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

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.