CHARLOTTE AMALIE, U.S. Virgin Islands - Large species of coral that form underwater reefs and create rich habitat for marine life are disappearing from around the U.S. Virgin Islands, Jamaica and elsewhere in the Caribbean, a leading researcher said Tuesday.

The larger species are being replaced by smaller varieties, which don't grow high enough to protect the fish, lobster and other sea life that rely on the underwater reefs, said Peter Edmunds, a biology professor at California State University, Northridge.

Abnormally warm weather, coupled with pollution and overfishing, have contributed to a rapid decline in large coral, Edmunds said during a talk at the University of the Virgin Islands.

Species such as the boulder star coral, which stretch several yards across, take hundreds of years to grow. Edmunds predicted the boulder star coral could be gone from much of the U.S. Virgin Islands in less than 50 years. In Jamaica, the species has almost been replaced by mustard hill coral, a smaller species unable to make large reefs, he said.

"The big guys are becoming rarer. The small guys are becoming more common," said Edmunds, who recently began projects near Tahiti and Taiwan, where he plans to compare Pacific data with that gathered in the U.S. Caribbean territory.

Mark Eakin, director of the U.S. National Oceanic and Atmospheric Administration's Coral Reef Watch, said the coral study documents an even more widespread phenomenon.

"That's a general pattern we have seen in other places as well," Eakin said, referring to the Caribbean. "The remaining large coral, such as star coral, is dropping away" and the smaller coral is moving in.

A vital building block of marine life, coral grows and reproduce best at about 81.5 degrees Fahrenheit in the Caribbean, said Edmunds, who has studied Virgin Islands coral for two decades.

Edmunds said his research suggests coral in warmer water grows more slowly.

U.S. government scientists also warned for a second time this year on Tuesday that sea temperatures around Puerto Rico have exceeded healthy levels for coral, saying the fragile undersea life could become more susceptible to damage and disease during overheating.

Seas reached 85.3 degrees Fahrenheit, temperatures at which coral can be damaged if waters do not cool after a few weeks, Eakin said.

The U.S. atmospheric administration issued a similar warning in September, when seas reached 85.5 degrees Fahrenheit around the U.S. Virgin Islands and 85.1 degrees Fahrenheit in waters off Puerto Rico.

After hot summers, sea temperatures usually cool in late October, Eakin said in a telephone interview.

"We'd expect it to start cooling down soon," he said. "Hopefully we're right."

The government warning urges scuba-dive operators and underwater researchers in the U.S. Caribbean territories to look for coral damage and use caution around the fragile reefs, which are easily damaged by physical contact.

At the Coral Reef Task Force's biannual meeting in St. Thomas last week, top researchers backed an Australian study that said up to 60 percent of the worlds coral reefs could die by 2030.