The Ecology of Nematodes in Antarctic Dry Valleys

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Nematodes are microscopic invertebrates found in all ecosystems. They are particularly abundant in soils, where they live in water films surrounding soil particles. They play an important role in nutrient cycling in soil food webs by feeding on microscopic plants and animals as well as bacteria and other decomposers. This study will continue the first intensive ecological investigation of nematodes in the Dry Valley ecosystems in Antarctica. During the 1990 and 1991 austral summers, Nematodes were found to occur in Dry Valley soils over a wide range of soil properties (moisture, salinity, nitrogen and carbon contents). The proposed research will increase our understanding of the abundance and trophic role of nematodes by sampling them in various habitats (soil properties and microbial activity) from a wide range of soil formations, elevations and locales in the Dry Valley region of southern Victoria Land. In response to harsh conditions nematodes can assume a cryptobiotic state in which their metabolism becomes undetectable and there are both physiological and morphological changes to the animals. Studies of cryptobiosis in the field and laboratory will determine the potential duration of nematode activity in this cold desert and will complement research on nematode population dynamics. A field experiment will be conducted to examine the response of nematodes and total soil microbial activity to temperature, moisture and energy availability in the soil. Total soil response will be determined as carbon dioxide efflux and substrate-induced respiration, a measure related to soil microbial biomass. The genetic diversity of populations of the dominant nematode in the Dry Valleys will be evaluated using molecular biology techniques. It is hypothesized that if nematodes are easily dispersed by wind, this diversity will be comparable over a wide area.