Coral is dying to tell us something
HUMAN activity in coastal areas is responsible for killing coral, say a pair of researchers who've been tracking coral disease. This means that local measures such as reducing soil run-off or sewage discharges might help save corals that fall ill. Sick coral also provides an early warning that entire ecosystems are in danger, according to the researchers.
For 20 years, marine biologists have watched in dismay as corals succumbed to a dozen apparently new infections. Now a global map of coral diseases has pointed the finger at human development of coastal zones.
Most coral diseases are known by their symptoms, such as white band or yellow pox. According to Laurie Richardson of Florida International University in Miami, only three of these coral ailments have a known cause.
The diseases can be devastating. During the 1980s, white band disease, caused by a bacterium related to cholera, nearly wiped out Acropora corals across the Caribbean, where they had dominated coral communities for at least 4000 years. The soil bacterium Aspergillus causes waves of mass mortality among gorgonian corals, or sea fans.
But until now, no one understood the pattern of disease: why Caribbean reefs were the hardest hit, for example. So to learn more about the causes of coral disease, Ed Green of the World Conservation Monitoring Centre in Cambridge and Andrew Bruckner of the US National Marine Fisheries Service in Silver Spring, Maryland, mapped coral diseases in the same way human epidemics are plotted.
They conclude that human activity is probably the major factor in areas already predicted to be suffering environmental stress. In the Caribbean, they found disease was most prevalent in areas threatened by a range of human activities including intense coastal development and overfishing.
The researchers suggest sick coral might be a good early warning signal for creeping damage to entire marine ecosystems, which can be hard to detect. "Coral diseases are big and visible," says Green. "If the relationship holds, they could signal when protective measures are needed." He likens corals around the world to canaries in coal mines. "And this canary is singing," he warns.
Author: Debora MacKenzie
Source: Biological Conservation (vol 96, p 347)
New Scientist issue: 16th September 2000
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