More plastic debris in the deep sea than previously thought

Plastic waste in the oceans is broken down into ever smaller particles. Microplastics are particles less than 5 millimeters in diameter. Photo: Shutterstock

07/21/2022, 19:4122/07/2022, 11:19

Millions of tonnes of plastic waste end up in the oceans every year, most of which accumulates as tiny particles in sediments. The study found that the bottom of the sea depths is even more contaminated with microplastics than previously assumed.

This is the conclusion reached by scientists from the Senckenberg Nature Research Society, Goethe University in Frankfurt and the Alfred Wegener Institute (AWI) in Bremerhaven.

In 2016, they collected sediment samples in the Kuril-Kamchatka ditch in the Western Pacific. According to the Senckenberg Society, 215 to 1,596 tiny plastic particles per kilogram of sediment were detected in them, more than before. The enormous biodiversity at the deepest seabed is seriously threatened by pollution.

microplastic

Plastic particles smaller than 5 mm in diameter are referred to as microplastics. Even smaller particles – from 1 to a maximum of 1000 nm – are called nanoplastics. There are microplastics that are produced for consumer purposes, such as cosmetics, toothpaste and baby diapers. In addition, microplastics are formed by the breakdown of larger objects. On land, the largest source of microplastics is the wear of car tires, while at sea it is trawl and weir nets.

Much of the plastic waste in the seas comes from land, for example through rivers or our sewage. Larger pieces of plastic are shredded into smaller and smaller pieces over the decades. Some of the garbage accumulates in huge piles of garbage on the surface of the oceans, but most of it sinks into sea ditches thousands of meters below the surface.

94% of the plastic that enters the sea ends up on the seabed. At every kilometer2 The average seabed currently contains around 70 kg of plastic.

No microplastics free sample

“We took a total of 13 samples at seven different stations in the trench at depths ranging from 5,740 to 9,450 meters. None of them were microplastic-free, »said Serena Abel, a marine biologist at the Senckenberg Research Institute and the Frankfurt Natural History Museum. Nobody had expected such a large amount of microplastics before.

Scientists detected microplastic particles in each of the sediment samples they collected, ranging from 215 to 1,596 particles per kilogram of sediment.

Scientists detected microplastic particles in each of the sediment samples they collected, ranging from 215 to 1,596 particles per kilogram of sediment.Image: AWI

According to a study by Empa, 600 tons of microplastics end up in Swiss soil and 15 tons in water every year.

“Every year, about 2.4 to 4 million tonnes of plastic end up in the sea through rivers as a result of extreme global plastic consumption and poorly organized waste disposal,” said researcher Angelika Brandt. The sea depths are becoming a “landfill”.

In total, 14 different types of plastic were discovered. The researchers presented their results in the journal Science of the Total Environment.

Various plastic products take this time to decompose

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The deepest seabed was previously considered stable

“Until now, the deepest seabed has been considered a relatively intact and stable environment where microplastics settle and stay in one place,” said Abel. The researchers were amazed that the samples taken several meters away had a completely different structure. “It shows how dynamic the environment the deepest parts of the sea really are.” Eddies, currents, and organisms would keep the sediment in motion.

Creatures such as deep sea prawns keep sediment moving at the bottom of the Kuril-Kamchatka ditch and spread microplastics there.

Creatures such as deep sea prawns keep sediment moving at the bottom of the Kuril-Kamchatka ditch and spread microplastics there.Photo: Nils Brenke, Senckenberg

The lagoon of trash is likely to increase in the future. According to earlier AWI data, global plastics production is expected to double by 2045. An analysis carried out two years ago shows that the amount of plastic waste in the oceans could triple by 2040 if no action is taken.

More than a million seabirds and 100,000 marine mammals are lost in the ocean each year

After all, this study also gives cause for hope: the annual flow of plastic waste to the world’s oceans could be reduced by 80 percent – just by using existing technologies and methods. An important measure would be to transform the global plastics industry into a circular economy with a focus on recycling. (dh / sda / dpa)

Microplastics set new records in the Mediterranean Sea

Video: srf

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