Investigation of the effects of nickel and zincnanoparticles on the antioxidant system of mussels (uniodelicatus)

Mussels are important bioindicator organisms for aquatic environments due to their sessile lifestyle and filter-feeding habits. In this study, the responses of antioxidant systems and the levels of organic molecules that serve as energy sources (carbohydrates, lipids, and proteins) were investigated in freshwater mussels (Unio delicatus) exposed for 14 days to different concentrations (0, 0.5, 2.5, 12.5 mg/L) of nickel (NiO) and zinc (ZnO) nanoparticles (18 nm). The mussels were fed in the laboratory with cultured unicellular algae (Chlorella vulgaris) at a concentration of 250.000 cells/mL. At the end of the experiments, no mortality was observed among the mussels; however, the nanoparticles had significant effects on antioxidant enzyme activities in the hepatopancreas tissue. Significant (p<0.05) changes were detected in the activities of catalase, glutathione peroxidase, glutathione reductase, and glutathione S-transferase in mussels exposed to NiO and ZnO nanoparticles. Furthermore, at the highest concentration, significant (p<0.05) decreases were observed in glucose and lipid levels—the primary energy sources—while no significant change (p>0.05) was detected in protein levels. These findings indicate that exposure to NiO and ZnO nanoparticles induces oxidative stress in mussels and that the animals increase their energy consumption as a compensatory response to counteract this stress.