Alarming study

Millions of tons of plastic waste lie at the bottom of the sea

On average, a full garbage truck load of plastic enters the world's oceans every minute and floats in the water. However, a large proportion of this also sinks into the depths: more than half of the estimated plastic mass in the oceans could have been deposited in the depths, according to a new study.

It is estimated that there are already three to eleven million tons of plastic waste at the bottom of the oceans today, according to a study by the Australian science agency CSIRO and the Canadian University of Toronto.

With the help of remotely operated underwater vehicles (ROVs), it was possible for the first time to quantify approximately how much plastic waste ends up on the seabed and exactly where it accumulates before it is broken down into smaller pieces and mixed with the marine sediment, said CSIRO researcher Denise Hardesty.

(Bild: CSIRO)

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

Plastic consumption will double by 2040
As plastic consumption is expected to double by 2040, understanding how and where plastic waste is transported in the sea is crucial for the protection of marine ecosystems and wildlife, according to the study, which has now been published in the journal "Deep Sea Research Part I: Oceanographic Research Papers".

Plastic pollution on the seabed could be up to 100 times greater than the amount of plastic floating on the ocean surface, according to estimates, said Alice Zhu, a doctoral student at the University of Toronto who led the study. The ocean floor has thus become a long-term resting place or reservoir for much of the plastic pollution.

Waste at depths of up to eleven kilometers
"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 study states. According to the results, almost half (46 percent) of the estimated plastic mass is found above 200 meters water depth, the rest (54 percent) in the following ocean depths of up to 11,000 meters.