Study finds high concentration of microplastics in algae growing in Arctic

Scientists found microplastic particles were about 10 times higher in the algae samples than the surrounding waters, which they are now equating with microplastics found in the deep sea.

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Image Credit: Supplied/University of Canterbury.

A new study discovered higher concentrations of microplastics in Melosira arctica, a type of algae growing under the sea ice in the Arctic, than in surrounding sea waters. The study was led by researchers from Alfred Wegener Institute for Polar and Marine Research and published in Environmental Science & Technology.

Scientists found microplastic particles about 10 times higher in the algae samples, which they are now equating with microplastics found in the deep sea.

“We have finally found a plausible explanation for why we always measure the largest amounts of microplastics in the area of the ice edge, even in deep-sea sediment,” Melanie Bergmann, biologist for the Alfred Wegener Institute, said. “The speed at which the Alga descends means that it falls almost in a straight line below the edge of the ice. Marine snow, on the other hand, is slower and gets pushed sideways by currents so sinks further away. With the Melosira taking microplastics directly to the bottom, it helps explain why we measure higher microplastic numbers under the ice edge.”

The algae, which grows in clusters along the underside of sea ice during spring and summer, poses a risk to animals that feed on the algae, a nutrition source at the bottom of the food web, according to the study. The algae is sticky, which allows it to trap microplastics from surrounding waters. Dead clumps of algae that break off from the Arctic sea ice take high concentrations of microplastic pollutants to the sea bed.

“Since ice algae are hot spots of biological activity and an important food source for grazing organisms, they could be a vector into under-ice food webs,” the scientists said in the study.

According to the study, the microplastics collected were from a variety of plastic materials, including polyethylene and polypropylene to nylon and acrylic, but polyethylene terephthalate (PET) was the most present in the algae. Much of the microplastics found in the Melosira arctica were 10 μm or smaller.

Scientists concluded that the high concentration of microplastics not only poses a risk to wildlife, it could damage the algae’s ability to store carbon.

“Arctic biota are already under serious pressure from global heating, which progresses four times faster in the Arctic compared with the globe,” the study said. “Plastic pollution likely exacerbates this pressure, so it needs to be tackled efficiently.”

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