Pacific bluefin tuna were exposed to radioactivity as a result of the leaks at Japan's Fukushima Dai-ichi power plants and have carried those levels to the California coast – following the March 2011 earthquake and tsunami, according to a new study by scientists at Stony Brook along with Stanford University’s Hopkins Marine Station.
The study, published in the Proceedings of the National Academy of Sciences of the U.S., documented the first instance in which radioactive materials were transported via a biological migration through the ocean. The study showed the bluefin tuna that migrated to the California coast posed no public health threat.
According to the study, pacific bluefin tuna spawn in the western part of the Pacific Ocean and often migrate to the eastern end of the world's largest ocean. Scientists tested the bluefin tuna caught in August of 2011 off the coast of San Diego, California, and measured the levels of two radioactive isotopes of cesium in those fish.
SoMAS professor Nicholas Fisher, postdoctoral scholar Zofia Baumann and Stanford's Daniel Madigan concluded that analyzing the radioactivity in top marine predators such as bluefin tuna should "provide unequivocal evidence of migratory routes and timing of these animals."
"We were surprised to find this radioactivity in all bluefin tested, but we were also surprised that, to our knowledge, no other animals far from Japan have been tested,” Madigan said in a statement. “From a terrible event, we have found what should prove to be a very useful tool to examine migratory patterns of Pacific bluefin tuna and many other important species in the Pacific Ocean. These also provide a clear example of nature simply being amazing."