SYRACUSE, N.Y. - An expansive ecosystem of knee-high mud volcanoes, snowy microbial mats and flourishing clam communities lies beneath the collapsed Larsen Ice Shelf in Antarctica, say researchers.

The discovery made in February in a deep glacial trough in the northwestern Weddell Sea was detailed this week in Eos, the weekly newspaper of the American Geophysical Union.

Such sunless, cold-vent ecosystems have been found elsewhere - near Monterey, Calif., in the Gulf of Mexico and in the Sea of Japan - but never in Antarctica, the report said.

"Seeing those organisms on the ocean bottom, it's like lifting the carpet off the floor and finding a layer that you never knew was there," said Eugene Domack, the report's lead author and a professor of geosciences at Hamilton College, an upstate New York school located 30 miles east of Syracuse.

Domack hopes scientists find new species as they study the site and that the discovery will open the door to future Antarctic expeditions, including more exploration of Lake Vostok, a freshwater lake that sits locked in the ice two miles below the surface.

The discovery will certainly help scientists better understand the dynamics of life in such an inhospitable setting 2,800 feet below the sea surface, he said. The ice shelves cover nearly 580,000 square miles of sea floor - an area equivalent in size to the Sahara Desert or the Amazon River basin.

"We're not marine biologists or ecosystem experts. We will leave it to them to jump on this and go forward," Domack said.

The discovery interested Jim McClintock, a University of Alabama-Birmingham professor who has made a dozen trips to Antarctica over the past 15 years to study the chemical ecology of aquatic plants and marine invertebrates.

"We haven't seen this here before. It shows there is no latitudinal component to finding these cold-water methane systems. They can happen in various seas around the world," McClintock said. "It will be exciting to learn what other organisms might be down there."

The discovery of the ecosystem came by chance, said Domack, who has conducted research in Antarctica since 1987.

Domack's expedition - consisting of students from Hamilton and five other colleges - was finishing up the second season of a three-year investigation into the possible causes of the massive 2002 collapse of part of the Larsen Ice Shelf, when a Rhode Island-sized chunk of ice broke off into the ocean.

Domack's team studied the underwater sediment record in the area vacated by the former ice shelf. As part of their mission, they used a camera to take video footage of the sea floor terrain. Some curious echo soundings induced them to drop the camera in the area that day, Domack said. Because of technical problems, they were able to record only about 25 to 30 minutes of the two-hour tape.

The group was aboard ship, headed back to port and several hours away from the site, when they were reviewing the tape and spotted the unexpected underwater world.

"We weren't looking for this. It came out of the blue. None of us are experts, but we recognized the significance of what we were seeing," he said.

It appeared to be a cold-vent, or cold-seep, ecosystem, fed by chemical energy from the Earth, rather than one driven by photosynthesis from the sun or hot emissions rising from inside the planet. Domack said the likely energy source was methane from deep underwater vents raked open by receding glaciers.

"It looked like a thin slice of cheese had been laid over the sea floor. Sporadically placed, there were mud mounds, little volcanoes, two- to three-feet high and several feet across, spewing out fluid and mud particles," Domack said.

Surrounding the mud volcanoes were clusters of large clams. The ecosystem covered about a 3-square-mile area.

It will require remote-operated underwater vehicles to properly study and actually collect samples from the site, said Domack, adding there is some urgency to exploring the area.

Domack believes the ice shelf likely provided a protective shelter, allowing the chemical habitat to thrive on the sea floor over the centuries.

Now that the ecosystem has been exposed, it is imperiled by fattening deposits of sediment produced through erosion run-off from the advancing glaciers and from dying algae settling to the bottom. The sediment is not only burying the ecosystem, but it is also introducing carbon and other new chemicals into the methane-powered environment, he said.

"It is an ecosystem in flux, in change, and that's a rare opportunity for scientists," he said.

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On the Net:

American Geophysical Union: http://www.agu.org

Hamilton College: http://www.hamilton.edu