Some of the most stunning reefs in the “Coral Triangle”, the world’s richest area of coral biodiversity, have been destroyed by crown-of-thorns starfish, which feed by spreading their stomachs over coral.
That’s the dismal result of a survey last month of reefs around Halmahera, an Indonesian island at the heart of the triangle, which stretches from the Philippines to the Malaysian peninsula to the Solomon Islands.
“There have been ongoing outbreaks throughout the triangle, but at the isolated centre we hoped to find pristine reefs,” says team member Andrew Baird. “We were disappointed.” Baird and colleagues from James Cook University in Townsville, Australia, conducted the survey with the Wildlife Conservation Society’s Indonesia Programme.
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The survey found that starfish had attacked about 20 per cent of the Halmahera reefs and reduced coral coverage in these areas by 95 per cent. Starfish-free reefs in the heart of the triangle had 30 per cent more coral diversity than reefs further out.
The most likely cause of the rise in crown-of-thorns numbers is pollution from sewage and agricultural run-off, Baird says. Microalgae bloom in the nutrients and are eaten by starfish larvae. However, other biologists argue that crown-of-thorns outbreaks are a natural part of reef ecosystems.
The need to find the answer will be used to pressure the Coral Triangle Initiative, set up to protect the reefs, to conduct basic research into how the ecosystem functions.
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