East coast threatened by coral-eating star fish

As the world celebrated World Oceans Day on June 8, environmentalists here are concerned about a rapidly growing coral-eating startfish, in the East coast.

Marine naturalist Prasanna Weerakkody issued this warning after spotting an increased population of the Crown of Thorn Starfish in certain areas of the Coral Reef in Pigeon Island, in Trincomalee.The Crown of Thorn Starfish (COT) is a large sea starfish that lives and preys on live coral, destroying them in the process. They have an interesting way of feeding on the corals by turning inside out their gastric sac (stomach) through their mouth, covering their food with the sac and digesting it with enzymes.

Mr. Weerakkody had observed 28 large Crown of Thorn starfish in a southern section of Pigeon Island reef and extensive feeding scars on the coral.

 Crown of Thorn starfish feeding on the corals at Pigeon Island

If the population density of Crown of Thorn is spread over more than 20-30 per hectare it is considered an outbreak . The present density observed on a casual dive was about double that density, he said. Therefore the true extent of the infestation is expected to be much higher as a greater part of the population may not be visible on a casual observation.

The Crown of Thorn has a mysterious life cycle. The starfish releases eggs and sperm into the water and when the eggs are fertilized naturally, they develop into a microscopic larvae stage that spends two to four weeks drifting as plankton in ocean currents. The juveniles settle on the reef . They live among rocks and rubble on the reef and are almost invisible until they are about six months old.

Arjan Rajasuriya of NARA too has observed the increase of Crown of Thorn starfish on a nearby coral reef in Dutch Bay in Trincomalee during a dive about two weeks ago. Mr. Rajasuriya recalling an outbreak of COT in the mid 70s said it had damaged many of the coral reefs in the East coast. He said a large number of snorkeling volunteers were employed to pick the COTs and bury them in the sand.

Mr. Rajasuriya fears that changing environmental conditions in the reef  could result in another outbreak. The floods in the East last year too may have contributed to an increased population of the star fish, the coral expert points out. The runoff water that ended in the sea that brings with it large amount of sediments and enriches the sea water with nutrients could have assisted the Crown of Thorn larvae to survive by producing enough food.

Global Warming too could have provided conditions for larvae to survive. Mr. Rajasuriya said that a single COT can lay more than two million eggs, so given the right conditions they can survive and an outbreak of Thorn of Crown can be as devastating as an outbreak of a swarm of Locust. Mr. Rajasuriya stressed the importance of monitoring the Crown of Thorn populations .

Two of the most widely tested and successful ways of controlling an outbreak of the Crown of Thorn Starfish are the physical removal of each and every star fish or killing them by injecting sodium bisulfate (dry acid) solution, he said.

DWC needs a dedicated Marine Unit
Pigeon Island has been declared a Marine National Park together with Hikkaduwa and Kalpitiya’s Bar Reef. The management of these marine national parks comes under the purview of the Department of Wildlife Conservation. But the department does not have a proper marine unit which has been highlighted by the Sunday Times.

An outbreak of Crown of Thorn starfish doesn’t happen overnight and a well equipped marine unit would have been able to detect such a situation. But the department is trying to manage the Marine National Parks similarly to the way they administer the terrestrial national parks such as Yala, the Sunday Times learns. Even officers who have been trained in diving have been transferred to land based national parks.

Source:http://www.sundaytimes.lk/120610/News/nws_47.html