Uneasy lies the coral

Unprecedented depletion of corals threatens marine ecosystems in the tropics

Published: Monday 30 November 1998

THE us National Oceanic and Atmospheric Administration (NOAA) has come out with alarming findings about corals, tiny marine organisms which secrete calcareous shells that combine to form coral reefs. Record-breaking depletion of corals and extremely warm waters occurred throughout the tropics during the first half of 1998, the NOAA announced on October 16.

Coral reefs - the rainforests of the sea - are some of the oldest and most biologically diverse ecosystems on the Earth. Important assets to local and national economies, corals produce fisheries for food, materials for new medicines, and income from tourism and recreation. They also protect coastal communities from storms. "Coral bleaching is a sign that reefs are under severe stress and may be seriously damaged," said NOAA administrator D James Baker. Coral bleaching results from a number of factors including pollution, sedimentation or changes in salinity. "With 1998 named the Year of the Ocean, it is appropriate that we focus our attention on these extremely important and fragile coral reef ecosystems," Baker added.

Corals thrive as long as temperatures remain at or below certain temperatures for a given site. An slight increase above the usual maximum temperatures can be deadly for them. While many corals normally recover from short bleaching events, long-term or frequent bleaching may severely weaken the corals leaving them more vulnerable to disease, damage or death.

Data from NOAA'S satellites show that during the first half of 1998, more ocean area in the tropics experienced exceptionally high sea surface temperatures, or "hot spots", than observed in any full year since 1982. Approximately 50 countries have reported coral bleaching since 1997. During the El Nifio of 1982-83, large areas of coral reef around the world were severely damaged by high water temperatures associated with coral bleaching. Before this, the annual record for high ocean temperature events was in 1988, which also followed an El Nino, year.

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