Effects of Microplastics on the Activity of Digestive-, Antioxidative- and Immune-related Enzymes in Soiny Mullet (Liza haematocheila Temminck & Schlegel, 1845) Larvae

Microplastics (MPs), novel pollutants in the water environment, can cause damage to fish, especially to fish larvae. However, the effects of MPs on fish in estuarine areas with high levels of MPs pollution are unknown. In this study, a 14-day exposure test was conducted to analyze the effects of MPs on soiny mullet larvae by measuring the activities of digestive enzymes, antioxidant enzymes, and immune enzymes in soiny mullet larvae after exposure to MPs of different particle sizes (0.5 μm, 0.1mg/L; 6 μm, 0.1mg/L).Results showed that MPs exposure significantly decreased the activities of pepsin (PPS), alpha-amylase (α-AMS), catalase (CAT), and superoxide dismutase (SOD), and significantly increased the activities of acid phosphatase (ACP) and alkaline phosphatase (ALP), among which the PPS, CAT, SOD, ACP, and ALP were more sensitive to exposure to small particle size MPs (0.5 μm).Overall, exposure to MPs reduced digestion, destroyed the antioxidant system, and triggered an immune response in soiny mullet larvae, especially the small particles of MPs (0.5 μm). The results provide basis for understanding the detriment of microplastic in fish.