Tritium forms and food availability modulate biological effects in marine mussels

During the decommissioning and normal operation of nuclear facilities, radionuclides like tritium (³H) that are associated with building materials (e.g., steel and cement), may be released as dusts. Tritiated particles ultimately reach the hydrosphere where they can bioaccumulate. In the present study, tissue-specific bioaccumulation and a range of biological responses were determined in the marine mussel, Mytilus galloprovincialis. Mussels were exposed for 72 h to: (a) tritiated stainless steel particles (T-SSPs), (b) T-SSPs + Algae, (c) tritiated water (HTO), (d) HTO + Algae. Use of HTO allowed discrimination between dissolved and particulate ³H accumulation while algae enabled assessment of the influence of food. Results showed that ³H accumulated mainly in the digestive gland (DG), and its accumulation was significantly higher in mussels exposed to T-SSPs compared to HTO at the same activity concentration, regardless of the presence of food. DNA damage determined using comet assay in haemocytes was evidenced after T-SSPs treatments, but not for mussels exposed to HTO. Clearance rate, a physiological parameter, was significantly increased after exposure to T-SSPs + Algae. Biochemical assays conducted in the DG showed a decrease in protein carbonyl content after exposure to HTO + Algae and T-SSPs + Algae, while autophagy levels increased following exposure to HTO regardless of the presence of food, and in mussels exposed to T-SSPs in the absence of food. Multivariate analysis and predicted 'scope for growth' suggested an adverse effect at the whole organism level following treatment with both T-SSPs and HTO, while the presence of food altered ³H bioaccumulation distribution. Our findings highlight the importance of studying accumulation of T-SSPs and the potential for biomagnification of radionuclides.