IWAKI, Japan — The overpowering earthquake and tsunami that ripped through northern Japan in March 2011 took so much from Tatsuo Niitsuma, a commercial fisherman in this coastal city in Fukushima Prefecture.

The tsunami pulverized his fishing boat. It demolished his home. Most devastating of all, it took the life of his daughter.

Now, nearly nine years after the disaster, Mr. Niitsuma, 77, is at risk of losing his entire livelihood, too, as the government considers releasing tainted water from a nuclear power plant destroyed by the tsunami’s waves.

Prime Minister Shinzo Abe’s cabinet and the Tokyo Electric Power Company — the operator of the Fukushima Daiichi plant, where a triple meltdown led to the worst nuclear crisis since Chernobyl — must decide what to do with more than one million tons of contaminated water stored in about 1,000 giant tanks on the plant site.