Status of Coral Reefs of the World 2000

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Status of Coral Reefs of the World: 2000 CASE STUDY 4: BLEACHING ON THE REEFS OF SOUTHERN JAPAN There was unprecedented mass coral mortality in Okinawa, Japan, with the local extinction of at least 4 coral species and a loss of hard and soft coral cover from 70% to 10%. A strong La Niña coincided with mid summer, no typhoons and low cloud cover and this raised water temperatures around Okinawa to 2.8 o C above the 10 year average. Bleaching started in mid-July and ended with the first typhoon of the season in September. Locals reported seeing nothing like this during the 35 years of coral reef research, and elderly Okinawans said they “have never seen such beautiful white corals”. Coral cover virtually did not change between 1995 and 1997 at Sesoko Island (26 o 38’N, 127 o 52’E), but after the bleaching, mean coral cover decreased by 73%, the number of species decreased by 61% and number of colonies per m 2 dropped to less than half. Furthermore the living cover of soft corals decreased by 99%. Branching Acropora species which were once the most prolific corals on Okinawan reefs, were most severely affected; 3 species of branching corals species (Seriatopora hystrix, S. caliendrum, Stylophora pistillata and Pocillopora damicornis) and the branched fire coral Millepora intricata are now locally extinct and no new recruits were found around Okinawa in 1999. Curiously, many juvenile Acropora colonies (< 5cm in diameter) survived on the reef flats, where they are likely to be killed when exposed to air and high irradiance during midday low tides. Bleaching also affected other common corals, whereas many of the less common species survived and are now the most abundant e.g. massive and encrusting colonies of Porites, Goniastrea, Leptastrea, Platygyra, Favia and Favites. The chances for recovery of the missing species depends on coral populations on distant offshore reefs (15-30km from Okinawa) which may provide larvae for re-settlement, provided currents are favourable. Report from Yossi Loya Department of Zoology, Tel-Aviv University, Israel 69978, e-mail: yosiloya@post.tau.ac.il impacts were often minor on inshore areas which experience natural variations in temperature and water clarity. On the northern Ngeruangel atolls, bleaching deaths varied between 10% and 70% at all depths, with a mean of 53.4% of corals at 3–5m, 68.9% at 10–12m, and 70% at 30m (Peleliu, the Blue Corner, the Big Drop-off, Iwayama Bay - Rock Islands). Severe bleaching occurred in Arakabasan and Cemetary island. The major damage was to corals in oceanic waters, with much less bleaching and mortality in shallow areas and close to the more turbid and stressed habitats near the shore. The least effect was to corals around the sewage outfall near Koror (John Bruno, e-mail: John_Bruno@Brown.edu). All adult jellyfish in the famous marine lake (Ongeim’l Tketau) were killed, but live polyps were found in 1999. About 20% of corals, including a wide variety of hard and soft coral species, bleached to 20m depth on the north of Yap, Federated States of Micronesia in September 1998,. Other parts of Micronesia reported only minor bleaching. 28
The 1997-98 Mass Coral Bleaching and Mortality Event Northeast Pacific Ocean No bleaching was reported in 1997-98, and water temperatures were often colder than usual. Pacific Coast of the Americas When the pool of warm water associated with the El Niño banked up on the Pacific coast of central America, bleaching soon followed in Colombia, Mexico and Panama between May and September 1997. However, the bleaching was usually partial and only occasional complete bleaching on some corals. The resultant mortality was usually less than 5% or not detectable. This episode of bleaching was very minor compared to the disastrous events of 1982-83 when there was 50-100% coral mortality on most reefs, which have yet to recover from those losses. When this pool of warm water expanded to reach the Galapagos Islands in mid-December 1997 there was some bleaching of the coral communities that had recovered after the major bleaching of 1982-83. Bleaching continued affecting most corals by March 1998. CASE STUDY 5: GBR BLEACHING UPDATE - SEPTEMBER 2000 Around 28% of offshore reefs, which make up the bulk of GBR reefs, were bleached in early 1998, but the majority showed full recovery by the end of 1998. The inshore reefs bleached more extensively (87% of the reefs with some bleaching), with 55% showing high to extreme bleaching and recovery was patchy. Reefs in the Keppel Island group (inshore southern GBR) recovered well, while reefs on the Palm Island group (inshore central GBR) suffered high mortality. Overall, hard coral cover at Orpheus and Pelorus Islands (northern Palm group) declined from an average of 13.1% to 5% at 4 sites, while soft coral cover declined only marginally from 18.4 to 16%. The biggest impact was on two hard coral families: the Acroporidae, which suffered a 91% relative decline and the Milleporidae, which suffered >99.99% decline. Attempts to find living colonies of Millepora tenella (a previously dominant species), failed to find any living colonies around Orpheus Island, however, there was an anecdotal report of a single small colony in deep water. Two years after the bleaching, recovery of Acropora species is slow in the Palm Islands. At Northeast Reef on Orpheus Island, staghorn coral patches (A. nobilis), which were initially thought dead, are showing signs of recovery with many new branches (10-15cm) growing out of the dead skeleton. These are not new recruits, and they presumably derive from residual live tissue within the skeleton or underneath the colony. Other staghorn species (A. formosa and A. grandis) do not show this recovery pattern. Plating Acropora species (particularly A. hyacinthus and A. cytherea) suffered near total mortality and have not recovered, and recruitement of all Acropora species is very low. Thick tissued and massive coral species (poritids, favids, mussids, fungiids) generally recovered well, and pocilloporid recovery is intermediate and patchy. From: Ray Berkelmans, Australian Institute of Marine Science, Townsville (r.berkelmans@aims.gov.au) 29
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
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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
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Status of Coral Reefs of the World:
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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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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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