Beach wrack as a potential microplastic hot spot in the South-Eastern Baltic Sea environment

Beach wrack is considered as a major source of nutrients to the sandy coast ecosystems in the South-East Baltic Sea, and it serves as the natural beach sediment storage and habitat formation material. However, it also could be a hot spot for microplastic and other types of marine litter accumulation. We carried out the recovery rate experiments to determine the most reliable method for a rapid and cost-effective application to extract microplastics from the beach wrack. The aeration of media in a saturated solution of sodium chloride revealed to be statistically significant and reliable, therefore was selected as a most suitable to extract the microplastics from the beach wrack. This study shows that the concentration of microplastics is significantly different between the four analyzed compartments in the coastal zone. The microplastic concentration in a beach wrack, with a mean value of 0.47 ± 0.17 items/cm³, contained 4.7 times more microplastics than observed in the surface sand samples. This study estimated that on average over 450 million microplastic items could be found during the castaway event in the South-East Baltic Sea coast.