Unveiling small microplastics in Norwegian coastal sediment cores

Microplastics (MPs) have been found in high concentrations within surface sediments (top 5 cm) of the Arctic Ocean's deep sea, yet studies on the high-resolution vertical distribution of MPs in sediment from European waters to the Arctic are scarce. The European-wide project FACTS (Fluxes and Fate of Microplastics in Northern European Waters), funded by JPI Oceans, aimed to address the vertical transport of MPs in this study area. Here, we collected five sediment cores along the Norwegian Coastal Current (NCC) using a Multi-corer (MUC) equipped with four stainless steel cores at the corner to minimize potential MP contamination. This study presents data on MP concentrations, polymer compositions, and size distributions in both the water-sediment interface and sediment layers, reaching depths of up to 19 cm down to 11 μm in size. Our findings reveal the widespread presence of MPs across sediment cores, spanning layers predating the introduction of plastics. MP concentrations exhibit significant variation across the sediment cores with the smallest size class (11 μm) predominating all sediment layers. A total of 18 different polymer types were identified across all the sediment layers, with correlations between polymer diversity and depth showing high variability between stations. Our results suggest that differences in seafloor topography and the impact of anthropogenic activities (e.g. fishing) lead to varying environmental conditions at the sampling sites, influencing the vertical distribution of MPs. This calls into question the reliability of using environmental parameters to predict MP accumulation zones and MPs in sediment cores as indicators of the Anthropocene. Also see: https://micro2024.sciencesconf.org/557755/document