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Seasonal variations in the sinking fluxes of microplastics and textile fibers in an Arctic fjord (Kongsfjorden, Svalbard)
Summary
Researchers measured seasonal variations in microplastic and microfiber sinking fluxes in Kongsfjorden fjord, Svalbard, using a moored sediment trap rotating monthly over one year from September 2021 to September 2022. By capturing sinking particles at 61 m depth where Atlantic water masses interact with glacial melt fronts, they documented temporal variability in vertical microplastic export and identified seasonal drivers affecting particle flux to the Arctic seafloor.
The magnitude of microplastics (MPs) and microfibers (MFs) sinking flux and its temporal variability is crucial to understanding their global fate in the ocean. MPs have been reported in deep Arctic sediments as well as in the water column; however, the mechanisms driving their vertical transport are still unclear, and little is known about their sinking dynamics and export to the seafloor. We measured seasonal variations in MPs and MFs vertical fluxes along the water column in an Arctic Fjord (Kongsfjorden, Svalbard archipelago). Sinking particles have been collected for one year using a moored sediment trap located in a hydrological and depositional strategic location, where Atlantic water masses entering the fjord interact with glacial melt water fronts. The rotating sediment trap equipped with 12 receiving cups was placed at 61 m depth in September 2021 and retrieved in September 2022. The interval of trap rotation was set at 30 days allowing the study of seasonal variations in MPs deposition rates. MPs were extracted through multi-enzymatic digestion, catalyzed oxidation and density separations, and analyzed using FPA-µFTIR-Imaging. Microfibers (MF) were also quantified. Both sediments and MPs fluxes showed a marked seasonality. Sediment flux was higher in July-September due to glacier melting by solar radiation, higher air temperature, rain precipitation and runoff. Annual mean fluxes of 5.6 ± 2.6 MP Day-1 and 4.2 ± 2.4 MF Day-1 were measured. The highest MP deposition was measured in September (12.6 vs 2.9 MP Day-1 in May) while the highest MF deposition was recorded in winter (8.2 MF Day-1 vs 0.8 MF Day-1 at the end of spring). These results shed new light on the temporal variability of MPs and MFs vertical fluxes in the Arctic region, providing crucial information about their sources and export mechanisms to the seafloor. Also see: https://micro2024.sciencesconf.org/558776/document