CORDIO Status Report 2000

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In April 1998, close to the peak of the coral bleaching event, 41% of corals (coral coverage = 37%) were bleached or displayed recent mortality on the outer reef slopes (3 m -25 m) from the western to north-eastern sides of Aldabra (Cambridge Coastal Research Unit (CCRU), Southern Seychelles Atoll Research Programme – SSARP). Bleaching intensity in Aldabra was not as high as other areas in the southern Seychelles possibly because peak warming was 0.5º C lower than other areas in the region (Spencer et al., in press). Bleaching and related mortality was primarily seen in the branching and tabular species of coral (Pocillopora and Acropora), and partial to patchy in most massive species (Porites and Pavona). Bleaching in some areas was confined to a single side of the coral colony. However, a high proportion of the massive species of corals displayed signs of previous mortality, as indicated by a thick layer of algal overgrowth and the presence of encrusting and boring invertebrates. As in other areas, soft corals showed high levels of bleaching and mortality. Although no quantitative data were gathered for the reef communities in the lagoon, extensive observations were made in all of the channels and in the western half of the lagoon. Most of the coral species found in the channels, with the exception of isolated incidences of branching corals, were observed to be alive and displaying no obvious signs of perturbation. Lagoonal patch reefs and individual heads of massive coral species displayed very limited bleaching. Distinctive species such as Galaxea, Seriatopora, Acropora and Pocillopora were completely bleached, particularly with increased distance from the flux of water within the channels. METHODS In November 1999, a series of seven permanent transects were established on the northern and western coasts of Aldabra Atoll (Figure 1). At each site quantitative baseline surveys of the corals and reef fishes were conducted along each transect. Primary transects were placed from a depth of 20 m to the reef crest at 3 m - 5 m. Secondary transects were established at 20 m and 10 m following the depth contour. The benthos at each site was surveyed using digital videography. Video imagery was analysed recording live and dead, hard and soft coral growth forms (branching, tabular, massive, encrusting and foliose). The occurrence of coral genera within each of these growth form categories was also noted, as well as incidences of mushroom corals, Heliopora (blue coral) and Millepora (fire coral). Additional observations of the substrate were noted in predefined categories: sand, rubble, rock, turf, Halimeda and other macro-algae. Settlement plates were located at six sites, three on reefs around the outside of the atoll, and three within the atoll (Figure 1). Of the six tiles, two were oriented in the horizontal plane, two at approximately 45° to the horizontal, and two in the vertical plane. Rapid visual fish surveys were conducted using species, number and size of fish recorded in a 2 m corridor extending out from either side of the transect, and vertically to the surface. Six total length categories were used: 0-5 cm, 6-10 cm, 11-20 cm, 21-30 cm, 31-40 cm and >40 cm. Each section was first surveyed for larger/ conspicuous fishes, and then immediately re-surveyed for small/cryptic fishes. Fish size classes have been condensed to three grouped categories for this paper. RESULTS Coral and general benthic composition There was a range of variation in percent cover of live coral (11% - 27% ± 6% (± 1 standard deviation)) and of dead coral (11% - 30% ± 7%). Live coral cover was strongly correlated with depth. From the shallow depths of 5 m - 10 m to >15 m there was an increase of 10% - 20% of live coral cover. Conversely, dead coral cover was higher in shallow waters (20 m) to 10% - 20% of the coral cover. There was a general increasing trend for cover of live and dead coral from east to west on the whole atoll (Figure 4), coinciding with decreasing levels of exposure to strong hydrodynamic conditions. The least exposed – 117 –
Figure 4. Calculated general substrate cover for the transect sites around Aldabra. 6 2 3 4 5 1 7 Sand, Rock, Rubble Algae Live Coral Dead Coral sites with the highest mean live coral cover were sites 1 (25%), 2 (24%), 6 (16%) and 7 (21%) (Figure 4). Note that site 5, at the highly exposed eastern corner of the atoll, was treated separately from other sites as it was distinctly different from the others surveyed, dominated by a high percentage of a sand, rubble and rock matrix (56%) and macro-algae, primarily Halimeda spp. (40%). Site 5 did have isolated coral heads but only 1.5% live coral and 2.0% dead coral of the total substrate cover. Across the range of the sites examined Halimeda spp. was the dominant macro-alga, with localised high concentrations of Dictyota spp., Caulerpa spp. and Lobophora spp.. Thalassodendron spp. was present but was not considered to be a major component of the outer reef slopes. In most areas red encrusting coralline algae were observed especially where incidences of dead upright coral and coral rubble were present. On massive coral heads small patches of red encrusting algae were beginning to colonise in presumed bleaching related dead areas. Soft corals (Sinularia spp., Lobophytum spp. and Sarcophyton spp.) were present as small isolated colonies and comprised no more than 5% of the substrate at any given location. Soft corals show a slight increase in abundance moving east along the northern coast. The dominant live coral growth forms were massive, branching, encrusting and foliose at both shallow and deep sites. Massive corals were dominant at deep and shallow sites (63% and 45% of live coral cover, respectively). Physogyra sp. was the dominant massive coral on deeper transects (65% of massive spp.) but was virtually absent (3%) from 10 m depth sites. Other prominent massive genera were Favia, Favites, Galaxea, Gardineroseris, Goniastrea, Leptoria, Lobophyllia and Porites. The majority of branching corals found at both shallow and deep sites were Pocillopora and Porites spp., representing 20% of the total live coral cover. Live tabular coral species were not encountered at any of the sites surveyed but they were noted at the seaward edge of the western channels to the lagoon. Foliose (Echinopora, – 118 –
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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
Page 68 and 69: Table 4. Summary data from transect
Page 70 and 71: 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 120 and 121: Pachyseris, Turbinaria spp.) and en
Page 122 and 123: Partial mortality of Favites flexuo
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
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to assess ciguatera risk by impleme
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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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