Comparative investigations of microplastic (MP) occurrence in the global ocean are often hampered by the application of different methods. In this study, the same sampling and analytical approach was applied during five different cruises to investigate MP covering a route from the East-Siberian Sea in the Arctic, through the Atlantic, and into the Antarctic Peninsula. A total of 121 subsurface water samples were collected using underway pump-through system on two different vessels. This approach allowed subsurface MP (100 μm-5 mm) to be evaluated in five regions of the World Ocean (Antarctic, Central Atlantic, North Atlantic, Barents Sea and Siberian Arctic) and to assess regional differences in MP characteristics. The average abundance of MP for whole studied area was 0.7 ± 0.6 items/m³ (ranging from 0 to 2.6 items/m³), with an equal average abundance for both fragments and fibers (0.34 items/m³). Although no statistical difference was found for MP abundance between the studied regions. Differences were found between the size, morphology, polymer types and weight concentrations. The Central Atlantic and Barents Sea appeared to have more MP in terms of weight concentration (7-7.5 μg/m³) than the North Atlantic and Siberian Arctic (0.6 μg/m³). A comparison of MP characteristics between the two Hemispheres appears to indicate that MP in the Northern Hemisphere mostly originate from terrestrial input, while offshore industries play an important role as a source of MP in the Southern Hemisphere. The waters of the Northern Hemisphere were found to be more polluted by fibers than those of the Southern Hemisphere. The results presented here suggest that fibers can be transported by air and water over long distances from the source, while distribution of fragments is limited mainly to the water mass where the source is located.

Plastic pollution in the marine environment has turned into an important research topic in recent decades. Until recently, studies were often based on visual assessment only, which is not enough to draw any conclusion about the chemical nature of found plastic items and could lead to incorrect results. Standardized, fast, and efficient low-cost methods for marine plastic litter identification are urgently needed to monitor the occurrence and distribution worldwide. In this paper, we demonstrate that a miniaturized handheld near-infrared spectrometer—MicroNIR—can be used for on-site identification of different plastic polymers. A database containing polymer spectra of the most produced and reported polymer types in the marine environment was created including polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), polyvinyl chloride (PVC), polyamide (PA), polycarbonate (PC), polyurethane (PUR), and Silicone. Using spectral match value (SMV, included in the instrument software) for spectra analysis resulted in an accurate classification of all nine polymer types. The method was used for the identification of marine macro-, meso-, and microplastic litter collected on beaches in sediments and seawater and enabled the correct identification of marine plastic litter for macro-, meso- (96%), and microplastics (73%) with exception of totally black items and items less than 1 mm in size. The method and instrumentation presented here are very well suited to support “Citizen Science” marine litter monitoring projects during beach cleaning and similar activities.

Plastic is recognized as a threat to marine ecosystems, and estimating the level of plastic and microplastics (MPs) pollution of the World Ocean is, nowadays, the goal of many studies. However, the use of different methods for the sampling and analysis of MPs leads to the problem of comparing the results obtained. Studies on surface MPs pollution of the surface sea water are based on the application of the manta or neuston nets that collect water from the upper 10–20 cm layer (the “surface” MPs) or submersible pumping systems that collect water from the water layer 3 to 5 m below the sea surface (the “subsurface” MPs). These two techniques allow the collection of particles of different size fractions, i.e., >300 µm for the surface MPs and >100 µm for the subsurface MP. However, it is shown that microplastics found in the surface and subsurface layers differ not only in the size of the items found, but also in morphology, types of polymers, abundance, weight concentration and their spatial distribution. Different hydrodynamic processes affect the fate of the plastic found exactly at the sea surface and several meters deeper. The aim of this work was to study the distribution of surface and subsurface MPs and to reveal an influence of oceanographic conditions on their spatial distribution, using as an example the open ocean waters of the Central Atlantic.

Plastic is recognized as a threat to marine ecosystems and estimating the level of plastic and microplastics (MP) pollution of the World Ocean is nowadays the goal of many studies. However, the use of different methods for sampling and analysis of MPs leads to the problem of comparing the results obtained. Studies on surface MP pollution of the surface sea water are based on the application of the manta or neuston nets that collect water from the upper 10-20 cm layer (the “surface” MP) or submersible pumping systems, that collect water from the water layer 3-5 m below the sea surface (the “subsurface” MP). These two techniques allow to collect particles of different size fraction, i.e. >300 µm for the surface MP and >100 µm for subsurface MP. The aim of this work was to study the distribution of surface and subsurface MPs and to reveal an influence of oceanographic conditions on their spatial distribution as an example of the open ocean waters of the Central Atlantic and coastal water in Norwegian fjords. It was shown that microplastics found in the surface and subsurface layers differ not only in the size of the items found, but also in morphology, types of polymers, abundance, weight concentration and their spatial distribution. Different hydrodynamic processes affect the fate of plastic occurring exactly at the sea surface and several meters deeper. MPs inhabiting the subsurface waters (about 3-5 m depth) have buoyancy close to neutral and appear to be suspended in the surface mixed layer and are readily transported from the sources to the distant regions by ocean currents. Subsurface turbulence is probably the main process that maintains the MPs in the near-surface part of the water column. In contrast, the surface MPs (which are captured by sampling with surface nets) have positive buoyancy and its spatial distribution is significantly influenced by water dynamics, wind and waves, which led to a more scattered distribution on the ocean surface. It was shown that surface and subsurface microplastics differ significantly in a number of properties and, apparently, they should be considered as two independent groups that may have different sources, and their distribution is driven by different hydrophysical processes. Thus, MPs data collected using both methods simultaneously could provide additional information about MPs fate in the ocean.

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.

Among other marine environmental problems, the issue of marine litter accumulation in the World Oceans is of increased interest. It is relevant not only in areas with direct intense anthropogenic pressure, but also in remote and presumably pristine areas, such as the Arctic Sea. As the concentration of plastic waste in the marine environment increases, it can have impacts on various components of the marine ecosystem, at sea, on the seafloor, on the coasts and in particular in accumulation areas, while it also can negatively affect human social and economic activities. To reduce the release of plastic debris into the marine environment, litter occurrence and pathways need to be studied in order to identify litter sources, requiring monitoring studies that provide comparable results. Here we present the results of studies of the level of pollution by floating marine debris carried out using ship-based visual observations through a harmonised methodology, developed to obtain comparable data. The observations were carried out in the White Sea, Barents Sea and the Kara Seas during a research cruise of the Floating University project by the Shirshov Institute of Oceanology Russian Academy of Sciences in 2021. The studies included training and involvement of a large number of students as observers. Floating macro litter was observed in all study areas along the vessel’s route. In total 2500 km route and 19,8 km2 were covered with observations. The concentration of litter varied on observed transects from 0 to 226 items/km2, with a mean value of 10.1 items/km². 95% of registered items were made of plastic, the most common were unidentified, weathered plastic objects that could indicate the long presence of litter items in the environment.