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Plastic, as a form of marine litter, is found in varying quantities and sizes around the globe from surface waters to deep-sea sediments. Identifying patterns of microplastic distribution will benefit an understanding of the scale of their potential effect on the environment and organisms. As sea ice extent is reducing in the Arctic, heightened shipping and fishing activity may increase marine pollution in the area. Microplastics may enter the region following ocean transport and local input, although baseline contamination measurements are still required. Here we present the first study of microplastics in Arctic waters, south and southwest of Svalbard, Norway. Microplastics were found in surface (top 16 cm) and sub-surface (6 m depth) samples using two independent techniques. Origins and pathways bringing microplastic to the Arctic remain unclear. Particle composition (95% fibres) suggests they may either result from the breakdown of larger items (transported over large distances by prevailing currents, or derived from local vessel activity), or input in sewage and wastewater from coastal areas. Concurrent observations of high zooplankton abundance suggest a high probability for marine biota to encounter microplastics and a potential for trophic interactions. Further research is required to understand the effects of microplastic-biota interaction within this productive environment.

Infrastructure is often a limiting factor in microplastics research impacting the production of scientific outputs and monitoring data. International projects are therefore required to promote collaboration and development of national and regional scientific hubs. The Commonwealth Litter Programme and the Ocean Country Partnership Programme were developed to support Global South countries to take actions on plastics entering the oceans. An international laboratory network was developed to provide the infrastructure and in country capacity to conduct the collection and processing of microplastics in environmental samples. The laboratory network was also extended to include a network developed by the University of East Anglia, UK. All the laboratories were provided with similar equipment for the collection, processing and analysis of microplastics in environmental samples. Harmonised protocols and training were also provided in country during laboratory setup to ensure comparability of quality-controlled outputs between laboratories. Such large networks are needed to produce comparable baseline and monitoring assessments.

In this review, we investigated published data on the occurrence of microplastic in Arctic fish, and the suitability of the data and species for risk assessment and monitoring. As of 11.11.2021, we found nine studies in the peer-reviewed literature, one thesis and one report, confirming the occurrence of microplastic in fishes from multiple Arctic regions. The studies varied in methodology, detection and quantification limitations, reported categories of size, shape, and chemical identity. All these factors influence the numbers of microplastic reported, thus limiting comparability and hindering integrative analysis. The physiological impacts of the reported microplastic contamination cannot be determined, as all studies targeted stomach/intestine contents and did not use methods with limits of detection low enough to determine particle translocation from the intestine to other organs, tissues or body fluids within the fish. Furthermore, there is a fundamental lack of understanding the transfer and the effects of plastic additives to Arctic fishes. In addition to discussing methodological challenges and knowledge gaps, we consider ecosystem needs, commercial interests, Indigenous people’s subsistence, food safety and food sovereignty concerns, and developed a framework to harmonize and facilitate pan-Arctic microplastic monitoring.

Few studies have been published on occurrence and distribution on microplastics (MPs) in invertebrates from the Arctic. We still need to develop harmonised methods to enable good comparison between studies taking into account recovery rates, size ranges, shapes and polymer types. Here, we review studies on MPs in invertebrates from the Arctic and present suggestions on sampling protocols and potential indicator species. Since information on MPs in Arctic invertebrates is vastly lacking, we recommend to at least include suspension feeding bivalves like mussels in monitoring programmes to function as indicator species in the Arctic. Mussels have also been suggested as indicator species for MP monitoring in coastal regions further south. Although we recognise the challenge with particle selection and egestion in mussels as well as the relatively low concentrations of MPs in Arctic waters, uptake levels seem to represent recent exposures. More research is needed to understand these selection processes and how they affect the bioaccumulation processes. Future research should include studies on whether different functional groups of invertebrates have different exposures to MPs, e.g., if there are differences between sessile versus motile species or different feeding strategies. More knowledge on monitoring strategies for pelagic and benthic species is needed.

The Arctic Monitoring and Assessment Programme has published a plan and guidelines for the monitoring of litter and microplastics (MP) in the Arctic. Here, we look beyond suggestions for immediate monitoring and discuss challenges, opportunities, and future strategies in the long-term monitoring of litter and MP in the Arctic. Challenges are related to environmental conditions, lack of harmonization and standardization of measurements, and long-term coordinated and harmonized data storage. Furthermore, major knowledge gaps exist with regard to benchmark levels, transport, sources, and effects, which should be considered in future monitoring strategies. Their development could build on the existing infrastructure and networks established in other monitoring initiatives in the Arctic, while taking into account specific requirements for litter and MP monitoring. Knowledge existing in northern and Indigenous communities, as well as their research priorities, should be integrated into collaborative approaches. The monitoring plan for litter and MP in the Arctic allows for an ecosystem-based approach, which will improve the understanding of linkages between environmental media of the Arctic, as well as links to the global problem of litter and MP pollution.

Litter and microplastic assessments are being carried out worldwide. Arctic ecosystems are no exception and plastic pollution is high on the Arctic Council's agenda. Water and sediment have been identified as two of the priority compartments for monitoring plastics under the Arctic Monitoring and Assessment Programme (AMAP). Recommendations for monitoring both compartments are presented in this publication. Alone, such samples can provide information on presence, fate, and potential impacts to ecosystems. Together, the quantification of microplastics in sediment and water from the same region produce a three-dimensional picture of plastics, not only a snapshot of floating or buoyant plastics in the surface water or water column but also a picture of the plastics reaching the shoreline or benthic sediments, in lakes, rivers, and the ocean. Assessment methodologies must be adapted to the ecosystems of interest to generate reliable data. In its current form, published data on plastic pollution in the Arctic is sporadic and collected using a wide spectrum of methods which limits the extent to which data can be compared. A harmonised and coordinated effort is needed to gather data on plastic pollution for the Pan-Arctic. Such information will aid in identifying priority regions and focusing mitigation efforts.

A total of 8218 pelagic microplastic samples from the world’s oceans were synthesized to create a dataset composed of raw, calibrated, processed, and gridded data which are made available to the public. The raw microplastic abundance data were obtained by different research projects using surface net tows or continuous seawater intake. Fibrous microplastics were removed from the calibrated dataset. Microplastic abundance which fluctuates due to vertical mixing under different oceanic conditions was standardized. An optimum interpolation method was used to create the gridded data; in total, there were 24.4 trillion pieces (8.2 × 104 ~ 57.8 × 104 tons) of microplastics in the world’s upper oceans.

The pollution of the environment with plastics is of growing concern worldwide, including the Arctic region. While larger plastic pieces are a visible pollution issue, smaller microplastics are not visible with the naked eye. These particles are available for interaction by Arctic biota and have become a concern for animal and human health. The determination of microplastic properties includes several methodological steps, i.e., sampling, extraction, quantification, and chemical identification. This review discusses suitable analytical tools for the identification, quantification, and characterization of microplastics in the context of monitoring in the Arctic. It further addresses quality assurance and quality control (QA/QC), which is particularly important for the determination of microplastic in the Arctic, as both contamination and analyte losses can occur. It presents specific QA/QC measures for sampling procedures and for the handling of samples in the laboratory, either on land or on ship, and considering the small size of microplastics as well as the high risk of contamination. The review depicts which data should be mandatory to report, thereby supporting a framework for harmonized data reporting.

The rapid growth in microplastic pollution research is influencing funding priorities, environmental policy, and public perceptions of risks to water quality and environmental and human health. Ensuring that environmental microplastics research data are findable, accessible, interoperable, and reusable (FAIR) is essential to inform policy and mitigation strategies. We present a bibliographic analysis of data sharing practices in the environmental microplastics research community, highlighting the state of openness of microplastics data. A stratified (by year) random subset of 785 of 6,608 microplastics articles indexed in Web of Science indicates that, since 2006, less than a third (28.5%) contained a data sharing statement. These statements further show that most often, the data were provided in the articles’ supplementary material (38.8%) and only 13.8% via a data repository. Of the 279 microplastics datasets found in online data repositories, 20.4% presented only metadata with access to the data requiring additional approval. Although increasing, the rate of microplastic data sharing still lags behind that of publication of peer-reviewed articles on environmental microplastics. About a quarter of the repository data originated from North America (12.8%) and Europe (13.4%). Marine and estuarine environments are the most frequently sampled systems (26.2%); sediments (18.8%) and water (15.3%) are the predominant media. Of the available datasets accessible, 15.4% and 18.2% do not have adequate metadata to determine the sampling location and media type, respectively. We discuss five recommendations to strengthen data sharing practices in the environmental microplastic research community.

Endocrine disruption has rarely been reported in field populations of the edible cockle and the context with the general health of the shellfish is unclear. This study examined the reproductive state of two Cerastoderma edule populations over a 6-month period to assess their reproductive condition, the incidence of intersex and presence of parasitic infection. A further seven native sites from south-west England were examined during the peak reproductive season to identify the presence of intersex within the region. Laboratory exposures of organisms collected from field populations showed a significantly female-biased sex ratio compared with controls when exposed to the endocrine disrupting chemicals, bisphenol-A (nominal concentration: 0.1 µg L-1) and 17[...]-oestradiol (nominal concentration: 0.1 µg L-1), but none of the chemical exposures induced intersex. Intersex was revealed in seven out of the nine native populations of C. edule sampled at peak reproductive season. The highest incidence and most severe case of intersex were reported at Lower Anderton on the River Tamer which also had a significantly female-biased sex ratio. Additionally, the dominant trematode family was the Bucephalaidae. Parasitic infection influences the maturity of C. edule by lowering both mean gonad index and condition index. These results suggest that endocrine disrupting chemicals could be contributing factors towards the development of intersex in C. edule.