Effect of polystyrene nanoplastics on the intestinal histopathology, oxidative stress, and microbiota of Acrossocheilus yunnanensis

Even though extensive research exists on the negative impact of nanoplastics on fish, their effect on the microbiota and intestinal health of freshwater fish remains unclear. This study investigated the impact of polystyrene nanoplastics (PS-NPs) on the microbiota, oxidative stress, and intestinal morphology of the Acrossocheilus yunnanensis (A. yunnanensis) freshwater fish species. The findings demonstrated that PS-NPs induced structural changes (e.g., epithelial rupture and microvilli damage) in the intestinal tissue of A. yunnanensis. Meanwhile, they increased the level of malondialdehyde (MDA) and the activity of superoxide dismutase (SOD) in the intestine, but did not significantly cause changes in the activities of catalase (CAT) and glutathione S-transferase (GST) enzymes. The microbiome results indicated that PS-NPs increased gut microbial community diversity and Proteobacteria abundance while decreasing the Fusobacteriota content. Furthermore, PS-NPs significantly improved multiple microbial functions such as amino acid and lipid transfer and metabolism, as well as energy generation and conversion. Overall, this study revealed that PS-NPs caused oxidative stress and microbiota dysbiosis in A. yunnanensis, possibly causing intestinal epithelial damage. This research elucidates the mechanism underlying PS-NP toxicity to freshwater fish and its subsequent impact.