Microplastics: How deep-sea trenches become garbage dumps

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Krahn of the research vessel »Sonne« during operation over the Kuril-Kamchatka Trench

Photo: Senckenberg

When the adventurer Victor Vescovo was traveling in a mini submarine in the Mariana Trench in April 2019, he was amazed at an unusual find.

At a depth of almost 11,000 meters, the American discovered a plastic bag that was lying on the ocean floor.

The discovery made headlines because it made it clear that discarded plastic waste makes it into even the most remote corners of ecosystems.

A team led by Serena Abel and Angelika Brandt from the Senckenberg Research Institute in Frankfurt am Main has now been able to show that much smaller plastic particles are floating around in the deep sea.

They found microplastics in sediment samples from the Kuril-Kamchatka Trench.

One kilogram of the sample contained between 14 and 209 such tiny particles.

The researchers were able to find a total of 15 different types of plastic, they report in their study in the specialist magazine "Environmental Pollution".

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Plastic parts are distributed over great distances in the sea

Photo: iStockphoto / Getty Images

The eight sediment samples come from depths of 5143, 6065, 7138 and 8255 meters.

The team found the highest proportion of plastic in the samples that were the lowest.

“This is probably due to the situation that the particles get into this area well, but are then trapped there.

These trenches are real plastic traps, "Abel is quoted in a communication.

The plastic particles were less than 375 micrometers in size, most were smaller than 125 micrometers, i.e. about an eighth of a millimeter.

Much is still unclear about the effects of microplastics on the ecosystems and organisms of marine animals.

But the fact that such particles sink in large quantities so deep in the sea also means that the base of the food chain is affected, as many invertebrates eat sediment including the microplastic particles.

"Unfortunately, future generations will therefore be confronted with the traces of today's pollution for a long time to come," says marine researcher Brandt.

This has been confirmed by a study by the Max Planck Institute for Marine Microbiology in Bremen on the long-term effects of the amount of plastic in the deep sea.

Even after 20 years, the researchers could not find any traces of degradation or decomposition at a depth of more than 4,000 meters.

The samples of the current study were obtained in 2016 during an expedition with the research vessel "Sonne".

The Kuril-Kamchatka Rift, which is over 2200 kilometers long, lies in the northwestern Pacific.

In addition to the Kamchatka Peninsula, it is named after the Kuriles, a group of islands belonging to Russia.

The researchers cannot say how much plastic waste is stored in the deep-sea trench.

Scientists from Australia recently estimated that globally there could be between 9 and around 16 million tons stuck in the soil.

Plastic islands made from packaging

The origin of the garbage in the seas appears clear.

The most common types of plastic found were polypropylene.

The material is often used for packaging.

The global flow of plastic waste mostly begins in the river systems and on the coasts of the earth.

From there, the garbage is distributed in the oceans, where it sometimes agglomerates to form gigantic islands.

In the process, the plastics grind into smaller and smaller particles, which are distributed all over the oceans.

The deep-sea trenches threaten to become the garbage dumps of the oceans.

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