From fashion to the marine environments: Adverse effects of textile microfibers on <i>Crassostrea gasar</i>

The contamination of aquatic ecosystems by textile microfibers is a growing concern. Because bivalves continuously filter large volumes of water, they are particularly vulnerable to microfiber exposure, making them important indicators of emerging pollutants. The ingestion of microfibers by marine organisms can lead to bioaccumulation and biomagnification across the food chain, putting higher trophic levels at risk. This study evaluated the sublethal effects of three textile microfiber types and a mixed-fiber treatment (conventional cotton, polyester, their mixture and, organic cotton) at two exposure concentrations, a wastewater-impacted hotspot concentration (0.11 mg. L-1) and a higher level (1.00 mg. L-1), on the gills, and digestive gland, of Crassostrea gasar across 7, 14, and 21 days. Responses were assessed using biomarkers of biotransformation, antioxidant defenses, oxidative damage, genotoxicity, neurotoxicity, cytotoxicity, and survival rate. Exposure to microfibers induced multi-system toxicity with organ-specific response patterns. Reduced glutathione (GSH) levels and glutathione S-transferase (GST) activity increased in the gills but decreased in the digestive gland, whereas lipid peroxidation and DNA damage occurred in both organs. In addition, survival decreased significantly in oysters exposed to conventional cotton and mixed fibers at both concentrations (Log-rank test: cotton, P = 0.0302; mix, P = 0.0247). Among the evaluated microfiber types, organic cotton elicited the most pronounced integrated sublethal responses, as shown by notable biochemical and cellular disturbances. However, conventional cotton and mixed fibers had a more significant impact on survival, indicating that the microfiber hazard varies depending on the biological endpoint considered. These findings demonstrate that both natural and synthetic textile microfibers impair C. gasar's redox and cellular homeostasis, leading to oxidative damage and reduced survival, underscoring their ecological relevance as emerging contaminants, and the magnitude and dynamics of this toxicity depend on fiber type and exposure duration.