Concentrations of microplastics in hadal bottom waters range from 2.06 to 13.51 pieces per liter.
No place on Earth remains as remote from us as the Mariana Trench, the deepest point on the planet. Located in the western Pacific, near the Philippines, part of the 2,550km-long crescent-shaped crevice is 11km deep. The Mariana Trench is so deep, in fact, that if Mount Everest were somehow to be dropped into it, its peak would still be 1.6km underwater.
Yet we’ve already been colonizing this deep trough … with our plastic waste.
Chinese researchers from the Institute of Deep Sea Science and Engineering in Hainan have just discovered a very high level of microplastics right near the lowest place on Earth. These tiny plastics have permeated the world’s oceans, posing grave threats to marine ecosystems.
And not even the deepest places on Earth can escape their presence.
“Manmade plastics have contaminated the most remote and deepest places on the planet,” note the researchers, who have published their findings in a scientific journal. “The hadal zone (the deepest region of the oceans) is likely one of the largest sinks for microplastic debris on Earth, with unknown but potentially damaging impacts on this fragile ecosystem.”
The researchers found that concentrations of microplastics in hadal bottom waters range from 2.06 to 13.51 pieces per liter, which is several times higher than those in open ocean subsurface water. “Moreover, microplastic abundances in hadal sediments of the Mariana Trench vary from 200 to 2,200 pieces per litre, distinctly higher than those in most deep sea sediments,” the explain.
Most of the microplastics were fibers only a few millimeters long and likely came from plastic bottles, packaging and discarded nets. The most commonly found plastic in the sediments was polyester, while polyethylene terephthalate, which is used in bottles and clothes, was most frequent in water samples. The scientists believe that these plastic residues came from industrialized nations in East Asia such as China and Japan.