Positively buoyant but sinking: Polymer identification and composition of marine litter at the seafloor of the North Sea and Baltic Sea. (November 2021) - Int-Veen, Ivo
Abstract: Different litter types accumulate in all marine environments. Plastics are of special interest because of their high abundance and possible threats to marine organisms. Polymer type is crucial for their distribution and fate in marine environments. Seafloor litter abundance and composition in the Baltic and North Sea were analysed based on three sampling campaigns according to the protocol of ICES International Bottom Trawl Survey. Polymers were identified via attenuated total reflection-Fourier transform infrared spectroscopy. General litter abundances differed significantly between the Baltic and North Sea with 9.6 items/km 2 and 70.7 items/km 2, respectively. Plastic built the dominating litter group in both seas (62.2% and 91.3%, respectively). Polymer identification revealed clear dominance of polyethylene, polypropylene and polyamide. Most polymers were positively buoyant in seawater (89.5%), thereby excluding polymer density as the main driver of vertical plastic litter transportation. Plastics at the seafloor basically reflected the entirety of polymers entering marine environments. Graphical abstract: Unlabelled Image Highlights: Majority of litter at the seafloor of the North Sea and Baltic Sea are plastics. Polymers of plastic seafloor litter were identified by ATR-FTIR. Most abundant polymers are polyethylene, polypropylene and polyamide. Almost 90% of polymers show initial positive buoyancy in seawater. Polymer density is not a main driving factor of vertical plastic litter transport.