On a Polarstern expedition in the Arctic, researchers led by biologist Melanie Bergmann from the Alfred Wegener Institute investigated how much microplastic is in aggregates of the ice alga Melosira arctica and the seawater directly next to ice floes. Credit: Alfred-Wegener-Institut/Mario Hoppmann
Key points:
- Arctic ice alga was found to contain extremely high levels of microplastic particles.
- This type of contamination at the base of the food chain poses a threat not only to creatures that feed on the algae at the surface, but humans as well.
- Scientists say this finding should help prioritize microplastics pollution in the global plastics agreement currently being negotiated.
Researchers at the Alfred Wegener Institute have discovered that the alga Melosira arctica—which grows under Arctic sea ice—contains 10 times as many microplastic particles as the surrounding seawater. This contamination at the base of the food chain poses a threat to creatures that feed on the algae at the surface.
It is a food lift for bottom-dwelling animals in the deep sea: Melosira arctica grows under the sea ice during spring and summer months and forms meter-long cell chains. When the cells die and the ice they adhere to melts, they sink to the bottom of the deep sea where they form an important food source for bottom-dwelling animals and bacteria.
In the summer of 2021, researchers collected samples of Melosira algae and the surrounding water from ice floes and analyzed the samples for microplastic content. To their surprise the clumps of algae contained an average of 31,000 ± 19,000 microplastic particles per cubic meter, about 10 times the concentration of the surrounding water.
The detailed analysis of plastic composition showed a variety of plastics, including polyethylene, nylon, polyester, polypropylene, acrylic and many more.
“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,” said study author Melanie Bergmann from the Alfred Wegener Institute. “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.”
In addition to the plastic, various chemicals and dyes detected in the samples creates a mix of substances whose impact on the environment and living creatures is difficult to assess.
“Micro and nano plastics have basically been detected in every place scientists have looked in the human body and within a plethora of other species. It is known to change behaviors, growth, fecundity and mortality rates in organisms and many plastic chemicals are known toxins to humans,” said study co-author Steve Allen, a researcher at Dalhousie University.
Bergmann said she plans to attend the next round of negotiations on the global plastics agreement in Paris at the end of May.
“Scientific calculations have shown that the most effective way to reduce plastic pollution is to reduce the production of new plastic,” said Bergmann. “This should therefore be prioritized in the global plastics agreement that is currently being negotiated.”