Ecotoxic effects of low concentrations of polyethylene and polylactic acid microplastics on juvenile marine medaka (oryzias melastigma)

The ecotoxicological impacts of microplastics (MPs) on aquatic organisms have garnered considerable attention; however, the toxic effects of MPs on aquatic organisms at environmentally relevant concentrations have been underreported. In this study, juvenile marine medaka were exposed to polyethylene and polylactic acid at concentrations of 20 μg/L for a duration of 60 days. The findings revealed that prolonged exposure to different types of MPs at low concentrations did not exhibit significant detrimental effects on the growth and intestinal tissues of juvenile fish. Nonetheless, long-term exposure led to alterations in gut microbial composition in juvenile fish, potentially influencing their functional roles. PICRUSt2 prediction analysis demonstrated a significant down-regulation in Isoleucine Biosynthesis function within the PE-exposed group at Level 3. Overall, further attention is warranted regarding the adverse consequences associated with prolonged exposure to environmental MPs on aquatic organisms.