Banned chemicals in the 1970s found in the trenches

Crustaceans from the deepest ocean trenches were found to contain ten times more industrial pollution than the average earthworm, scientists have shown.

A study, led by Dr Alan Jamieson of Newcastle University in the UK, uncovered the first evidence that man-made pollutants have now reached the deepest parts of the ocean.

By sampling amphipods from the Pacific Ocean’s Mariana and Kermadec trenches – which are more than 10 kilometers (six miles) deep and 7,000 kilometers (4,300 miles) away – his research team found extremely high levels of persistent organic pollutants in the adipose tissue of the body. These include polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) which are commonly used as electrical insulators and flame retardants.

From the 1930s until PCBs were banned in the 1970s, the total global production of these chemicals was in the region of 1.3 million tons.

Released into the environment as a result of industrial accidents and discharges and spills from landfills, these pollutants resist natural degradation and persist in the environment for decades.

The team from Newcastle University, the University of Aberdeen and the James Hutton Institute say the next step is to understand the consequences of this contamination and what the knock-on effects could be for the wider ecosystem.

Jamieson said: “We still think the deep ocean is this remote and pristine kingdom, safe from human impact, but our research shows that sadly, this couldn’t be further from the truth.

“In fact, the amphipods we sampled contained levels of contamination similar to those found in Suruga Bay, one of the most polluted industrial areas in the Pacific Northwest.

“What we don’t know yet is what this means for the wider ecosystem and understand that it will be the next big challenge.”

The research team suggests that the pollutants most likely found their way to the trenches through contaminated plastic debris and dead animals that sink to the ocean floor, where they are then consumed by amphipods and other fauna, which in turn become food. for the larger fauna. .

“The fact that we have found such extraordinary levels of these pollutants in one of the most remote and inaccessible habitats on earth really brings home the devastating long-term impact humanity is having on the planet,” says Jamieson. “It is not a great legacy that we are leaving behind.”