Toxicity of Silver Nanoparticles in Aquatic Ecosystems: Salinity as the Main Cause in Reducing Toxicity

Background: In recent years, silver nanoparticles due to their antimicrobial properties, have formed about 56% of nanoparticles global production. Since the released nanoparticles ultimately enter water ecosystems, their maximum toxic effects are magnified in aquatic ecosystems. The aim of this study is to show how salinity can decrease the toxic effects of silver nanoparticles on exposed rainbow trout fry (Oncorhynchus mykiss), as a model in aquatic eco-toxicological studies. Methods: The effects of colloidal silver nanoparticles on rainbow trout fry (n=540, 10-week-old 1000 ± 35.0 mg) were examined in two different salinities (6±0.3ppt, and 12±0.2 ppt) in comparison with de-chlorinated tap water (0.4ppt). Median lethal concentration (LC50) of various concentrations of the Ag-NPs (ranging from 0.25 up to 80 ppm) was determined through a 6-day static-renewal exposure of tested fish fry to the salinities. Results: LC50 of the colloidal Ag-NPs for rainbow trout fry in 12±0.2 ppt salinity was almost 20 and 2 times greater than 0.4 and 6±0.3ppt salinities, respectively. Conclusion: The release of silver nanoprticles into fresh water ecosystems can lead to more biological, physical, and chemical irrecoverable impacts on the ecosystems and their fishes in comparison with saline water ecosystems.