Bacteria thriving along ocean floor off Antarctica

Bacteria live everywhere: in the acidic pit of your stomach and in the hot springs of the Galapagos Rift. Now, scientists have discovered them in another unlikely location: at the bottom of the near-freezing waters of Antarctica.

In March, researchers accidentally discovered a vast community of bacteria and clams on the ocean floor while exploring Antarctic waters that opened up after the vast Larsen B ice shelf collapsed in 2002.

The area had been isolated under the ice for at least 10,000 years, and the discovery means that "the chance of life happening in other places that are even more restricted is increased," said Eugene Domack, a professor of geosciences at Hamilton College in Clinton, N.Y., who led the international team to Antarctica earlier this year.

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

Bacteria are the simplest and most ancient life forms, and with their ability to break down organic matter, they are essential to keeping the cycle of life going.

Their presence at a depth of 2,800 feet, in an environment that Domack called the "coldest of the cold," may be the reason life has been possible under a 600-foot layer of ice. The bacteria form a white, ruglike sheet as thick as one-third of an inch. On top of the mat lie clusters of clams.

Similar communities have been found around the world, but "never in such an extreme region," said Jim Barry, a deep-sea ecologist at Monterey Bay Aquarium Research Institute in California.

Researchers are not sure what species the microbes and the clams are, or where and how they get their food and energy.

Cold-seep communities are usually found deep in the oceans where no sunlight penetrates, and the bacteria obtain their energy from other sources. The new finding "could take us a step further to understanding life where there's no photosynthesis," Domack said.

The bacteria under the Larsen B ice shelf evolved in far colder conditions than other known cold-seep communities, and may have unique properties. Studying them could lead to discovery of "enzymes that could be used in different aspects of industry," said Barbara Methe, assistant investigator at the Institute for Genomic Research in Rockville, Md.

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 2 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 could not collect samples. Manned or unmanned submersibles will be needed 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 still seems to be independent of usual oceanic food sources.