Cryospheric and Polar Processes Seminar

McMurdo Dry Valleys: Ecosystems waiting for water by Dr. Diane McKnight, Professor

ABSTRACT:  The McMurdo Dry Valleys region in Antarctica is comprised of alpine and terminal glaciers, large expanses of patterned ground, and permanently ice-covered lakes in the valley floors, which are linked by glacial meltwater streams that flow during the austral summer. These valleys were first explored by Robert Scott and his party in 1903. In 1968 the New Zealand Antarctic Program began a gauging network on the Onyx River, a 32 km river that is the longest river in Antarctica. As part of the McMurdo Dry Valleys Long-Term Ecological Research project, our research group has continued to monitor streamflow in the Onyx River and 15 other first-order streams in adjacent valleys. We studied the linkages between hydrology, biogeochemistry and microbial community ecology in stream ecosystems through a period of climatic extremes. In the 1990’s, a cooling period continued that was driven by atmospheric changes associated with the ozone hole. In the summer of 2001/002, this cooling period was interrupted by several warm and sunny summers that created "flood events" in the valleys and caused much greater ecological connectivity. Further, we found that flow regime strongly influences the composition of the diatom community in the algal mats that are abundant in many of the streams. Many of the diatom taxa are endemic to the region, with a few endemic taxa being most abundant in wetland systems that only become active during flood events. During floods, the microbial mats are scoured from the streambed and mat material is transported to the closed basin lakes. Thus, understanding the relationship between mat communities and hydrology is useful for interpretation of the record of the stream diatoms preserved in lake sediments and perched deltas to reconstruct the hydrologic record beyond the limited instrumental record of the Dry Valleys.

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