BYRON BAY, Australia — The Great Barrier Reef is literally being eaten alive.
Deadly starfish are feasting on parts of the world’s largest reef system, which is already threatened by rising ocean temperatures, the Great Barrier Reef Marine Park Authority said on Friday.
Crown-of-thorns starfish, a native species whose numbers occasionally grow so out of control they endanger the reef, have been detected on 37 sections of the southerly Swain Reef, more than 60 miles offshore, according to the park authority.
“Whenever coral in any location in the Great Barrier Reef is threatened or stressed, it is of concern,” said Fred Nucifora, a spokesman for the authority.
The reef is one of the planet’s largest living structures — big enough to be seen from space — and is home to thousands of species, including sharks, turtles and whales. Australia relies on it for about 70,000 jobs and billions of dollars annually in tourism revenue.
Normally, the starfish contribute to the reef’s diversity by eating faster-growing coral species, which allow for slower-growing species to thrive. But at outbreak levels, the starfish are able to eat coral — a polyp that builds the limestone reefs on which they communally live — faster than the coral can reproduce.
To eat the hard coral, the starfish has an extrudable stomach that wraps around the coral and ingests it. A starfish can eat its body diameter in coral every night.
Since the inception of a control program in 2012, the marine park authority has culled more than 600,000 starfish from the northern and central reef areas, Mr. Nucifora said.
One study found that between 1985 and 2012, the reef lost an average of 50 percent of its coral cover. Starfish predation was responsible for almost half that decline, along with tropical cyclones and bleaching.
The cause of the outbreak is unknown. One hypothesis is that currents are bringing nutrient-rich water from the deep sea up into the shelf, which correlates with starfish larvae growth.
The new outbreak comes as scientists warn that coral bleaching — death caused by the stress of rising ocean temperatures — is straining the reef’s ecosystem. According to a study published Thursday in the journal Science, the frequency of coral bleaching has increased to the point that reefs no longer have sufficient recovery time between episodes.
Mr. Nucifora said that two control vessels with divers travel to the reef 250 days a year to cull the crown-of-thorns population.
“Active control of the starfish is the most feasible and scalable action that we can take at this point in time,” he said.
The divers inject the starfish with a solution of bile salts or white vinegar, which kill the starfish without hurting other marine life.
Last year, the Australian government committed 14.4 million Australian dollars, or $11.2 million, to finance a third control vessel for the marine park authority.
Since the control program began in 2012, Mr. Nucifora said, the government has committed 34.4 million Australian dollars to the problem through 2020.
Coral reefs are constantly undergoing change, and they follow a cycle of death and renewal, said Hugh Sweatman, a scientist from the Australian Institute of Marine Sciences.
“The critical question,” Mr. Sweatman said, “is how long will they get to recover?”
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