A combined hydraulic and toxicological approach to assess re-suspended sediments during simulated flood events. Part I-multiple biomarkers in rainbow trout

Purpose One of the central issues related to global changes in weather is the increasing occurrence of flood events that can result in the re-suspension of contaminated sediments in rivers. Here, we report on a proof-of-concept study combining hydraulic engineering and ecotoxicology in a new interdisciplinary approach to assess the toxicity of re-suspended polluted sediments after a simulated flood event. Materials and methods Rainbow trout (Oncorhynchus mykiss) were exposed for 5 days under simulated flood conditions in an annular flume with artificial sediments that were spiked with a mixture of polycyclic aromatic hydrocarbons (PAH) at environmentally relevant concentrations. Specifically, the objective of this study was to bridge the gap between the physical re-suspension of pollutants and resulting toxicological impacts on aquatic organisms. A suite of different molecular, biochemical and histological markers was used to test the hypothesis that re-suspension of sediments can lead to re-mobilization of PAHs and subsequently to effects on aquatic organisms. Results and discussion The micronucleus frequency was significantly 4.3-fold elevated after exposure. There was no significant indication of Aryl hydrocarbon receptor signaling (no EROD induction or increased CYP1A protein content, only slight induction of CYP1A gene expression). Biliary metabolite concentration was the most sensitive marker of PAH exposure. Results for other biomarkers (glutathione-S-transferase, catalase and lipid peroxidation) were inconclusive. Conclusions In combination with chemical analyses of suspended matter, the presented approach will be used to improve understanding of the re-mobilization of pollutants from sediments in support of environmental risk assessment.