Arctic ice algae heavily contaminated with microplastics

21 Apr. (EUROPE PRESS) –

The alga Melosira arctica, which grows under the Arctic sea ice, contains ten times more microplastic particles than the surrounding seawaterreveals new research.

This concentration at the base of the food web poses a threat to creatures that feed on algae at the sea’s surface. The dead algae clumps also transport the plastic with its pollutants particularly quickly to the depths of the sea and thus may explain the high concentrations of microplastics in the sediment there.

Researchers led by the Alfred Wegener Institute (AWI) present these findings in the journal Environmental Science and Technology.

It is a food elevator for animals that live at the bottom of the sea: the algae Melosira arctica grows at a rapid rate under the sea ice during the spring and summer months, forming meter-long cell chains there. When the cells die and the ice to which they are attached melts, they coalesce to form clumps that can sink several thousand meters to the bottom of the deep sea in a single day. There they form an important food source for animals and bottom-dwelling bacteria. However, in addition to food, these aggregates also carry a dubious cargo into the depths of the Arctic: microplastics.

“We have finally found a plausible explanation for why we always measure the highest amount of microplastics in the ice edge area, even in deep-sea sediments”reports Melanie Bergmann, AWI biologist, it’s a statement.

Until now, researchers only knew from previous measurements that microplastics are concentrated in the ice during sea ice formation and released into the surrounding water when it melts. “The speed at which the Alga descends means that it falls almost straight below the edge of the ice. Marine snow, on the other hand, is slower and is pushed to the sides by currents, so it sinks further.” The fact that Melosira brings microplastics directly to the fund helps to explain why we measure higher amounts of microplastics below the ice edge“, Explain.

On an expedition with the research vessel Polarstern in the summer of 2021, she and a research team collected samples of Melosira algae and the surrounding water from ice floes. The partners of the Ocean Frontier Institute (OFI), Dalhousie University and the University of Canterbury they then analyzed these in the lab 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. “Filamentous algae have a slimy, sticky texture, so they potentially collect microplastics from atmospheric deposition in the sea, the seawater itself, the surrounding ice, and any other sources it passes through. Once trapped in the silt of algae, they travel as if in an elevator to the bottom of the sea, or are eaten by marine animals“, explains Deonie Allen, from the University of Canterbury and the University of Birmingham, who is part of the research team.

Since ice algae are an important food source for many deep-sea dwellers, microplastic could enter the food web there. But it is also an important food source at the sea surface and could explain why microplastics were particularly widespread among ice-associated zooplankton organisms, as an earlier study involving AWI shows. In this way, it can also enter the food chain here when zooplankton are eaten by fish such as polar cod and these are eaten by seabirds and seals. and these in turn by polar bears.

Detailed plastic composition analysis showed that a variety of different plastics are found in the Arctic, including polyethylene, polyester, polypropylene, nylon, acrylic, and many more. In addition to various chemicals and dyes, this creates a mixture of substances whose impact on the environment and living beings is difficult to assess.

“People in the Arctic are particularly dependent on the marine food web for their protein supply, for example through hunting or fishing. This means they are also exposed to the microplastics and chemicals it contains. These have already been detected microplastics in human intestines, blood, veins, lungs, placenta and breast milk and can cause inflammatory reactions, but so far the general consequences have hardly been investigated,” reports Melanie Bergmann.

“Basically, micro- and nanoplastics have been detected in all the places that scientists have looked for in the human body and within a plethora of other species. It is known to change behaviors, growth, fecundity, and mortality rates in humans.” organisms and many plastic chemicals are known toxins to humans,” says Steve Allen, a member of the OFI Dalhousie University research team.