Spatiotemporal trends in microplastic pollution of surface waters of the Eurasian Arctic

The present study addresses spatial and temporal distribution of floating microplastics (MPs) in the Eurasian part of the Arctic Ocean. In this study we used a harmonized methods from sample collection to data reporting according to the latest recommendations of AMAP for MPs research. Studies were carried out in 6 cruises: in August-October 2019, 2020, 2021 and 2022 onboard R/V Akademik Mstislav Keldysh and R/V Akademik Ioffe. A total of 200 surface water samples were collected in the Barents, Kara, Laptev, and East-Siberian seas, comprising by far the most extensive dataset on floating microplastics in the Eurasian Arctic. Floating debris were sampled using a Neuston net with mesh size 0.33 mm, each catch lasted an average 20 minutes. All potential plastic particles were identified on ATR -FTIR (Spectrum Two, Perkin Elmer). It was revealed that MPs pollution significantly decreases from the West to East in the Eurasian Arctic, from 19.0 µg/m3 in the Barents Sea to 11.2 µg/m3 in the Kara Sea, 3.6 µg/m3 in the Laptev Sea and 2.0 µg/m3 in the East-Siberian Sea. Less MPs were found in the Great Siberian River plumes than in high saline water. The maximum concentration of MPs was found in the Kara Gates Straight (640 µg/m3) in August in the waters flowing from the Barents Sea. This can indicate that the main source of MPs in the Siberian Arctic is located in the Barents Sea. Variability of MPs abundance was found in the Kara Sea for different years, 1000 – 5000 items/km2 on average without a clear trend. Possible influence of several factors effecting MPs fate here was discussed, i.e. interannual changes in riverine discharge, shipping activity, Atlantic water inflow, ice cover.