Cesium which is believed to have been released from the Fukushima Daiichi reators has been found in plankton over 600 km east of the facility. Follow -up studies will be necessary because the radioactive cesium is likely to have accumulated in fish that eat plankton, according to a Japan-U.S. joint research team.
The research team collected animal plankton at 17 locations out to 600 kilometers (372.8 miles) east of the plant in June last year, about three months after the March 11 earthquake and tsunami that triggered the nuclear crisis. Cesium-137 was detected in all of the collected plankton, which in a dry state was found to contain 0.3 to 56.4 becquerels per kilogram. The team also found cesium-134 – which has a two-year half-life – in plankton at the same levels as cesium-137.