The presence of microplastics (MPs) reduces the toxicity of cadmium (Cd) to Cirrhinus mrigala larva

Abstract

Cumulative studies have shown that microplastics (MPs) and cadmium (Cd) co-exist widely, but their combined toxic effects on aquatic organisms are still not well understood. In this study, Cirrhinus mrigala larvae were exposed to single and binary combinations for 7 days, and the growth performance, survival, intestinal contaminant migration, intestinal histopathology, enzyme activity, and expression of antioxidant-related and detoxification-related genes were measured. The results showed that PS-MPs, Cd, and their combined exposure cause intestinal tissue damage, which in turn affects the growth and survival of C. mrigala larvae, and combined exposure of PS-MPs and Cd reduces stagnant growth and death caused by single Cd exposure. Under both single and binary exposure, PS-MPs can accumulate in the intestine of C. mrigala larvae, but Cd-induced damage to intestinal tissues can increase the accumulation of PS-MPs in the intestine of C. mrigala larvae. PS-MPs, Cd and their combined exposure can cause abnormalities in enzyme activity and expression of antioxidant genes and detoxification genes. The results of continuous 7-day dynamic monitoring showed that the relative expression of cat in the Cd exposure group was significantly higher than that of the control group on days 1, 2 and 4; the relative expression of gpx was significantly higher than that of the control group on days 3, 4 and 7; the relative expression of mnsod was significantly higher than that of the control group on days 1, 3 and 7; and the relative expression of cusod was significantly higher than that of the control group on days 4, 6 and 7. These results indicated that the presence of MPs acted as an antagonist, reducing the toxicity of Cd to aquatic organisms. Overall, this study contributes to further understanding of the inter-regulatory relationship between MPs and Cd and the combined toxic effects on aquatic organisms.