Two commensal amphipods on a sponge stem in the Mariana Trench. (Photo: NOAA Office of Exploration and Research)

High levels of pollutants found in the deepest parts of the ocean

WORLDWIDE
Tuesday, February 14, 2017, 23:50 (GMT + 9)

“Extraordinary” high levels of toxic pollution have been discovered in the most remote and inaccessible place on the planet – the 10km deep Mariana trench in the Pacific Ocean.

By using a robotic submarine, scientist could capture small crustaceans that live in the pitch-black waters of the trench, which were contaminated with 50 times more toxic chemicals than crabs that survive in heavily polluted rivers in China.

"Pollutants were there in every single sample, regardless of depth, regardless of species," lead author Alan Jamieson, of Newcastle University in the UK, said.

The team of researchers verified that tiny crustaceans, such as yellowish Hirondellea gigas living in darkness about 10,000 meters down in the Pacific Ocean, were found to be polluted by PCBs, used in electric transformers or paints, and PBDE chemicals used as flame retardants, Reuters reported.

These industrial chemicals were banned in the late 1970s and do not break down in the environment, therefore, they are known as persistent organic pollutants (POPs).

These substances have previously been found at high levels in Inuit people (inhabitants of the Arctic regions) in the Canadian Arctic and in killer whales and dolphins in Western Europe.

The results of the research, published in the journal Nature Ecology and Evolution, suggests that the POPs infiltrate the deepest parts of the oceans as dead animals and particles of plastic fall downwards.

POPs accumulate in fat and are therefore concentrated in creatures up the food chain. They are also water-repellent and so stick to plastic waste.

Jamieson explained that although it was somehow expected that some POPs would be found in the deepest parts of the oceans, as when they sink there, it is impossible for them to move, the surprise was the extraordinary high levels of contamination.

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