Indian Ocean coral reefs suffer worst die-off on record


Heavy losses from bleaching: The study focused on reefs near Africa’s Seychelles islands, north of Madagascar, which sustained heavy losses from bleaching in 1998.

Outlook “quite bleak”: "The outlook for recovery is quite bleak for the Seychelles," said lead study author Nicholas Graham, a tropical marine biologist at England’s University of Newcastle Upon Tyne. The study, in the Proceedings of the National Academy of Sciences, predicted that isolated reef ecosystems like that around the Seychelles would suffer the most from global warming-caused bleaching events.

Temperature rises cause algae to be expelled: Small but prolonged rises in sea temperature forced coral colonies to expel their symbiotic, food-producing algae, a process known as bleaching. While the dying reefs, which turn ghostly white, could recover from such events, many did not.

Over 16 per cent of coral reefs lost in one year: In 1998 an El Nino weather pattern sparked the worst coral-bleaching event observed. "Over 16 per cent of the world’s reefs … were lost in that one year," said Graham.

Study in 2005: In the western Indian Ocean, regional currents compounded the heat effect, bleaching 90 per cent of the coral reefs there. With data from a 1994 survey in hand, researchers returned to the Seychelles in 2005 to study the bleaching event’s long-term impact on coral reefs and fish communities.

50,000 square metres surveyed: Surveying 50,000 square metres of coral reef across 21 sites, researchers found that fish diversity declined the most on reefs that had sustained physical and biological erosion.

Reference: Digest of latest news reported on website of Climate Change Secretariat of United Nations Framework on Climate Change Control (UNFCCC). 17 May 2006. Address: PO Box 260 124, D-53153 Bonn. Germany. Phone: : (49-228) 815-1005, Fax: (49-228) 815-1999. Email:

Erisk Net, 22/5/2006

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