Status of Coral Reefs of the World 2000

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Status of Coral Reefs of the World: 2000 1998 CORAL BLEACHING IN THE MESOAMERICAN BARRIER REEF SYSTEM (MBRS) There were few large-scale bleaching events in the north Central American region compared to other areas in the Western Atlantic because high temperature stresses were infrequent and other environmental stresses were relatively minor. For example, coral bleaching was reported for much of the Caribbean during 1983 and 1987, and the first well-documented mass bleaching event in Belize occurred in 1995 where 52% of coral colonies bleached, although only 10% of the corals suffered subsequent partial mortality (10-13% loss of coral cover). These impacts in 1995 were also observed in Cayos Cochinos, Honduras, where 73% of scleractinian corals and 92% of hydrocorals bleached and slightly higher mortality was reported. A less severe bleaching event was reported in 1997, although the extent of damage is not known. Then there were major disturbances during 1998. First high sea-surface temperatures appeared during August and intensified during September. Reports of intense bleaching (>50% of colonies) started in the Yucatan in August/September, followed by reports in Belize (September) and Honduras (September/October). Coral mortality was first reported in the Yucatan in early October, particularly on Agaricia tenuifolia colonies. Reports of massive bleaching and mortality of A. tenuifolia and Millepora spp. in the central and southern Belize barrier soon followed. Then severe Hurricane Mitch passed over in October; sea surface temperatures decreased and recovery of some branching corals was reported while massive corals continued to remain bleached into 1999. Extensive surveys conducted indicated that the 1998 bleaching event affected the entire MBRS region, and was possibly more severe than mass bleaching in 1995. Shallow reef corals tended to either die immediately or recover more rapidly from bleaching compared to deeper depths, where coral recovery from bleaching proceeded more slowly. The magnitude of the bleaching was evident in deep fore reef sites where significant remnant bleaching was observed up to 10 months after the initial bleaching. Specific findings from this study showed: • Regional average of 18% recent coral mortality on shallow reefs, 14% on fore reefs; • Up to 75% recent coral mortality on localised patch and barrier reefs in southern Belize; • Highest mortality observed for A. tenuifolia (>35%), M. complanata (28%), and Montastraea annularis complex (25-50%); • Regionally high recent mortality and disease on Montastraea annularis complex; • Low to moderate levels of recent mortality in Acropora palmata from bleaching; • Remnant bleaching still evident on fore reefs 10 months later (up to 44% of corals still bleached); and • High incidence of coral disease following the bleaching event on Belize shallow reefs (black band) and Honduras and Belize fore reefs (white plague). 292
Status of Coral Reefs of Northern Central America In 1998, a sequence of catastrophic disturbance events impacted the region: unprecedented coral bleaching was documented throughout the region as well as elevated incidences of disease and in late October 1998, Hurricane Mitch impacted much of the coast from Nicaragua northwards to Yucatan. The synergistic effects of these events are expected to have long-term ecological consequences for the coral reefs. Mexico These reefs are among the best studied in the region. The main disturbances to Pacific reefs are strong El Niño events and extremely low winter water temperatures. Since most Pacific corals are found as small isolated communities, they are susceptible to disturbance and local extinctions can result, i.e. Leptoseris papyracea is probably extinct along the Mexican mainland and the distribution of Porites sverdrupi has been reduced to only 500km. Atlantic reefs of the SW Gulf, particularly the nearshore reefs near Veracruz receive intense anthropogenic impacts from agricultural, industrial, and urban wastes, over-fishing, oil spills, and ship groundings. Extensive mortality of Acropora has been documented at Isla de Sacrificios, whereas the offshore reefs of Campeche Bank are remote from direct human impacts, although occasional oil leaks and damage from the oil facility have some impacts. Coral cover ranged from 2 to 28% in 1981, but was 1 to 6% in 1993 at the CARICOMP monitoring site of Puerto Morelos. Much of the loss was due to Hurricane Gilbert in 1988 and the mass coal bleaching in 1995, although this was not measured. The largest decline in coral cover was on the back reef, from 28 to 5%, and the reef crest 27 to 6%. Despite these losses prior to 1998, these reefs showed evidence of recovery with little extreme bleaching or algal overgrowth, and some signs of re-establishing Diadema populations. AGRRA surveys (1999) in Veracruz found 17% average coral cover, low recent mortality, low coral disease and bleaching, evidence of coral recruits, few Diadema, and low macroalgae. The ENSO event impacted reefs in the Gulf of California (18% coral mortality) and Bahia de Banderas (more than 70%). Oaxaca reefs were affected by the La Niña of late 1998 (more than 70% mortality). On the Atlantic coast, the 1998 bleaching and Hurricane Mitch impacts were lower in Mexico than in Belize or Honduras; only 4 of 27 reefs surveyed after the event had higher than normal recent mortality, averaging 11% on fore reefs and 7% on shallow reefs. The southern area was impacted by bleaching, disease, and minor hurricane impacts while the north and central region had low disturbance. In 1999 AGRRA surveys in the central and southern regions of the Mexican Caribbean, there was 12% average coral cover (10m depth), 37% total coral tissue mortality, greater average algal turf cover than macroalgae and crustose coralline algal cover, and evidence of coral recruitment, although there was an almost total absence of Diadema. Belize While there have been extensive studies on several select reefs in Belize, much of the barrier reef has not been studied. Some of the earliest disturbances reported were severe storms and hurricanes, such as Hurricane Hattie (1961) which reduced living coral cover by 80% and destroyed spur and groove structure along sections of the barrier reef. Prior to the mid-1980s, A. cervicornis was the dominant reef-builder on the fore-reef slope until populations were devastated, presumably by white band disease i.e. coral cover near Carrie Bow Cay shallow fore reef dropped from 30-35% in the late 1970s to 12-20% now. These losses were followed by increases (up to 60%) in fleshy macroalgal cover, primarily 293
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Status of Coral Reefs of the World:
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FOREWORD Over the past few years, I
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CONTENTS COUNTRIES, STATES AND TERR
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COUNTRIES, STATES AND TERRITORIES A
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Countries, States and Territories T
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EXECUTIVE SUMMARY CLIVE WILKINSON T
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Executive Summary CORAL BLEACHING I
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Executive Summary South Asia Most r
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Executive Summary parts of Fiji and
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Executive Summary management and mo
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Executive Summary tourism developme
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Executive Summary problem is loomin
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6. STATUS OF CORAL REEFS IN SOUTH A
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Status of Coral Reefs in South Asia
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8. STATUS OF CORAL REEFS OF EAST AN
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Status of Coral Reefs of East and N
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9. STATUS OF CORAL REEFS OF AUSTRAL
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Status of Coral Reefs of Australasi
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10. STATUS OF CORAL REEFS IN THE SO
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Status of Coral Reefs in the Southw
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11. STATUS OF SOUTHEAST AND CENTRAL
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Status of Southeast and Central Pac
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12. STATUS OF CORAL REEFS OF AMERIC
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Status of Coral Reefs of American S
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Status of Coral Reefs in Southern T
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19. SPONSORING ORGANISATIONS, CORAL
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Sponsoring Organisations, Coral Ree
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LIST OF ACRONYMS AGRRA AIMS ASEAN B
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