New control for coral killing starfish has 'double whammy' effect

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A team of marine scientists based in Australia has developed what may prove an effective control for the dreaded Crown of Thorns starfish (COTS), which periodically ravages coral reefs across the Pacific and Indian Oceans.

With signs that the starfish is building up for another huge attack in the Pacific and Australian region, their solution could come in the nick of time.

The researchers from the ARC Centre of Excellence for Coral Reef Studies (CoECRS) at James Cook University (JCU) have discovered that a harmless protein mixture used to grow bacteria in the laboratory can destroy the starfish in as little as 24 hours.

If subsequent tests show it is safe for other sea life, their breakthrough could yield a dramatic improvement in ability to control COTS outbreaks, even if only to protect sites that are intensively used for tourism.

"A Crown of Thorns outbreak can destroy from 40-90% of the corals on a reef. Over the past 50 years it has caused more damage than bleaching,” says Dr Jairo Rivera Posada. "There were massive outbreaks in many countries in the 1960s and 1980s – and a new one is well underway on the Great Barrier Reef."

Dr Posada was on the beach with Professor Morgan Pratchett at Lizard Island in the Northern Great Barrier Reef when he wondered if the substance he was using in the lab to selectively culture the Vibrio bacteria that naturally inhabit the starfish could give the bugs enough of a boost to damage their host.

Rushing back to their tanks, they injected five starfish with the media culture solution and were astonished when the starfish rapidly began to fall apart and die as the bacteria attacked them.

The researchers found that the solution had caused the bacteria to bloom and attack the starfish; at the same time the starfish suffered an acute allergic reaction to the unfamiliar animal proteins (mainly derived from cattle). Furthermore, the bacteria also spread under favourable conditions to other starfish, which came in contact or close to the infected individual.

Professor Morgan Pratchett said that this ‘double whammy’ effect caused by an otherwise harmless protein mixture had opened up the possibility of developing a safe, convenient and fast way of killing Crown of Thorns starfish.

The protein solution needs only a single jab into a starfish, enabling a diver to kill as many as 500 Crown of Thorns in a single dive – compared with 40 or so using the poison injection currently used.

The team is about to embark on extensive testing to establish the technique is safe for use around corals, fish, other types of starfish, sea urchins and sea cucumbers.

They are also exploring other natural parasites and disease-causing organisms for controlling Crown of Thorns, as well as simple protein injections which trigger a fatal allergic reaction.

However, any attempts to control these outbreaks will be futile without also addressing the root cause of outbreaks, including loss of starfish predators as well as increased nutrients that provide food for larval starfishes.

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