Joint effects of climate-driven temperature changes and sublethal concentrations of copper oxide nanoparticles on a freshwater outdoor mesocosm community

Climate change, in particular temperature, modifies seasonal weather periods. These changes directly influence freshwater ecosystems and their communities. As a part of an unprecedented long-term study, we analyzed the impact of two environmentally relevant copper oxide nanoparticle (CuO-NP) concentrations (0.008 and 0.100 mg Cu L-) and copper sulfate (CuSO4) (0.010 mg Cu L-) on the zooplankton community in outdoor freshwater mesocosms during a naturally heat wave in summer. Our results show an overall negative effect of the CuO-NP treatments on the zooplankton community and a change in community composition during the warming period. The strongest effect was found for the low concentration of CuO-NP while CuSO4 hardly deviated from the control. In turn, at the end of the year CuSO4 still exhibited some impact on the community, unlike the CuO-NP treatments. Overall, the Cladocera were the most affected taxon. Due to their fundamental importance for freshwater food webs, this could result in a long-term change in the community composition of freshwater ecosystems, with potentially large consequences for their functioning. These results are an important contribution to better comprehend, predict and prevent long-term effects of nanomaterials on freshwater community dynamics in the context of climate change. To cope with challenges of global environmental change, we strongly recommend, that future research focus on multiple stressors.