New Expedition to Study Mysterious Deep-Sea Corals

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These cold-water corals, which can build up over as much as two million years, have become a focus for scientists trying to understand both deep-sea evolution and climate history.

Many corals grow their skeletons like tree trunks, laying down growth rings that represent the ocean conditions at the time.

"Deep-sea corals have the potential to record such things as temperature changes and changes in ocean circulation," said Brendan Roark, a paleoceanographer at Stanford University in Palo Alto, California.

"We can look at changes in carbon dioxide as it moves from [the] atmosphere to water to the deep ocean, and all that is important to understand the past and future of climate change."

Invaders From the Deep

In a surprise find, one diverse group of corals originated in the deep sea and not in shallow waters as previously thought, scientists said.

Using DNA analysis, Alberto Lindner, a coral researcher at the University of São Paolo in Brazil, showed that stylasterids, or lace corals, evolved in deep waters before moving into shallow waters during at least three time periods in the past 30 million years.

Lace corals make up much of the Alaska Deep Sea Gardens off the Aleutian Islands. (See a Alaska map.)

The findings contradict earlier theories suggesting that corals and other marine animals all evolved in shallow waters before migrating into deeper habitats.

"It shows that deep-sea ecosystems are not isolated and static," Lindner said. "They are a source of diversity and evolutionary innovation."

Stephen Cairns is a research scientist at the Smithsonian Institution in Washington, D.C.

"I can remember for several decades when I was the only one working on deep-water Atlantic [stony] corals," Cairns said.

"so it is refreshing and gratifying to see these rather obscure animals in the limelight, and being used to help solve paleoclimatology and paleocurrent issues."

Ecosystems Connected

However, deep-sea corals are both difficult and costly to study because of their remote location.

Many of the reefs are found in the waters of developing countries, which cannot afford to organize expeditions to the ocean floor.

"We can't offer a single image of these corals from a developing country," said Lindner, the Brazilian scientist.

The best known cold-water ecosystems are in the North Atlantic, but these corals have also never been studied and compared across the ocean basin.

With the new program, researchers are planning exploratory cruises across the North Atlantic to study the environmental and ecological history of coral communities.

"We need to understand how one ecosystem is connected to the other," Roberts, the TRACES coordinator, said.

John Guinotte is a marine biogeographer at the Marine Conservation Biology Institute in Bellevue, Washington.

"Deep-sea corals are important sources of diversity for shallow-water regions of the ocean," Guinotte said.

"What this says to me is we should really question the wisdom of permitting destructive fishing gears, such as bottom trawling, in the deep sea where recovery of these ecosystems is incredibly slow, if not impossible, on human timescales."

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