Concentration‐Dependent Growth, Survival and Tissue Responses of Asian Seabass ( Lates calcarifer ) Fingerlings Following Short‐Term Dietary Exposure to Polyethylene Microplastic

ABSTRACT

Microplastics (MPs) are emerging aquatic pollutants that may impair fish health through ingestion and tissue‐level toxicity. This study evaluated whether short‐term dietary exposure to fluorescently labeled polyethylene microplastics (PE‐MPs) produced concentration‐dependent changes in growth, survival, intestinal morphology, and skeletal‐muscle integrity in Asian seabass fingerlings. Fish were fed diets containing 0, 1, 10, and 100 g PE‐MPs/kg diet until cumulative mortality reached the predefined 50% endpoint in the highest exposure group, which occurred on day 16. Growth performance, survival, apparent dietary LC50, intestinal morphometry, muscle histopathology, and PE‐MPs‐associated fluorescent signals were assessed. Dietary PE‐MPs exposure reduced growth performance and survival in a concentration‐dependent manner. The control group exhibited 76.67% survival with mortality primarily attributed to observed cannibalism. Although no cannibalistic behavior was observed in the PE‐MP‐treated groups, survival was progressively reduced with increasing dietary PE‐MPs concentration, reaching 43.33% at 100 g PE‐MPs/kg. After correction for background mortality, the apparent dietary LC50 was estimated at 20.19 g PE‐MPs/kg diet, although this value should be interpreted cautiously due to elevated control mortality associated with cannibalism, which was not observed in PE‐MPs‐treated groups. Histological analysis revealed reduced villus height, increased villus width and intestinal diameter, and progressive disruption of intestinal architecture. Muscle tissues showed fiber disconnection, degeneration, edema, fiber splitting, shrinkage, inflammatory cell infiltration, and necrosis, particularly at higher PE‐MPs levels. PE‐MPs‐associated fluorescent signals were detected in intestinal and muscle sections of exposed fish, especially at 10 and 100 g PE‐MPs/kg diet, but not in controls. These findings suggest that dietary PE‐MPs can impair survival, growth, and tissue integrity in L. calcarifer fingerlings, highlighting potential risks to aquaculture nursery systems.