Consequences of short-term feeding inhibition from exposure to pesticides for individuals and populations of aquatic invertebrates

Recently, several scientific committees of the European Commission have identified research needs to enhance the risk assessment of plant protection products (PPPs). This PhD explicitly focuses on contributing to the research needs of assessing effects under highly time-variable exposure, increasing the ecological realism in effect assessment approaches, considering effect assessment of combined stressors (natural and anthropogenic) and improving ecological modelling. The presented work focuses on the observation of potential impacts of PPPs (imidacloprid and carbaryl) on feeding of aquatic invertebrates (Gammarus pulex and Daphnia magna) under more environmentally-realistic exposures. Isolated feeding depression and its combination with additional stress is explored. Investigations include the determination of consequences of alterations in feeding for further behavioural traits of individuals and its transposition to the population level. An ecological model is used as a virtual laboratory to allow the interpretation of complex impacts observed which in turn helps to evaluate the model used. A key finding is that feeding assays with G. pulex are able to reveal impacts of PPPs at environmentally-relevant concentrations and that the measurement of recovery potential is important. However, the method used requires further improvement in order to extrapolate impacts to the population and ecosystem level. The possibility of short-term impacts on feeding causing severe impacts at the individual and population level is shown for D. magna. Direct extrapolation from the feeding assay with imidacloprid to other individual traits is not possible. Impacts are found to depend on food availability and the individual’s reproductive strategy, which is found to be more flexible under multiple stresses than has been reported in the literature. Further research is required in order to generalise these findings.