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marineresources Fish Near Fukushima's Damaged Nuclear Plant Still Contaminated The majority of fsh caught off the northeast coast of Japan remain below limits for seafood consumption, even though the Japanese government tightened those limits in April 2012, Woods Hole Oceanographic Institution (WHOI) marine chemist Ken Buesseler found after analyzing data made publicly available by the Japanese Ministry of Agriculture, Forestry and Fisheries on radiation levels in fsh, shellfsh and seaweed collected at ports and inland sites in Fukushima Prefecture. Nearly 9,000 samples describe the complex interplay between the marine environment and radionuclides released from the Fukushima Dai-Ichi nuclear power plant following the 2011 Tohoku earthquake and tsunami. Buesseler's fndings, published in October in Science, also point out that the most highly contaminated fsh continue to be caught off Fukushima prefecture's coast and that bottom-dwelling fsh consistently show the highest Wideband Echosounder Works on 100 Frequencies Simultaneously level of contamination by a radioactive isotope of cesium from the damaged nuclear power plant. Additionally, levels of contamination in almost all classifcations of fsh are not declining, although not all types are showing the same levels, and some are not showing any appreciable contamination. Buesseler concludes that there may be a continuing source of radionuclides into the ocean, either in the form of low-level leaks from the reactor site itself or contaminated sediment on the seafoor. In addition, the varying levels of contamination across fsh types points to complex methods of uptake and release by different species, making regulation and communication of the reasons behind decision making to the fsh-hungry Japanese public all the more diffcult. "What we really need is a better understanding of the sources and sinks of cesium and other radionuclides that continue to drive what we're seeing in the ocean off Fukushima," Buesseler said. Norwegian researchers are fnishing the development of a wideband echosounder that works on 100 frequencies simultaneously, making it much easier to identify fsh and zooplankton. Research vessels and many fshing vessels typically use echosounders that send and receive signals on up to six frequencies. Currently, multiple echosounders working in parallel on different frequencies are needed to identify marine organisms below the surface. A specifc target can be singled out by analyzing all the elements within the echosounder image and removing the echoes from other species. The project WESTZOO (Exploiting new wideband echosounder technology for zooplankton characterization, sizing and abundance estimation) has received funding from the Research Council of Norway. Initially, the project researchers focused on zooplankton, since the echo from these marine organisms was well suited to the available frequency band. Later, they tried out the wideband echosounder on fsh and other targets. Access Sea Technology Anywhere Sea Technology magazine will soon be available on iOS and Android devices. With the launch of our new online viewer, you'll be able to securely log in to read current and past issues using a pre-provided password. To make sure you receive our Àrst mobile-friendly issue, subscribe for free at: http://sea-technology.com/ebookinfo.html Questions? Contact us at: seatechads@sea-technology.com or +703 524 3136. 80 st / DECEMBER 2012 www.sea-technology.com