Researchers in a new U.K.-led study found a staggering volume of microplastics on the seafloor. At up to 1.9 million pieces on a single square meter, it’s the highest level on record.

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microplastics and other debris on the coast of the ocean

“We were really shocked by the volume of microplastics we found deposited on the deep seafloor bed,” Dr. Ian Kane of the University of Manchester, lead author of the study, told CNN. “It was much higher than anything we have seen before.” Researchers collected sediment samples from the Tyrrhenian Sea off Italy’s west coast.

While garbage patches composed of plastic bags, bottles and straws are old news, scientists say the floating plastic doesn’t even account for 1% of the 10 million tons of plastic that wind up in the oceans annually. The new study seems to confirm what scientists have suspected: much of that plastic is deep down on the seafloor.

The study, published in Science, concludes that episodic turbidity currents, which are akin to underwater avalanches, rapidly transport microplastics down to the seafloor. Then, deep-sea currents work like conveyor belts, transporting microplastics along the bottom of the ocean and accumulating in what researchers called “microplastic hotspots.” Most of these microplastics are fibers from clothes and textiles that waste water treatment plants fail to filter out because they are so tiny.

microplastics and other pollutants in the water on the shore

This is the first time scientists have directly linked currents to plastic concentrations on the seafloor. The study’s authors hope this work will help predict future hotspots and the impact of microplastics on marine life.

Unfortunately, though the plastics may be tiny, they can have a huge impact. “Microplastics can be ingested by many forms of marine life,” said Chris Thorne, oceans campaigner at Greenpeace U.K., “and the chemical contaminants they carry may even end up being passed along the food chain all the way to our plates.” Thorne has called for people to rethink “throwaway plastic.”


Images via Oregon State University, Bo Eide, and Dronepicr