Antarctic lakes may harbor microbial life under ice

Researchers have discovered that the permanent ice covering Antarctic lakes may be teeming with microbial life even though the areas could not have been exposed to open air for millions of years.

Feb. 18, 2001—Researchers have discovered that the permanent ice covering Antarctic lakes may be teeming with microbial life even though the areas could not have been exposed to open air for millions of years.

The lakes, located in the McMurdo Dry Valleys, are unique geophysical features of our planet which have only recently been recognized as being capable of supporting resident microbial life, according to a recently released study from Montana State University.

The researchers are especially interested in the largest of the many lakes found in the region, Lake Vostok, which has a liquid pool about 4 km below the surface.

Ice samples from holes drilled through the frozen shield atop the lake contain microbes that can live in a frozen state for thousands of years.

The same type of microbes are thought to live in the lake, the researchers said.

Previously, the permanent ice covers have been considered primarily as physical barriers to wind mixing, material transport, and solar radiation necessary for photosynthesis in the lake's water columns.

The realization that these features support viable microbial habitats and populations was only recognized once 1) anomalous nitrous oxide gas was measured in the ice cover, 2) microalgal (primarily cyanobacterial) and bacterial cells were found in tight association with resident sediment inclusions within the interior of several permanent ice covers, and 3) historical temperature records were analyzed which indicated that substantial amounts of liquid water (up to 70% by ice volume) were generated in the regions of sediment inclusions in the ice during the summer months.

A permanent ice sheet covered Lake Vostok about 15 million years ago, isolating it from the atmosphere, researchers said. Geochemical and crystallographic measurements, in concert with airborne radar studies, indicate regions of frozen lake water moved to the bottom of the permanent ice sheet.

There is evidence that the shifted ice from Lake Vostok contains microbes, implying that a microbial assemblage exists within the lake itself. A collaborative group of five institutions and nine investigators will be the first to examine physical stresses in deep glacial and accretion ice, the role of clathrates on gas dynamics within the lake, the origin of microbes in accretion ice, the physiological state of ice-bound microbes, the geochemistry of the ice column and living microbes in ice veins that form at triple junctions in the ice crystal matrix.

The researchers hope that results from this study will provide new information on the deepest ice yet collected and allow boundaries to be placed on conditions within Lake Vostok.

Considering the enormous financial and logistic effort that will be required to obtain uncontaminated samples from Lake Vostok, it is imperative that conditions within the overlying ice, which presumably supplies the nutrients and biological seed to the lake, be understood before any attempt is made to sample the actual lake water.

The information will allow reliable hypotheses to be drawn regarding the physical, chemical and biological properties of the lake, and will provide critical background for the development and implementation of a sterile sample recovery system.

For more information, visit http://www.homepage.montana.edu/~lkbonney/DOCS/Vostok%20summary.htm.

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