Status of Coral Reefs of the World 2000

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Status of Coral Reefs of the World: 2000 CASE STUDY 1: CHAGOS ARCHIPELAGO, CENTRAL INDIAN OCEAN An error was made in the 1998 report with no bleaching reported on Chagos. In fact these remote reefs were severely damaged like others in the Indian Ocean. The 1998 El Niño resulted in a major losses in coral cover and abundance across the Archipelago. The El Niño came at the end of a chain of events that had caused hard coral cover to decline from 50-75% (plus 10-20% soft coral) to only 12% live cover over the last 20 years. These are very remote reefs with high biodiversity (220 and 770 fish species) which experience virtually no human impacts. The 1998 ‘Hotspot’ sat over Chagos for 2 months, so that in early 1999 seaward reefs of the 6 Chagos atolls had 40% cover of recently dead coral and 40% bare rock. The 50% of corals lost in the lagoon has turned into loose rubble. It is probable that earlier El Niño events (1982- 83 and 1987-88) resulted in conversion of much live coral to rock and rubble, but the 1998 event caused a major sudden loss of corals. Meteorological records show a 1-2 o C rise in mean air temperature, lower annual atmospheric pressure, reduced cloud cover, and more variable winds during the last 25 years; strong evidence for global climate change. In the 1970s, seaward and lagoonal reefs had high coral cover and diversity, with many large table Acropora spp. in 5–15m depth, and A. palifera in the turbulent shallows. By February 1999, most of these corals and soft corals were dead with only a few large Porites heads having more living than dead tissue. There were also losses of calcareous red algae, Millepora, and blue Heliopora corals from shallow areas. Soft corals were almost totally eliminated from seaward slopes after 1998, resulting in large areas of bare substrate. There was much lower coral mortality on lagoon reefs, probably because these experience large normal fluctuations in temperature and the corals presumably have adapted to higher temperatures. The massive Porites in lagoons survived better than those on ocean facing reefs. The effects on Chagos have been catastrophic, particularly for the dominant genus Acropora. In early 1999, it was possible to snorkel for 15 minutes in areas of northwestern Salomon and western Blenheim and not see any live coral amongst the stillstanding coral skeletons. Whereas before then, there was 50-75% cover. There were only occasional sites with more than 10% of colonies were alive, with Porites lutea and other similar large massive Porites species being the best survivors (average cover of 8% on all reefs). The immediate consequences will be a reduction in reef growth to at least 20m depth, and delayed recovery of corals and the coral community. Erosion of the coral skeletons will produce unstable rubble and sand, which will prevent the settling of new larvae from the few living parent colonies. The scale of the losses, including coral colonies that were 200-300 years old, indicates that partial recovery will take several decades at least, and may be a few hundred years before a similar community of corals is re-established. (Charles R.C. Sheppard, 1999. Coral decline and weather patterns over 20 years in the Chagos Archipelago, Central Indian Ocean. Ambio, 28, 472-478, E-mail: sh@dna.bio.warwick.ac.uk.) 24
The 1997-98 Mass Coral Bleaching and Mortality Event the living corals or more. These now appear as virtually barren reefs with just a few percent of coral cover. The critical problem for these reefs is that there are few remaining adult colonies to provide coral larvae, thus it is probable that many reefs will have lower coral diversity for the next 20 to 40 years. Bleaching throughout the Maldives was extreme, with many reefs now having less than 5% live coral cover. There are, however, encouraging signs of recovery with many small corals surviving after the bleaching and many new recruits appearing. The ‘new’ reefs, however, will have a very different appearance with dominance by slow growing massive corals, instead of branching and plate Acropora. Southeast and East Asia Bleaching was variable across the region, with most countries reporting severe bleaching, but generally low levels of coral mortality. The exceptions were parts of Vietnam and the northern Philippines where up to 80% corals bleached, and mortality was high. Singapore reported the first major bleaching in the island’s history. The large La Niña event that started in June 1998 occurred during the northern summer and resulted in serious bleaching in the region, particularly in Taiwan and Japan. This area is frequently impacted by typhoons travelling to the northwest, which mix the waters and maintain them below 30 o C, but the summer of ’98 was particularly calm with the first typhoon being delayed until September. By then there had been massive damage to the coral reefs. Bleaching was variable with less than 20% in the north around Kyushu and Shikoku, 30–40% on the eastern Hachijo Islands (maximum of 80 – 90% in places), and CASE STUDY 2: BLEACHING OF REEFS IN THE LAKSHADWEEP ISLANDS, INDIA First reports from the Lakshadweep Islands off the west coast of India were of catastrophic bleaching, but follow-up surveys in mid-2000 showed that bleaching mortality was very variable between reefs, but more uniform within a reef. After the 1998 El Niño bleaching, live coral cover on Kadmat Island was 2.4% and 6.7% on Agatti, whereas on Kavaratti there was 14.3% cover. Turf and coralline algae growing on dead coral were the dominant cover at all sites, and there was clear evidence at Agatti and Kadmat that the dead Acropora skeletons were breaking down. An encouraging sign was that there were many small coral colonies (
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Page 3 and 4: FOREWORD Over the past few years, I
Page 5 and 6: CONTENTS COUNTRIES, STATES AND TERR
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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
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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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15. STATUS OF CORAL REEFS IN THE NO
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17. STATUS OF CORAL REEFS IN THE EA
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Status of Coral Reefs in the Easter
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18. STATUS OF CORAL REEFS IN SOUTHE
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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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