BIG FISH STORIES: Nuclear Japan's Curious Lessons

At a decontamination facility in the ill-fated Fukushima nuclear power plant, liquid radwaste is pumped into 1,000 temporary storage tanks. This decontamination process has sparked a debate over how the 1.2 million tons of radioactive water should be handled. The international community has been keeping a close eye on the matter since the plant executing the cleanup announced that it needed to free up space around these tanks in order to decommission the damaged reactors before the 2020 Tokyo Olympics (which have since been postponed). One of the key issues involves the company’s plans to release the water into the ocean after receiving permission to do so from the Japanese government.

At present, radioactive cooling water from the melted reactors has been leaking into the groundwater, requiring that it be pumped back up to prevent it from seeping into the nearby sea and local aquifers. Officials have provided repeated reassurances, but there are still worries about the consumption of fish that may be affected due to the low dose radiation since effects of such contamination have not been fully studied and determined. The plant—backed by government officials—has issued promises that the water will be treated for a second time prior to any release. In addition, a recent report permitted two water disposal methods: dilute the treated water to below allowable safety limits before releasing it into the sea, or allow the water to evaporate in a process that could take many years.

While Fukushima offers a cautionary tale for the global nuclear energy community, the Takahama plant offers a tale of a slightly different kind – one that provides information on the effects of climate change with perhaps a touch of unexpected beauty. It seems that treated wastewater discharges are warming adjacent coastal seawater and creating a nurturing environment for tropical fish and other species. This phenomenon provides some visible evidence for how marine ecosystems could be dramatically altered by global warming over the ensuing decades.

Because the sea near Takahuma is warmed by the water used to cool its nuclear power plant, winter water temperatures have stabilized to around 13.6°C. As a result, a greater number and diversity of fish have been observed, including several tropical varieties. Even invertebrates like the long-spined urchin (see photo) have been identified. Since these sea urchins have no local predators, their numbers are staggering. The findings come as something of a surprise since operations at the plant were suspended following the accident at Fukushima. During that time, winter water temperatures fell by 3°C and all of the tropical species disappeared. However, once operations at the plant restarted in 2017, the tropical species began to return.

This data shows that winter water temperatures in the region fall just under the temperatures that tropical species need to survive. With water temperatures around the more temperate regions rising as a result of climate change, tropical species may soon be able to colonize vast areas of the coast. As beautiful as that sounds, their presence in vast numbers could alter coastal ecosystems and cause lasting and unfathomable repercussions. However, in cooler waters, similar temperature increases could produce a decreased effect. Recent studies in the tropical waters around Taiwan, for example, showed no evidence that warmer water from nuclear plants has impacted fish species and populations.

The tales of the two nuclear plant conditions continue, each with their own set of warning signs and reassurances. Still, the opinion of local fishermen paints an anxious picture. In the case of Fukushima, the plans to release the treated wastewater—no matter the levels—conjures fear as growing concerns about the damaged reputations of already suffering fisheries takes further and greater hold. Despite a series of positive tests, sales remain at half the original totals since the accident.

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