NOAA Public Affairs



Washington, October 15 -- NOAA announced today that unprecedented coral bleaching and extremely warm waters occurred throughout the Tropics during the first half of 1998.

Coral reefs -- the "rainforests of the sea" – are some of the oldest and most biologically diverse ecosystems on earth. Important assets to local and national economies, they produce fisheries for food, materials for new medicines, and income from tourism and recreation, as well as 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. "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."

Corals thrive as long as temperatures remain at or below certain temperatures for a given site. An increase of one or two degrees above the usual maximum temperatures can be deadly to these animals. The temperature range for corals to thrive varies from site to site by only a few degrees. 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 Niño of 1982-83, large areas of coral reef around the world were severely damaged by high water temperatures associated with coral bleaching. The previous annual record for high ocean temperature events was in 1988, which also followed an El Niño event the year before.

Using satellites to measure sea surface temperatures and identify hot spots, NOAA has been able to predict coral reef bleaching events in real time over large ocean areas since 1997, reports NOAA oceanographer Al Strong. Hot spots are identified when satellite-derived sea surface temperatures exceed by 1.0 degree Celsius the monthly average temperature expected during the warm season.

Coral bleaching can be a sign that the coral is being stressed by a number of factors, including pollution, sedimentation or changes in salinity. Increases in water temperature of one degree or more for one month often result in extensive coral bleaching, making these hot spots prime candidates for bleaching events.

From January to July the coral bleaching events were concentrated in the Southern Hemisphere during its warm season. Since July, the reports of extensive coral bleaching have spread into regions of the Northern Hemisphere following abnormally high sea surface temperatures, especially around the Philippines and throughout the Caribbean Basin, Bahamas, Bermuda and Florida Keys.

With collaborators Ray Hayes of Howard University and Tom Goreau of the Coral Reef Alliance, Strong is planning to summarize the year's coral bleaching events in the December issue of Reef Encounters.

Bleaching and other problems facing coral reefs will be the topic of a high-level government meeting in Key Biscayne, Fla., on Oct. 19 and 20. The Coral Reef Task Force was created by an executive order signed June 11 by President Clinton as part of the Year of the Ocean observance and the National Ocean Conference held in Monterey, Calif., last June. The first meeting of the task force will be hosted by the Commerce and Interior Departments.


Coral bleaching charts: Florida, Puerto Rico and Guam
Click here to see chart legend.

Videotape animation of hot spots conducive to coral bleaching is available from Video Transfer, Rockville, Md. Telephone: 301-881-0270.

Maps showing twice-weekly distributions of hot spots are available at:

Movie/animations are posted at:

Maps showing the annual distribution of bleaching from 1969 through 1997 are posted at:

To subscribe to the Global Coral Reef Monitoring Network, go to:

For more information contact Patricia Viets at (301) 457-5005.