The combined anthropogenic pressures of predator loss and warming challenge our understanding of ecosystem function. Predator effects cascade down food webs via predator-prey interactions while warming increases metabolic rates, suggesting that climate change effects interact with predators and their prey through consumer processes. However, the direction of effects will depend on both the food web structure and the ability of the consumers to adapt to changing temperatures. We tested the interactive effects of predator loss and warming on trophic interactions by conducting a mesocosm study, using a simplified shallow coastal food web as a model system. We included three trophic levels (predators: three-spined stickleback, Gasterosteus aculeatus; grazers: gastropods, amphipods, and isopods; and macroalgal foundation species: Fucus vesiculosus and F. radicans) and two temperature treatments (ambient and +4° C) to assess how predators and warming altered traits at each trophic level. Predator removal modified grazer trait responses to warming, and this effect cascaded further down the food web. Warming and predator presence together reduced crustacean biomass and increased diatom biomass. Predator removal increased the survival and recruitment of crustaceans but decreased gastropod biomass. The results illustrate that warming and predator loss impact both food web dynamics and traits at different trophic levels. 

Primary Presenter: Tiina Salo, Åbo Akademi (tsalo@abo.fi)

Authors:

Tiina Salo, Åbo Akademi University  (tsalo@abo.fi)

Casey Yanos, University of Groningen  ()

Britas Klemens Eriksson, University of Groningen  ()

Andrea De Cervo, Stockholm University  ()

Maïté Jacquot, Åbo Akademi University  ()

Johan Eklöf, Stockholm University  ()