The role of oceanographic processes and sedimentological settings on the deposition of microplastics in marine sediment: Icelandic waters
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Secondary research area:
Christine Loughlin(1), Ana R. Marques Mendes(2), Liam Morrison(2), Audrey Morley(1)*
(1)School of Geography and Archaeology and Ryan Institute, National University of Ireland, Galway University Road, Galway, Ireland; (2)Earth and Ocean Sciences, School of Natural Sciences and Ryan Institute, National University of Ireland, Galway, Ireland
Marine Geology, Oceanography
The presence of microplastics have been recorded globally in all types of marine environments, from coastal ecosystems to remote Polar regions and the deep-sea. The sea floor is considered a sink for microplastics as the plastics fall out of the water column and settle in the sediment. Due to the small size of microplastics a wide range of organisms are at risk from microplastics settling at the seafloor. This is because they can easily be ingested throughout the entire food chain from phytoplankton to mammals in the water column, and by benthic invertebrates at the sea floor. As a result, the long-term effects of marine microplastics on organisms and ecosystems is an area of active research and of major concerns to policy makers.
This study assesses the presence, depth, and distribution of microplastics (classified here as 63 μm - 5 mm) collected via multicore sampling from the Iceland shelf and surrounding areas. Microplastics were extracted from sediments following methods described in Martin et al. (2017). Furthermore, we investigate the potential role of oceanic surface and bottom water currents, organic content, and sediment type on the distribution, deposition, and burial of microplastics in marine sediments. The results provide the first record of microplastic pollution in marine sediments from the Iceland shelf and explore the deposition of microplastics within varying oceanographic conditions.
We find that microplastic pollution is omnipresent within the top 5 cm of marine sediments, regardless of depositional environments, pathways, or distance to anthropogenic activities.
Further, our results suggest that microplastic depositional hotspots could be related to sediments with high OM and/or fine-grained sediments linked to low energy environments. We highlight that active feeding grounds for cod in this investigation showed an exceptionally high microplastic count. These locations also coincide with heavily trawled fishing grounds which could contribute microplastic loading in these areas. Based on our findings, we recommend that future investigations and monitoring efforts exceed 5 cm depth and include special considerations to seabed topography, oceanographic transport pathways, and biological settings. In combination, these parameters could be modelled numerically to predict likely depositional hotspots.
Geological Survey of Ireland Short-calls Programme 2015 and JPI Oceans (PLASTOX)
Microplastic; Shelf; Sediment; Raman spectroscopy; Microfiber