In classical toxicity evaluations, an organism is exposed to a single chemical in the lab under constant, favourable conditions. However, in aquatic ecosystems chemicals often occur in mixtures, where they can interact and possibly result in enhanced or weakened toxic effects. Besides pollution, natural stressors, such as temperature fluctuations or predators, are present as well, which could also influence the toxicity. In the lab, we performed experiments on Asellus aquaticus, exposing this freshwater isopod to a combination of metal mixtures and natural stressors. This way we could study effects on the individual level and relate metal accumulation to relevant sublethal endpoints (e.g., growth rate, feeding rate). To gain more insight into the effects of metals on populations and communities, we also executed a microcosm experiment in the Mesodrome. Small ecosystems with several species of macroinvertebrates were exposed to Cu, Cd, Pb and a mixture of these three metals under semi-natural conditions. For two months, we observed the combined effects of metals and natural stressors on the individual level (accumulated metals, survival), the population level (species density, biomass) and the community level (species richness, evenness).
In these buckets, we exposed small communities (with midge larvae, isopods, molluscs,…) to single metals and metal mixtures.