ORIGINAL ABSTRACT

Glyphosate (GLY) and Atrazine (ATZ) rank among the most widely used herbicides globally and frequently co-occur in coastal waters. These substances threaten the physiological integrity of filter-feeding bivalves like Mytilus galloprovincialis, which bioaccumulate contaminants, with consequent implications for the overall health of coastal ecosystems. Mussels were exposed for 14 days under controlled laboratory conditions to individual herbicides and their mixture. Biomarkers of metabolic function (electron transport system, ETS), antioxidant defense (SOD, GPx, TAC), detoxification (GST, CbE), oxidative damage (lipid peroxidation, LPO), and neurotoxicity (AChE) were analyzed in the digestive gland and gills. Furthermore, the transcriptional expression of stress-response genes (MT10, MT20, HSP70) and the DNA-damage marker p53 were analyzed via RT-qPCR to elucidate the molecular mechanisms of toxicity. The combined exposure to GLY and ATZ significantly elevated ETS activity and LPO levels while disrupting antioxidant and detoxification enzymes in both tissues, with responses most evident under the mixture treatment. At the molecular level, the combined treatment induced a significant upregulation of all tested genes, with p53 and HSP70 showing the most pronounced increases, indicating significant genotoxic and proteotoxic impairment. AChE inhibition in these organs indicated sublethal neurotoxicity. These findings reveal the complex toxicological effects of combined herbicide residues at environmentally relevant levels, providing data for ecological risk assessment in contaminated coastal ecosystems.