Warming reshapes the invertebrate predation pressure on the plankton community

Abstract

Climate change stressors, including warming and heatwaves, can alter plankton composition and dominance patterns in temperate shallow lakes, which can disrupt ecosystem function and curtail ecosystem services. Understanding how these alterations could take place under future climates is therefore important. To understand such changes, we performed a year-long mesocosm experiment with controls reflecting present temperature conditions and a treatment reflecting a future climate change scenario, including heatwaves of 5–8°C above ambient water temperatures. In the warmer conditions, the predatory invertebrate Mesostoma, exerted a strong top-down control on Daphnia, resulting in a switch in herbivore dominance to Ceriodaphnia in contrast to the controls where Daphnia remained dominant. A complementary predation experiment revealed that Mesostoma fed at a higher rate on Daphnia than on Ceriodaphnia and cyclopoid copepods. Cyclopoids were the least affected taxon but showed tendencies to sustain populations longer into the winter at elevated temperatures. Moreover, both total algal and cyanobacteria biomass increased with warming. Our experiments suggest that predator–prey dynamics may alter plankton community composition and dominance patterns in a warmer climate because thermophilic predatory invertebrates have the potential to induce cascading food-chain effects and alter the herbivore dominance patterns in lake zooplankton. This may have implications for the algal population dynamics and overall ecosystem function and processes in shallow lakes.