Reproducible (1)H NMR-based metabolomic responses in fish exposed to different sewage effluents in two separate...

Treated sewage effluents contain complex mixtures of micropollutants, raising concerns about effects on aquatic organisms. The addition of advanced treatment steps has therefore been suggested. However, some of these could potentially produce effluents affecting exposed organisms by unknown modes of action. Here, (1)H NMR (proton nuclear magnetic resonance spectroscopy) metabolomics of fish blood plasma was used to explore potential responses not identified by more targeted (chemical or biological) assays. Rainbow trout was exposed in parallel to six differently treated effluents (e.g., conventional activated sludge, addition of sand filter, further addition of ozonation and/or a moving bed biofilm reactor or a separate membrane bioreactor line). Multivariate data analysis showed changes in the metabolome (HDL, LDL, VLDL and glycerol-containing lipids, cholesterol, glucose, phosphatidylcholine, glutamine, and alanine) between treatment groups. This formed the basis for postulating a hypothesis on how exposure to effluent treated by certain processes, including ozonation, would affect the metabolic profiles of exposed fish. The hypothesis withstood testing in an independent study the following year. To conclude, (1)H NMR metabolomics proved suitable for identifying physiological responses not identified by more targeted assays used in parallel studies. Whether these changes are linked to adverse effects remains to be tested.