Traces of nuclear bombs found in marine life at Earth's deepest spot: Study

The study shows human pollution can quickly enter the food web and make its way to the deep ocean, researchers said.

Scientists have found traces of radioactive carbon -- released into the atmosphere from 20th-century nuclear bomb tests -- in marine organisms that inhabit the Mariana Trench, the deepest spot on Earth.

Organisms at the ocean surface have incorporated this "bomb carbon" into the molecules that make up their bodies since the late 1950s.

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The study, published in the journal Geophysical Research Letters, finds crustaceans in deep ocean trenches are feeding on organic matter from these organisms when it falls to the ocean floor.

The results show human pollution can quickly enter the food web and make its way to the deep ocean, researchers said.

"Although the oceanic circulation takes hundreds of years to bring water containing bomb carbon to the deepest trench, the food chain achieves this much faster," said Ning Wang, a geochemist at the Chinese Academy of Sciences in China.

"There's a very strong interaction between the surface and the bottom, in terms of biologic systems, and human activities can affect the biosystems even down to 11,000 metres, so we need to be careful about our future behaviours," said Weidong Sun, a geochemist at the Chinese Academy of Sciences.

"It's not expected, but it's understandable, because it's controlled by the food chain," said Sun.

The results also help scientists better understand how creatures have adapted to living in the nutrient-poor environment of the deep ocean, researchers said.

The crustaceans they studied live for an unexpectedly long time by having extremely slow metabolisms, which they suspect may be an adaptation to living in this impoverished and harsh environment.

Carbon-14 is radioactive carbon that is created naturally when cosmic rays interact with nitrogen in the atmosphere.

Carbon-14 is much less abundant than non-radioactive carbon, but scientists can detect it in nearly all living organisms and use it to determine the ages of archeological and geological samples.

Thermonuclear weapons tests conducted during the 1950s and 1960s doubled the amount of carbon-14 in the atmosphere when neutrons released from the bombs reacted with nitrogen in the air.