WHIT GIBBONS’ ECOVIEWS: Life in the ice can be nice
I was walking around in a desert near Albuquerque around noon in the middle of July. Not surprisingly, my mind wandered now and again to thoughts of cooler situations. An air-conditioned restaurant was one such thought. Another idea was the desert at night, which is usually pleasant and has an added advantage, it’s when the animals come out. Then I recalled an ecological study in an extreme habitat I once wrote about. Scientists described it as “one of the coldest and driest deserts on Earth” –definitely a far cry from a New Mexico desert in midsummer. The researchers were conducting studies in Antarctica in a region where freshwater lakes are covered year-round by sheets of ice.
One question being asked was whether any life would be found. Considering that living organisms have been discovered inside volcanoes, deep underground in the darkest caves, and even in scorching hot deserts, perhaps it should come as no surprise that scientists found an “oasis for life in a polar desert.”
During Antarctic summers, up to 40 percent of the ice melts in layers in ice packs that are up to 20 feet thick and sit above freshwater lakes. Melting occurs when sunlight warms thin layers of sediment lying within the ice. The sediment layers, up to a few inches thick, are presumably the result of windblown debris deposited when the layer was on the surface. Once deep inside the ice pack, the sediments heat up more than the surrounding ice during sunny periods and layers of water form within the ice. These layers and pockets of meltwater within the ice packs support an array of living organisms.
Researchers took ice samples, using four-inch-diameter cores. They removed and melted the ice cores to determine the depths at which sediments and their 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 embedded in the ice not only provide heat to melt ice but also serve as a source of nutrients. The habitat, one of the most inhospitable environments imaginable, does not support large mammals, big fish, or giant squids. It is, however, home to a variety of bacteria and algae. The researchers discovered that even in a thick ice pack, separate and identifiable ecosystems exist.
After finding that life existed 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 freshwater lakes in Antarctica are continually inhabited by an array of plankton and other microorganisms, the species living in the incredibly thick layer of ice above are different.
The bacteria and algae living in the ice thrive independently from the lake water below, with which they have no contact. 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.
Ironically, the discovery that life persists in such an extreme situation might be used by some people to justify any environmental modification or destruction in the name of progress. That is, no matter what we do to the earth, life will go on. But the fact that life will exist in some form in any place with water, light, and nutrients (as well as in a few places without light) is no excuse for intentionally creating hostile conditions for any plant or animal species. Life will indeed go on, but the disappearance of the obvious and exciting life forms around us may signal that we are on the verge of creating conditions unsuitable for human life, too. Surely none of us would look forward to our last living companions in the world being mostly bacteria and algae.
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Whit Gibbons is an ecologist and environmental educator with the University of Georgia’s Savannah River Ecology Laboratory.