Salinity gradients exacerbate the genotoxicity and bioaccumulation of silver nanoparticles in fingerling Persian sturgeon (Acipenser persicus)

As nanoparticles are extensively applied in a vast range of products and so are released into marine environments, their effects and the involved mechanisms on such ecosystems need to be further investigated. Therefore, the present study examined the effects of salinity on the toxicity of silver nanoparticles (AgNPs) using DNA damage biomarker and bioaccumulation process in fingerling Persian sturgeon (Acipenser persicus). A total of 360 fingerling fish with an average weight of 2.95 ± 0.25, 3.49 ± 0.35 and 4.04 ± 0.35 were used for the salinity gradients of 0.4, 6 and 12 g L⁻¹ (ppt), respectively. Fish acclimated to freshwater (0.4 ppt) for 14 d were exposed to 0, 0.07, 0.1, and 0.2 mg L⁻¹ AgNPs, while those kept in brackish water (6 and 12 ppt) were exposed to 0, 0.2, 0.3, and 0.6 mg L⁻¹ AgNPs through a sub-chronic exposure test. Fish sampling was conducted on the day 0 and 14 and bioaccumulation and DNA damage tests were implemented using liver, gills and intestine organs. Results showed that AgNPs exposure could induce concentration-dependent DNA damage in the liver single cells, while elevating salinity significantly increased tail moment index in the fish. Ag bioaccumulation in the investigated tissues was greatest in liver, followed by gill, then intestine. Furthermore, elevated salinity significantly increased the bioaccumulation of Ag in the liver. Behavioral analysis showed the marked emergence of abnormal manners with the increase of salinity and AgNPs concentrations. Together, salinity changes, as one of the most important environmental stressors, can significantly affect the toxicity of emerging pollutants such as AgNPs in the marine biota, and ecologically- and commercially-important fish species like Persian sturgeon are in a cautious status in the Caspian Sea.