With its unforgiving and extreme conditions, Antarctica represents a region where life approaches its environmental limits. Terrestrial life must survive in the few, isolated pockets not continually covered by ice and snow. The McMurdo Dry Valleys of southern Victoria Land are of particular interest. There, scientists find extremely basic ecosystems with organisms showing remarkable adaptations.
All aspects of life are studied, from the bacterial organisms living on sandstone outcroppings to microscopic worms, called nematodes, that live in the gravelly, dry soil.
The Dry Valleys, unlike most other ecosystems, are dominated by microorganisms, mosses, lichens, and relatively few groups of invertebrates; higher forms of life are virtually non-existent. Organisms have, over eons of evolution, developed mechanisms to survive under conditions of desiccation, extreme cold temperatures and with limited food or light for photosynthesis. These organisms are unique and only exist in the frozen Antarctic continent.
All ecosystems are dependent upon liquid water and shaped to varying degrees by climate and material transport, but nowhere is this more apparent than in the McMurdo Dry Valleys. In very few places on this planet are there environments where minor changes in climate so dramatically affect the capabilities of organisms to grow and reproduce.
Biological studies in the dry valleys have revealed life forms that have colonized rocks, soils, glaciers, glacial meltwater streams, and lakes. Bacteria, fungi, algae, mosses protozoa, tardigrades, rotifers, and nematode worms are the most common types of organisms encountered. Algae and lichens are found growing inside sandstone rocks, in which these endolithic microorganisms are living in a relatively stable environment with high humidity and protected from the rigors of the external world. Lichens are found on rock surfaces, from the valley floors to the summits of some mountains. The dry-valley soils, once thought sterile, contain numerous bacteria, fungi, and algae. In damper soils along meltwater streams, mosses are found. Small holes and ponds on the surface of glaciers also provide a habitat for algae and other organisms transported by wind.
The only plants that are relatively “luxuriant” in Antarctica are found in the northernmost parts of the Antarctic Peninsula and some sub-Antarctic islands. They include mosses lichens grasses liverworts, and a few ferns. The animals native to Antarctica include a few species of ducks, a pipet, flies, midges, moths, beetles, and earthworms, nearly all of these occurring on the Antarctic Peninsula and certain islands. Also found are microscopic protozoa, rotifers, and tardigrades, which inhabit moist soils and mosses.