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Assessing Fukushima-derived radiocesium in migratory Pacific predators Daniel James Madigan, Zofia Baumann, Owyn E Snodgrass, Heidi Dewar, Michelle BermanKowalewski, Kevin C. Weng, Jun Nishikawa, Peter H Dutton, and Nicholas S. Fisher Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b00680 • Publication Date (Web): 17 Jul 2017 Downloaded from http://pubs.acs.org on July 18, 2017
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Assessing Fukushima-derived radiocesium in migratory Pacific predators
Daniel J. Madigan*1,2, Zofia Baumann2,3, Owyn E. Snodgrass4, Heidi Dewar5, Michelle BermanKowalewski6, Kevin C. Weng7, Jun Nishikawa8, Peter H. Dutton5 & Nicholas S. Fisher2
1
Harvard University Center for the Environment, Harvard University, Cambridge, Massachusetts 02138, United States 2 School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York 11794, United States 3 Department of Marine Sciences, University of Connecticut, 1080 Shenneconsett Road, Groton, CT 06340 4 Ocean Associates, Southwest Fisheries Science Center, NMFS, NOAA, La Jolla, California 92037, United States 5 Southwest Fisheries Science Center, National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), La Jolla, California 92037, United States 6 Channel Islands Cetacean Research Unit, Santa Barbara, California 93101, United States 7 Department of Fisheries Science, Virginia Institute of Marine Science, Gloucester Point, Virginia 23062, United States 8 Department of Marine Biology, School of Marine Science and Technology, Tokai University, 3-20-1, Orido, Shimizu, Shizuoka 424-8610, Japan
*corresponding author Harvard University 26 Oxford Street Cambridge, MA 02138 Ph: (617) 496-7199 Fax: (617) 496-7205 Email:
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ABSTRACT
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The 2011 release of Fukushima-derived radionuclides into the Pacific Ocean made migratory
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sharks, teleosts, and marine mammals a source of speculation and anxiety regarding radiocesium
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(134+137Cs) contamination, despite a lack of actual radiocesium measurements for these taxa. We
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measured radiocesium in a diverse suite of large predators from the North Pacific Ocean and
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report no detectable (i.e., ≥ 0.1 Bq kg-1 dry wt) of Fukushima-derived 134Cs in all samples, except
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in one olive ridley sea turtle (Lepidochelys olivacea) with trace levels (0.1 Bq kg-1). Levels of
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137
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were lower than naturally-occurring 40K by one to two orders of magnitude. Predator size had a
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weaker effect on 137Cs and 40K levels than tissue lipid content. Predator stable isotope values
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(δ13C and δ15N) were used to infer recent migration patterns, and showed that predators in the
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central, eastern, and western Pacific should not be assumed to accumulate detectable levels of
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radiocesium a priori. Non-detection of 134Cs and low levels of 137Cs in diverse marine
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megafauna far from Fukushima confirms negligible increases in radiocesium, with levels
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comparable to those prior to the release from Fukushima. Reported levels can inform recently
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developed models of cesium transport and bioaccumulation in marine species.
Cs varied within and across taxa, but were generally consistent with pre-Fukushima levels and
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INTRODUCTION The 2011 release of radionuclides from the damaged Fukushima Dai-ichi plant in Japan
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was historically the largest accidental release of radioactivity into global oceans, with an
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introduced inventory of at least 2.2 PBq to the North Pacific Ocean1. This event prompted
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radioactivity measurements in marine fish near Japan and, to a much lesser extent, in migratory
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species far from the release site. Radiocesium isotopes (134Cs and 137Cs) were of particular
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concern due to the large quantities discharged, their relatively long half-lives (2.1 and 30 y,
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respectively), and their tendency to accumulate in muscle tissue2. While low levels (~1.5 mBq L-
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1
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lived 134Cs had been undetectable in seawater and biota prior to the Fukushima release3.
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Therefore 134Cs in particular served as a distinct fingerprint of Fukushima-derived radiocesium in
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the North Pacific Ocean4-6.
) of longer-lived 137Cs persisted in the North Pacific Ocean due to weapons testing, the short-
Following the radioactive spill from the damaged power plant into coastal Pacific,
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Fukushima radiocesium began dispersing throughout the North Pacific, with concentrations
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ranging from 100 mBq L-1 in the western waters in 2011 to 10 mBq L-1 in 20127. In 2011 the
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elevated 137Cs levels were constrained to the western basin (140-180°E), and were on the order of
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102 -103 and decreased by an order of magnitude during 2012. In the months following the spill
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134
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1.8 mBq L-1)8. Interestingly, two months following the disaster 134Cs was detected at mid-latitude
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areas across the North Pacific, with levels
