Combined Effects of Nano-Polystyrene and Heavy Metal Mixture on the Bioaccumulation of Heavy Metals and Physiological Changes in Macrobrachium rosenbergii

Contaminants such as nano-polystyrenes (NPs) and heavy metal cocktail (HMC) have been found to disrupt physiological functions in aquatic organisms. Although HMC and NPs alone induce oxidative stress, their combined effects are not well understood. This study aimed to assess the combined effects of HMC and NPs on the freshwater shrimp (Macrobrachium rosenbergii). Shrimp were divided into seven groups, including the control group, and the experimental groups co-exposed to 0, 50, 100, 150, 200, and 250 µg/L NPs combined with 0.5 mg/L HMC. After 14 days, shrimp were sampled, and their hepatopancreas and muscle tissues were analyzed for oxidative biomarkers, biochemical parameters, and metabolic profiles. Moreover, the bioaccumulation rate of heavy metals was measured. Results showed that co-exposure to NPs and HMC increased superoxide dismutase, glutathione peroxidase, glutathione reductase activities, and malondialdehyde levels, while reducing glutathione and total antioxidant capacity. The integrated biomarker response indicated that co-exposure to HMC and NPs induces oxidative stress. A significant decrease was observed in aspartate aminotransferase, gamma-glutamyl transpeptidase, and alkaline phosphatase activities, glycogen, triglyceride, and total protein levels. However, lactate dehydrogenase activity was significantly increased. Co-exposure to HMC and NPs increased heavy metal bioaccumulation, induced oxidative stress, biochemical changes, and enhanced HMC toxicity in shrimp.