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Marine Ecology Progress Series

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MEPS 535:1-9 (2015)  -  DOI:

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

Tuguya Nakamura1, Osamu Kimura2, Ayaka Matsuda3, Takashi Matsuishi3, Mari Kobayashi4, Tetsuya Endo2,*

1Hokkaido Pharmaceutical Association Public Health Examination Center, 1-8-6-6 Hiragishi, Toyohira-Ku, Sapporo, Hokkaido 062-0931, Japan
2School of Pharmaceutical Sciences, Health Sciences University of Hokkaido, 1757 Kanazawa, Ishikari-Tobetsu, Hokkaido 061-0293, Japan
3Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido 041-8611, Japan
4Faculty of Bioindustry, Tokyo University of Agriculture, 196 Yasaka, Abashiri, Hokkaido 099-2493, Japan
*Corresponding author:

ABSTRACT: We analyzed radiocesium (134Cs and 137Cs) levels in the muscle tissue of several odontocetes and mysticetes stranded on the coast of Hokkaido (the northernmost island of Japan) in 2011 and 2012, following the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March 2011. Since most of the radiocesium from the FDNPP was released into the western North Pacific Ocean and carried eastward from the Japan coast, there was little radiocesium contamination in the seawater around Hokkaido. Hokkaido is surrounded by the North Pacific Ocean, the Japan Sea, and the Okhotsk Sea, but radiocesium was predominantly detected in the cetaceans stranded along the North Pacific coast between June and October 2011. Among the stranded cetaceans, which included the Pacific white-sided dolphin, harbour porpoise and Dall’s porpoise (odontocetes) as well as the common minke whale and humpback whale (mysticetes), the highest level of contamination was found in a common minke whale. The radiocesium contamination of these cetaceans suggests that they moved seasonally from the south of Hokkaido, particularly through the contaminated area of the western North Pacific Ocean. The radiocesium levels in the tissues of these animals is likely a result of the contamination level of the seawater along their travel route, rather than their trophic level, because of the sudden changes in radiocesium transport and diffusion in seawater that occurred in 2011.

KEY WORDS: 134Cs · 137Cs · Lagenorhynchus obliquidens · Phocoena phocoena · Phocoenoides dalli · Balaenoptera acutorostrata · Megaptera novaeangliae

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Cite this article as: Nakamura T, Kimura O, Matsuda A, Matsuishi T, Kobayashi M, Endo T (2015) Radiocesium contamination of cetaceans stranded along the coast of Hokkaido, Japan, and an estimation of their travel routes. Mar Ecol Prog Ser 535:1-9.

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