Effects of nanosilver in a short term waterbourne exposure of salmon (Salmo salar)

Silver nanoparticles (Ag-NPs) have applications in commercial products, and pose a risk to aquatic systems. A comprehensive study was set up to evaluate toxic effects in Atlantic salmon from both Ag+ and Ag-NP covering a variety of biological responses, including at the transcriptome and functional level. Water-borne exposures in natural lake water were performed for 48 h with Ag-NP concentrations 20 and 100 µg/L. In addition a 20 ug/L Ag+ (AgNO3) exposure was included to represent the effect posed by Ag+ proportion of the Ag-NP colloidal suspension. The Ag-NPs were characterized by transmission electron microscopy as well as ICP-MS Ag measurements of fractions resulting from 0.22 µm filtration and 10 kDa hollow fibre cross-flow ultrafiltration. Results show a particle size distribution in the range of 5-50 nm for the Ag-NPs mixed with natural water. Fish exposed to 100 µg/L Ag-NP had high mortality, whereas fish exposed to 20 µg/L Ag-NP and Ag+ displayed various osmoregulatory effects. Focusing on possible mechanisms of toxicity of Ag-NPs to Atlantic salmon, a 44k oligoarray was used to perform a genome wide analysis in fish from this experiment. Hierarchical clustering of the groups indicated both Ag-NP and Ag+ exposed fish to have similar relationships, although some differences were observed. It is clear that that Ag-NP may cause effects to non-target organisms in the recipient, but that there are some similarities between Ag+ and Ag-NP toxicity.