Marine Litter Pollution in Baltic Sea Beaches - Application of the Sand Rake Method

Most marine litter monitoring methods used on beaches focus on macro-litter (>25 mm) only and show shortcomings regarding smaller litter classes (<25 mm), especially at Baltic Sea beaches. Therefore, we used a sand rake method developed for large micro- (2-5 mm), and meso- (5-25 mm) litter to quantify the overall pollution status of Baltic Sea beaches and to test if the method is useful in terms of the requirements of the Marine Strategy Framework Directive (MSFD). Between July 2017 and October 2019, 197 sand rake method surveys were carried out at 35 regions around the Baltic Sea. In total, 9345 litter pieces were found on an area of 10,271 m(2) of which 69.9% were 2-25 mm in size. Artificial polymers (4921 litter pieces) were predominant (mean 52.7% +/- 13.3). Abundance of litter was 0.91 pieces/m(2) +/- 1.50 (median 0.40 pieces/m(2)). The most common litter were industrial pellets (19.8%), non-identifiable plastic pieces 2-25 mm (17.3%), cigarette butts (15.3%), and paraffin (11.9%). At 15 surveys at the German North Sea island of Sylt the litter abundance ranged from 0.45 pieces/m(2) (median) to 0.59 pieces/m(2) +/- 0.37 (mean). Here, 69.2% of the litter was 2-25 mm in size and paraffin was predominant (69.2%). Beaches show a high pollution level with large micro- and meso-litter (2-25 mm) and our data can serve as a Baltic-wide pollution baseline. In contrast to the naked eye OSPAR method for macro-litter, the sand rake method is generally applicable on all sandy beaches, both urban and remote. This method also allows for the provision of a full spatial pollution pattern and can serve for assessing the effectiveness of marine litter mitigation measures.