Sediment samples from the West Pacific Kuril-Kamchatka Trench show that the deep sea is even more heavily polluted with microplastics than previously thought.

Bremerhaven (Germany). In May 2022, scientists from the University of Manchester found a microplastic record on the seabed in the Tyrrhenian Sea off Corsica. This is due to ocean currents close to the ground, which ensure that the small plastic particles are concentrated in deep-sea trenches and undersea canyons. An investigation of Senckenberg Society for Natural Researchthe Frankfurt Goethe University and the Alfred Wegener Institute (AWI) now shows that the seabed in the deep sea is even more heavily contaminated with microplastics than science has previously assumed.

According to their publication in the specialist magazine Science of the Total Environment For their 2016 study, the researchers led by Serena Abel and Angelika Brandt took sediment samples from the West Pacific Kuril-Kamchatka Trench. Subsequent analysis of the samples using the micro-FTIR method shows that the seabed contains between 215 and 1596 microplastic particles per kilogram, which is significantly more than has ever been detected before.

Microplastics in all sediment samples

“We took a total of 13 samples at seven different stations along the trench, at depths ranging from 5740 to 9450 meters. Not one of them was free of microplastics,” explains Abel. The researchers had not previously expected such a large amount of microplastics.

Much of the plastic particles come from plastic waste that is dumped illegally in the oceans. Over the course of decades, the large pieces of plastic continue to be crushed by ocean currents. A large part of the plastic waste sinks into the maritime trenches thousands of meters below the surface.

deep sea as repository

“Every year, an estimated 2.4 to 4 million tons of plastic end up in the ocean via the rivers as a result of extreme global plastic consumption and poorly organized waste disposal,” says Brandt. As a result, the deep sea is increasingly becoming a repository for waste.

“Until now, the deepest seabed was considered a comparatively unaffected and stable environment in which the microplastics are deposited and remain in one place,” explains Abel. However, the samples now taken contained completely different plastic particles a few meters away. “This shows what a dynamic environment the deepest parts of the deep sea actually are,” the authors state. Currents, eddies and deep-sea organisms ensure that the microplastics in the sediment are constantly moving.

Science of The Total Environment, doi: 10.1016/j.scitotenv.2022.156035