Individual and Combined Toxic Effects of Nano-ZnO and Polyethylene Microplastics on Mosquito Fish (Gambusia holbrooki)

Abstract

The omnipresence of microplastics and nanoparticles has led to their entry into the fresh and marine aquatic systems and affected the biota. The present study aims to evaluate the impact of the interaction of polyethylene microplastic (PE-MPs) and zinc oxide nanoparticles (ZnO-NPs) in mosquito fish, Gambusia holbrooki. For this, fish were exposed to 100 µg L−1 PE-MPs (group 2), 200 µg L−1 PE-MPs (group 3), 50 µg L−1 ZnO-NPs (group 4), 50 µg L−1 ZnO-NPs combined with 100 µg L−1 PE-MPs (group 5), and 200 µg L−1 PE-MPs (group 6) and control (group 1) for 14 days. The assessment was made through accumulation studies (MPs and Zn) and antioxidant assay. Significant elevation in the activity of catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase levels was observed in ZnO-NPs alone and in combination with PE-MPs (100 and 200 µg L−1) groups only. High malondialdehyde levels were observed in all the exposed groups. Concordantly total antioxidant (TAN) levels displayed a significant reduction in all treated groups compared to control. Accumulation study on microplastic suggested liver-targeted accumulation of PE-MPs, while for ZnO-NPs, observed PE-MPs assisted accumulation. The study affirms the induction of oxidative stress and ZnO-NPs-induced toxicity facilitated by PE-MPs in fish.