Researchers found that the North Atlantic gyre had much higher concentrations of plastic, made up of polymers derived from packaging, rope, and paint particles, compared to other open ocean regions.
Anthropogenic marine debris becomes stuck in one of the planet’s five big oceanic gyres, a circular ocean current that extends from the east coast of North America to the west coasts of Europe and Africa.
According to a new study published in Marine Pollution Bulletin, it has higher amounts of polyethylene, polypropylene, acrylic, and polyamide. In contrast, other offshore regions have higher levels of PVC and polystyrene.
On the other hand, seawater closer to land has significantly more variation in its polymer composition, which scientists believe is impacted by its closeness to a range of land-based sources of plastics.
Scientists from the University of Plymouth, Mercator-Océan International, and eXXpedition conducted the research with samples gathered during eXXpedition's pioneering all-women Round the World sailing mission.
The findings are based on over 30 samples collected across the Atlantic Ocean, allowing scientists to investigate differences in microplastic concentration and type in the upper ocean, both on the surface and to a depth of 25 meters.
The study's general goal was to offer more data on plastic levels in the region and cover areas of the ocean where data was few, such as the eastern edge of the North Atlantic gyre.
The presence of plastic pollution within the North Atlantic, and its subtropical gyre, have been reported for 50 years. However, this research shows that the types of polymers differ between different regions of the North Atlantic.
Dr Winnie Courtene-Jones, eXXpedition Science Lead and Post-Doctoral Research Fellow, International Marine Litter Research Unit, University of Plymouth
Dr. Winnie Courtene-Jones, the lead author of the study, adds: “The high diversity of polymers identified in inshore waters may simply be down to the numerous and varied source of plastic inputs coming directly from land, meanwhile the gyre appears to be more closely associated with items that may come from maritime industries or been transported from the countries which border the Atlantic Ocean via ocean currents.”
The gyre water samples included an average of 0.62 microplastics per m3 of seawater, compared to 0.19MP/m3 in other open ocean locations and 0.4MP/m3 in inshore areas.
The study team explained how particles discovered on the surface of the gyre would have reached this region by utilizing tracking models built by scientists at Mercator-Océan International.
Models indicate they might have entered the sea from anywhere in North America, Western Europe, or northwestern Africa, considering the North Atlantic's incredibly diverse currents.
According to the researchers, this also demonstrates some difficulties in regulating the flow of plastic pollution from the source to the sea.
The Round the World trip of eXXpedition set sail from Plymouth in October 2019 to visit some of the world's most significant and diverse marine habitats, to motivate a network of changemakers, educating successful solutions with industry, and influence policy change on land.
The remarkable discovery from our research was the huge diversity of polymer types, particularly in the inshore regions. It tells us that the pollution has come from many different sources—be it clothing, paint fragments or car tyres—and as a result means the solutions need to be diverse too.
Emily Penn BEM, Study Co-Author and Founder, eXXpedition
Emily Penn concludes, “We set out to pinpoint where the solutions lie on land by better understanding the location the pollution had come from in the first place, but in fact the results just reinforce how much of an international challenge this is. The ocean connects us all and your pollution is my pollution – we need to solve it together.”
Courtene-Jones, W., et al. (2022) Synthetic microplastic abundance and composition along a longitudinal gradient traversing the subtropical gyre in the North Atlantic Ocean. Marine Pollution Bulletin. doi.org/10.1016/j.marpolbul.2022.114371.