Researchers have found evidence that radioactive carbon emitted during thermonuclear weapons testing in the past has found its way to the deep ocean.
In the 1950s and 1960s, radioactive carbon (carbon-14) from thermonuclear weapons tests was released into the atmosphere. It soon found its way to the ocean surface and became incorporated into the molecules of marine organisms at the ocean surface. When these organisms died, their organic matter fell to the bottom of the ocean.
In a new study published in the Geophysical Research Letters journal, researchers have discovered the first evidence of Carbon-14 in the muscle tissues of crustaceans living in the ocean trenches. This meant that the crustaceans had consumed the remains, which in turn indicated that human pollution was present in the deep ocean.
“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 lead author Ning Wang, a geochemist at the Chinese Academy of Sciences in Guangzhou, China.
For the research, Wang and her colleagues analysed amphipods collected in 2017 from the Mariana, Mussau, and New Britain Trenches in the tropical West Pacific Ocean, as far down as 11 kilometres below the surface.
“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 co-author Weidong Sun, a geochemist at the Chinese Academy of Sciences in Qingdao, China.