The 1997-1998 Mass Bleaching Event Around the World

Caribbean Sea

The most notable prior bleaching evente were 1983 and 1995. In 1983, there was large-scale mortality of corals along the Caribbean coasts of Panama and Costa Rica. Many of the affected reefs have not recovered their previous levels of coral cover, with the predominant shallow water corals of Agaricia and Acropora now being much reduced. Bleaching this time appears to be spread over a very long time span and in widely separate locations.

Bahamas

Corals of the central Bahamas showed extensive bleaching in August 1998, with over 60% of all head corals bleached to 20 m around New Providence Island. Extensive bleaching of around 80% was seen between 15-20 m depth. Montastrea cavernosa was not bleached, and Acropora palmata bleached on the upper sides only of branches in shallow water. Near complete bleaching of all the corals and some gorgonians seen at Little Inagua, Sweetings Cay, Chubb Cay, Little San Salvador, San Salvador and Egg Is. Samana Cay was much less effected. Hurricane Bonnie then dropped water temperatures by 2^oC. There was also extensive bleaching at Walker's Cay in the northern Bahamas, with many types of coral affected.

(Benjamin Mcpherson, Eleanor Phillips, Bill Precht)

Belize

Large areas of the Belize coral reef ecosystem experienced massive coral bleaching in early September 1998 and is continuing in October 1998. There was severe bleaching to at least 8 m on the fore-reef, and on the reef top and back-reef of the following: the main barrier reef at Ranguana Pass; patch reefs at Bird, Crawl, Laughing Bird, Scipio, South Water, and Cocoplum Cayes; pinnacle reefs between Ranguana Pass and Lighthouse Caye off Placencia; offshore reefs of Glover's Reef Atoll and Ambergris Caye; and shallow banks off Rum Point. On Glovers, bleaching was measured at 76% on the western fore reef (near Baking Swash) at 12-15m, and estimated at 70-80% on the shallow patch reefs in the lagoon and on the eastern fore reef down to at least 25m. Bleaching was between 25-30% on barrier reef sites (Gallows Reef, near Goffs and Alligator Cayes and near Calabash Caye, Turneffe Atoll) to depths of 14-18m. The bleaching is correlated with exceptionally warm water, and calm weather. Water temperatures have been consistently between 30-32^oC, and on the surface near some of the cayes, it was between 36-38^oC. Almost all hard corals and the zooanthid Palythoa exhibited some bleaching. Total to high bleaching was prevalent in Millepora, Agaricia, and Porites. High to moderate bleaching affected Montastrea, Siderastrea, and Diploria. Moderate to low bleaching occurred in Dendrogyra and Acropora, although A. palmata was only moderately bleached on the main Barrier Reef, but some totally bleached colonies were seen lagoon patch reef. Low to moderate bleaching was seen on the Central Barrier Reef and Turneffe Atoll. Mortality of bleached corals throughout Belize appears to be about 20-25%. Similar bleaching was seen in 1995, but not to this extent

(Tom Bright, Melanie McField)

Bonaire (Dutch Antilles)

Less than 15% of corals bleached in August and September 1998, with partial bleaching in Montastrea annularis between 10 and 20 m and in Agaricia below 20 m. Only a few, small corals in shallow water appear to have bleached. Later in September, nearly 100% of all Agaricia bleached from 8 m to 30 m, but bleaching was not observed in other species with water temperatures of 30^oC at the surface to 30 m and 29.5^oC below that.

(Kalli De Meyer, John Ware)

Cayman Islands

Unprecedented bleaching has occurred during late September 1998 on Little Cayman and Grand Cayman, with all species affected and possibly 90% of all corals heavily bleached. There was some bleaching of Acropora palmata and Montastrea annularis at 1-5 m depth, and widespread bleaching and some mortality to the abundant Millepora. Even previously resilient Montastrea cavernosa partly bleached. Between 50 and 60% of large colonies of Montastraea faveolata bleached around Grand Cayman, but with less bleaching on the West Wall.

(Phil Bush, Jason DeSalvo)

Colombia

Only a few bleached corals seen at Isla San Andres in September 1998. By early October, there was minor bleaching (5-10%) at Islas del Rosario affecting Millepora, Acropora palmata, Siderastrea, Agaricia, Porites, Montastraea and some gorgonians. No significant bleaching seen in the Santa Marta area, in October.

(Jeremy Woodley)

Cuba

No bleaching has been reported on southern Cuba, however there is a report of extensive bleaching at Herradura and Varadero (west and east of Havana respectively) in late August 1998 for 2 weeks. Millepora was extensively bleached, as well as some Montastrea annularis, (colony tops), Porites and zoanthids (nearly 30% of all colonies). Near Santiago, there was bleaching down to 35m depth, probably of Agaricia. Bleaching was seen in places where it was rare or never seen before.

(Pedro Alcolado, Judy Lang, Alan Logan, Peter Sale)

Dominican Republic

No mass bleaching was seen by dive operators who dive all over the country.

(Paul Medley)

Florida (USA)

Scattered bleaching was observed in inshore waters of the Florida Keys in early August 1997, with some colonies partially bleached and others extremely mottled or blotched. Small colonies were entirely bleached. Extensive bleaching to large coral heads in the Gulf of Mexico area of the Keys (Boca Grande Channel, between Boca Grande Key and the Marquesas Keys) was also reported. There was significant recovery.

In July and August 1998 there was bleaching at Coffins Patch Light in the Florida Keys, with water temperatures of 30-31^oC. Minimal bleaching was observed in Millepora colonies, but there was none on nearby Coffins Patch Special Protected Area (SPA). In late August1998 extensive bleaching was seen in Western Sambo Ecological Reserve, Florida Keys. Surface water temperatures were 30-32^oC, but only 26^oC at 10 m. Bleaching was seen in up to 90% of Acropora palmata, with some mortality, 50-80% of Montastrea annularis and A. cervicornis, and 40-60% of other corals. There was moderate bleaching between 10 and 30 m in Dry Tortugas National Park and on the Tortugas Banks in early September 1998. Approximately 15-25% of colonies were affected with water temperatures around 30^oC. There was also evidence of bleaching at Ft. Jefferson. In September there was significant recovery of corals on an inshore patch reef known as the Rocks, that had been severely bleached in June and very little mortality was evident. Hurricane Georges dropped temperatures to 28^oC and did little physical damage. However corals in many areas still appeared bleached with brain corals not showing the recovery seen in other species.

(Billy Causey, George Garrett, Ben Haskell, Walt Jaap, Alina Szmant)

Guadeloupe

Severe bleaching is reported.

Claude Bouchon)

Haiti

An extensive coral bleaching event was reported after Hurricane Georges in September.

(Jean Wiener)

Honduras

Up to 50% of live coral cover showed bleaching from 10 to 25 m around Roatan from mid-September 1998, with most species affected, especially Agaricia, Montastrea and some Diploria. Small amounts of Acropora and Millepora were only slightly affected. No bleaching seen around the Bay Islands.

(Marea Hatziolos)

Jamaica

Temperatures rose to 29^-30^oC in late September, at Discovery Bay below 30 m. By early October, 70-75% of all Montastrea colonies were bleached, and were still mostly white by mid-October (temperature maximum of 31.5^oC). In Portland Bight (south coast) in early October, divers were astonished to see both bleached corals and white gorgonian sea-whips.

(Jeremy Woodley, Ian Sandeman)

Mexico

Bleaching started in late August in Quintana Roo with temperatures around 30^oC, and near 33^oC in the lagoon. They were still high in September (29.5^oC - 30.5^oC). By mid-October, 15 coral species had some bleaching, but it was variable, with Agaricia and Millepora more affected than Montastraea and Diploria. Acropora not affected so far. By October 16, bleaching was widespread. Earlier some bleaching was reported for the Yucatan coast, but no bleaching was seen near Cozumel. This bleaching event is less severe than in 1995.

(Eric Jordan, Judy Lang, Peter Sale)

Panama

Extensive bleaching was reported in October in western Panama.

(Hector Guzman)

Puerto Rico

There was no bleaching in 1997. There was, however, moderate bleaching in 1996 after Hurricane Hortense hit the south coast, and all colonies recovered well from partial or total bleaching. In 1998, there has been sporadic, but low frequency bleaching, in several species down to 30 m deep. The most affected were a zoanthid (Palythoa caribbaeroun), and Millepora, but most other corals were normal.

(Ernesto Weil)

St. Lucia

Bleaching in the Soufriere area is the worst ever seen with 100% of all Diploria affected and bleaching in other species including Monrastrea annularis, Porites astreoides, and Agaricia. No mortality yet, but it is expected.

(Allan Smith)

St. Vincent and the Grenadines

There are second hand reports of severe bleaching.

(Allan Smith)

Virgin Islands (UK)

Widespread coral bleaching was seen in mid-September 1998 on 5 reefs south of St. Thomas, which were unaffected in early August. At least 50% of colonies of numerous species were affected, including Montastrea annularis, Porites (branching and massive), Colpophyllia, some Millepora, agaricids, some Siderastrea. But bleaching was patchy with some normal coloured tissue remaining and there was little evidence of mortality by mid-October. There was moderate bleaching on Virgin Gorda, affecting about 20% of the coral population. The coral community was healthy and probably recovering from an earlier, possibly more serious, beaching event.

(Les Kaufman, Barbara Kojis, John Ogden)

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Last updated - 7 December 98

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