Polar desert ecosystems are expected to experience future rises in temperature, which may result in increased soil moisture from glacier and permafrost melt. The McMurdo Dry Valleys of Antarctica are an ice-free polar desert ecosystem characterized by limitations of water and carbon, where small increases in temperature and moisture may contribute to spurts of biological activity. Recently, occurrences of subsurface ice melt have resulted from warming events in the dry valleys. We examined soils in two sites across the valleys, to test the hypothesis that increases in soil moisture alter nematode demographics, community structure, and depth distribution. We compared sites that had no seepage (dry soils) with those having visible seepage, and dug soil pits to the surface of the ice-cemented permafrost. We sampled the soils in ten cm depth increments through the active layer to and including the permafrost surface, to investigate whether seepage increases moisture throughout the soil profile and alters the depth distribution and community structure of nematodes. This experiment included three replicates of each treatment (seep versus dry soils) per site, across two watersheds in the dry valleys.  
Results/Conclusions

An NMS ordination was used to examine the differences in nematode community structure between seep versus dry sites as well as between depth increments.  The ordination showed that 91% of the variance in the data is explained by the treatments. These preliminary results suggest that subsurface ice melt events alter the soil conditions throughout the soil profile, and in turn affect nematode assemblages and abundances. The study has implications for how terrestrial polar desert ecosystems might be altered by changes in climate, as the region is expected to experience both periodic short-term warming events as well as future increased long-term warming trends.  An understanding of how the biota in these systems may be impacted by such changes will in turn contribute to the understanding of consequent changes in the ecosystem’s functioning.