Integrated multi-tissue analysis reveals distinct oxidative and metabolic reprogramming in response to contrasting microplastics in Mytilus coruscus.

Microplastic (MP) pollution poses increasing ecological risks to marine filter feeders, yet how different MP characteristics collectively influence biological toxicity and environmental redistribution remains poorly understood. In this study, the mussel Mytilus coruscus was exposed to two representative MPs, laboratory-model polyethylene (PE) microbeads and environmentally relevant and polyethylene terephthalate (PET) microfibers, to investigate particle fate, tissue distribution, energy metabolism, and antioxidant responses. Mussels rapidly removed >90% of suspended MPs from the water column within 72 h, facilitating particle transfer to tissues and sediments. However, the two MPs induced markedly different distribution patterns and physiological responses. PET microfibers showed substantially greater retention in gill tissues (∼30%) than PE microbeads (<10%), accompanied by reduced clearance efficiency and persistent oxidative stress characterized by elevated lipid peroxidation after depuration. In contrast, PE microbeads mainly induced metabolic compensation through enhanced ETS activity and mobilization of energy reserves. Tissue-specific responses further revealed functional differentiation between gills and digestive glands in particle processing and physiological regulation. The results demonstrate that combined differences in MP morphology, composition, and structure are likely associated with distinct environmental fates and organismal stress strategies. These findings provide new insight into how environmentally realistic MPs shape tissue-specific physiological strategies in marine filter feeders and highlight the importance of particle heterogeneity in MP ecotoxicology.