A study has revealed that the radioactive carbon released into the atmosphere by nuclear bomb tests has reached the deepest parts of the ocean.
The researchers found the first evidence of radioactive carbon in the nuclear bomb tests on the muscle tissues of the crustaceans that inhabit the Earth's trenches, including the Mariana trench, which houses the deepest part of the ocean.
Organisms on the surface of the ocean have incorporated "carbon bombs" into the molecules that make up their bodies since the late 1950s, they discovered.
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The new study, published in the journal. Geophysical research lettersThe crustaceans found in the trenches of the deep oceans feed on organic matter from organisms when it falls to the bottom of the ocean.
According to the authors of the study, the findings show that human contamination can quickly enter the food web and make its way to the depths of the ocean.
"Although ocean circulation takes hundreds of years to carry the water that contains the carbon bomb to the deepest ditch, the food chain accomplishes this much more quickly," said lead author Dr. Ning Wang, geochemist at the Academy. Science China
The co-author, Dr. 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 at 11,000 meters, so we must be careful with our future behaviors. " .
"It is not expected, but it is understandable, because it is controlled by the food chain."
The research team said its results also help scientists better understand how creatures have adapted to living in the nutrient-poor environment of the deep ocean.
The crustaceans they studied live for an unexpectedly long time having an extremely slow metabolism, which they suspect may be an adaptation to living 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 ages of archaeological and geological samples.
Tests of thermonuclear weapons conducted during the 1950s and 1960s doubled the amount of carbon-14 in the atmosphere when the neutrons released from the bombs reacted with nitrogen in the air.
The "carbon bomb" levels reached their peak in the mid-1960s and then fell when the atmospheric nuclear tests stopped.
By the 1990s, carbon-14 levels in the atmosphere had dropped to around 20 percent above their pre-test levels.
The carbon bomb fell rapidly out of the atmosphere and mixed with the surface of the ocean.
For decades, marine organisms have used the carbon bomb to build molecules within their cells, and scientists have observed elevated levels of carbon-14 in marine organisms since shortly after the bomb tests began.
The deepest parts of the ocean are the fairy trenches; those areas where the ocean floor is more than four miles below the surface.
The amphipods are a type of small crustacean that lives in the ocean and obtains food from the collection of dead organisms or the consumption of marine detritus.
In the new study, the researchers wanted to use the carbon bomb as an indicator of organic material in the trenches to better understand the organisms that live there.
Dr. Wang and her colleagues badyzed the amphipods collected in 2017 from the trenches of Mariana, Mussau and New Britain in the tropical Western Pacific Ocean, up to seven miles below the surface.
They found that the carbon-14 levels in the muscle tissues of the amphipods were much higher than the levels of carbon-14 in the organic matter found in water from the depths of the ocean.
The team also discovered that amphipods living in the trenches grow larger and live longer than their counterparts in shallower waters.
The researchers suspect that the large size and long life of the amphipods are probably the byproducts of their evolution to living in the environment of low temperatures, high pressure and a limited supply of food.
Dr. Wang said: "In addition to the fact that the material comes mainly from the surface, age-related bioaccumulation also increases these concentrations of pollutants, posing a greater threat to more remote ecosystems."
Dr. Rose Cory, an badociate professor of earth and environmental sciences at the University of Michigan who was not involved in the study, said the findings show that even ocean trenches are not isolated from human activities,
She added: "What is really novel here is not only that the carbon from the surface of the ocean can reach the depths of the ocean at relatively short time scales, but that the" young "carbon produced on the surface of the ocean is feeding or sustaining life in the deepest, trenches. "