CONTRASTRESS · Contradicting responses to multiple stressors reduce the resilience of zooplankton community

The aim of the project is to find out what happens within zooplankton communitiy when various chemicals (cyanotoxins and infochemicals) force organisms to use contradictory strategies. Aquatic ecosystems are subject to many anthropogenic stressors, which includes eutrophication with toxic cyanobacterial blooms, chemical pollution (e.g. pesticides) and invasive species linked with climate change. These factors modify populations and whole lake ecosystem as well. Also natural factors like predation, resource competition and food quality may cause substantial changes in populations and communities. Organisms need to use different strategies to cope with these stressors and these strategies exclude each other. This situation may lead to losses in genetic biodiversity or even to exclusion of a species. Zooplankton plays important role in aquatic food webs and it is crucial to know how chemical interactions affect population dynamics and community structure. The aim of this study is to check what are the strategies of individuals to cope with such contrasting conditions and what is their role in biodiversity loss. To answer these questions several approaches will be used to bring together paleolimnology, evolutionary ecology and ecotoxicology. Molecular biology will be included as well in order to asses the genetic biodiversity and to develop a new tool for testing the response of an organism to chemical stressors. Two main hypotheses will be tested (1) Hormesis of a trait is maladaptive (i.e. strategy ‘bigger is better’ decreases fitness and hence indicates a negative response), (2) Interaction of cyanotoxins (hormesis) with fish infochemicals can induce developement of a new zooplankton community. Based on these working hypotheses we set several objectives: - to describe the effects of contradicting chemical signals on life history traits, - testing hormetic effects on several clones of Daphnia adapted to ‘good’ and ‘bad’ conditions, - reconstruct zooplankton com