High microplastic concentration found at the bottom of the ocean


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Media captionWhat happens to microplastics in the ocean?

Scientists have identified the highest levels of microplastics ever recorded on the seabed.

The contamination was found in sediments from the bottom of the Mediterranean, near Italy.

The analysis, led by the University of Manchester, found up to 1.9 million plastic parts per square meter.

These items likely included fibers from clothing and other synthetic textiles, and tiny fragments of larger objects that had degraded over time.

Researchers’ research leads them to believe that microplastics (less than 1 mm) are concentrated at specific locations on the bottom of the ocean by strong bottom currents.

“These currents build what are called drift deposits; think of the underwater sand dunes, “said Dr. Ian Kane, who led the international team.

“They can be tens of kilometers long and hundreds of meters high. They are among the largest accumulations of sediment on Earth. They are mostly made of very fine silt, so it’s intuitive to expect microplastics to be in them, “he told the BBC. New.

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Source: I.Kane / Uni of Manchester

It has been calculated that something in the order of four to 12 million tonnes of plastic waste enters the oceans each year, mainly through rivers.

Media headlines have focused on large aggregations of debris that float in gyres or wash with the tides on the coasts.

But this visible trash would only represent 1% of the marine plastic budget. The exact location of the remaining 99% is unknown.

Some of them have almost certainly been consumed by sea creatures, but perhaps the much larger proportion has fragmented and simply sank.


Much of the fiber will come from clothing and other textiles

Dr. Kane’s team has already shown that ocean trenches and canyons can contain high concentrations of microplastics in their sediments.

In fact, the group’s simulations of water reservoirs have shown how the flows of mud, sand and silt of the type that occur in canyons entrain and move fibers to even greater depths. .

“Only one of these underwater avalanches (” turbidity currents “) can transport huge volumes of sediment hundreds of miles across the ocean floor,” said Dr. Florian Pohl of the University of Durham.

“We are just beginning to understand, thanks to recent laboratory experiments, how these fluxes transport and bury microplastics.”

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Media captionTank experiments show how underwater avalanches could transport plastic particles to the depths

The study area of ​​the Tyrrhenian basin between Italy, Corsica and Sardinia is nothing unusual.

Many other parts of the globe have strong deep water currents which are driven by contrasts in temperature and salinity. The problem will be that these currents also supply oxygen and nutrients to deep sea creatures. Thus, following the same route, microplastics could settle in biodiversity hotspots, increasing the risk of ingestion by marine life.

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Beach plastic can be a very small fraction of the waste

Professor Elda Miramontes of the University of Bremen, Germany, is co-author of the article in the journal Science describing the discovery of the Mediterranean.

She says the same effort shown in the battle against the coronavirus must now take the plague of plastic pollution of the oceans.

“We are all making an effort to improve our safety and we all stay at home and change our lives – change our life at work, or even stop working,” she told BBC News. “We are doing all of this so that people are not affected by this disease. We have to think the same way when we protect our oceans. “

Roland Geyer is a professor of industrial ecology at the Bren School of Environmental Science and Management, University of California at Santa Barbara.

He was at the forefront of the investigation and description of the waste streams through which plastic enters the oceans.

He commented, “We still have a very poor understanding of the total amount of plastic that has accumulated in the oceans. There seems to be an emerging scientific consensus, which is that most of this plastic is do not floating on the surface of the ocean.

“Many scientists now believe that most of the plastic is probably at the bottom of the ocean, but the water column and beaches are also likely to contain significant amounts.

“We all really need to focus on stopping plastics first. “

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I.Kane / United of Manchester


Sediment was brought in as part of work on a seabed pipeline


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