 152 and 153: Therefore, it must be concluded tha
Page 154 and 155: ▲ Level of importance 35 30 25 20
Page 156 and 157: very few come specifically for reef
Page 158 and 159: Percentage 28% Food and beverages w
Page 160 and 161: Anonymous. 1998b. Basic Fisheries S
Page 162 and 163: has a 4 m tidal range) dominated by
Page 164 and 165: Table 1. Comparison of the gross be
Page 166 and 167: Greenstein, B.J., Curran, H.A. & Po
Page 168 and 169: to assess ciguatera risk by impleme
Page 170 and 171: Evaluation of succession and coral
Page 172 and 173: within each depth zone (5 m and 10
Page 174 and 175: The taxonomic patterns of coral rec
Page 176 and 177: dives, this study has demonstrated
Page 178 and 179: Bioerosive processes An important a
Page 180 and 181: each of the three different fish co
Page 182 and 183: Figure 1. Coral fragments transplan
Page 184 and 185: Pavona Echinopora 50 100 50 100 Gro
Page 186 and 187: A low-tech method for reef rehabili
Page 190 and 191: anching and massive corals (Plate 1
Page 192 and 193: es, metal bars and PVC surfaces. No
Page 194 and 195: strate that supports a low percenta
Page 196 and 197: egeneration and prevent further des
Page 198 and 199: APPENDICES - 197 -
Page 200 and 201: Coral Reef Degradation in the India
Page 202 and 203: LIST OF PARTICIPANTS LIONEL BIGOT A
Page 204 and 205: AGNETHA NILSSON Programme Officer U
Page 206 and 207: DR. SUE WELLS Co-ordinator, E.A. Ma
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CORDIO Status Report 2000

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