Effects of increased salinity on oxidative stress status in the freshwater mussel Unio ravoisieri

Freshwater salinisation is an environmental challenge that threatens freshwater species survival. We investigated the influence of increased water salinity on the oxidative status in the bivalve Unio ravoisieri. Under laboratory conditions, 3 sodium chloride (NaCl) concentrations (2.5, 5 and 7.5) were tested for 7 days compared to a control salinity concentration (0.7), mimicking sampling site condition. Biomarkers of oxidative stress including superoxide dismutase (SOD) and catalase (CAT) activities and glutathione (GSH) and malondialdehyde (MDA) were assessed in gills and digestive gland. Furthermore, acetylcholinesterase (AChE) activity was assessed, as a marker of neurotoxicity. Findings showed that the highest concentration of salinity has significantly disturbed oxidative metabolism in both gills and digestive gland by modulating the activity of CAT and the levels of GSH and MDA compared to the control condition (all p < 0.05). Moreover, significant enhance of AChE activity has been found in both gills and digestive gland with the three concentrations (all p < 0.05), except for 2.5 in gills (p > 0.05) compared to control condition. Overall, our study has shown that water salinity constitutes a serious challenge for Unio ravoisieri, and that CAT activity could be used as a sensitive marker for the evaluation of the effect of freshwater salinisation on freshwater.