Banned pollutants found in deepest reaches of our oceans

"The next step is to understand how these pollutants reach such remote environments, the consequences of this pollution and what the knock-on effects might be for the wider ecosystem"

A research collaboration featuring scientists from the James Hutton Institute, Newcastle University and the University of Aberdeen has uncovered evidence that man-made pollutants have now reached the most remote habitats of our planet.

Sampling marine organisms from the Pacific Ocean's Mariana and Kermadec trenches, which are over 10 kilometres deep and 7,000 km apart, the team found extremely high levels of persistent organic pollutants in the organisms' fatty tissues. These include polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), commonly used in the past 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 1.3m tonnes. Released into the environment through industrial accidents and discharges and leakage from landfills, these pollutants do not naturally degrade and instead remain in the environment for decades.

Dr Zulin Zhang, a senior research scientist at the James Hutton Institute’s Environmental and Biochemical Sciences group and co-author of the study, said: “In this research collaboration, we’ve found that the reach of human influence on the planet is most evident by its impact on inaccessible habitats.

“The levels of pollutants detected were considerably higher than those documented in heavily industrialised regions, which might support the idea that deep marine trenches represent contaminant sinks and that these pollutants are pervasive across our oceans.”

The research team used deep-sea landers to plumb the depths of the Pacific Ocean in order to bring up samples of the organisms that live in the deepest levels of the trenches, which were then analysed at the James Hutton Institute’s Aberdeen site by environmental chemists.

The authors suggest 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 marine fauna which in turn become food for larger fauna still.

The study team say the next step is to understand how these pollutants reach such remote environments, the consequences of this pollution and what the knock-on effects might be for the wider ecosystem.

The paper “Bioaccumulation of persistent organic pollutants in the deepest ocean fauna” is in the latest issue of Nature Ecology & Evolution, and Newcastle University's press release is available on EurekAlert.

Paper: "Bioaccumulation of persistent organic pollutants in the deepest ocean fauna”. Alan J. Jamieson, Tamas Malkocs, Stuart B. Piertney, Toyonobu Fujii and Zulin Zhang. Nature Ecology & Evolution, 1, 0051 (2017), doi:10.1038/s41559-016-0051.