2nd Place: Exposure of Diamesa mendotae, a cold-adapted chironomid, to short-term high temperature

Climate change is increasing mean winter temperatures and the frequency of short-term high temperatures. Diamesa mendotae is a cold-adapted, winter-emerging chironomid common in groundwater-dominated streams in Minnesota. Previous studies have found constant exposure to high air temperatures reduces adult D. mendotae survivorship, but no research has assessed the effects of short-term high air temperatures on this species. D. mendotae collected from two groundwater-dominated trout streams in Minnesota were incubated at either constant 6°C or 6°C with 24 or 48 hr exposure to 22°C to determine how winter temperature spikes may affect D. mendotae survivorship and reproduction. We found short-term exposure to 22°C decreased adult D. mendotae longevity and reduced oviposition, embryogenesis, and larval hatch success. These findings suggest climate change may reduce D. mendotae population sizes. Disruptions in D. mendotae and other cold-adapted insect populations may have broad ramifications for groundwater-fed stream ecosystems. Our study highlights the need for further research on cold-adapted insect survivorship after short-term winter temperature spikes to understand the impacts of climate change beyond mean annual temperature increases.