MEPS 160:109-120 (1997)  -  doi:10.3354/meps160109

Natural variation of radionuclide 137Cs concentration in marine organisms with special reference to the effect of food habits and trophic level

Fujio Kasamatsu*, Yusuke Ishikawa

Marine Ecology Research Institute, Tokyo Head Office, Teikoku Shoin Bldg, 3-29 Jinbo-cho, Kanda, Chiyoda, Tokyo 101, Japan

Although a number of measurements have been made on radiocesium concentrations in aquatic organisms, no clear agreement has been reached on the factors affecting accumulation of these radionuclides. Natural variations in the concentration of the long-lived artificial radionuclide 137Cs in marine organisms and factors affecting variations in marine fishes were investigated through long-term and systematic measurements in coastal waters of Japan from 1984 to 1995. Concentrations of 137Cs were measured in more than 30 species of crustaceans, cephalopods and teleosts considered representative of the marine biotic community. A clear positive correlation (p < 0.05) was found between mean weight and concentration of 137Cs in 276 fish samples. However, different relationships between 137Cs concentration and weight of fish were observed in different species. Within 16 studied species 137Cs concentration increased with growth for 4 species, while no specific correlation was observed in the remaining species. These different patterns depended on a change of food habits with growth. Analysis of 6066 stomach contents of fish samples together with 137Cs concentrations in the stomach contents demonstrated that 137Cs concentration increased with rising trophic level and that the biomagnification factor (137Cs in predator/137Cs in prey) was 2.0 (95% confidence interval 1.8 to 2.2). From the yearly change of 137Cs in 24 marine fish species, a mean effective environmental half-life of 137Cs of 13 ± 3 yr (range 10 to 17 yr) was calculated.

Trophic level · Food habits · Marine organisms · Bioaccumulation · 137Cs · Size-dependence · Environmental half-life

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