Environmental contamination with polystyrene micro and nano plastic affects Mytilus galloprovincialis ovaries.

Polystyrene micro- and nanoplastics (MNP) are persistent pollutants in aquatic environments worldwide. Once ingested, they accumulate in tissues and induce oxidative and cellular stress responses, leading to various adverse effects. However, their impacts on invertebrate reproductive systems remain poorly understood. In this study, we examined the effects of 5 μm microplastics (MP) and 0.1 μm nanoplastics (NP) on the ovaries of Mytilus galloprovincialis, a species commonly used as a bioindicator of coastal pollution. Both particles increased reactive oxygen species and lipid peroxidation while decreasing superoxide dismutase 2 expression. The redox imbalance was closely associated with significant changes in protein expression and cytoskeletal organisation. Disruption of vimentin and tubulin expression occurred alongside a displacement of cytosolic actin. Especially in ovaries exposed to NPs, these effects were accompanied by a markedly reduced oogonial proliferation and a higher rate of oocyte atresia. Caspase-3 activity and the BCL2 antagonist/killer Bak BAK expression corroborated these findings. Lectin-based analyses revealed significant changes in fucose, mannose, and N-acetylglucosamine residues in oocytes and adipogranular cells, confirming disturbances in protein glycosylation. Overall, the combined biochemical, structural, and molecular evidence suggests that both MP and NP severely disrupt oocyte maturation and diminish reproductive potential in M. galloprovincialis. Given mussels' ecological role as essential benthic filter feeders and sentinel organisms, these findings raise concerns about potential long-term impacts on population dynamics and coastal ecosystem resilience and highlight the urgent need for risk mitigation measures.