Chemicals Banned in the 1970s Found in Trenches

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

A study, led by U.K. Newcastle University’s Dr Alan Jamieson has uncovered the first evidence that man-made pollutants have now reached the deepest parts of the ocean.

Sampling amphipods from the Pacific Ocean’s Mariana and Kermadec trenches - which are over 10 kilometers (six miles) deep and 7,000 kilometers (4,300 miles) apart - his research team found extremely high levels of persistent organic pollutants in the organism’s fatty tissue. These include polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) which are commonly used as electrical insulators and flame retardants.

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

Released into the environment through industrial accidents and discharges and leakage from landfills, these pollutants resist natural degradation and so persist in the environment for decades.

The team from Newcastle University, 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 might be for the wider ecosystem.

Jamieson, said: “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.

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

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

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

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