Spatial and vertical distribution of microplastics in Arctic waters around Svalbard

Abstract

Microplastic (MP) pollution in the aquatic environment is increasing, even in remote locations. Despite their remoteness, Arctic marine ecosystems are increasingly recognized as sinks and redistribution zones for microplastics. This study investigated the occurrence of MPs in surface and subsurface waters around the Svalbard archipelago. MP concentrations ranged from approximately 0.03 to 1.34 MP m−3 in horizontal tows and from 0.02 to 2.2 MP m−3 in vertical tows, with significantly higher mean concentrations in vertical samples (0.64 ± 0.08 MP m−3) than in horizontal samples (0.27 ± 0.04 MP m−3). A total of 17 polymer types were identified. Polyethylene terephthalate dominated both sampling modes, accounting for 68.6% of particles in horizontal tows and 64.2% in vertical tows, followed by polyethylene, polypropylene, polyamide. Polymer diversity was significantly higher in vertical samples than in horizontal ones, with Shannon index values of 0.65 ± 0.09 and 0.33 ± 0.07, respectively, although overall multivariate polymer composition did not differ significantly between sampling strategies. Vertical samples also exhibited broader heterogeneity, including increased representation of PAN, HIPS/ABS-type polymers, and rubber-derived particles at some stations. Fibers were the dominant particle shape in both sampling modes, representing 87.59% of particles in horizontal tows and 79.2% in vertical tows, while fragments, films, and beads were proportionally more frequent in vertical samples. Color composition was similarly broader in vertical tows, although black, green, and blue particles dominated both datasets. Particle size ranged from 220 to 4824 μm in horizontal samples and from 128 to 4888 μm in vertical samples, with no significant difference between sampling modes. Concentrations did not differ significantly among fjord, shelf, and offshore stations, or between stations close to and distant from settlements, once corrected for multiple testing. These results show widespread MP occurrence around Svalbard and indicate that surface-only sampling may underestimate particle abundance and compositional heterogeneity in the upper water column. Long-term monitoring that includes water-column sampling is therefore needed to improve assessments of MP transport, retention, and ecological exposure in polar marine systems. For management, these findings argue for depth-resolved sampling to be built into harmonized pan-Arctic monitoring frameworks, and for local measures, in particular improved wastewater treatment at Svalbard settlements and more strict control of fishing- and shipping-related plastic losses, to complement international action on long-range plastic transport.