Ecotoxicological assessment of microplastics and florfenicol on Acanthopagrus latus: mucus, humoral immune responses and DNA damage

This study evaluated the adverse effects of florfenicol (FLO) (15 mg/kg diet) and microplastics (MPs) (100 and 500 mg/kg diet) on yellowfin seabream, Acanthopagrus latus, over a 10-day exposure period. Fish were exposed to these substances individually and in combination. Tissue, blood, and skin mucus samples were collected on days 1, 4, 7, and 14 post-exposure. Results indicated that both MPs alone and combined with FLO elevated cholesterol, triglyceride, urea, creatinine, and glucose levels. The activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase, alkaline phosphatase (ALP), and creatine kinase were also increased. Conversely, immunological markers such as complement 3, complement 4, immunoglobulin M, lysozyme activity, phagocytic activity, respiratory burst activity, and total protein concentrations decreased. Similar to blood results, the concentrations of alternative complement, total immunoglobulin, lysozyme, and total protein in the mucus were reduced, whereas ALP levels in the mucus increased. These biomarkers did not recover by day 14 in groups exposed to MPs alone or with the antibiotic. FLO concentration in muscle peaked on day 1 and declined by the end of the trial. The FLO alone affected creatinine, cholesterol, total protein, AST, ALT, ALP, and immunological markers, all of which returned to normal by the conclusion of the trial. FLO did not influence the total immunoglobulin in the mucus. MPs, individually and in combination, increased DNA damage in the liver, kidney, spleen, and intestinal tissues. The findings demonstrate that FLO and MPs detrimentally impact fish health, with a more pronounced effect when combined, indicating synergistic toxicity.