Thursday, 9 April 2015

Coral-killers

Nguồn tin: nguontinviet.com



SINCE scientists first raised the alarm 50 years ago about crown-of-thorns starfish chomping their way through the Great Barrier Reef, there have been three big outbreaks. A fourth, perhaps the most serious, is now under way. The Australian Institute of Marine Science rates the “massive explosion” of this lethal starfish strain as second only to cyclones as a cause of the reef’s decline. Several interventions, including fencing coral zones and using navy divers to remove starfish by hand, have in the past proved ineffectual. But scientists at James Cook University in Townsville, a city facing the reef, may finally have found a way to fight back.


Divers have started to inject starfish with a solution made of salts from cattle-bile. A single shot of the substance, discovered by chance during research into starfish diseases, triggers a lethal reaction. So far it has only been used in areas prized by divers and tourists for coral. It has killed more than 300,000 starfish in its first year of use.



Unfortunately, that is only a fraction of the tens of millions of crown-of-thorns starfish thought to inhabit the entire reef. The species has few predators, reproduces profusely and can devastate a reef in months. But it is also native to reefs throughout the Pacific and Indian oceans, raising questions about the impact on ecosystems of slaughtering them wholesale. Normally, their numbers are quite low. Strong evidence links population explosions to floods that wash high levels of nutrients from farms onto the reef.


Australia’s latest plan for the Great Barrier Reef, which it hopes will convince the World Heritage Committee not to classify it as endangered, sets targets to cut nitrogen loads in half by 2018 and by four-fifths seven years later. Some sugar-cane farmers along the reef have started cutting back on fertilisers and pesticides; more must follow if the plan is to work. The intensity of cyclones is predicted to rise, John Gunn, the head of the Australian Institute of Marine Science, points out. He argues that enlightened human intervention is essential if the Great Barrier Reef is to be saved from the combined threat of storms, nutrients and the plague of starfish.





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