Microplastics induce toxic effects in fish: Bioaccumulation, hematological parameters and antioxidant responses.

This study investigates the toxic effects of microplastics by assessing bioaccumulation, hematological parameters, and antioxidant responses in juvenile Korean bullhead (Pseudobagrus fulvidraco) exposed to polyamide microplastics (PA-MPs). The increasing release of plastics into aquatic environments leads to their degradation into microplastics, which pose a significant threat to freshwater ecosystems. To evaluate these impacts, P. fulvidraco (mean length: 16.3 ± 1.1 cm, mean weight: 38.2 ± 6.6 g) were exposed to waterborne PA-MPs (white, spherical particles) at concentrations of 0, 10, 20, 5000 and 10,000 mg/L for 96 h. Bioaccumulation analysis revealed that PA-MPs primarily accumulated in the intestine, followed by the gills and liver. Hematological assessments showed significant reductions in hemoglobin and hematocrit levels at high PA-MP concentrations (5000 and 10,000 mg/L). Plasma biochemical analysis indicated significant alterations in calcium, magnesium, glucose, cholesterol, total protein, AST, ALT and ALP levels. In terms of antioxidant responses, superoxide dismutase (SOD) and catalase (CAT) activities increased significantly with PA-MP exposure, while glutathione S-transferase (GST) activity showed a marked decrease. These findings suggest that PA-MP exposure leads to bioaccumulation in key tissues and induces physiological stress in P. fulvidraco by altering hematological and antioxidant defense mechanisms, highlighting the potential toxicity of microplastics in freshwater fish.