LIFE IN THE ICE CAN BE NICE

by Whit Gibbons

November 30, 2003


Scientists have discovered life almost everywhere on earth that scientists have looked, including inside volcanoes, in volcanic-heated water on the ocean bottom, and deep underground in the darkest caves. Who would be surprised that living organisms have been discovered in a region in Antarctica that has been referred to as "life in a polar desert"?

The area in the frozen south actually has freshwater lakes, but they are covered year-round by sheets of ice that range from 10 to 20 feet thick. During the summers, which are not particularly reminiscent of the South I am accustomed to, up to 40% of the ice melts inside the ice layers.

Melting occurs when sunlight warms sediment layers within the ice. The sediment layers, each no more than a few inches thick, are presumably the result of windblown deposits. They move up and down over the course of a year as the ice melts on the top and freezes from the bottom. The sediments heat up more than the surrounding ice during sunny periods, so that layers of water also form. These layers and pockets of melt water found deep within the ice packs support an unexpected array of living organisms.

Researchers conducting studies in the regions took ice samples from lakes by using ice cores that were about four inches in diameter. They removed the cores of ice and melted them to determine the depths at which sediments and associated living organisms occurred. In one lake the sediment layer was about halfway down in an ice layer more than 12 feet thick.

The layers of sediments not only provide the heat to melt ice but also serve as a source of nutrients. In one of the most inhospitable environments imaginable, the scientists found a variety of bacteria and algae. Although the habitat does not support large mammals, big fish, or giant squids, the very fact that any living beings are present is remarkable.

After finding that life exists in the ice layers and identifying the species present, the researchers were in for another surprise--the organisms living in the ice did not resemble those found in the permanent lake waters far below. Thus, although the deepest lakes in Antarctica are continually occupied by an array of plankton and other microorganisms, the species living in the incredibly thick layer of ice differ from those found in the waters below.

The fact that the ice life differs from that in the lake indicates that bacteria and algae living in the ice thrive independently from the liquid water below. In some manner the organisms in the ice are able to live indefinitely in an environment that is frozen solid and in total darkness half the year. Yet when summer comes and the sediment layers warm up enough to create thin layers of water, life reappears.

The permanent layers of ice above the freshwater lakes of Antarctica differ both physically and biologically from the ice packs covering saltwater areas and the winter ice that forms on continental lakes in temperate regions. Both of these habitats, marine pack ice and ice on temperate lakes, result from a cycle of melting and refreezing snowfall. Microorganisms inhabiting such areas originate from the water underlying the ice. In contrast, the microorganisms in the Antarctic lakes are permanently maintained in the sediment and water layers within the ice sheet and have no contact with the water below.

Ironically, the discovery that life persists in such an extreme situation might be used by some people to justify environmental modification or destruction in the name of progress--the argument being, no matter what we do to the earth, life will go on. But the fact that life will exist in some form as long as water, light, and nutrients are available (as well as in a few places without light) is no excuse for intentionally creating hostile conditions for any plant or animal species. The disappearance of some obvious life forms around us may signal that we are on the verge of creating conditions unsuitable for human life, too. Life will indeed go on, but what form that life would take is another issue.



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