Effect of sediment-bound radionuclides on marine organisms

Seashore sediments labeled with radioisotopes were administered to a marine demersal fish, right-eye flounder assuming the ingestion of radioactive sediment with prey by the fishes. Whole-body retention of radioactivity was observed for about a week. The leaching rates of the radionuclides from the sediment suggested that a notable fraction of 54Mn, 60Co, 65Zn, and 137Cs is desorbed from the sediment in the digestive tract of the fishes, whereas 59Fe, 95Zr - 95Nb, 106Ru, and 144Ce are not easily leached. The whole-body retention patterns of the radionuclides, characterized by the peeling off method, showed elimination of radioactivity in two components by the fishes. Rapid loss of radioactivity during 2 or 3 days after administration suggested the elimination of unassimilated radionuclides with excretion of the sediment; the following slower decrease of radioactivity was considered to represent the loss of radionuclides absorbed by the fishes. A higher contribution of the long component observed in the whole-body elimination patterns suggested the absorption of 54Mn, 60Co, 65Zn, and 137Cs through the digestive tract of the fishes, but more than 96% of the administered dose was lost with short half-lives in the case of 59Fe, 95Zr - 95Nb, 106Ru, and 144Ce. Distribution of radioactivity in the fish bodies was examined by comparing the concentration of radionuclide in the intestine with that in other parts of the fishes and showed a rapid transfer of most of the nuclides to the liver and kidney despite the short period after a single administration of the sediment. (author)