Biotransformation and toxicity of prometryn in mussel (Mytilus galloprovincialis): Carrier effects of polystyrene microplastics on biochemical and histopathological alterations.

Prometryn (PRO) is frequently detected marine contaminant that poses growing threats to aquatic products and human health. While the environmental risks of this pollutant have garnered increased attention, the biochemical and physiological effects of PRO on marine organisms in the presence of microplastics remain poorly understood. In this study, the bioaccumulation and toxicity of PRO in marine blue mussel (Mytilus galloprovincialis) at three concentrations, with the presence and absence of polystyrene microplastics (PS), were investigated using a semi-static seawater exposure system. Biomarkers related to antioxidant response (SOD, CAT, GSH-Px), metabolic detoxification (GSH, GST), and oxidative damage (MDA) were measured. Four metabolites of PRO were initially identified and quantified by Q Exactive Orbitrap high-resolution mass spectrometry. Histopathological alterations were examined using both light and electron microscopy. The results showed that PS significantly enhanced the uptake of PRO during co-exposure and accelerated its elimination during depuration. Most biomarkers exhibited concentration- and time-dependent changes, with the integrated biomarker response index (IBRv2) being higher in co-exposure groups than in those exposed to PRO or PS alone. Tissue damage, including structural disintegration of the digestive tubules, formation of cavities, and disorganization of the gill filaments, was markedly aggravated under combined exposure, with pronounced cellular vacuolation observed in the high concentration treated group. These findings provide critical insights into the synergistic impact of pesticides and microplastics in marine bivalves and highlight the need for comprehensive risk assessments of mixed pollution in aquatic products.