COS 83-1 - Summer warming and the activation of an ephemeral wetland ecosystem in the McMurdo Dry Valleys, Antarctica

Thursday, August 6, 2009: 8:00 AM
Taos, Albuquerque Convention Center
Uffe N. Nielsen , Hawkesbury Institute for the Environment & School of Science and Health, University of Western Sydney, Australia
Diane M. McKnight , Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO
Diana H. Wall , Department of Biology and Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO
Byron J. Adams , Department of Biology and Evolutionary Ecology Laboratories, Brigham Young University, Provo, UT
Ross A. Virginia , Environmental Studies Program, Dartmouth College, Hanover, NH
Background/Question/Methods The ecosystems of polar regions are controlled by climate extremes and are generally predicted to experience substantial climate changes over the next century. In the McMurdo Dry Valleys of East Antarctica, a recent trend of cooler summers has been observed and is expected to persist for the duration of the “ozone hole” phenomenon. The terrestrial ecosystem consequences of these cooler summers have been interrupted by infrequent warm summers. During such warm years water run-off from snow-packs, glaciers and permafrost increase dramatically, resulting in the in the appearance of wetlands and spring-like features in a desert landscape. One such wetland is Wormherder Creek, which was observed for the first time during the warm summer of 2001/02 and which appeared again during the warm summer of 2008/09.
We seized this opportunity to set up a short-term experiment to understand how these desert ephemeral wetlands influence the soil and aquatic biota, and soil biogeochemistry. We added a solution containing conservative (non-reactive) inorganic tracers (Li and Cl) near the source of a spring that feeds Wormherder Creek, and traced the distribution of the tracers over time throughout the wetland. We then compared the patterns of water flow with the distribution of soil fauna and biogeochemistry.
Results/Conclusions Our results allow for the quantification of the processes mobilizing the solutes in Wormherder Creek and its wetland. The results revealed that the visible spring is augmented by other large sources of water that discharge into the wetland. The soil fauna within the wetland was dominated by the nematode Scottnema lindsayae, a species which is generally found in dry soils, with abundances ranging between 54 and 1495 individuals per kg soil. However, two other species of nematodes (Eudorylaimus spp. and Plectus spp.), and tardigrades and rotifers, were common occupants of the soil within the wetland. The presence of below-ground communities dominated by tardigrades, rotifers and the nematode genus Plectus indicate the presence of soil communities adapted to more moist soils. Thus, there is a clear distinction between wet and dry soil communities. We found that the composition of the below-ground communities, and the biogeochemical properties of the sediment, was associated with the flowpaths in the wetland. These patterns can be used to predict how the McMurdo Dry Valleys landscape may change as the cooling trend comes to a close with the eventual reduction in atmospheric chlorofluorocarbons in the future.
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