Contaminated green under the ice: Arctic seaweed collects microplastics from the environment, a study shows. As they form an important base of the food chain, the ecological consequences of this pressure are potentially far-reaching. The scientists say that clumps of algae even sink to the bottom of the sea. The results could therefore also explain why surprisingly high concentrations of microplastics have already been found in sediments of the Arctic Ocean.
Artificial midgets are causing trouble in the world: The gigantic amounts of plastic waste that end up in the environment every year are not biologically degraded, but only break down into smaller and smaller pieces. Studies show that many different living things absorb these microscopic particles and are affected by them in sometimes complex ways. The plastic pollution of the world can then ultimately reach the polluters again via the food chain: microplastics have already been detected in food and various tissues of the human body. Scientists therefore warn that global microplastic pollution can be associated with complex risks for the environment and people.
Loaded Lining
It has also already been shown that the particles have a surprisingly intense impact on even remote areas of the earth: Significant amounts of microplastics have been detected in animal life in the Arctic waters and in the deep-sea sediments there. As part of the current study, an international team of researchers has now investigated the suspicion that an important biomass producer in the Arctic Sea could play a fundamental role: the alga Melosira arctica. It grows under the sea ice in the summer half-year, where it forms meter-long chains of cells. This biomass then often sticks together into lumps that serve as food for other living beings. The structures also sink to great depths. At the bottom, they also form an important food source for the organisms living there.
For their study, the researchers collected and analyzed samples of Melosira algae and the surrounding water in Arctic waters on an expedition with the research ship Polarstern. A surprisingly high level of microplastic pollution was found: The clumps of algae contained an average of around 31,000 particles per cubic meter, about ten times the concentration of the surrounding water, reports the team. The accumulation probably has something to do with the consistency of these organisms, the scientists explain: “The filamentous algae have a slimy-sticky texture, so they may collect microplastics from atmospheric precipitation, the seawater itself and the surrounding ice,” says co-author Deonie Allen from the University of Canterbury.
Algae transport microplastics underground
It is now becoming apparent that these organisms are involved in the problematic accumulation of particles in the Arctic environment, the researchers explain: “Once trapped in the algal slime, they are eaten by marine animals or travel down to the sea floor like in an elevator,” says Allen. Lead author Melanie Bergmann from the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research in Bremerhaven goes on to say: “We have now found a plausible explanation as to why we find the largest in the deep-sea sediment in the area of the ice edge Find amounts of microplastics,” says the researcher.
The background to another previously identified accumulation is also clear: the microplastics apparently get into the ice-associated zooplankton via the algal biomass in the higher water layers. These organisms then in turn serve as food for other living beings and so the contamination can reach higher and higher levels of the food chain. The researchers say that the consequences for the sensitive and already stressed Arctic ecosystems could be complex. In addition, the problem can ultimately reach people via fisheries. “Microplastics have already been detected in human intestines, blood, veins, lungs, placenta and breast milk and can cause inflammatory reactions, but the overall consequences have hardly been researched,” says Bergmann.
In order to counteract the risky development, it is now necessary to combat the causes, says the researcher: “Scientific calculations show that plastic pollution can be reduced most effectively by reducing the production of new plastic. This should therefore definitely be prioritized,” says Bergmann. This is exactly what she now wants to do intensively in the forthcoming negotiations on the global plastics agreement in Paris.
Source: Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, specialist article: Environmental Science and Technology, doi: 10.1021/acs.est.2c08010