Short-time salinity fluctuations are strong activators of oxidative stress in Mediterranean mussel (Mytilus galloprovincialis)

Abstract

Salinity stress is an emerging key factor affecting aquatic animals in coastal waters. In bivalves, physiological responses to anisosmotic conditions are frequently associated with excessive reactive oxygen species (ROS) formation, lipid peroxidation processes and alterations of the antioxidant enzyme activity in tissues. In this study, we investigated whether short-time exposure to high (20-40 ‰) or low (6-14 ‰) salinity induces oxidative stress in hemocytes and gills of Mediterranean mussel (Mytilus galloprovincialis). Our findings showed that both hypoosmotic and hyperosmotic stress enhanced formation of ROS in hemocytes, which was accompanied by an increase in DNA damage. Experimental acclimation to low salinity (6‰, 10 ‰) led to a decrease of the activity of superoxide dismutase but did not affect catalase activity in gills. Exposure to high salinity (24 ‰) inhibited activities of both antioxidant enzymes, whereas at 30 ‰ activity of both enzymes recovered up to controls. We found that exposure to high salinity was associated with lower risks of oxidative stress in mussels, and changes in redox balance are observed in hemocytes and gills even if the range of salinity changes is in range of species adaptive potential. Taken together, this study suggests that short-time salinity fluctuations promote oxidative stress in bivalves.