(CNN)Decades after the nuclear bomb tests of the Cold War, traces of radioactive carbon have been found in the deepest parts of the ocean.
Radioactive carbon from Cold War nuclear tests has been found deep in the ocean
Crustaceans found in the deepest trenches of the Pacific Ocean showed high levels of radioactive carbon in their muscle tissues, according to a study published in the journal Geophysical Research Letters in April.
The "bomb carbon" found its way into their molecules from nuclear tests performed in the 1950s and '60s -- and it's been found miles down into the ocean where these creatures live. The results show how quickly human pollution can enter the ocean's food chain and reach the deep ocean, according to the study's authors.
It's a disturbing discovery that shows how the actions of humans can harm the planet.
"We didn't expect such high levels of carbon-14 (radioactive carbon)," co-author Weidong Sun, a professor of marine geology at the Chinese Academy of Sciences in Qingdao, China, told CNN. "That means the ocean has been polluted by human activities."
During the nuclear tests of the Cold War era, the radioactive carbon in the atmosphere doubled. The neutrons released in the bombs reacted with the nitrogen in the air, creating a radioactive carbon, or carbon-14.
When the nuclear tests stopped, the levels of radioactive carbon went down. But it was already too late. The "bomb carbon" fell from the atmosphere to the surface of the ocean. Marine animals have been eating things in the ocean over decades and scientists have seen increased levels of carbon-14 since the bomb tests.
Researchers from China and the United States used the "bomb carbon" to trace organic material in organisms that live in deepest parts of the ocean. They studied crustaceans that live in hadal trenches, which are found 6,000 to 11,000 meters ( 20,000 to 36,000 feet) below the ocean's surface.