Poisonous Thorny Starfish Is Destroying the Coral Reefs

As if pollution, global warming and overharvesting were not been enough, a new menace comes to complete the coral bleaching.

A bloom of predator poisonous and spiny starfish, named crown-of-thorns is destroying large areas of coral reef throughout the Philippines.

These voracious predators can wipe out large areas of coral; an adult can clean up to 6 square meters of living reef annually. As the crown-of-thorns presents long spines, that inflict severe stings causing swelling, erythema, pain and nausea that can last for days, it is well protected against predators, and very few species can attack it.

This species normally experiences outbreaks when ocean temperatures and nutrient levels increase, but the current situation is due more to the decline of its major predators: the humphead wrasse is overfished while the giant triton, a huge predatory sea snail, with a striking shell, up to 50 cm (1.6 ft long) and extremely attractive for people, being overcollected.

The humphead wrasse eats starfish larvae and small individuals, while the giant triton grips the starfish with its huge muscular feet and uses its toothy "tongue" saws through its hard limy skin. Once the snail has penetrated, it uses a paralyzing saliva to subdue the starfish, feeding after that at leisure.

"We are experiencing a return of the starfish in greater numbers. The situation facing our reefs is far from normal," said WWF-Philippines CEO Lory Tan. The Philippines' former 25,000km2 area of coral reef, just 1 % remains pristine, and over 50 % is now in decline or unhealthy.

WWF-Philippines is trying to fight the invasion by employing beachgoers to decrease the number of starfish but the measure is not very effective.

The most recent action took place in the world-class diving site of Apo Reef off the west coast of the Mindoro Island. "In the long term, the best response to the situation is by putting a stop to overfishing and agricultural runoff, and to better manage sewage. It's important to keep our oceans clean and our reefs well balanced", added Tan.

A WWF survey detected outbreaks of crown-of-thorns starfish at Apo Reef and Puerto Galera in Mindoro, Mabini in Batangas, Roxas in Palawan, Bolinao in Lingayen Gulf, and Kiamba and Glan in Sarangani Bay, but many other coastal areas have been affected as well. This starfish is also causing problems in the Great Reef Barrier.