WINTER SEVERITY SHAPES UNDER-ICE DYNAMICS IN TWO LAKES OF CONTRASTING TROPHIC STATUS

Winters are rapidly changing with significant effects on lake ecosystems.  Extreme fluctuations in winter air temperatures, snow fall, and freeze-thaw patterns can change abiotic conditions under lake ice but we have yet to understand how fluctuations in winter severity shape winter biological activity. We monitored ice and snow cover, dissolved oxygen, chlorophyll, and zooplankton during a severe (2022-2023) and mild (2023-2024) winter in an eutrophic and oligotrophic lake. In both lakes, ice and snow cover were significantly thinner and oxygen was supersaturated directly under the ice during the mild winter. Chlorophyll a and zooplankton abundance were significantly higher during the mild winter, especially in the eutrophic lake. There was strong evidence of a negative effect of winter anoxia on zooplankton in the eutrophic lake during the severe winter. Lower trophic levels play a major role in lake nutrient processing, including during winter periods. Linking winter severity to food web structure is important to understand how lake ecosystems will change as winters continue to grow more unpredictable. 

Presentation Preference: Oral

Primary Presenter: Alia Benedict, University of Minnesota Duluth (bened109@umn.edu)

Authors:

Alia Benedict, University of Minnesota Duluth  (bened109@umn.edu)

Ted Ozersky, University of Minnesota Duluth  (tozersky@d.umn.edu)