Metabolic and oxidative stress biomarker responses to enhanced levels of natural radioactivity in three edible bivalve species

Despite the known contribution of industrially derived natural radioactivity, also known as Naturally Occurring Radioactive Material (NORM), to animal and human radiation dose via seafood consumption, its ecotoxicological effects on marine organisms remain poorly understood. In particular, the physiological responses of bivalve molluscs to enhanced natural radioactivity have not been studied under controlled conditions. We conducted laboratory exposure experiments on three edible bivalve species, Cresstoderma edule, Mytilus edulis and Magallana gigas, selected for their ecological relevance and economic importance, with the aim to evaluate metabolic and oxidative stress responses to enhanced levels of natural radioactivity. Cellular energy allocation (CEA) and glutathione S-transferase (GST) assays were used as indicators of physiological stress. These assays commonly provide insight into energy budgeting and detoxification processes and are widely used in ecotoxicological studies. Results revealed significant metabolic and oxidative stress effects in all exposed groups with evidence of 210 Po and 210 Pb bioaccumulation from the surrounding water. These findings suggest that bivalves under radiological stress may experience compromised physiological function, with potential implications for population health and welfare. Importantly, this study represents the first experimental investigation linking biomarker responses to natural radioactivity in edible bivalves, offering a novel approach for assessing the ecological risks associated with the presence of NORM in coastal environments.