Abstract

Microplastics (MPs), as a ubiquitous environmental contaminant in marine and freshwater systems, produced a significant influence on the physiological characteristics of aquatic organisms, and inevitably posed unknown effects on their swimming capacity. Herein, we evaluated the MPs accumulation in potamodromous fish, Ctenopharyngodon idellus, and their potential effects on oxidative stress, neurotoxicity, gut microbial diversity, and swimming capability through a toxic-control experiment. Juvenile fish were exposed to 5 µm polystyrene-MPs (PS-MPs) for 6 days at concentrations of 0.1, 1, and 10 mg/L. Exposure to PS-MPs resulted in significant inhibition of acetylcholinesterase (AChE) in the brain of fish, with significant increases in superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels at 1 and 10 mg/L exposures. Meanwhile, MPs altered grass carp gut microbiota and reduced the Shannon diversity index. In addition, MPs significantly increased induced swimming speed by observing the flow rate at which grass carp happened to produce a reverse current behavioral response. The 1 and 10 mg/L of MPs treatments can significantly reduce the critical swimming speed of grass carp, meaning that the completion of the life history of grass carp may be delayed. Furthermore, there were significant correlations between biomarkers and indicators of swimming capacity. Therefore, the present study suggests that MPs produced a negative effect on the physiological properties of fish, reducing the swimming capacity of migratory fish.