Toxic Impact of Polystyrene Microplastics (PS-MPs) on Freshwater Mussel Lamellidens marginalis

Microplastics are among the most emerging environmental micro-threats to aquatic ecosystems. Bivalves are filter-feeding benthic organisms and are often considered excellent bioindicators of contamination in aquatic bodies. This study focuses on the toxic effects of fibrous polystyrene microplastics (1 mg/L) on biochemical parameters of the freshwater bivalve Lamellidens marginalis after exposure periods of 7, 10, and 15 days (Experimental groups I, II, and III, respectively). Biochemical analysis showed reduced protein, ACP, and ALP activities in all tissues except for a significant increase in ACP in the mantle and foot of group III. AST activity increased in the gill and hepatopancreas but declined in the mantle and foot. ALT activity consistently decreased across all experimental tissues relative to the control. The Integrated Biomarker Response Index increased over time for gill, mantle, and foot tissue. For the hepatopancreas, the values were 11, 8.82, and 9.02 for Experimental groups I, II, and III, respectively. From Biomarker Response Index values, group I gill tissue (2.2) was most severely altered. Major alterations occurred in the hepatopancreas, mantle, and foot of groups II and III. Hepatopancreas generally acts as a site of detoxification, digestion, and absorption, and exposure to microplastics can lead to the accumulation in hepatopancreas.