Status of Coral Reefs of the World 2000

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Status of Coral Reefs of the World: 2000 CASE STUDY 7: CORAL BLEACHING AND RECOVERY IN PUERTO RICO Wide-spread and intense bleaching events usually result in mass coral mortalities. During the 1998-99 La Niña bleaching event, many reefs in the Caribbean were affected by wide-spread and intense bleaching, however, there were generally low levels of mortality, especially in Puerto Rico. Here, 386 colonies of 18 reef-building, hard coral species were tagged in August of 1998, when they started to bleach, on an offshore bank reef, an inshore patch reef, and a fringing reef off the southwest coast of Puerto Rico. These colonies were monitored for 7 months in 1998-99 and 5 months in 1999-2000. Many colonies were 100% bleached for more than 150 days before recovering completely; only 3 small colonies died (0.8%), 14 suffered partial tissue mortality (3.6%), 357 recovered by February 1999 (92.4%), and 12 remained pale until March, 1999 (3.1%). Fifty nine tagged colonies (15%) bleached again in the second week in September, 1999 at slightly lower water temperatures than 1998, but bleaching was less intense and all recovered after 5 months. This illustrates that bleached corals need to be observed for recovery before they are declared as dead. Recovery after 5-7 months of bleaching is possible, but it will usually depend on whether other stress factors intervene, or on the severity of the original temperature stress. Many Caribbean reefs experienced similar situations in the big bleaching events of 1997-98, and the event of 99, and recovered (with the exception of some reefs in Belize), whereas reefs in the Indian Ocean were devastated. Recent observations and surveys of the area indicate no wide-spread bleaching, and no tagged colonies had bleached by September, 2000. There are a few colonies show some slight paling over small areas. Ernesto Weil. Department of Marine Sciences, University of Puerto Rico, Lajas PR 00667, e-mail: eweil@caribe.net. The El Niño dissipated rapidly in May 1998 and between June 1998 and April 1999 there was a major La Niña event with a SOI of about plus 12 or higher for these 10 months. From June to September 1998, this coincided with the northern summer with bleaching reported in South East and East Asia from July to October 1998, in: Singapore, Sumatra, Indonesia and Vietnam in July in July; Philippines from July to September; and Japan and Taiwan from July to September. Simultaneously, there was bleaching in the Arabian/Persian Gulf and Red Sea from August to October 1998, in: Bahrain, Qatar and UAE in August–September; and Eritrea and Saudi Arabia (Red Sea) in August–September. There was also bleaching throughout the Caribbean Sea and Atlantic Ocean from August to October 1998, in: Florida from July to September; Bahamas, Bonaire, Bermuda in August – September; Barbados, BVI, Caymans, Colombia, Honduras, Jamaica and Mexico in September. However, most of this bleaching resulted in minimal coral mortality. 32
The 1997-98 Mass Coral Bleaching and Mortality Event Bleaching then followed the path of the solar zenith in the far West Pacific from September to November 1998, in: the Federated States of Micronesia in September; and Palau in September to November when there was unprecedented coral mortality. A consistent feature of the weather during all these bleaching events was the coincidence of a major shift of the SOI away from zero, which apparently induced particularly calm weather. For example, in the Indian Ocean, the monsoon winds stopped almost completely, resulting in doldrum-calm conditions and weak currents. Under these conditions sea surface waters warmed above the temperature tolerance limits for corals and other symbiotic animals, without mixing with cooler oceanic and deeper waters. Warm waters often extended down as far as 30m or more. Coral bleaching consistently started about 4 to 6 weeks after the passage of the solar zenith. A critical question remains; was the 1997-98 event a one-in-a-thousand year event killing off large old corals, or will bleaching events like 1997-98 become more frequent and severe in the future? Coral bleaching and mortality levels were closely associated with the El Niño and La Niña switches in climate that started in 1997 and ended in early 1999, with large deviations in the SOI. Many scientists now predict that major climate change events will become more frequent and severe, resulting in greater bleaching. It is apparent that when a strong La Niña (positive SOI) coincides with the northern summer, bleaching will follow; likewise the major trigger for bleaching in the southern hemisphere is when a strong El Niño (negative SOI) occurs in summer. Reefs closer to the equator will probably experience bleaching under either El Niño or La Niña conditions. Thus, these predicted scenarios mean that coral reefs will change in structure over the next few decades with a major reduction in the branching and plate forming species that are the fastest growers and major contributors to coral reef accretion. In their place, reefs will have a lower profile of slow growing, massive species, with lower coral cover and lower diversity in the medium term. This will probably reduce the capacity of reefs to act as breakwaters for fragile shorelines and provide sand and rock as building materials on low islands. Fish populations will probably drop as there will be reduced structural complexity to shelter juveniles and the many small species, but changes will be gradual. The impacts on tourism are harder to predict. Coral reef tourism, one of the fastest growing sectors of the market, and growth will continue via the many tourists visiting coral reef destinations for the first time. The only adverse affects may be felt with those few tourists who revisit coral reefs for diving, and become disillusioned with large areas of dead corals. However, these tourists will probably seek new experiences and go to the many areas that will escape damage in the immediate future. Surveys of many tourists indicate that many are unaware that the corals are dead, as they focus on fish and above water activities in the tourist resorts. 33
Page 1 and 2: Status of Coral Reefs of the World:
Page 3 and 4: FOREWORD Over the past few years, I
Page 5 and 6: CONTENTS COUNTRIES, STATES AND TERR
Page 7 and 8: COUNTRIES, STATES AND TERRITORIES A
Page 9: Countries, States and Territories T
Page 19 and 20: EXECUTIVE SUMMARY CLIVE WILKINSON T
Page 21 and 22: Executive Summary CORAL BLEACHING I
Page 23 and 24: Executive Summary South Asia Most r
Page 25 and 26: Executive Summary parts of Fiji and
Page 27 and 28: Executive Summary management and mo
Page 29 and 30: Executive Summary tourism developme
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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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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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15. STATUS OF CORAL REEFS IN THE NO
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17. STATUS OF CORAL REEFS IN THE EA
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19. SPONSORING ORGANISATIONS, CORAL
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LIST OF ACRONYMS AGRRA AIMS ASEAN B
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Status of Coral Reefs of the World 2000

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