Lake Vida
The McMurdo Dry Valleys represent a cold desert, receiving less
than 0.1 m of snowfall annually and having mean annual temperatures
on the valley floors ranging from -15 to -30C (at Lake Vida).
The existence of the numerous closed-basin lakes in the region
results from a few weeks during the summer when the melting point
on nearby glaciers is exceeded and ephemeral streams flow into
the lakes. These perennially ice-covered lakes have long been
studied as extreme biological environments. The liquid water columns
of these lakes are substantial (up to 70 m deep) and range from
fresh to highly saline. Lake Vida in Victoria Valley (77°23-S,
161°56-E) is one of the largest (7 sq. km.) of these lakes. It
contains brine with a salinity seven times sea water and temperature
constantly below -10C lies beneath about 20 m of ice that is at
least 3000 years old. Microbial mats occur throughout the ice
column and are viable upon thawing. Sediment layers in the ice
effectively block incoming solar radiation. Ice below 16 m depth
and the brine body have never been sampled directly due to logistical
constraints.
In 2005-06 Peter Doran (University of Illinois at Chicago) and
colleagues will use a novel ultrasonic corer ("gopher")being
developed a Caltech's Jet Propulsion Laboratory to make in situ
ecosystem measurements and acquire samples to be further analyzed
to detect and describe life in a previously unstudied extreme
ecosystem. Two general hypotheses will be tested:
- Microbial communities within the brine (including brine
pockets in the deep ice) and benthic sediments are currently
viable and active and affect the present-day geochemistry of
the lake.
- The ice, brine, and benthos of Lake Vida contain
geochemical signatures of past microbiological activity.
The role of ICDS in this project is twofold - to provide a secondary
means of access to the lake water if the gopher fails and to provide
a means of rescuing the gopher if it should become stuck in the
ice.
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