Ocean pollution is commonly believed to be a relatively localised problem occurring close to centres of human activity, but a new scientific study suggests that in the most remote and inaccessible ocean depths, human litter is having even worse effects.
“Extraordinary levels” of pollutants have been identified by scientists in endemic amphipods or shrimps living in two of the world’s deepest ocean trenches.
A team led by Alan Jamieson of the School of Marine Science & Technology at Newcastle University studied life found on the seabed beyond a depth of 10km in the Mariana (North Pacific) and Kermadec (South Pacific) trenches.
Deep trenches had previously been considered as pristine environments, yet the researchers have concluded that the contamination levels there are “considerably higher” than in shallower waters in nearby areas of heavy industrialisation. This, they infer, indicates an accumulation of pollutants that seems likely to pervade all the oceans to their full depth.
The team describes the deep ocean as “a potential sink for the pollutants and litter that are discarded into the seas.”
Of particular concern are “persistent organic pollutants” or POPs – chemicals such as PCBs or PBDEs that were banned in the 1970s and that do not break down in the environment. Deposited in seabed sediments, they accumulate in the food chain in far higher concentrations than they do in nearby surface-water species, but had not been identified at such great depths before.
The report Bioaccumulation of Persistent Organic Pollutants in the Deepest Ocean Fauna is published in Nature Ecology & Evolution and can be read here
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