Bluefin Tuna Still Contaminated With Fukushima Radiation

A Stanford University study measures, and finds, radioactive cesium levels in bluefin tuna for the second year in a row. They showed that a bluefin tuna is capable of picking up radioactive material and transporting it across the ocean.

In 2011, radiocesium from Fukushima was detected in Pacific bluefin tuna, Thunnus orientalis, that had recently traversed the North Pacific Ocean, suggesting the potential for Fukushima-derived radionuclides to serve as tracers of long distance migrations by highly migratory species in the Pacific Ocean.

Upon analysis, the researchers found signals from Fukushima—isotopes called Cesium-134 and Cesium-137 — in all 15 samples they tested.  When the team tested for the isotopes in bluefin tuna that migrated to California before the disaster and yellowfin tuna that are native to California waters, the radioactivity wasn’t present, which indicated that it came from Fukushima.

While Cesium (Cs137) still exists throughout the Pacific in low, “background” levels as a result of nuclear weapons testing that peaked in the 1960s, the shorter lived Cesium (Cs 134) from nuclear weapons testing has long since decayed. A point source of anthropogenic radionuclides such as Fukushima is therefore the only substantial source of Cs134 in the Pacific Ocean, and consequently the presence of Cs134 indicates recent migration from the contaminated region.

A Stanford University study measures, and finds, radioactive cesium levels in bluefin tuna for the second year in a row. They showed that a bluefin tuna is capable of picking up radioactive material and transporting it across the ocean.

In 2011, radiocesium from Fukushima was detected in Pacific bluefin tuna, Thunnus orientalis, that had recently traversed the North Pacific Ocean, suggesting the potential for Fukushima-derived radionuclides to serve as tracers of long distance migrations by highly migratory species in the Pacific Ocean.

Upon analysis, the researchers found signals from Fukushima—isotopes called Cesium-134 and Cesium-137 — in all 15 samples they tested.  When the team tested for the isotopes in bluefin tuna that migrated to California before the disaster and yellowfin tuna that are native to California waters, the radioactivity wasn’t present, which indicated that it came from Fukushima.

While Cesium (Cs137) still exists throughout the Pacific in low, “background” levels as a result of nuclear weapons testing that peaked in the 1960s, the shorter lived Cesium (Cs 134) from nuclear weapons testing has long since decayed. A point source of anthropogenic radionuclides such as Fukushima is therefore the only substantial source of Cs134 in the Pacific Ocean, and consequently the presence of Cs134 indicates recent migration from the contaminated region.

The detection of Fukushima-derived radionuclides in Pacific bluefin tuna (PBFT) that crossed the Pacific Ocean to the California Current Large Marine Ecosystem (CCLME) in 2011 presented the potential to use radiocesium as a tracer in highly migratory species. This tracer requires that all western Pacific Ocean emigrants acquire the 134Cs signal, a radioisotope undetectable in Pacific biota prior to the Fukushima accident in 2011. We tested the efficacy of the radiocesium tracer by measuring 134Cs and 137Cs in PBFT (n = 50) caught in the CCLME in 2012, more than a year after the Fukushima accident. All small PBFT (n = 28; recent migrants from Japan) had 134Cs (0.7 ± 0.2 Bq kg–1) and elevated 137Cs (2.0 ± 0.5 Bq kg–1) in their white muscle tissue. Most larger, older fish (n = 22) had no 134Cs and only background levels of 137Cs, showing that one year in the CCLME is sufficient for 134Cs and137Cs values in PBFT to reach pre-Fukushima levels. Radiocesium concentrations in 2012 PBFT were less than half those from 2011 and well below safety guidelines for public health. Detection of 134Cs in all recent migrant PBFT supports the use of radiocesium as a tracer in migratory animals in 2012. Study excerpts

• Three core-melts, permanently intake of contaminated water thru hundred of holes into the pacific ocean.
• Three core-melts, permanently intake of contaminated water thru hundred of holes into the pacific ocean.
• It will be more contaminated in the future.
• The cesium is going to continue to accumulate, spreading to other species.