Integrating ecology and evolution in aquatic toxicology: insights from damselflies

Current legislation and ecological risk assessment fails to protect aquatic biodiversity at low levels of contaminants. We addressed 3 topics embedded in general stress ecology and evolutionary ecology that are relevant to arrive at a better evaluation of the risk of low contaminant levels in aquatic systems: 1) delayed effects of contaminants, 2) interactions between contaminants and biotic interactors, and 3) vulnerability to contaminants under global warming. We developed these topics by capitalizing on the key insights obtained using damselflies as model organisms. First, delayed contaminant effects on important fitness-related effects exist during the larval stage and after metamorphosis in the adult stage. Second, synergistic interactions of contaminants with bacteria and predation risk have been demonstrated, and we present advances in the mechanistic understanding of these synergisms with biotic interactors. Third, we illustrate the strength of assessing the effect of contaminants under global warming using a space-for-time substitution approach and the need to consider temperature extremes. These studies using damselflies as model organisms highlight the relevance of considering contaminant effects after the exposure period and in the presence of natural stressors, such as predation risk and higher temperatures. They further highlight the need for spatially explicit risk-assessment and conservation tools. These insights are relevant for most aquatic taxa. Indeed most aquatic taxa have a complex life cycle, are strongly affected by predation risk and by warming, and show latitudinal gradients. Better integration of these topics in ecological risk assessment will be a major challenge for both scientists and policy makers, but of crucial importance to preserve aquatic biodiversity.