The bleaching, in which normally brown corals turn snowy white, occurs when the coral animals expel algae with which they normally live in symbiosis. If the process is severe enough, the weakened corals, no longer obtaining energy and oxygen from the algae, may die.

In the past, bleaching has occurred sporadically in the Caribbean in response to environmental stresses such as pollution and changes in water temperature or salinity. But worried scientists said they had never seen such widespread bleaching. The chief suspect is warmer waters. It is too soon to know how widespread coral mortality will be, scientists said.

To assess the extent of the bleaching and possible causes, Ogden's laboratory was host to a conference of 40 marine biologists, microbiologists, oceanographers and geologists from marine research stations in Venezuela, Jamaica, Panama, Puerto Rico, Bermuda and the United States. Robert Wicklund, director of the Caribbean Marine Research Center on Lee Stocking Island in the Bahamas, was the meeting's co-organizer. Funds for the conference were provided by the National Oceanographic and Atmospheric Administration.