UV-aging exacerbates the diversified toxicity of microplastics in the gut of gibel carp (Carassius auratus gibelio)

Freshwater aquaculture systems are among the ecosystems most severely impacted by microplastics (MPs) pollution. Of particular concern is that the aging of MPs may further intensify their adverse effects on these systems. However, the impacts of aging on MPs toxicity remain inadequately characterized, particularly regarding how aging affects different types of MPs. Herein, we selected virgin and aged polyethylene (PE) and poly (butyleneadipate-co-terephthalate) (PBAT) MPs to investigate how ultraviolet (UV) aging impacts the toxicity of MPs to intestinal health and microbial community in an economically important fish species, gibel carp (Carassius auratus gibelio). Results demonstrated that both virgin and UV-aged MPs (PE and PBAT) induced intestinal damage and microbial dysbiosis in gibel carp. Comparatively, UV-aging significantly exacerbated these adverse effects. Notably, UV-aged PE-MPs were more prone to aggravating intestinal damage, while UV-aged PBAT-MPs exhibited a greater propensity to disrupt the gut microbial community. We speculate that the underlying causes for this phenomenon are related to the physicochemical properties of MPs. Overall, the structurally stable aged PE-MPs, with their increased surface roughness accompanied by reactive oxygen species generation, exacerbate intestinal damage; whereas the unstable nature of aged PBAT-MPs induces the release of low-molecular-weight substances that lead to more severe disruption of the gut microbial community. In conclusion, this study underscores the differential toxicity and potential threats posed by UV-aged MPs to economically important fish species, providing valuable insights for assessing ecological risks of MPs in freshwater aquaculture environments.