IGN 15-2
More summer, more nitrogen and thinner ice: Long-term trends in summertime phytoplankton abundance in an alpine lake in the Colorado Rocky Mountains

Thursday, August 13, 2015
345, Baltimore Convention Center
Diane McKnight, Institute of Arctic and Alpine Research, Univerisity of Colorado, Boulder, CO
Mark Williams, Department of Geography, University of Colorado, Boulder, CO
Pieter T. J. Johnson, Ecology and Evolutionary Biology, University of Colorado at Boulder, CO
Katherina Hell, INSTAAR, University of Colorado, Boulder, CO
Alpine ecosystems worldwide are responding to too much summer.  The sedimentary record of Green Lake 4, a sentinel lake of the NWT-LTER, shows that benthic primary production increased in importance compared to planktonic primary production in response to mid-20th century grazing by sheep and nitrogen deposition. Currently, planktonic primary production is rebounding and the lake is shifting from an oligotrophic state to becoming intermittently mesotrophic during drought summers. We predict that in the future zooplankton will exert top-down control on planktonic primary production, potentially allowing for benthic primary production to once again become dominant.