The Fukushima Daiichi power station released several radionuclides into the Pacific following the March 2011 earthquake and tsunami. A total of 26 Pacific albacore (Thunnus alalunga) caught off the Pacific Northwest U.S. coast between 2008 and 2012 were analyzed for (137)Cs and Fukushima-attributed (134)Cs. Both 2011 (2 of 2) and several 2012 (10 of 17) edible tissue samples exhibited increased activity concentrations of (137)Cs (234-824 mBq/kg of wet weight) and (134)Cs (18.2-356 mBq/kg of wet weight). The remaining 2012 samples and all pre-Fukushima (2008-2009) samples possessed lower (137)Cs activity concentrations (103-272 mBq/kg of wet weight) with no detectable (134)Cs activity. Age, as indicated by fork length, was a strong predictor for both the presence and concentration of (134)Cs (p< 0.001). Notably, many migration-aged fish did not exhibit any (134)Cs, suggesting that they had not recently migrated near Japan. None of the tested samples would represent a significant change in annual radiation dose if consumed by humans.
Bioaccumulation of cesium with increasing trophic position is well known across nearly every ecosystem for most organisms. In the marine environmental, typical (concentration ratios (Bq/kg in tissue: Bq/kg in seawater) range from 50-100 in lower trophic levels to 300-10,000+ for apex predators. Recent surveys of 7 gelatinous organisms off the coast of Oregon ranging in trophic position from 1.0 to 3.0 revealed a concentration ratio maximum of 12.5 and typical concentration ratios no higher than 4.4. The implications on human diets and ecosystem shifts for large radiocesium releases are discussed.
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