Revealing the effects of polystyrene microplastics and di(2-ethylhexyl) phthalate on mussels:An evidence chain of gill-intestine-hemolymph

Polystyrene microplastics (PS-MPs) and di(2-ethylhexyl) phthalate (DEHP) are widespread contaminants in marine ecosystems, posing significant risks to marine life due to their toxicity and interactions with other pollutants. This study evaluates the combined effects of PS-MPs and DEHP on Mytilus coruscus, focusing on physiological and immune responses over a 30-day exposure. Results showed significant morphological changes in gill structures, including reduced lamella dimensions and thinner stromal tissue, impairing gas exchange. Key enzymatic activities related to energy metabolism were altered, with LDH, SDH, and HK activities suppressed and PK activity increased, indicating a shift in energy regulation. ATPase activity decreased while ROS activity rose, suggesting oxidative stress. Changes in digestive enzyme lipase activity were noted alongside modifications in gut microbiota under high pollutant concentrations. Immune markers showed decreased THC, PHA, and EA levels, with increased HM, indicating immune disruption. Antioxidant defenses were activated, evidenced by elevated SOD, CAT, GPX, and GSH activities, yet increased MDA levels indicated lipid peroxidation. These findings establish a pollutant cascade mechanism linking tissue damage, metabolic reprogramming, and microbial imbalance, providing critical data for marine risk assessment.