The Australian national science agency, CSIRO (Hobart; www.csiro.au) has unveiled what it calls the first global estimate for the amount of microplastics – pieces less than 5 mm in diameter – on the seafloor. The whopping 14m t of refuse “is more than double the amount of plastic pollution estimated to be on the ocean’s surface,” the agency said.

The study, “Microplastic Pollution in Deep-Sea Sediments From the Great Australian Bight”, adds to the knowledge about the amount of plastics pollution in the oceans and the impact of plastic items, both large and small, according to CSIRO’s Justine Barret, who led the research. “Plastic pollution that ends up in the ocean deteriorates and breaks down, ending up as microplastics.”

The estimate for the total amount of microplastics on the world’s seafloor was based on samples collected using a robotic submarine in depths to 3,000 m at sites up to 380 km offshore from South Australia, according to the agency, which noted that the amount of microplastics recorded was 25 times higher than previous deep-sea studies.

“Our research found that the deep ocean is a sink for microplastics,” said Denise Hardesty, the study’s co-author. The number of microplastic fragments on the seafloor was generally higher in areas where there was also more floating rubbish, CSIRO noted.

Focusing on the Atlantic Ocean, the UK National Oceanography Centre (NOC, Southampton; www.noc.ac.uk) in August 2020 published a similar study on microplastics in the marine environment. The NOC reasearchers estimate the amount of polyethylene, polypropylene and polystyrene microplastics alone in the Atlantic Ocean could be about 200m t (see Plasteurope.com of 28.08.2020).