super(137)Cs concentration in zooplankton and its relation to taxonomic composition in the western North Pacific Ocean

• Published in: Journal of environmental radioactivity Vol. 99; no. 12; pp. 1838 - 1845
• Main Authors: Kaeriyama, Hideki, Watabe, Teruhisa, Kusakabe, Masashi
• Format: Journal Article
• Language: English
• Published: 01.01.2008
• Subjects: Copepoda; Marine; IN, North Pacific
• ISSN: 0265-931X
• DOI: 10.1016/j.envrad.2008.08.006

To study the role of zooplankton in the transport of super(137)Cs in the ocean, zooplankton samples were collected in October 2005 and June 2006 in the western North Pacific Ocean. The peak zooplankton biomass was observed in the surface layer, and gelatinous plankton was more abundant in October 2005 than in June 2006 reflecting exchange of water masses. The concentrations of super(137)Cs in zooplankton varied from 11 to 24 mBq kg wet super(-1) and were higher in October 2005 than in June 2006. The elevated abundance of gelatinous zooplankton probably led to higher concentration of super(137)Cs in zooplankton in October 2005. Annual export fluxes of super(137)Cs by ontogenetic vertical migrant copepods were estimated to be 0.8 and 0.6 mBq m super(-2) year super(-1) at 200 and 1000 m depths, respectively; this suggested that transport of super(137)Cs by zooplankton may be no trivial pathway. [Plankton samples were collected off the Rokkasho-mura coast.]