An Aug. 1 Science article about life in Antarctica incorrectly described the publication in which Eugene Domack and his colleagues recently published a study. The publication is Eos, a weekly newspaper of the American Geophysical Union. (Published 8/2/2005)
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.
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 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, rug-like sheet as thick as one centimeter (a 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. Barry has studied these so-called cold-seep communities in the Monterey Bay area, but the recent discovery "gives us the ability to see what these communities look like at the end of the spectrum," he said.
"This is yet another place on our planet where we found something we didn't expect," David Karl, a professor of oceanography at the University of Hawaii who studies bacteria in extreme environments, said in an interview. "It's as if we were back 100 years ago and we found the first deep-sea organisms."
Many mysteries remain. 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 there is no sunlight, and the bacteria obtain their energy from sources other than the sun. 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, thriving in near- or below-freezing temperatures, 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.
Methe's team recently sequenced the genome of a different type of bacterium that thrives in extremely cold environments, but at this point, scientists can do little more than speculate about the properties of the organisms Domack found.
"We don't know if these bacteria are the same as the ones we have found in [Monterey Bay], because the Antarctic Ocean is the most isolated ocean on Earth," Barry said.
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 last 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!"