"The world's sea floor is littered with an estimated 14 million tonnes of microplastics, broken down from the masses of rubbish entering the oceans every year, according to Australia's national science agency.

The quantity of the tiny pollutants was 25 times greater than previous localised studies had shown, the agency said, calling it the first global estimate of sea-floor microplastics.

Researchers at the agency, known as CSIRO, used a robotic submarine to collect samples from sites up to 3,000 metres (9,850 feet) deep, off the South Australian coast.

"Our research found that the deep ocean is a sink for microplastics," principal research scientist Denise Hardesty said."

Phys.org had the story October 7, 2020. [2]