Scientists found radioactive carbon-14 in the tissues of tiny animals like these that live at the ocean's farthest depths.

(Ning Wang)

At a Glance

A recent study found radioactive carbon-14 in tiny animals that live at the ocean's deepest depths. Researchers say the observation highlights how the compound moves through the food chain."Bomb carbon" is a byproduct of nuclear testing.

Even the deepest, darkest depths of the ocean can't escape the radioactive fallout from a nuclear explosion.

Scientists recently discovered radioactive carbon-14, a byproduct of 1950s- and 60s-era nuclear bomb testing, in the tissue of tiny animals called amphipods that live underwater at the bottom of the Pacific Ocean's Mariana Trench, nearly seven miles below the earth's surface.

The was published in the journal Geophyisical Research Letters.

“Typically, we say the trenches are far away from us - they’re very deep and they’re pristine. But actually, ,” Jiasong Fang an earth scientist at Shanghai Ocean University who worked on the study, said in a press release. “Everything can get into the trenches.”

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Radioactive carbon-14 was also found in amphipods collected from the bottoms of the massive Mussau and New Britain Trenches. The researchers said the compound made its way to the rarely seen sea creatures through the food chain.

Amphipods are a type of small, shrimp-like crustacean that live in the ocean and get food from scavenging dead or decaying organisms. The amount of carbon-14 in Earth's atmosphere doubled after the U.S. tested hundreds of nitrogen bombs in the 1950s and 1960s. That "bomb carbon" is still hanging around, and is absorbed by plants, which are in turn eaten by animals who then pass it on to other animals as the life cycle progresses.

“There’s a very between the surface and the bottom, in terms of biologic systems, and human activities can affect the biosystems even down to 11,000 meters (7 miles), so we need to be careful about our future behaviors,” Weidong Sun, a geochemist at the Chinese Academy of Sciences in Qingdao, China, and co-author of the study, said. “It’s not expected, but it’s understandable, because it’s controlled by the food chain.”

Scientists say discoveries like this, and another recent study that found high levels of in glaciers, are indicators of fundamental changes in Earth's geology caused by humans.

“It just shows that the is getting even to places that were thought to be distant or remote from human influence,” says Jan Zalasiewicz, a paleobiologist at the University of Leicester in the U.K., told Scientific American.