Deep-sea trenches are naturally among the most difficult regions on earth to study. However, our garbage finds its way there without any problems, as a team led by Serena Abel from the Helmholtz Center for Polar and Marine Research in Bremerhaven discovered. The working group measured surprisingly large amounts of microplastics in the West Pacific Kuril-Kamchatka Trench, as they write in the journal “Science of The Total Environment”: In each of a total of 13 sediment samples from a depth of more than 9000 meters, the participants found between 215 and 1596 tiny particles per kilogram of sludge. “No one would have expected such a large number before,” said the zoologist Angelika Brandt from the Senckenberg Research Institute and Natural History Museum in Frankfurt, who was involved in the study.
Millions of tons of plastic waste end up in the ocean every year. Only part of it is washed back onto the shores; a large amount remains in the water and gradually breaks down into smaller and smaller particles. These are ingested by organisms, end up in the ice at the poles, or sink into the deep sea over time. There they are also transported by currents until they are finally deposited in the deep-sea trenches. Abel and Co were able to identify a total of 14 different types of plastic in the samples. Polypropylene, one of the standard plastics used for packaging worldwide, is among the most common materials, as well as acrylates and polyurethane used for paints.
However, the waste is not evenly distributed across the floor. »Until now, the deepest seabed was considered to be a comparatively unaffected and stable environment in which the microplastics are deposited and remain in one place. We were all the more amazed that samples that were taken just a few meters apart had a very different structure,” says Abel. In addition to currents, animals obviously also contribute to the rearrangements when they search the sediment for food.