Radioactive remains of nuclear bomb tests discovered deep in the world's oceans

One study found that radioactive carbon released into the atmosphere by nuclear bomb tests had reached the deepest parts of the ocean.

The researchers found the first evidence of radioactive carbon from nuclear bomb tests in the muscle tissue of crustaceans living in the Earth's trenches, including the Mariana Pit, home to the deepest point of the ocean .

The organisms on the surface of the ocean have incorporated "carbon bombs" into the molecules that make up their body since the late 1950s, when it was discovered.

The new study, published in the journal Geophysical Research Letterscrustaceans found in deep ocean trenches feed on the organic matter of organisms that fall to the bottom of the ocean.

According to the authors of the study, the results show that human pollution can quickly enter the food web and end up in the depths of the ocean.

"Although ocean circulation takes hundreds of years to bring water containing carbon bombs into the deepest trench, the food chain does so much faster," said Dr. Ning Wang, lead author, geochemist at the Chinese Academy of Sciences.

The co-author, Weidong Sun, said: "There is a very strong interaction between the surface and the bottom, in terms of biological systems, and human activities can affect the biosystems even up to 11,000 meters. We must therefore pay attention to our future behaviors. .

"This is not expected, but it is understandable because it is controlled by the food chain."

The research team said their findings also help scientists better understand how creatures have adapted to life in the nutrient-poor environment of the deep ocean.

The crustaceans they studied live unexpectedly long and have an extremely slow metabolism, which they suspect to be an adaptation to life in such a harsh environment.

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

Scientists can detect it in almost all living organisms and use it to determine the age of archaeological and geological samples.

Thermonuclear weapons testing in the 1950s and 1960s doubled the amount of carbon 14 in the atmosphere when the neutrons released by the bombs reacted with nitrogen in the air.

"Carbon bomb" levels reached their peak in the mid – 1960s, then dropped at the end of nuclear tests in the atmosphere.

In the 1990s, carbon levels 14 in the atmosphere had dropped to about 20% above their pre-test levels.

The carbon bomb quickly fell out of the atmosphere and mixed with the surface of the ocean.

In the decades that followed, marine organisms used carbon bombs to build molecules in their cells, and scientists observed high levels of carbon 14 in marine organisms shortly after the start of bomb tests.

The deepest parts of the ocean are the hadal trenches; areas where the bottom of the ocean is more than four miles below the surface.

Amphipods are a type of small crustacean that lives in the ocean and feeds on dead organisms that search or consume marine litter.

In the new study, researchers wanted to use the carbon of the bomb as a tracer of organic matter in the trenches of hadal to better understand the organisms that live there.

Ms. Wang and her colleagues analyzed the amphipods collected in 2017 in the trenches of Mariana, Mussau and New Britain, in the tropical western Pacific Ocean, about ten kilometers from the surface.

They found that carbon-14 concentrations in muscle tissue of amphipods were much higher than those of carbon-14 in organic matter found in deep ocean waters.

The team also discovered that amphipods living in trenches are growing and living longer than their counterparts in shallower waters.

Researchers suspect that the large size and long life of amphipods are likely the by-products of their evolution to life in an environment characterized by low temperatures, high pressures and a limited food supply.

Dr. Wang said, "In addition to the fact that materials come mainly from the surface, age-related bioaccumulation also increases these pollutant concentrations, which increases the threat to these more distant ecosystems."

Dr. Rose Cory, an associate professor of Earth and Environmental Sciences at the University of Michigan, who did not participate in the study, said the results show that even deep ocean trenches are not isolated from human activities,

She added, "What is really innovative here is not just that the carbon of the ocean surface can reach the depths of the oceans over relatively short time scales, but also sliced. "

SWNS