Fast-growing corals key to Caribbean reef -study

Michael Kahn, Reuters 13 Mar 08;

LONDON (Reuters) - Two dominant coral species have built a good chunk of the Caribbean reef, and their ability to grow quickly may help the region's coral reefs keep pace with rising sea levels caused by global warming, researchers say.

The endangered staghorn and elkhorn corals grow about 10 times faster than any other in the Caribbean and reproduce in part by breaking into bits for easy ocean spread.

Ken Johnson, who led the study published in the journal Science, said researchers had found that the staghorn and elkhorn coral were not that important until about 1 million years ago, when half the Caribbean coral species went extinct.

Today about 60 coral species remain.

Johnson said one reason they quickly became dominant was they may have been able to keep up with rapid sea level rise by growing quickly, Johnson said.

And if sea levels rise as predicted in the coming centuries, they may have to reprise this role.

"These are the species that are going to help coral reefs keep up with sea level change," Johnson, a paleontologist at the Natural History Museum in London, said in a telephone interview.

Coral reefs, delicate undersea structures resembling rocky gardens that are made by animals called coral polyps, are important nurseries and shelters for fish and other sea life.

They are also considered valuable protection for coastlines from high seas, a critical source of food, important for tourism and a potential storehouse of medicines for cancer and other diseases.

But researchers say overfishing, climate change and human development are threatening reefs worldwide. Even the dominant staghorn and elkhorn species are considered threatened under the U.S. Endangered Species Act.

In the Caribbean, an added concern is that the reefs are especially sensitive because they are dominated by just two species, Johnson said.

"If these two species die out and become extinct, the Caribbean is in trouble," he said.

The researchers produced their conclusions by using fossils to compare changes in coral diversity and reef development in the Caribbean over the past 28 million years.

They showed that the characteristics of a dominant species were more important than the simple number of species, a finding that can better direct conservation efforts, Johnson said.

(Editing by Maggie Fox and Catherine Evans)