Sunday, January 31, 2010

Scientists dive to explore unique bacterial community

There’s not much in the ice-covered lakes in the McMurdo Dry Valleys to interest anglers looking to land the big one. But for scientists who want to know more about some of Earth’s earliest organisms — and, by extension, to recognize what life may look like on other planets — those unique ecosystems represent a useful portal to the past.

Indeed, the lack of fish or other animals high on the food chain has allowed the microorganisms that live within the lakes to flourish unmolested, developing into communities thick enough to accumulate in layers on the lake bottoms.

“The cool part is that you can see microbial ecosystems on a landscape scale. There aren’t too many places around the world where you can do that,” noted Dale Andersen, with the SETI Institute’s Carl Sagan Center for the Study of Life in the Universe and principal investigator on a project to learn more about the microorganisms that dwell in Lake Joyce.

Lake Joyce — one of about a dozen perennially ice-crusted lakes spread throughout the valleys — is all the more unique in that it is one of only two known lakes in the region where the microbes have produced microbialites. These carbonate structures, composed of the same minerals that make up a coral reef, grow right in the layers of cyanobacteria, called microbial mats.

Andersen explained that his team, funded by NASA’s Exobiology Program and supported in the field by the National Science Foundation (NSF), is interested in learning more about the conditions that allow these organisms to grow and flourish in their dark and cold ecosystem. In turn, that information should shed light on the behavior of similar organisms billions of years ago.

“There are only a few places in the world where you can go to find living examples of those earlier ecosystems,” Andersen stressed. “The lakes in the Dry Valleys actually provide a very nice window back in time to compare notes, so to speak, with the fossil record.”

Andersen has made two previous trips to Lake Joyce, where he first discovered the carbonate structures growing from the microbial mat communities at about 20 meters depth. This will be the first extended study of the carbonate structures in a Dry Valleys lake, he said.

“The initial observations that we have are that the structures are pretty cool and there’s lots going on, but we don’t know much about them,” Andersen said.

“Each lake is totally different,” he added. “The external factors seem to be pushing the communities in different directions. That’s part of what makes these very unique ecosystems interesting to study — they’re essentially right next to one another and they’re each so very distinctive.”

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