CORDIO Status Report 2000

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Partial mortality of Favites flexuosa and Acropora spp. colonies at 20 m depth with blacktip grouper (Epinephelus fasciatus) and evidence of the macroalgae Halimeda spp. in the lower left corner. This photo illustrates well the variability of mortality on the reefs of Aldabra. NASA space shuttle image (Atlantis - STS044-082-057) Aldabra Atoll, Indian Ocean - 29 November 1991. – 121 –
DISCUSSION The 1998 coral bleaching event had pronounced effects upon the reef complex. Shallow corals suffered the greatest mortality and lowest recovery, perhaps due to the long period of exposure to high and increasing SSTs as shown in figure 2. Although bleaching levels were greater for deeper corals in 1998, recovery was higher and mortality lower than for shallow corals. It may be that penetration of warmer SSTs to deep water sites took longer and may have had a shorter duration than in the shallows. Shorter duration and magnitude of anomalous temperatures may have led to high recovery at depth (see Brown, 1997), and the timing of the onset of bleaching may be important. The 1998 survey was conducted at the end of the anomalous period, recording high bleaching cover. This suggests that the bleaching may only have started at the end of the three-month period of anomalous SSTs. Coral communities in Aldabra may have undergone a shift in species composition as a result of the bleaching, which is likely due to susceptibility to bleaching. Physogyra sp., abundant between 15 m and 25 m, and Pachyseris, abundant below 20 m - 25 m, are now dominant corals. The dominance of Physogyra sp. across all deep water sites suggests a particular robustness of this species to the perturbation of the ambient environment. In areas where currents were strong, particularly the channel exits, Tubastraea micrantha is abundant. There is no evidence that the death of large numbers of corals has led to an explosion of macro-algae, as these were not abundant on dead coral surfaces. Dead corals had been covered or partially covered by red encrusting algae which not only cement and maintain the structural integrity of the coral, but may also create suitable substrate for coral larval settlement. It is essential that the substrate be fixed and/or consolidated for coral development to occur. The recovery of reefs at Aldabra from the bleaching event is underway. In areas where coral had died, there was evidence of acroporid and pocilloporid recruits up to 3 cm in diameter. Many corals suffered only partial, not full, mortality, and the live patches will be monitored to assess whether these will re-grow over the dead areas. With live coral colonies on the deeper outer slopes, in the lagoon and channels local coral larval recharge may occur. Future recovery of settlement plates put out during the surveys will provide insight into coral recruitment levels in and around Aldabra, and to further monitor and understand the recovery process. The diversity of fish species and families found in coral reef ecosystems is indicative of the productivity or health of the system (Sale, 1991). The vertical relief and three dimensional complexity of the reef habitat provided by both live coral and erect dead coral structures is not only crucial for fish survival, but is also an aggregation attractant for reef fishes. This habitat complexity is often positively correlated with the diversity of fishes on the reef (see Ebeling & Hixon, 1991; Sebens, 1991; Williams, 1991; Turner et al., 1999). Alterations and reorganisations of the reef structure following a bleaching related mortality event may, in turn, have varied spatial affects through a range of temporal scales on non reef dwelling fishes in the system. There is often a time-lag in the responses of reef fishes to the loss of live coral habitat (Turner et al., 1999). The November 1999 surveys may have captured essentially pre-bleaching event diversity of the fishes at Aldabra Atoll. This makes the quantified baseline information from these surveys exceedingly valuable for long-term monitoring of the natural recovery of this remote coral and reef fish ecosystem. Future surveys will be critical to fully understand the responses of the ecosystem, and for developing a comprehensive management plan for this and similar coral reefs. – 122 –
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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
Page 72 and 73: Relative importance in total landin
Page 74 and 75: Small pelagics Large pelagics Demer
Page 76 and 77: Indian Ocean Islands - Summary SUSI
Page 78 and 79: The reefs of the granitic islands o
Page 80 and 81: onies damaged was recorded using th
Page 82 and 83: FAMILY GENUS SPECIES DEAD SURVIVING
Page 84 and 85: FAMILY GENUS SPECIES DEAD SURVIVING
Page 86 and 87: Figure 10. Recruit on consolidated
Page 88 and 89: Reef systems of the islands of the
Page 90 and 91: Figure 2. Coral condition by locati
Page 92 and 93: At the Bank’s northern and southe
Page 94 and 95: chelles (Turner et al., this volume
Page 96 and 97: the shallow bays of Balaclava Marin
Page 98 and 99: Development of a geographical infor
Page 100 and 101: 2 1,8 1,6 Mean Bleaching Score 1,4
Page 102 and 103: Meteorological data from the period
Page 104 and 105: Figure 16. Total sunshine (hrs) per
Page 106 and 107: solar irradiance. In Thailand, loca
Page 108 and 109: Harriott, V.J. 1985. Mortality rate
Page 110 and 111: Table 1. Location of CORDIO monitor
Page 112 and 113: Figure 1. Recovery from settlement
Page 114 and 115: that due to its low impact, dead co
Page 116 and 117: Map of the Western Indian Ocean wit
Page 118 and 119: In April 1998, close to the peak of
Page 120 and 121: Pachyseris, Turbinaria spp.) and en
Page 124 and 125: REFERENCES Barnes, J., Bellamy, D.J
Page 126 and 127: SECTION II Environmental Monitoring
Page 128 and 129: Sea surface temperature in the west
Page 130 and 131: Temperature and water exchange in a
Page 132 and 133: Figure 2a. Time series temperature
Page 134 and 135: ACKNOWLEDGEMENTS I would like to th
Page 136 and 137: 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
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within each depth zone (5 m and 10
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The taxonomic patterns of coral rec
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dives, this study has demonstrated
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Bioerosive processes An important a
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each of the three different fish co
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Figure 1. Coral fragments transplan
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Pavona Echinopora 50 100 50 100 Gro
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A low-tech method for reef rehabili
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Impacts of bleaching on coral commu
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anching and massive corals (Plate 1
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es, metal bars and PVC surfaces. No
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strate that supports a low percenta
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egeneration and prevent further des
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APPENDICES - 197 -
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Coral Reef Degradation in the India
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LIST OF PARTICIPANTS LIONEL BIGOT A
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AGNETHA NILSSON Programme Officer U
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DR. SUE WELLS Co-ordinator, E.A. Ma
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