Coexistence, Stress, and Aquatic ecosystem functioning

Conserving biodiversity (B) and ecosystem functioning (EF) is one of today’s key challenges. Meeting this challenge is only possible if the effects of environmental stressors such as anthropogenic chemicals on B and EF are well understood. To this end, I propose to test if ecological theory on coexistence can be used as an elegant approach to correctly predict the response of B and EF to chemicals. Based on this theory and associated models, I present hypotheses that I now propose to test in microcosm experiments containing freshwater phytoplankton. Testing these hypotheses will (1) critically enhance understanding of how species interactions determines chemical effects on B and EF; and (2) enable testing to what extent chemicals may directly impact on EF without affecting B, a topic less

well covered by contemporary research. Lastly, the influence of initial richness on the validity of the tested hypotheses will be evaluated, recognizing the buffering effect B may have on community and ecosystem robustness. In conclusion, I propose a project that will significantly contribute to the emerging field of community and ecosystem ecotoxicology and allow revisiting classic questions in ecology.