Muti-Biomarker Approach and IBR Index to Evaluate the Oxidative Stress of Nanoplastic on the Clams, Meretrix meretrix and Sinonovacula constricta

Nanoplastic (NP) contaminants are receiving increasing attention due to the harm they can cause to aquatic organisms and their accumulation in the human body through the food web. The goal of this study was to evaluate the oxidative stress caused by NPs on the clams Meretrix meretrix and Sinonovacula constricta. Specimens were exposed to three concentrations of fluorescently labeled polystyrene NPs (PS-NPs; 0, 0.1, and 1 mg L−1) for 7 d followed by a 3 d recovery period. The activities of antioxidant enzymes, such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and the content of malonaldehyde (MDA) were measured in the digestive gland, gills, and mantle tissues. Results showed that the SOD activity in the gills of M. meretrix was significantly higher than that of the control at day 1, and PS-NPs exposure inhibited the CAT activity in the gills and SOD and GPx activities in the mantle. Exposure to low or high concentrations of PS-NPs increased the activities of both CAT and GPx in the gills of S. constricta at day 3. The oxidative damage was more severe in the digestive gland of M. meretrix and in the mantle of S. constricta based on MDA level, and it returned to normal after recovery. Integrated biomarker response, index version 2 (IBRv2) values showed that the gills were more sensitive to PS-NPs than mantle and digestive gland. Therefore, the oxidative stress by PS-NPs depended on exposure time, dose, organ, and species.