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1970s pollutants found in Kermadec Trench

NZ Newswire logoNZ Newswire 13/02/2017 Tom Wilkinson

Pollutants banned in the 1970s have been found in the deepest reaches of the Pacific Ocean, scientists say.

High levels of persistent organic pollutants were discovered in the fatty tissue of scavengers living more than 10km down in two trenches 7000km apart.

The chemicals include polychlorinated biphenyls (PCBs) which have been defined as carcinogens and do not break down for decades.

Researchers sampled the 2-3cm amphipods, similar to sand hopping insects, that they brought back to the surface from the Mariana Trench, east of the Philippines, and the Kermadec Trench, north of New Zealand.

The crustaceans from the deepest ocean trenches were found to contain 10 times the level of industrial pollution than the average earthworm.

"We still think of the deep ocean as being this remote and pristine realm, safe from human impact, but our research shows that, sadly, this could not be further from the truth," said lead author Alan Jamieson.

Along with the PCBs, once commonly used in industry, they found polybrominated diphenyl ethers which were used as flame retardants and are known to reduce fertility.

Between the 1930s to the 1970s, when they were banned, the total global production of PCBs was about 1.3 million tonnes.

Industrial accidents and leakage from landfill have seen them released into the sea.

Scientists believe the pollutants have found their way into the remote trenches through contaminated plastic debris and dead animals sinking to the ocean floor.

They would then be eaten by the voracious amphipods.

Dr Jamieson, of Newcastle University's School of Marine Science and Technology, says such extraordinary levels of pollutants in remote and inaccessible habitats brings home the long term, devastating impact that mankind is having on the planet.

"It's not a great legacy that we're leaving behind."

"This research shows that far from being remote the deep ocean is highly connected to the surface waters and this means that what we dump at the bottom of the sea will one day come back up in some form another."

Publishing their findings in Nature Ecology & Evolution, the study team - from Newcastle University, University of Aberdeen and the James Hutton Institute - will now investigate the consequences for the wider ecosystem.

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