Voracious crown-of-thorns starfish are dealing another severe blow to the already struggling Great Barrier Reef in Australia.

On the heels of news that the world’s coral reefs are unlikely to recover from frequent mass-bleaching events, now comes news that the Great Barrier Reef is suffering another setback from an outbreak of crown-of-thorns starfish. As reported by the New York Times, the Great Barrier Reef Marine Park Authority (GBRMPA) announced that the “crown-of-thorns population has exploded in the Swain Reefs, “the southernmost location in the Great Barrier Reef Marine Park found to have the starfish during the current outbreak.”

Ordinarily, the starfish are good for the reef, as they eat faster-growing corals and give the slow-growing species room to develop. But when crown-of-thorns populations spiral out of control, they eat the coral faster than it can reproduce.

What is the crown-of-thorns starfish?

These thorny sea stars are named for the venomous, thorn-like spines that cover their upper surface. They range in size from 10 to 14 inches (25 to 35 cm) and have up to 21 arms. They in tropical and subtropical climes from the Red Sea and East Africa, through the Indian Ocean and across the Pacific all the way to the west coast of Central America. The starfish eat primarily hard-coral polyps — consuming their body width in coral each night — with an extrudable stomach that wraps around the corals. The GBRMPA found them on 37 sections of the reef off Brisbane, according to the Times. 

This isn’t the first time the crown-of-thorns has devastated the Great Barrier Reef. They were responsible for a significant loss of coral between 1985 and 2012. During that time, 50 percent of live coral polyps disappeared due to predation by the starfish. Since then, a culling program has removed more than 600,000 starfish from the reef.

What’s causing the outbreak?

Officials don’t yet know what’s causing the starfish explosion. But scientists hypothesize that currents carrying nutrient-rich water from the deep ocean to the reef could be creating a perfect breeding ground for the starfish. To help alleviate the problem, park officials send divers out to the reef to cull the starfish 250 days a year. Divers inject the sea stars with a solution of bile salts or white vinegar to kill them.

“Active control of the starfish is the most feasible and scalable action that we can take at this point in time,” Fred Nucifora, a spokesman for the Great Barrier Reef Marine Park Authority, told the Times.

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