Warmer oceans threaten coral reefs

CHARLOTTE AMALIE, U.S. Virgin Islands – Warmer sea temperatures could worsen the widespread destruction of coral reefs that hit the Caribbean in 2005, scientists fear.

In the waters around the U.S. Virgin Islands, as much as 40 percent of coral died in some reefs last year, and the coral that survived probably isn’t healthy enough to survive another hot summer, said Caroline Rogers, a U.S. Geological Survey biologist.

“It worries me. It’s looking so similar” to last year, said Rogers, who has studied coral in the Virgin Islands for 22 years. “It’s impossible to overstate how important this is.”

Reefs are vital habitat for fish, lobsters and other sea life that feed and breed in the sheltered waters. The reefs also deflect storm waves that might otherwise wash away the beaches that are at the heart of the region’s multibillion-dollar tourism industry.

Bleached and infested with disease, coral off Puerto Rico and the Virgin Islands is in poor shape, scientists said in interviews last week. They said further bleaching wouldn’t be apparent before summer and it would take some time after that before they would know if more coral died.

“You don’t know how scary it looks down there,” said Zandy Starr, who monitors coral and sea turtles in St. Croix’s national parks. “All of us thought that by now, with all the cooler temperatures in January and February, we would have seen recovery, but they’re still sick.”

Glassy, calm seas have permitted coral-killing ultraviolet rays to penetrate to the ocean floor, warming water temperatures and making the fragile undersea life more susceptible to disease, Starr said.

A record 9 percent of elkhorn coral – vital for reef building – died last year and much more was damaged, Rogers said. Growing some eight inches a year, elkhorn is one of the faster generating coral, while other coral grows just a half-inch or so each year.

Scientists haven’t pinpointed what caused coral to become sick or led to the warm water, which stresses coral and makes it more susceptible to disease. They can’t say whether global warming is a factor.

“We don’t really have the data. You need a record over decades. There’s a lot of research that needs to happen,” said Alberto Sabat, a biology professor at the University of Puerto Rico.

But the trend of warmer waters isn’t limited to the Caribbean. The National Oceanic and Atmosphere Administration said waters were warmer than usual in the South Pacific, mid-Atlantic and Indian Ocean in mid-April.

Rogers said coral fared far better after hurricanes that devastated the U.S. Virgin Islands in 1989 and 1995 because the storms cooled the sea, allowing reefs to recover relatively quickly from damage.

Rising temperatures appear to be “something new that the corals aren’t used to,” said Tyler Smith, a marine researcher at the University of the Virgin Islands.