Radiation in Japan Seas: Risk of Animal Death, Mutation?

Aboard a boat pulling a barge with water for Japan's overheating Fukushima nuclear plant ThursdayNational Geographic News

Published April 1, 2011

If radioactive material from the Fukushima Daiichi nuclear power plant—disabled by the March11 Japan earthquake and tsunami—continues to enter the ocean, marine life could be threatened, experts say.

(See related photos: "Japan Tsunami: 20 Unforgettable Pictures.")

In the past week, seawater samples taken near the nuclear power plant, on Japan's eastern coast, have shown elevated levels of radioactive isotopes, including cesium 137 and iodine 131, according to the New York Times. (See "Japan Tries to Avert Nuclear Disaster.")

All life on Earth and in the oceans lives with exposure to natural levels of ionizing radiation—high-frequency radiation with enough energy to change DNA. Most such genetic damage heals, but the addition of human-made radiation can make it harder for the body to repair broken genes.

Radiation concentrations in the Japanese seawater samples have fluctuated in past days, but on Wednesday the amount of iodine spiked to 3,355 times the legal limit for seawater, Japanese nuclear safety officials told the Associated Press