Bleaching of Caribbean corals could surpass record loss of color set in 2005, experts say

By Danica Coto, AP
Tuesday, September 21, 2010

Experts: Caribbean corals could face record bleach

SAN JUAN, Puerto Rico — Caribbean corals are being exposed to water temperatures higher than those reported during a record bleaching period five years ago and could start dying in the coming weeks, scientists said Tuesday.

The warning comes after islands entered the warmest month of the year for water temperatures, which means the problem is just starting, said C. Mark Eakin, coordinator for the National Oceanic and Atmospheric Administration’s Coral Reef Watch network.

“I would love for the forecast to be wrong,” he said. “But the potential for bleaching this year is higher than in 2005.”

When corals are exposed to very warm water, they either expel or consume the colorful algae they host, which leads to the bleached color. If the stress is not too severe and decreases in time, the affected corals can regain their symbiotic algae. But if the stress is prolonged and the algae populations do not recover, the coral host eventually dies.

In 2005, up to 90 percent of corals in parts of the eastern Caribbean suffered bleaching, and more than half died.

This week, water temperatures surpassed those recorded in 2005, said Eakin, who blamed a mild winter and a second straight year of El Nino, a weather phenomenon that leads to unusually warm waters. A larger area also is being affected this year than in 2005, he said.

Scientists swimming in warm waters are reporting that chocolate-brown corals are turning shades of tan and gold, a precursor to bleaching. But they are celebrating that the reef-building elkhorn and staghorn corals have not yet been affected. They are the first corals to be listed as threatened under the U.S. federal Endangered Species Act.

A dozen named storms that have swirled through the Atlantic during this year’s hurricane season also have helped temporarily cool waters, said Jeff Miller, a fisheries biologist with the U.S. Virgin Islands National Park.

When Hurricane Earl barreled through, water temperatures dropped up to four degrees in one day, he said.

“Nobody likes to get hit by a hurricane,” he said. “But a nice near-miss is actually something that helps out a reef.”

Tourism-dependent islands worry about the effect that bleaching will have on the economy.

After the 2005 bleaching, the World Resources Institute estimated Caribbean reef degradation would cause between $350 million to $870 million in economic losses a year, according to a 2006 NOAA statement.

The institute, a U.S. environmental think tank, plans to release updated figures in February.

“When you have bleaching events like this and you knock back coral reefs, it takes a long time to recover,” Eakin said. “Unfortunately, the Caribbean doesn’t recover. There is so much other stress.”

Pollution, habitat destruction, improper fishing and overfishing have contributed to the problem, he said.

Corals in the eastern Caribbean are being hit hardest.

In Guadeloupe, ocean waters for the first time registered 86 degrees Fahrenheit (30 degrees Celsius) in the months of July and August, said Claude Bouchon, a marine biology professor and coral expert at the University of the Antilles and French Guiana.

Some bleaching has occurred, but no coral deaths have been observed, he said.

“The species that survived in 2005 are the most resilient ones,” Bouchon said. “I don’t know if they’re going to survive this time.”

will not be displayed