Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Counts and concentrations of Cs134, Cs137, Ag110m, and K40 detected in zooplankton and small fish samples are reported. Samples were collected as part of a radioecological study of biota in order to assess the impact of radiation leaks from the Fukushima Daiichi nuclear power facility, damaged by a March 11, 2011 earthquake and tsunami. Radionuclide results were determined from high purity germanium detectors and calibrated against IAEA standards as described in Buesseler et al. (PNAS, 2012).

Mixed zooplankton samples were sampled using Bongo nets (mesh size = 300 micromol and Methot net (mesh size = 4mm) to collect gelatinous zooplankton, larger crustaceans and fish. Samples collected were pooled together from several casts to achieve biomass needed for radioanalysis. Samples were frozen prior to freeze-drying. Samples that were freeze-dried and ground were stored and analyzed in straight side Nalgene 4oz jar; powdered mass was compressed by a polyacrilamide ring placed on top to assure uniform distribution of the sample in the jar. Biological samples were analyzed using a planar low energy germanium detector - LEGe, Canberra, Model GLP 3830 with a 3800 mm2 active area; Genie 2000 software was used for spectrum analysis.

Total counting efficiencies that accounted for sample geometry and for energy emission were calculated based on standards composed of Se-75, Cs-137 and Eu-152 (265 keV, 662 keV and 1408 keV, respectively). We also accounted for the branching ratio and the concentrations were decay-corrected back to April 6th, 2011 The error reported reflects the % counting error. The lower end of the detection was decided based on the lowest among the samples radionuclide concentration minus one error. We did not correct for coincidence summing. An algorithm used for making these corrections - i.e. total % counting efficiency was: CEtot% = ((-6.24 * ln(sample volume) + 48.23) * (13.74 * energy * ^(-0.79)))/100;

nd = not determined
bd = below detection

The March 11, 2011 earthquake in Japan and the subsequent tsunami damaged and disrupted cooling systems at the Fukushima Daiichi nuclear power facility causing contamination of land and seas surrounding the site, as well as food supplies and drinking water. Small but measurable quantities of radioactivity have been detected in the atmosphere over the United States, including aerosol samples collected at the Woods Hole Oceanographic Institution, where I-131 was seen to increase to detectable levels as of March 21-22, 2011.

With major funding from the Moore Foundation, as well as a contribution from the National Science Foundation through a 2011 Grant for Rapid Response Research (RAPID) and support from the Woods Hole Oceanographic Institution, collaborating investigators from the United States, Japan, Spain, Monaco, and the United Kingdom were able to obtain samples off Japan for an early assessment of impacts.

From June 4 through June 19, 2011, a research cruise was carried out aboard the RV Kaimikai-O-Kanaloa, a research vessel operated by the University of Hawaii. During the cruise, hundreds of samples were collected in an area off the coast of Japan as close as 30 kilometers from the Fukushima Nuclear Power Plant and extending as far out as 600 kilometers off shore. The essential components of the program include: radionuclide measurements of water and particles; a radioecological study of biota, especially species at the base of the food chain and key fish species and a physical oceanographic study to characterize transport and water masses. A baseline radionuclide data set for the Atlantic and Pacific was obtained along an east to west network of sampling stations. Three hundred sampling events took place at thirty major stations for a total of more than 1500 samples. Along with 41 CTD stations, bottle samples of salinity, oxygen, radionuclides, and particulates were taken to depths of about 1000 meters. A list of the radionuclides sampled and a sampling summary map is available. One hundred net tows resulted in approximately fifty pounds of biological samples, including plankton and small fish. Daily samples of aerosol were also taken.

Early investigation following an accidental release of man-made radionuclides is key to understanding the magnitude of the release and the relationship to public health issues The research results also set the stage for the use of the longer lived radionuclides as tracers in subsequent studies by the community to understand ocean processes.