Enlarge image

Plastic bottle on the seabed off the coast near the Syria-Turkey border

Photo: Sebnem Coskun / Anadolu Agency / Getty Images

On average, a full garbage truck load of plastic ends up in the world's oceans about every minute. A large part of it sinks into the depths: a total of three to eleven million tonnes of plastic waste is currently estimated to be on the bottom of the ocean, according to a study by the Australian science agency Csiro and the Canadian University of Toronto. The paper was published in the specialist magazine “Deep Sea Research Part I: Oceanographic Research Papers”.

With the help of remotely operated underwater vehicles (ROVs), it was possible for the first time to roughly quantify how much plastic waste ends up on the seabed, said Csiro researcher Denise Hardesty. The team also analyzed where exactly the plastic collects before it is broken down into smaller pieces and mixed with the sea sediment.

It is estimated that plastic pollution on the seabed could be up to 100 times greater than the amount of plastic floating on the ocean's surface. According to the results, around half (46 percent) of the estimated plastic mass is located above a water depth of 200 meters, the rest (54 percent) in the following ocean depths of up to 11,000 meters.

According to the researchers, the bottom of the ocean has become a long-term resting place or a reservoir for much of the plastic pollution. "This is exacerbated by the extremely slow degradation of plastic in cold environments where there is a lack of both oxygen and UV radiation," the experts write in the study.

Plastic consumption will double by 2040

"We know that millions of tons of plastic waste end up in our oceans every year, but what we didn't know was how much of this pollution ends up on the ocean floor," Hardesty explained. While there have been estimates of microplastics in the past, the new study looks at larger items such as nets, cups or plastic bags.

Since plastic consumption is expected to double by 2040, understanding how and where plastic waste is transported in the sea is crucial to protecting marine ecosystems and wildlife, the researchers emphasize.

jme/dpa