Bioaccumulation, oxidative stress, immune disruption, and metabolic alterations in Mytilus galloprovincialis exposed to nano-copper oxide.

Nano‑copper oxide (CuO NPs), as a highly promising antibacterial agent in aquaculture, has demonstrated excellent performance against pathogens affecting cultured organisms. However, its application is accompanied by potential toxicity risks to both the cultured organisms and the entire aquatic ecosystem. In this study, CuO NPs was synthesised using a sodium hypophosphite liquid-phase reduction method, and then a toxicity experiment was conducted using 50 μg/L CuO NPs in M. galloprovincialis. Multiple endpoints at Cu distribution, enzyme activity, lipid peroxidation degree, immune-related gene expression, tissue pathology, and metabolic response were assessed in response to CuO NPs exposure. The multi-biomarker approach revealed that CuO NPs toxicity in M. galloprovincialis operated through a coordinated network of effects: tissue-specific Cu accumulation drives histopathological damage, oxidative stress, immune disruption and ultimately systemic metabolic reprogramming. At the metabolomic level, CuO NPs exposure induced a two-system metabolic shift in M. galloprovincialis, featuring lipid upregulation and amino acid downregulation, and six metabolites (three oxylipins up, three amino acids down) that highlighted their potential as sensitive biomarkers for nanomaterial contamination. These molecular-level alterations eventually led to pathological changes in the hepatopancreas and gills. The study could provide a theoretical basis for the toxicity assessment of nanomaterials in bivalves and offer effective support for environmental risk assessments.