Caribbean wins the seaweed Olympics

A new study finds that Caribbean seaweeds are far better competitors than their equivalents in the Indian and Pacific Oceans. But this triumph is bad news for Caribbean coral reefs.

The picture-postcard beauty of Caribbean reefs owes much to the living corals that build reefs and contribute startling white sand to beaches. Coral reefs might seem to be tranquil environment but in fact a battle is constantly waged between corals and seaweeds that fight over space. Scientists have known for some time that seaweeds can gain the upper hand if corals are damaged by hurricanes or excessively warm sea temperatures that cause coral bleaching. But a new study, published online today, reveals that Caribbean seaweeds are the equivalent of Olympian atheletes compared those found on coral reefs elsewhere.

"Seaweeds bloom four times faster in the Caribbean than the Pacific Ocean", exclaims study author, Dr George Roff, of the University of Queensland. "This helps explain why corals in the Caribbean seem to be such weak competitors against seaweeds".

The study raises concerns about the future of Caribbean coral reefs. If seaweeds bloom faster, corals are less likely to recover once they have been damaged.

Coauthor, Professor Peter Mumby, adds, "Seaweeds are able to bloom when we loosen their controls, either by polluting the sea with fertilizers or catching too many parrotfish, who treat seaweed as a delicacy. We now know that seaweeds will bloom if we give them the slightest chance. This means we should redouble our efforts to control pollution and fishing of parrotfishes".

The study, published in the journal Trends in Ecology and Evolution, cannot yet explain why Caribbean seaweeds are so prolific.

"It is intriguing to see such variability in seaweed behaviour around the world", says Dr Roff. "We raise a number of possible explanations that scientists will test over the next few years".