Table 1.

Concentrations of naturally occurring 40K and Fukushima-derived radionuclides (137Cs, 134Cs, and 110mAg) in marine organisms collected off Japan's coast (Bq⋅kg−1 dry weight)

137Cs134Cs137Cs134Cs110mAg40K
Sampling methodStationSample compositionAbundance of dominant species, %Bq⋅kg−1, dry weightCFBq⋅kg−1, dry weight134Cs:137Cs134Cs:110mAgAnthropogenic: natural radioactivity ratio
Bongo nets, 300 μm2Zooplankton mixedCopepods500.3bd134bd1.9217bdbd0.01
3706.46.2*bd1.32291.04.70.06
88014.315.19810518.33211.10.80.07
9921.21.216173.31561.00.40.04
10714.74.627266.51471.00.70.11
11613.13.929365.31261.30.70.10
12727.28.877988.71481.21.00.17
146556.445.5**0.01880.8bd0.54
17470.9bd255bd0.5195bdbd0.01
196512.815.0535912.02321.21.20.17
215217.320.7788811.12251.21.90.22
22794.54.220195.11290.90.80.11
235829.131.4343621.51811.11.50.45
246512.815.528535114.01971.21.10.21
255126.229.444496.32721.14.70.23
278419.925.4273312.41941.32.00.30
297634.238.0101014.42301.12.60.38
Median12.815.144366.5195
Mean14.817.779718.4199
SD14.913.785906.451
Methot net, 4 mm25ScyphomedusanChrysaora sp.10011.111.919203.41971.13.50.13
19EuphausiidsEuphausia pacifica882.34.591820.61962.00.20.14
2510023.427.2394515.72141.21.70.31
29EuphausiidsNematoscelis difficilis8615.116.34411.51821.11.40.24
32Fish, shrimps, euphausiids, pyrosomatids mixedndnd3.16.892023.62782.20.30.12
Median9.111.691918.2205
Mean11.013.7162217.9217
SD10.110.316175.342
19FishStenobrachius leucopsarus504.93.32013bd1440.7bd0.06
27FishCyclothone pseudopallida, Sigmops gracile40, 4011.411.91615bd2321.0bd0.10
29FishS. gracile6315.814.844bd1290.9bd0.24
Median11.411.91613bd144
Mean10.710.01311bd168
SD5.56.086bd55
  • Natural radioactivity refers to the sum of gamma radioactivity emitted by 40K (>99% of total natural radioactivity), 212Pb, 235U, 211Bi, and 7Be. Concentration factors (CFs) were calculated using surface ocean concentrations (Table S1). The biological composition of the samples is shown as percent of total abundance. bd, below detection; nd, not determined; sp, species unidentified.

  • *In this sample, CFs of 134Cs and 137Cs are five orders of magnitude higher due to very low surface ocean Cs, and therefore not included in mean or median CF values.

  • Considers nongelatinous zooplankton only.