Bioaccumulation and Toxicity of Tritiated Water in Jellyfish.

Global nuclear power capacity is expanding rapidly, with most facilities located along coastlines. Tritiated water (HTO) is a significant radioactive byproduct of nuclear power plants and is routinely discharged into the oceans. Despite widespread release, radioecological impacts of HTO on marine zooplankton remain poorly understood. Of particular concern are jellyfish, which are composed of >95% water and distributed throughout the oceans, potentially rendering them highly susceptible to tritium bioaccumulation. This study provides the first comprehensive assessment of HTO bioaccumulation, organically bound tritium (OBT) formation and toxicity in two common jellyfish species, Rhopilema esculentum and Aurelia aurita, after exposure to environmentally relevant levels of HTO. Both species demonstrated HTO bioaccumulation (factor of 23-43), with preferential formation of protein-associated organically bound tritium. Both species exhibited swimming impairments and tissue-level responses. R. esculentum showed dose-dependent dysfunction with vacuolization and apoptosis, while A. aurita displayed a general decline with preserved tissue architecture and negligible apoptosis. Human dietary risk assessment of jellyfish consumption yielded annual equivalent doses of 0.005-0.018 mSv yr-1, well below the ICRP public dose limit of 1 mSv yr-1. These findings demonstrate that jellyfish may serve as valuable bioindicators for assessing the impacts of nuclear wastewater (HTO).