Biomarker Responses in the Marine Mussel Mytilus Edulis Indicate Significant Toxicological Effects of Polyethylene...

This study investigated the short‑term effects of polyethylene microplastics (PE‑MPs) on the marine mussel Mytilus edulis using a suite of cellular and subcellular biomarkers. A total of 225 mussels were collected from Umluj, Saudi Arabia, a relatively unimpacted coastal area of the Red Sea, and experimentally exposed for 72 h to spherical PE‑MPs (50 μm diameter) at nominal concentrations of 5, 10, 20, and 60 particles L^-1. Genotoxicity, oxidative status, and cellular integrity were assessed by comet assay, thiobarbituric acid‑reactive substances (TBARS), superoxide dismutase (SOD) activity, and lysosomal membrane stability (LMS). At 60 particles L^-1, DNA strand breakage increased markedly in hemocytes (13.09%) and gill cells (12.21%) relative to controls (2.14%; p < 0.01). Lipid peroxidation was 1.28 nmol TBARS mg protein^-1, and activity of gill SOD was decreased by 16.13% of control. LMS was significantly reduced from 134.4 min in controls to 53.2 min in the highest exposure (p < 0.01), suggesting impaired cellular homeostasis. Given the short exposure duration, these results are preliminary. They indicate that acute PE-MP exposure at the tested concentrations is associated with measurable genotoxicity, oxidative stress, and reduced lysosomal stability. Longer-term ecological implications remain to be investigated.