Single and multiple stressor effect of road deicers and Cu on Atlantic salmon (Salmo salar) alevins from hatching till swim-up.

Road salts are frequently used for deicing of roads in the Nordic countries. During snow-melt, the road run-off containing high concentrations of road salt and various metals such as Cu remobilized from sand, silt and dust may negatively influence organisms in downstream receiving water bodies. The present work focuses on the impact of road salt (NaCl) and Cu, separately and in mixtures on Atlantic salmon alevins from hatching till swim-up. The results showed that high road salt concentrations could induce a series of negative effects in alevins such as reduced growth, deformities, delayed swim-up and mortality. For alevins exposed to all tested road salt concentrations (100-1000mg/L), mortality was significantly higher compared to control. In exposure to Cu solutions (5-20μgCu/L), no effects on growth, morphology, swim-up or mortality of alevins compared to control were observed. In mixture solutions (road salt and Cu), ultrafiltration of the exposure water demonstrated that only 20%-40% of Cu was present as positively charged low molecular mass (LMM) Cu species assumed to be bioavailable. When exposed to road salt and Cu mixtures, negative effects in alevins such as reduced growth, deformities, delayed swim-up and mortality were observed. The overall results indicated that the road salt application could seriously affect sensitive life stages of Atlantic salmon, and application of road salt should be avoided during the late winter-early spring period.