Unraveling exposure to toxicants in multiply stressed aquatic ecosystems
Aquatic ecosystems are exposed to many different stressors at the same time. Multiple stress includes chemical contaminants emitted by industry, cities and agriculture, high nutrient loads, channelization, flow modifications and invasive species. Together these stressors impact on ecosystem structures and functions. Within the UFZ IP “Healthy Aquatic Ecosystems”(link) we provide and apply tools to unravel the external and internal exposure of aquatic organisms to toxicants as well as the impact thereof. Using the river Holtemme (Saxony-Anhalt, Germany) as a common case study, we focus on the chemical and effect-based analysis of waters, sediments and biota tissues. This will help to identify toxic chemicals contributing to adverse effects on the ecosystem. These chemicals will be used for subsequent multiple stress assessment in on-site mesocosm experiments and modelling approaches.
Exposure of aquatic organisms to environmental toxicants strongly depends on bioavailability and bioaccumulation. Thus, we strive for a better understanding of bioavailability particularly of sediment-bound toxicants, which is crucial for reliable assessment of risks. We use bioavailability as criteria for toxicant prioritization by applying bioavailability-directed extraction techniques and passive dosing. With this approach we address and simulate partitioning, desorption and diffusion processes for example in contaminated sediments. Together with these physico-chemical processes active transport by living cells determines bioavailability and bioaccumulation. Using energy efflux transporters in cell membranes may reduce internal concentrations while chemicals known as environmental chemosensitizers may inhibit this active transport and enhance bioaccumulation of other chemicals. Thus, it is our goal to identify chemosensitizers in aquatic environments and to assess their impact on bioaccumulation in aquatic organisms using for example zebrafish embryos as a model system.