Beneath Ice Shelf's Remains, Life Blossoms

Domack and his team, who were on a geological mission funded by the National Science Foundation, were on their second trip to the Antarctic in March when they found the new ecosystem.

Investigating the geological features of the broken ice shelf and its collapse, they videotaped about two square miles of the ocean bottom, and "we just happened to cross this ecosystem," said Amy Leventer of Colgate University in Hamilton, N.Y.

From the images, the group found that about 70 percent of the area they filmed was covered with the white bacterial mat. They got glimpses of the clams, but they were not able to collect samples. It will take manned or unmanned submersibles to study the deep regions more closely.

Another feature of the newly discovered ecosystem is its isolation from the usual food sources of the open ocean.

"You do not expect to find a lot of food down there falling from the sea surface, because of the ice shelf," Barry said. Although this has changed since the collapse of the ice shelf, the sea-bottom life seems still to be independent of usual oceanic food sources.

Unlike organisms that obtain their energy from sunlight and carbon dioxide, these bacteria get energy from methane and sulfur compounds, which could be seeping from the ocean floor beneath the bacterial mat.

But Domack's team also saw strange "mud volcanoes," mounds on the ocean bottom that he said are several feet high, "look like a Hershey kiss," and appear to spew out cold fluid and suspended particles. The team speculated the mounds could also be a source of nutrients and energy.

The clams living on top of the mats "are very specialized, and they can live directly off of the bacteria," Karl said. Some of the clams appeared to host the bacteria in their gills, "as if they have a cafeteria there," Karl said. Cold-seep clams cannot live anywhere else and have to be around communities that are rich in sulfides, a type of sulfur compound.

Researchers are worried that the newly found ecosystem may not last long because of the changes caused by the collapse of the ice.

The new open ocean environment will allow plankton and other higher organisms to thrive and compete for the same resources as the bacteria and clams at the bottom of the ocean.

In addition, the bacterial mat is already being covered by what appears to be debris dropped by melting ice and by the remnants of organisms that have already moved in, Domack and his team wrote this month in the newsletter of the American Geophysical Union.

Domack's team will make its last trip to the area early next year, but he hopes that the discovery will excite other scientists.

John Priscu, an expert in Antarctic microbiology and a professor of microbial ecology at Montana State University, wrote in an e-mail: "This discovery could give us more evidence that there may also be life on other icy worlds like Mars!"