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

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