Heat Stress Is Hitting Caribbean Reefs Earlier Than Ever This Year

As the world’s coral reefs suffer a fourth global bleaching event, heat stress in the Caribbean is accumulating even earlier than it did in 2023, the previous record year for the region, according to data made public on Thursday by the National Oceanic and Atmospheric Administration.

“I hate that I have to keep using that word ‘unprecedented,’ said Derek Manzello, coordinator of the agency’s Coral Reef Watch Program. “But, again, we are seeing unprecedented patterns again this year.”

Scientists hope that relief will set in as the natural climate pattern known as El Niño, which is associated with warmer ocean temperatures, fades. Officials said conditions were quickly changing to a neutral state, with a cooler La Niña forecast for this summer or fall.

But right now, temperatures in the Caribbean off Panama, Costa Rica, Nicaragua and Colombia are hitting levels that previously haven’t been seen until weeks later, an ominous signal after the heat that ravaged reefs across the region last year. Scientists say they are still determining the scale of the death from last year’s bleaching. A study of the reefs off Huatulco in Oaxaca, Mexico, found coral mortality ranging from 50 percent to 93 percent, depending on the reef area.

Bleaching occurs when stressors cause coral to lose the symbiotic algae that help to nourish them. While coral can survive bleaching spells, exposure to prolonged or repeated bleaching can kill the tiny animals. Even those that recover initially may succumb to disease in the following year or two.

While all kinds of stressors can cause coral bleaching, including pollution or changes in salinity, the four global bleaching events on record, which started in 1998, have all been caused by warm ocean temperatures. Researchers have estimated that the world has lost half of its coral cover since 1950.