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Life in Don Juan Pond
 
Satelite picture by NASA

Don Juan Pond is a shallow lake in the Wright Valley in Victoria Land in Antarctica.  The Wright Valley is one of the “Dry Valleys” of Antarctica.  Clearly since it has a lake, it is not completely dry.

Salty

Don Juan Pond is the saltiest lake known on Earth.  It contains about 18 times as much total salts as the ocean.  As a comparison, the Dead Sea only has about 8 times as much as the ocean.  While the Dead Sea is mainly Sodium Chloride like the ocean, the main salt in Don Juan Pond is Calcium Chloride. 

Drying Agent

Calcium Chloride has been used in school laboratories as a drying agent.  Solid Calcium Chloride in a normal room atmosphere absorbs water from the air and becomes liquid.  If the liquid is left, it will continue to absorb water until it reaches equilibrium, depending on the actual humidity and temperature of the air. 

Calcium Chloride solution is also corrosive to metals, and it tastes bad.

Liquid

Another property of concentrated Calcium Chloride solutions is that they freeze at a much lower temperature than pure water.

Normally Don Juan Pond can drop to minus 53 degrees C (Minus 63 Degrees F) without freezing. Once, after more water had got into the lake than usual and the salt was diluted than normal, it did freeze.

Life

Despite this nasty chemical soup in Don Juan Pond and the low temperatures it does support life.

Algae Mats

Earlier reports that there were no photosynthetic organisms on this lake were incorrect. There is a fairly extensive mat of algae.  Only about 4 mm thick, but extending over perhaps 600 square metres.  This mat contains a wide variety of organisms, not all photosynthetic.  These include Algae like Cholera, diatoms, and fungus molds like Penicillin.

The presence of the photosynthetic organisms is very important to the ecosystem in general.