Application of the Marine organisms as a Biological Monitor to Evaluation of the Background Levels of Radioactivity in the Coastal Environment

A study was carried out for investigating the availability of marine organisms such as a common species of brown and green algae (Sargassum thunbergii and Bryopsis sp.), and mollusks including some species of gastropods of the family of Buccinum and squids (Todarodes pacificus, Thysanoteuthis rhombus, etc.) for exploring in the marine environment the background levels of 99Tc, radium and its progenies, and 108mAg, respectively. The geographically wide distribution of the organisms above mentioned made it possible to compare the background levels of radioactivity from coast to coast in Japan. In addition, the comparison of the specific activity of 108mAg in the viscera of the mollusks among the species inhabiting in the layers at different depths allowed drawing a general trend of vertical distribution for the nuclide. All the organisms except gastropods studied here were known to have one year\u27s span of life. The burden of radionuclides in the organisms, therefore, resulted from the uptake not in the past years, but that in the most recent year during which they lived. They are expected to be used as a monitor extremely sensitive to the counterpart radionuclides. The application of biological monitors to the environmental monitoring programme would be useful especially for tracing the behaviour of long-lived radionuclides such as 99Tc (half-life: 2.111 x 105 y) and 108mAg (half-life: 418.21 y) along with naturally occurring radionuclides, which might be accumulated in the marine ecosystem.11th International Congress of the International Radiation Protection Associatio