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End to the trend: Cold desert ecosystem response to climate variability in the McMurdo Dry Valleys

Tuesday, May 27, 2014, 12:00PM - 1:00PM


Michael Gooseff


RL-1 room 269

The McMurdo Dry Valleys (MDVs) of Antarctica represent a cold desert ecosystem defined by extensive soils (i.e., not ice-covered), glacier meltwater streams, and closed-basin, ice-covered lakes. Despite cold temperatures and very little precipitation, a vibrant ecosystem exists across these landscape units. Previous work in the McMurdo Dry Valleys, Antarctica documented significant responses of local aquatic and terrestrial ecosystems to a decadal scale cooling trend prior to 2000. However, an exceptionally high melt year occurred in 2002, influencing stream flow, lake dynamics and terrestrial ecosystems.

Here I will describe interannual variation in Dry Valley ecosystems, focusing on the contrasts in drivers of ecological responses pre- and post-2002, i.e., the flood year. In streams, black Nostoc sp.-dominated mats were observed to be decreasing in ash-free dry mass (AFDM) and chlorophyll-a concentration prior to 2002, increasing in AFDM since. Three MDV lakes were decreasing in volume and increasing in total chlorophyll-a mass in the photic zones prior to 2002 and have been increasing volume and decreasing total chlorophyll-a mass ever since. Soil nematode communities were decreasing prior to 2002, and show no significant trend since, but increased variability. Since 2002, the MDV ecosystem has ceased responding to only a local decadal cooling trend and is responding to several high-flow years with new trajectories in some cases and increased variability in others. The state change of the system provides several new opportunities to explore changing controls by an interdisciplinary group of collaborative scientists.