The long-suffering Costa Rican coral have yet another antagonist gaining ground. Coral reefs are important as home to marine species, and they suffer from a multitude of maladies, some natural and some man-made.
Add the crown-of-thorns starfish (Acanthaster planci). This creature, the world’s only poisonous starfish, actually eats the coral. Scientists are frustrated in efforts to control it.
James Cook University scientists reported a breakthrough in the war against the starfish Wednesday. A new academic paper shows injecting the coral-eating pest with simple household vinegar kills it just as effectively as a current drug, which can be expensive and difficult to source, said the university.
Yet researchers agree that having divers seek out and kill the marine pest is an expensive operation. A 2006 Miami of Ohio University study estimated that just clearing a square kilometer of the starfish might cost as much as $54,000.
The Australian university is at the forefront of research because the crown-of-thorns starfish showed up on the fabled Great Barrier Reef there in 1963.
Costa Rica’s corals have been under attack from storm damage, chemical changes in the sea and temperature changes caused, in part, by El Niño. When the temperature becomes too warm, coral sometimes dumps its symbiotic algae in a condition known as coral reef bleaching.
Other creatures also seek out and eat the soft tissue of living coral. The crown-of-thorns starfish does this, too, but it also emits a strong poison that actually dissolved the underlying coral. In one invasion in American Samoa in 1978 and 1979, the crown-of-thorns starfish destroyed 90 percent of the coral, said the National Oceanic and Atmospheric Administration.
In Costa Rica coral also has been damaged by shrimp trawlers to such an extent that the Sala IV constitutional court prohibited the practice, although the government is trying to work out a compromise.
The crown-of-thorns starfish has been detected at Isla del Coco, off mainland Costa Rica and also at Isla del Caño.
The starfish also has been seen in the Gulf of Chiriquí, Panamá, according to research reports. Isla del Coco is a world heritage site.
The starfish are breeding at epidemic levels and are one of the primary reasons for the decline in live coral, said the Australian university.
There are hardly any predators attacking adult starfish.
The lead author of the academic paper, Lisa Boström-Einarsson, said vinegar had been tried unsuccessfully before, but university scientists refined the process which resulted in a 100 percent kill rate, according to the university.
Ms. Boström-Einarsson said the findings were exciting. Currently divers use 10 or 12 milliliters of ox-bile to kill each starfish, she said. “It’s expensive, requires permits and has to be mixed to the right concentration,” she added. “We used 20 milliliters of vinegar, which is half the price and can be bought off the shelf at any local supermarket.”
“It has been estimated there are between 4 and 12 million of the starfish on the Great Barrier Reef alone and each female produce around 65 million eggs in a single breeding season. They managed to kill around 350,000 last year with two full-time boat crews. While it would take an insane effort to cull them all that way, we know that sustained efforts can save individual reefs,” Ms. Boström-Einarsson said.
She said other researchers were working on population-level controls of the animal, but killing the starfish one-by-one was the only method available at the moment.