Temporal Changes in Cs-137 Concentrations in Fish, Sediments, And Seawater off Fukushima Japan

We analyzed publicly available data of Fukushima Cs-137 concentrations in coastal fish, in surface and bottom waters, and in surface marine sediments and found that within the first year of the accident pelagic fish lost Cs-137 at much faster rates (mean of similar to 1.3% d(-1)) than benthic fish (mean of similar to 0.1% d(-1)), with benthopelagic fish having intermediate loss rates (mean of similar to 0.2% d(-1)). The loss rates of Cs-137 in benthic fish in the first year were more comparable to the decline of Cs-137 concentrations in sediments (0.03% d(-1)), and the declines in pelagic fish were more comparable to the declines in seawater. Retention patterns of Cs-137 in pelagic fish were comparable to that in laboratory studies of fish in which there were no sustained Cs-137 sources, whereas the benthopelagic and benthic fish species retained Cs-137 to a greater extent, consistent with the idea that there is a sustained additional Cs-137 source for these fish. These field data, based on 13 511 data points in which Cs-137 was above the detection limit, are consistent with conclusions from laboratory experiments that demonstrate that benthic fish can acquire Cs-137 from sediments, primarily through benthic invertebrates that contribute to the diet of these fish.