Who can forget the terror and devastation wrought when an earthquake and tsunami hit northeast Japan on March 11, 2011? The disaster took over 15,000 lives, destroyed or damaged nearly one million buildings, and caused great suffering across Japan and the world. In addition, the quake and tsunami lead to one of the worst nuclear disasters in history -the level 5 meltdown of 3 reactors in the Fukushima Daiichi nuclear power plant. 

Computer models have predicted the extent of radiation fallout from Fukushima, showing it to spread in a plume across  the Pacific ocean and eventually reach the US coast in March of 2014.  While the plume is expected to be dilute enough at this time and distance from Japan to be within safe levels (<10 becquerels/liter according to the World Health Organization), there is concern that migratory species caught in US or other national waters might pose a risk to human consumers. However, a recent study of Pacific bluefin tuna shows that levels of radioactive isotopes traceable to Fukushima are well below levels of other radionuclides naturally occurring in the fish.

A Lagrangian particle dispersal model for March 2012, one year after the disaster, shows the estimated spread of free-floating radioactive material (fish larvae, algae, phytoplankton, zooplankton, etc.) from the Fukushima disaster through the Pacific Ocean.   Courtesy: ASR

While global risks seem relatively low, the fallout within Japan continues. Vast quantities of water needed to cool the damaged reactors have become contaminated. Human error and poor planning have resulted in continued leakage or dumping of this contaminated water and other radioactive material into the sea. As recently as last week (9 October 2013), radiation levels reached a 2-year high when more than 7 tons of contaminated water from a treatment system were accidentally leaked into the harbor surrounding the plant. Not only that, but methods used to contain contaminated water at the reactor site are driving contaminated soil into ground water and into the harbor.  To date, Fukushima has leaked a total 20-40 trillion becquerels of radioactive material into the Pacific ocean.

In August, Prime Minister Shinzo Abe ordered the federal government to take over the remediation project from Tokyo Electric Power Company (TEPCO), and on October 7 Abe formally requested international assistance to decommission and dismantle the plant.

In the meantime, high levels of near-shore radiation continue to be of concern to Japan's food supply and ecosystems. Although data is still hard to come by, a 2012 study published in Environmental Science and Technology, showed little radioactive contamination in marine birds, but higher levels in fish, molluscs, and crustaceans (potentially sufficient to cause reproductive problems and deformities), and higher still in microalgae. However the downstream biological effects are difficult to assess in such a short time frame. 

Economic effects are more immediate. Commercial fishing has been indefinitely banned along Fukushima's coast, leaving local fishermen to survive on compensation provided by the Japanese government and TEPCO. In a recent survey of 170 types of fish caught off the Japan coast, 42 fish species tested as too radioactive for human consumption, while another 15 species showed little or no signs of contamination, according to a report by The Associated Press. While cesium-134 and -137 (the predominant radioisotopes originally released in the plant meltdown) were detected in few fish, strontium-90 and tritium (hydrogen-3) were more frequently detected - these radioisotopes are in high concentration in the contaminated cooling water.  Strontium can accumulate in bones and so officials are keen to watch out for it, the AP said. 

In a country like Japan where seafood is a primary staple for much of the population, the economic and human impacts of the Fukushima disaster are clearly evident.  However, only time will tell how this event will ultimately pan out for global marine ecosystems.

Wastewater containment tanks at Fukushima Daiichi nuclear power plant. Courtesy AP/TEPCO