A Changing Menu in a Changing Climate? Predicting the Availability of Fish Food in Warmer Arctic Lakes

In the face of a changing climate, fishes in arctic lakes will likely experience changing seasonality and novel temperature regimes. Predicting fish response (e.g., growth, condition) based primarily on temperature (bioenergetics) is well understood, but predicting the availability of lower trophic resources, as fish food, requires additional research.  To predict the response of zooplankton, a primary fish food in the Arctic, to climate change, we combined a laboratory experiment measuring zooplankton response to increased temperature with empirical modeling relating long-term zooplankton sampling to physical and chemical lake variables (e.g., temperature, nutrients). In the laboratory experiment, zooplankton generation time decreased in the warmer experimental treatment and the total biomass and abundance of zooplankton increased relative to the control; however, this pattern varied over the season.  Empirical modeling revealed that across lakes, seasonal patterns of zooplankton biomass varied annually, but were driven by temperature, with higher peaks during warmer years. However, during the late season, day length plays a much larger role in controlling zooplankton availability compared to the early season.  Future work will combine these models with whole ecosystem experiments to provide unique insight into likely responses of zooplankton, specifically as fish food, to a changing climate in the Arctic.