Advanced tents: Lake Vida in the Antarctic is located 125 kilometers from McMurdo Research Station. © Emanuele Kuhn, Desert Research Institute, Reno NV
Reading For nearly 3, 000 years, the waters of Lake Vida in the Antarctic have been completely cut off from the outside world. The 20-meter-thick ice sheet of the lake conceals a diverse and vibrant bacterial community, according to researchers led by Alison Murray. It is pitch-black in the lake, extremely salty, and the temperature is minus 13 degrees Celsius. The extreme habitat could be a model for ecosystems on other celestial bodies of the solar system? for instance in the Martian soil or in the subterranean ocean of the Jupiter moon Europe. Lake Vida is located in the bottom of the Victoria Valley, a valley in the Antarctic, where it rarely snow so that no glaciers have formed there. After the discovery of the lake, polar researchers first assumed that it was completely frozen. Ice radar measurements in the 1990s revealed, however, that there is still a liquid layer beneath a 20-meter-thick ice sheet. This water has been completely isolated from the outside world for at least 2, 800 years, according to a dating of the ice sheet. Also from below Lake Vida is encapsulated: The ground has also been frozen for millennia. Once dew water from the surrounding mountains runs into the valley, it collects on the ice and does not get into the lake.

In order to find out if life can flourish in this extreme system, researchers around Murray undertook two expeditions to Lake Vida in 2005 and 2010. In 2010, they managed to remove a 27 meter core from the ice cover. As they report, they encountered a mixture of ice, sediment and a salty, slightly acidic liquid below 21 meters. How deep the lake is, they can not say.

The seawater is therefore an unusual cocktail. It contains six times as much salt as seawater, no oxygen, but ammonia, hydrogen and organic carbon. In addition to these reduced compounds, the researchers also reported nitrous oxide, nitrate and sulfate? so oxidized compounds. They suggest that nitrous oxide and hydrogen are produced by chemical reactions between the seawater and the rock at the bottom of the lake. Hydrogen is probably the most important source of energy for the microbial community.

Although the ecosystem has been encapsulated for millennia and is on its own, it seems stable, the researchers report. Digested gases such as methane or hydrogen sulfide, which would indicate a progressive decline, did not detract from Murray and her colleagues. The microbes they identified in their samples belonged to very different groups. display

Alison Murray (Desert Research Institute, Reno, Nevada) et al .: PNAS, online pre-publication, doi: 10.1073 / pnas.1208607109 © science.de - Ute Kehse

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