From northern Norway to the edge of sea ice, microplastics have been present in every single water sample researchers had collected in the highly productive Barents Sea and measuring the highest concentrations in coastal waters and at the ice edge.
Poor waste disposal, fishing, shipping, tourism, ocean currents, ice melt – all are factors that, according to a British research team, influence microplastic concentrations in the Barents Sea, already one of the most impacted regions on Earth.
The team had filtered huge amounts of water – a total of almost 21,000 cubic metres – along the entire stretch from Tromsø to the ice edge during a research expedition in July 2018 and had discovered microplastics, mostly fibres, in every single sample. With an average of 0.011 microplastic particles per cubic metre, the concentrations found are low compared to other regions, but still pose a threat, especially to zooplankton.
Published in the journal Frontiers in Marine Science, the researchers report states that they had found the highest microplastic concentrations of 0.015 particles per cubic metre at the southern and northern ends of the study area: in the Norwegian coastal region off Tromsø and at the sea ice edge. At the central Barents Sea, concentrations were only about half as high, at 0.007 particles per cubic metre.
The majority of the particles were between about 40 micrometers and one millimeter in size, which corresponds to the size of the preferred diet of zooplankton such as krill, amphipods, and various species of copepods – and thus forms the entry point for microplastics into polar food web. Ingestion of microplastics can have negative effects on the growth and reproduction of these animals measuring only a few centimeters or millimeters, as previous studies have shown.
Numerous species of fish, whales, seals and seabirds benefit from the abundance of nutriens in the Barents Sea, one of the most productive marine regions in the world, and they depend on zooplankton as the basis of the food web. Together with their prey, they are very likely to ingest microplastics in even largre amounts, with potential negative consequences for them as well.
Determining the exact origin of the microplastic particles was not possible within the scope of the study and is generally very difficult anyway. However, studies have shown that microplastics reach the Arctic from far away via ocean currents, especially from the North Atlantic, and via the atmosphere. And due to ocean currents, the Barents Sea is considered a hotspot for microplastics.
On the other hand, the research team believes that local sources such as wastewater discharges and increased tourism also contribute to pollution. The latter turns into a problem especially where adequate waste and wastewater infrastructure is lacking. In addition, the Barents Sea is an economically highly developed region with industrial fishing, oil and gas production, and associated shipping – all of which further contributes to (microplastic) pollution, the study authors suggest.
The authors link the high concentrations off the coast of Norway to the proximity to the mainland, while at the ice edge, ice melt seems to be the reason. According to the researchers, the West Spitsbergen Current could transport microplastics towards the pack ice from the settlements on Svalbard, where large amounts of plastic wash up on the beaches every year. In winter, microplastic particles get trapped in the ice and are released again in summer.
Climate change and the resulting rapid loss of sea ice will cause microplastic concentrations in the water to continue to rise, increasing the likelihood of potentially negative impacts on zooplankton and other marine organisms.
Julia Hager, PolarJournal
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