It’s been just over a decade since the fourth most powerful earthquake of the modern era triggered a tsunami that struck Fukushima on the eastern coastline of Japan, causing thousands of deaths and leaving hundreds of thousands unable to return home. That tsunami was also responsible for the world’s worst nuclear accident since the Chernobyl disaster.

When the 14-metre wave flooded the Fukushima Daiichi plant, it shut down emergency generators, triggering a series of heat-induced meltdowns. Now, the Japanese government’s decision to allow the release of more than one million tonnes of radioactive water from the plant into the ocean has divided opinion. //

But since the tsunami hit in 2011, authorities have used more than a million tonnes of water to try and cool the plant’s disabled reactors, which are still hot thanks to the long-term release of energy from the nuclear power source. All that radioactive water – which is more contaminated than standard waste water – has to go somewhere. The decision to release it into the oceans is – some would argue – the most pragmatic long-term solution. //

The process of filtering and diluting the huge amounts of water to meet safety standards will take a few years to complete. Then, we’d usually expect the water to be released gradually in small volumes through coastal pipelines. That way, any potential effects of releasing the radioactive waste will be minimised. However, the fact is that we don’t know exactly what those effects will be on marine – or human – life, given the sheer volume of water set to be released from the Fukushima plant.

Our own research has shown that a number of marine species could have their DNA damaged through extended exposure to radionuclides in seawater. It’s important to note that our conclusions are mostly drawn from studies in the lab, rather than in the real world; when a nuclear accident takes place, human safety takes priority and biological assessment often takes place decades after the original event.