The carnivorous predator that feeds on coral will even survive being cut in half.
By Matt Skenazy
(Photo: jon hanson/Flickr)
Ian Moffitt stood behind the wheel of the RV Poge, a 24-foot Boston Whaler. It was the end of June — winter in American Samoa — and only mid-morning, but the temperature was already in the mid-80s. Moffitt’s dark hair was cropped short, and his stubble framed a slightly sunburnt nose. His shirt read Alamea Slayer. Death From Above.
With Moffitt were Ari Halperin, Kersten Schnurle, Karen Bryan, and Paolo Marra-Biggs. All five divers were working for the National Park of American Samoa, the second-smallest in the 59-park National Park Service. They rushed to dump small bags of fine brown ox-bile powder into containers filled with water.
The week before, the crew had taken turns towing each other face down behind the Poge on a rope. (They tow the entire north shore of Tutuila, the park’s main island, every month.)
They found a giant scar stretching for hundreds of yards: white on top, green a dozen meters deeper, and a sickly brown near the bottom. The scar was caused by hundreds, maybe thousands, of crowns-of-thorns starfish (alamea in Samoan), a carnivorous predator that feeds on coral. The animals cover the coral’s calcium carbonate skeleton with their everted stomachs, digesting the living polyps before sucking the resulting slurry back in.
A version of this story first appeared in the
of Pacific Standard.
The starfish decimate reef ecosystems, and it can take 30 to 40 years for reefs to recover from a bad outbreak. A park ecologist first spotted crowns-of-thorns in American Samoa five years ago. Moffitt and the crew had come back to the tip of Fagasa Bay on the edge of the national park to wipe the animals out.
Killing crowns-of-thorns is trickier than it sounds. Their 20 arms are covered in venomous spines, and they won’t die even if cut in half. The divers wear needle-proof gloves to protect their hands and use an injector gun designed for cattle to inject them with the ox bile.
On deck, Halperin and Schnurle prepped their dive equipment. Carly Rae Jepson’s “Call Me Maybe” played on a set of waterproof speakers. The fringing reef meant the boat was only about 100 yards away from shore. There was hardly any swell.
Bryan and Marra-Biggs were already in the water, 60 feet down. Bryan wore a black hood, black goggles, and a long black rash guard. “She looks like Batman,” Moffitt said before she dove in.
Underwater, Bryan was injecting each starfish with 10 milliliters of ox bile. Each one got a needle in one of its arms. The bile causes blisters to form on the animals. Their skin becomes discolored; their spines fall out; and, within 24 hours, they disintegrate.
Bryan had four liters of the ox-bile mixture. It should have been plenty. A dive lasts about an hour, and Moffitt’s highest kill total, 203, was still the record. But Bryan was moving fast, injecting one crown-of-thorns nearly every 10 seconds. Everywhere she turned, there were more and more. “See you in hell,” she said to herself. She kept injecting. After 53 minutes, she kicked to the surface. She had run out of poison.
Once back onboard the boat, she tallied her kills. “I just got 302,” she said.
“Holy shit,” Moffitt said, leaving his post at the wheel. “I want to see. I’m going down.”
He threw on a pair of fins and a mask, jumped in the water, and swam down with slow deliberate strokes. Crowns-of-thorns were stacked on each other like flapjacks. One table coral was covered in a mound of more than a dozen. It was the worst outbreak Moffitt or any of the crewmembers had ever seen. From a depth of 60 feet all the way to the seven-foot shallows, the coral was ghost white.
“It’s like the White Death down there,” Moffitt said when he resurfaced. Schnurle and Halperin dipped into the water. Over the course of three hours, the four divers killed 952 crowns-of-thorns. Moffitt spent the morning monitoring the divers’ progress, and didn’t get a chance to win his record back.