Nakamura T, Kimura O, Matsuda A, Matsuishi T, Kobayashi M, Endo T

Radiocesium contamination of cetaceans stranded along the coast of Hokkaido, Japan, and an estimation of their travel routes

The disruption to the Fukushima nuclear power plant in northern Japan in March 2011 resulted in ¹³⁴Cs and ¹³⁷Cs contamination over a large area of the western North Pacific Ocean. However, little radiocesium contamination was observed in the seawater around Hokkaido, the northernmost island of Japan, due to the Oyashio Cold Current that flows north to south along the western North Pacific Ocean. Nevertheless, radiocesium was detected in Pacific white-sided dolphins and some cetaceans stranded along the North Pacific Ocean coast of Hokkaido between June and October 2011. The radiocesium contamination in these cetaceans suggests that they had travelled from more southerly areas, particularly the contaminated area of the western North Pacific Ocean near the Fukushima nuclear power plant.

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