New research reveals significant microplastic contamination in Arctic ice algae

The algae Melosira arctica, which grows under Arctic sea ice, contains ten times as many microplastic particles as the surrounding seawater. This concentration at the base of the food web poses a threat to creatures that feed on algae at the sea surface. Dead algal clumps also transport plastic and its pollutants particularly quickly to the deep sea – and thus could explain the high concentrations of microplastics in the sediments there. Researchers led by the Alfred Wegener Institute have published this in the journal Environmental science and technology.

It’s a food elevator for deep-sea bottom-dwelling animals: Melosira arctica grows at a rapid pace under sea ice during the spring and summer months, forming meter-long chains of cells there. When the cells die and the ice to which they stick below melts, they stick together to form clumps that can sink several thousand meters to the deep sea floor within a day. There they constitute an important food source for bottom-dwelling animals and bacteria.

In addition to food, these aggregates also transport a questionable cargo to the Arctic sea depths: microplastics. A research team led by biologist Dr. Melanie Bergmann of the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI) has published their findings.

“We finally found a plausible explanation for why we always measured the largest amounts of microplastics in the ice-edge region, even in deep-sea sediments,” says Melanie Bergman.

Until now, researchers only knew from previous measurements that microplastics are concentrated in ice during sea ice formation and are released into the surrounding waters when they thaw. “The speed at which the algae descend means that it falls almost in a straight line below the edge of the ice. Marine snow, on the other hand, is slower and is pushed aside by the currents, so sinks away. With Milocera taking microplastics straight to the bottom, it helps in explain why we measured higher microplastic numbers below the edge of the ice,” explains an AWI biologist.

On an expedition with the research vessel Polarstern in the summer of 2021, she and a research team collected samples of Melosira algae and surrounding water from the ice floes. Partners from the Ocean Frontier Institute (OFI), Dalhousie University and the University of Canterbury then analyzed them in the laboratory for microplastic content. The surprising result: The algae clumps contained an average of 31,000 ± 19,000 microplastic particles per cubic meter, about ten times the concentration of the surrounding water.

“Filiform algae have a slimy, slimy texture, so they likely collect microplastics from atmospheric deposition on the sea, seawater itself, and from surrounding ice and whatever other source it passes through. Once it gets stuck in the algae slime, it travels in the form of microplastics,” explains Dionne Allen of University of Canterbury and the University of Birmingham, part of the research team, whether in the elevator to the sea floor, or eaten by marine animals.

Since ice algae is an important food source for many inhabitants of the deep sea, microplastics could enter the food web there. But it is also an important source of food at the sea surface and could explain why microplastics are particularly prevalent among organisms associated with ice, as a previous study involving AWI showed. In this way, it can also enter the food chain here when zooplankton are eaten by fish such as polar cod which are eaten by seabirds and seals and these in turn are eaten by polar bears.

Detailed analysis of the composition of plastics has shown that a variety of different plastics are found in the Arctic, including polyethylene, polyester, polypropylene, nylon, acrylic, and many others. Combined with various chemicals and dyes, this creates a mixture of substances whose impact on the environment and living organisms is difficult to assess.

“People in the Arctic in particular depend on the marine food web for their protein supply, for example through hunting or fishing. This means that they are also exposed to microplastics and the chemicals in them. Microplastics have already been detected in the human gut, blood veins, lungs, placenta, and breast milk and can cause inflammatory reactions, but the general consequences haven’t been researched yet,” says Melanie Bergman.

“Micro and nanoplastics have been discovered in basically every place that scientists have looked at in the human body and within a plethora of other species. They are known to alter the behaviors, growth, fertility, and mortality rates of organisms and many plastic chemicals are known to be toxic to humans,” says Steve. Allen, member of the OFI Dalhousie University research team.

Moreover, the Arctic ecosystem is already threatened by the profound environmental disruptions caused by the climate crisis. If organisms were now further exposed to microplastics and the chemicals they contain, this could weaken them further.

“So we have a set of planetary crises that we desperately need to address effectively. Scientific calculations have shown that the most effective way to reduce plastic pollution is to reduce the production of new plastic,” says Melanie Bergman. currently being negotiated. That is why Bergman is also accompanying the next round of negotiations, which will begin in Paris at the end of May.