Algae Growing Under Arctic Sea Ice Found Contaminated by Microplastics

A new study has noted concentrations of microplastics in Melosira arctica, a type of algae that grows underneath sea ice in the Arctic. As a nutrition source at the bottom of the food web, scientists are concerned about wildlife that eat the contaminated algae. 

In the study, led by researchers from Alfred Wegener Institute for Polar and Marine Research, scientists found 10 times higher amounts of microplastics in the Melosira arctica samples compared to the amount of microplastics found in surrounding seawater.

Not only could this pose a risk to animals that feed on the algae, but dead clumps of the algae can also break off from the Arctic sea ice and drift to the sea bed, carrying the microplastic pollutants with them. Scientists suggested this could help explain why microplastics have been 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, explained in a statement. “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 grows in clusters along the underside of sea ice during spring and summer, and the species is at the bottom of the food chain. Researchers collected samples of Melosira arctica as well as nearby water, and found microplastic particles were about 10 times higher in the algae samples. This could be because the algae is sticky, so it can collect and trap plastic fragments from surrounding waters, melting sea ice and other sources it passes by. Wildlife then feed on the algae, which could be an issue with such high concentrations of microplastics.

“Since ice algae are hotspots of biological activity and an important food source for grazing organisms, they could be a vector into under-ice food webs,” the scientists wrote in the study, published in Environmental Science & Technology. “Indeed, MPs were recently detected in grazing zooplankton from the Fram Strait.”

The microplastics came in a variety of different plastic materials, from polyethylene and polypropylene to nylon and acrylic, with polyethylene terephthalate (PET) being the most present. Most of the microplastic particles, around 94% on average, were 10 μm or smaller. The scientists are concerned that these tiny particles could enter and damage the Melosira arctica, ultimately impacting 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. Plastic pollution likely exacerbates this pressure, so it needs to be tackled efficiently,” the study concluded.