The Dry Valleys of Antarctica get virtually no snowfall or
moisture of any kind. Researchers come not only to study one of the world's
most delicate, yet simple ecosystems, but also to learn more about the unique
geological formations and processes occurring there. From south to north, the
principal ice-free valleys include the Taylor, Wright, McKelvey, Balham,
Victoria, and Barwick Valleys. Similar but smaller valleys also occur farther
south, along the coast of McMurdo Sound and the western margin of Koettlitz
Glacier; these include, from south to north, Miers, Marshall, and Garwood
Valleys, and the Salmon Stream valley.
Several lakes occupy parts of some valley floors, their surfaces frozen most of the year. Some lakes are over 30 meters deep and have perennial ice covers several meters thick.
Lake Vanda, which is typical, has 10
percent dissolved solids content in its lower few meters--three times as saline
as sea water-while the upper 50 meters has only 0.1 percent. Scientists have
noted high water temperatures in the lakes, with temperature inversions
resulting in bottom waters as warm as 25°C (75°F). These high temperatures are
due entirely to solar heating of the water through the ice, and not to any heat
from rocks at depth beneath the lakes.
The lakes are by far the most
interesting and diverse habitats in the Dry Valleys. Organisms are found
growing on and in the ice cover, in the water, and on the bottom of the lakes.
Exploration of lake bottoms by SCUBA-equipped divers, including core sampling
of bottom sediments, have disclosed the existence of algal mats on lake floors;
in certain respects these are analogous to some of the Earth's earliest life forms. The mats produce gases which
render them buoyant in marginal zones of the lake. There they form columns,
which detach from the bottom, rise, and then work their way upward through the
surface ice layers-as much as 5 meters thick-after which they dry out and blow
away, sometimes to colonize in other locations.
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