Some of the fallout from nuclear-bomb testing in the mid-20th century has wound up at the bottom of the deepest ocean trenches.
Radioactive carbon was found in the muscle tissues of crustaceans that live five miles beneath the ocean’s surface, according to a new study in the journal Geophysical Research Letters.
While the carbon itself is not a dangerous isotope, the fact that animals in the Mariana Trench – 20,000 feet under the sea – have the compound in their muscles shows how quickly man-made pollution can enter the food chain and make its way to even the most inaccessible part of the planet, the 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 study lead author Ning Wang, a geochemist at the Chinese Academy of Sciences in Guangzhou, China, in a statement.
Carbon-14, created naturally by collisions between cosmic rays and nitrogen in Earth’s atmosphere, is present in trace amounts in just about every living organism. It’s routinely used to determine the ages of archeological and geological samples, according to Phys.org.
During the 1950s and ’60s, nuclear testing doubled the amount of atmospheric carbon-14 when bomb-generated neutrons reacted with nitrogen. It mostly disappeared from the atmosphere after the testing stopped.
But much of it fell into the ocean, where it was absorbed and eaten by organisms, and introduced into the food chain, making its way to the ocean’s depths.
The research showed not only that this had happened, but also that the organisms at the bottom seek out food sources falling from the ocean’s surface rather than more local sources.
“What is really novel here is not just that carbon from the surface ocean can reach the deep ocean on relatively short timescales, but that the ‘young’ carbon produced in the surface ocean is fueling, or sustaining, life in the deepest trenches,” said Rose Cory, from the University of Michigan, to Newsweek. Cory was not involved in the study.
“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 meters, so we need to be careful about our future behaviors,” said Weidong Sun, a geochemist at the Chinese Academy of Sciences in Qingdao, China, and co-author of the study, in the statement. “It’s not expected, but it’s understandable, because it’s controlled by the food chain.”
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