Global warming and chemical pollution are two ubiquitous stressors that cause rapid environmental change and pose a major threat to biodiversity and ecosystem functioning. We investigated the combined effects of +4°C warming and a mixture of commonly used pharmaceutically active compounds (PhACs) on a pelagic invertebrate community in outdoor mesocosms that mimic small freshwater ponds (1 m³ volume). The experiment was conducted twice (in winter and summer). The effects of warming and PhACs differed greatly between seasons and trophic levels. The PhAC mixture reduced phytoplankton biomass and altered odonate larval development in summer, while it had only marginal effects on the community in winter. Warming reduced the survival of predatory aquatic insects in winter and accelerated their development in summer, partially releasing large zooplankton from top-down control. Finally, phytoplankton biomass increased with warming in the summer, but not in the winter experiment. Our results show that the effects of combined stressors on freshwater communities are context-dependent and that warming can either mask or amplify the effects of anthropogenic pollutants on freshwater communities.

Primary Presenter: David Boukal, University of South Bohemia in Ceske Budejovice (dboukal@prf.jcu.cz)

Authors:

David Boukal, University of South Bohemia, Faculty of Science  (dboukal@prf.jcu.cz)

Claire Duchet, University of South Bohemia, Faculty of Science  (cduchet@prf.jcu.cz)

Katerina Grabicova, University of South Bohemia, Faculty of Fisheries and Protection of Waters  (grabicova@frov.jcu.cz)

Vojtech Kolar, University of South Bohemia, Faculty of Science  (kolarvojta@seznam.cz)

Andras Csercsa, University of South Bohemia, Faculty of Science  (andras.csercsa@gmail.com)

Barbora Zdvihalova, University of South Bohemia, Faculty of Science  (barca.zdvihal@gmail.com)

Tomas Randak, University of South Bohemia, Faculty of Fisheries and Protection of Waters  (trandak@frov.jcu.cz)