Sea ice and a wastewater outlet identified as hotspots for anthropogenic microlitter in Svalbard waters

Human activities leave traces of marine litter around the globe. The Arctic is, despite its remoteness, emerging as an area of no exception of this environmental issue. Arctic sea ice has been found to constitute a temporal sink of microplastics, but empirical data on its potential release and subsequent dynamics in the water column are largely lacking. Furthermore, the relative importance of local sources of microplastics in the Arctic marine environment is under discussion. In this study, the concentration and distribution of anthropogenic microparticles (AMPs, <5 mm, including microplastics) in marine waters and sea ice of Svalbard have been investigated. Along a transect originating in Rijpfjorden, sea water samples throughout the water column and sea ice samples were obtained from within the fjord, northwards to the sea ice-edge. Along a transect extending westwards from head to mouth of Kongsfjorden, sea water samples were obtained throughout the water column with sampling stations positioned to enable detection of potential emissions of AMPs from the wastewater outlet of the settlement Ny-Alesund. Environmental parameters along both transects were measured to explore potential correlations with AMP distribution. High concentrations of AMPs were detected in sea ice (158±155 AMPs L⁻¹). AMPs sequestered by sea ice were further found to be released into the water column upon summer melting of the sea ice, coinciding with the ice-edge bloom and suggesting increased bioavailability to biota. In Kongsfjorden, up to an order of magnitude higher concentrations of AMPs (up to 48.0 AMPs L⁻¹) than in Rijpfjorden (up to 7.4 AMPs L⁻¹) were detected. The distribution and composition of AMPs in Kongsfjorden suggest the wastewater outlet from the local treatment plant of Ny-Alesund to be a likely source of origin. Our results emphasize the importance of local sources of AMPs in the Arctic and stresses the urgency of considering their associated environmental impact and regulation particularly since human activities are increasing in the arctic, which is already undergoing rapid environmental change with multiple pressures.