Traces of nuclear bomb tests have reached the deepest part of the ocean

The radioactive carbon created as a byproduct of nuclear bomb tests has reached the deepest parts of the ocean – and ends up ending up in the interior of marine creatures.

This discovery by Chinese researchers shows how human pollution can quickly enter the food chain and reach the bottom of the ocean.

However, this carbon bomb is helping scientists better understand how marine life manages to cope in such cold, dark, deep, nutrient-poor environments.

They discovered that tiny marine crustaceans can live much longer than their counterparts in shallow water and reach a much larger size.

This is probably due to the fact that animals have developed extremely slow metabolisms as an adaptation to life in the extreme conditions encountered in deep ocean trenches.

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Researchers led by the geochemist of the Chinese Academy of Sciences, Ning Wang, have used traces of carbon from nuclear bombs to analyze deep-sea amphipods, tiny marine crustaceans living in search of & Dead organisms and marine litter.

The animals were captured in 2017 in three trenches from the west Pacific Ocean – Mariana, Mussau and New Britain – up to depths up to 11 km below the surface of the ocean. ocean.

Experts were surprised to discover that carbon-14 levels in amphipod muscles were far superior to those found in organic matter floating in deep waters.

After analyzing the contents of the animal's intestines, they then discovered that the carbon levels derived from the bombs were also high and that they corresponded to the levels of carbon 14 found in the organic materials on the surface of the animal. the Pacific Ocean.

These results suggest amphipods selectively feed on debris from the ocean surface on the sea floor, rather than recovering the more local carbon sources found in nearby sediments.

& # 39; Although the ocean circulation takes hundreds of years to bring water containing bombs [carbon] in the deepest trench, the food chain gets there much faster, "said Ms. Wang.

The findings help researchers understand how creatures such as amphipods have adapted to life in the deepest parts of the ocean, located more than 6 km from the surface of the ocean, in the area called hadal.

Such deep chasms are only found in the oceanic trenches, narrow ocean-bottom depressions that form where one of the Earth's tectonic plates is subducted under another.

The animals inhabiting these trenches must be adapted to life under intense pressure and extremely cold temperatures, while being able to cope with the lack of light and nutrients available.

Ms. Wang and her colleagues found that the amphipods that live in these three ocean trenches tend to become larger and live longer than their counterparts.

Amphipods living in shallow waters generally live less than two years and average about 0.8 inches (2 centimeters) in length.

However, the researchers found that amphipods deep in ocean trenches were over 10 years old and 9.1 cm long.

Scientists believe that the size and longevity of deep amphipods can be attributed to the same evolutionary adaptations that allow them to live in such a cold, high pressure, low nutrient environment.

Slow metabolism and low cell replacement rates would allow tiny crustaceans to store energy over long periods of time.

However, this same longevity would probably mean that pollutants have the potential to accumulate at higher levels in these unusual creatures.

This brings[s] more threat to these more remote ecosystems, said Ms. Wang.

"There is a very strong interaction between the [ocean] the surface and the bottom, in terms of biological systems, "added a co-author of the article Weidong Sun, geochemist at the Chinese Academy of Sciences Qingdao.

"Human activities can affect biosystems up to 11,000 meters above sea level, so we must pay attention to our future behaviors." he said.

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

"What is truly innovative here is not just that the carbon of the ocean surface can reach the deep ocean at relatively short time scales," said Rose Cory, a science scientist. the land of the University of Michigan, who did not participate in the study.

Instead, she continued, the main novelty lies in the way "the young pro-carbonon the surface, the ocean feeds or supports life in the deepest trenches. COry said.

The complete results of the study were published in the journal Geophysical Research Letters.