The Toxicity of Polyethylene Microplastic Exposure and Its Concurrent Effect With Aeromonas Hydrophila Infection To Zebrafish

Abstract Microplastics that are widely distributed in the environment has raised great concerns due to their potential negative effects to humans. Zebrafish was used as the model organism in this study to assess the toxicity of microplastic exposure. The adult zebrafish were exposed to the PE microplastics in smooth clustered sphere shapes with diameters of 75-100 µm for 35 days, and the survival rate of the zebrafish were not significantly affected, whereas the growth rate was. Further analyses on the oxidative stress related enzyme activities showed that the production of GSH, GSH-PX, and GST in the intestine were stimulated when exposing to the microplastics of lower concentrations (0.1 and 1 mg/L), while the production of SOD, CAT, GSH, GSH-PX were suppressed when exposing to those of 10 mg/L. The activities of enzymes in the muscle were much less affected. The intestinal injury and changes of colony structure in the intestine were observed by exposure to the tested concentrations of microplastics. By exposure to the microplasctics for 35 days, a further concurrent exposure to microplasctics and Aeromonas hydrophila did not exacerbate the mortality of zebrafish due to bacterial infection; on the contrary, the mortality was reduced. This study confirmed the intestinal enzyme activity changes of zebrafish, but showed no sign of inducing higher mortality or exacerbating bacterial infection by chronic exposure to the microplastics.