| Popis: |
Zooplankton samples were collected at about 50 m depth with a large ring net (160-cm mouth diameter, 0.5-mm mesh) in May, June, October 2005 and June 2006 off Rokkasho, Japan where a nuclear fuel reprocessing plant will be in full-scale operation in the near future. Planktons in each sample were separated based on their species. Five samples were used for determination of 137Cs concentration and the other 21 samples for its stable isotope, Cs along with some other trace elements. All the samples were characterized by five dominant species, i.e. euphausiids, chaetognaths, copepods; Neocalanus spp., amphipods; Themisto spp. and Cyphocaris sp. Plankton samples were also taken at three to five discrete depths between the surface and ? 1,000 m in depth during daytime and nighttime for analysis of vertical distribution patterns of biomass, and for assessment of daily vertical migration activity. |
