(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.

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."

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