Coral catastrophe on the Corner Rise Seamounts.

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A research team has found that deep-sea coral communities that provide lush habitats for fish and other marine life have been extensively damaged, mostly likely by deep-sea fishing trawlers, atop two undersea mountains in the middle of the Atlantic Ocean.

A decade after the fishing a stopped, the once-abundant summits have been "effectively denuded" of bottom-dwelling animals and "no longer support habitat-forming corals in any significant numbers," scientists reported in the October 2007 issue of the Journal of the Marine Biological Association of the United Kingdom.

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The finding spotlights a rising concern: As fishing grounds closer to shore become overfished and increasingly regulated, deep-sea habitats in unregulated waters become more attractive targets for fishing fleets.

"Though a moratorium on deep-water trawling was proposed to the United Nations General Assembly in 2006, no consensus was reached," the scientists wrote. "The absence of strong international action on this issue therefore leaves coral communities vulnerable to anthropogenic damage."

The research team--Rhian Waller, a biologist at Woods Hole Oceanographic Institution (WHOI), Les Watling from the University of Maine and the University of Hawaii at Manoa, Peter Auster from the University of Connecticut, and Timothy Shank of WHOI--set out in 2005 to explore coral communities on the Corner Rise Seamounts, a cluster of about 20 ancient flat-topped volcanoes at least a half-mile below the sea surface and 1,240 miles away from shore in the northwest Atlantic.

The remotely operated deep-sea vehicle Hercules was dispatched to "fly" up the slope of one seamount. It showed video images of chewed-up branches of pink bubble gum corals, which usually grow large and abundantly atop seamounts.

Some trawl nets, which can weigh more than two tons, are big enough to carry six jumbo Boeing 747 airliners. The nets are weighted with metal balls or rollers to ensure they rake up everything in their path. In addition to coral corpses, the team documented an assortment of gouges and trawl scars leading in all directions, scattered coral fragments, and metallic waste.

The entire top of one seamount, Kukenthal Peak, is denuded, Waller said, and on another, Yakutat Seamount, "the number of live corals documented on the plateau was negligible," the scientists wrote.

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Fishing ships from the former Soviet Union used trawls to fish the Corner Rise Seamounts between 1976 and 1996, seeking the bug-eyed alfonsino fish--often sold in stores as snapper. They stopped fishing there because their catches had diminished, Wailer said.

"You can clearly see that these seamounts have not recovered from the trawling," she said. "There's a chance that abundant communities may never come back."

Unlike shallow-water tropical corals, deep-sea corals thrive in cold, deep, sunless waters--often on seamounts. About 30,000 seamounts dot the oceans worldwide, like underwater oases.

Seamounts in international waters come under the jurisdiction of regional management organizations involving several nations. So regulating their protection is hard, and enforcing the regulations even harder.

The research was funded by the National Oceanic and Atmospheric Administration's Ocean Exploration program.