There is at least 10 times more plastic in the Atlantic Ocean than previously thought, researchers say, and that’s only including the three most common types.
A team from the UK’s National Oceanography Centre found 12-21 million tonnes of “invisible” microplastics in just the upper 200 metres, comparable with previous estimates of how much has found its way into the ocean in the past 70 years.
In other words, they suggest in a paper in the journal Nature Communications, the supply of plastic to the ocean have been substantially underestimated.
“Previously, we couldn’t balance the mass of floating plastic we observed with the mass we thought had entered the ocean since 1950,” says lead author Katsiaryna Pabortsava.
“This is because earlier studies hadn’t been measuring the concentrations of invisible microplastic particles beneath the ocean surface. Our research is the first to have done this across the entire Atlantic, from the UK to the Falklands.”
Pabortsava and colleague Richard Lampitt visited 12 locations along a 10,000-kilometre north-south transect, assessing the abundance of polyethylene, polypropylene and polystyrene, which together make up over half of global plastic waste.
At each station, samples were collected from three depths: 10 metres, 10–30 metres below the mixed layer of the ocean, and 100 metres below the intermediate sample. Plastics were analysed down to a resolution of around 25 micrometres.
In the near surface ocean, they detected up to 7000 microplastic particles of these three polymer types (32-651 micrometres) per cubic metre of seawater.
“[I]f we assume that the concentration of microplastics we measured at around 200 metres deep is representative of that in the water mass to the seafloor below with an average depth of about 3000 metres, then the Atlantic Ocean might hold about 200 million tonnes of plastic litter in this limited polymer type and size category,” says Lampitt.
“This is much more than is thought to have been supplied. “
Nick Carne is the editor of Cosmos Online and editorial manager for The Royal Institution of Australia.
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