The mass of ‘invisible’ microplastics found in the upper waters of the Atlantic Ocean is approximately 12- 21 million tonnes, according to AMT research published in the journal Nature Communications.
Significantly, this figure is only for three of the most common types of plastic litter in a limited size range. Yet, it is comparable in magnitude to estimates of all plastic waste that has entered the Atlantic Ocean over the past 65 years: 17 million tonnes. This suggests that the supply of plastic to the ocean have been substantially underestimated.
The lead author of the paper, Dr Katsiaryna Pabortsava, who undertook the sampling on the AMT26 expedition said “Previously, we couldn’t balance the mass of floating plastic we observed with the mass we thought had entered the ocean since 1950. 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.”
Co-author, Professor Richard Lampitt, who has been associated with AMT programme for many years, added “if 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. This is much more than is thought to have been supplied. “
“In order to determine the dangers of plastic contamination to the environment and to humans we need good estimates of the amount and characteristics of this material, how it enters the ocean, how it degrades and then how toxic it is at these concentrations. This paper demonstrates that scientists have had a totally inadequate understanding of even the simplest of these factors, how much is there, and it would seem our estimates of how much is dumped into the ocean has been massively underestimated”.
The study involved filtering large volumes of seawater at three selected depths in the top 200 metres of the water column and detecting and identifying plastic contaminants using a state-of-the-art spectroscopic imaging technique. The study focussed on polyethylene, polypropylene and polystyrene, which are commercially most prominent and also most littered plastic types.