Microplastics distribution in bottom sediments of the Baltic Sea Proper

An abundance of microplastics particles (0.2-5 mm, MPs) in bottom sediments is analyzed based on 53 samples (3 to 215 m deep) obtained in 8 cruises of research vessels across the Baltic Sea Proper in March-October 2015-2016. MPs content varied between stations from 103 up to 10,179 items kg(-1) d.w., with the bulk mean of 863 +/- 1371 items kg(-1) d.w., showing a statistically significant increase with water depth. As many as 74.5% of MPs are of fibrous shape, followed by films (19.8%) and fragments (5.7%). The distributions of fibres, fragments, films, and different types of natural bottom sediments are significantly different, highlighting the specific behaviour of each of these kinds of bottom deposits. A statistically significant correlation between water depth and fibres content is found. Based on the analysis of oceanographic factors and sedimentological principles, an erosion/transition/accumulation pattern for fibres in the Baltic Sea Proper is outlined. Fibres can be considered as a specific type of synthetic sediment , while principles of distribution of other MPs are not yet certain.

Automated summary

This study analyzed the abundance of microplastic particles in bottom sediments of the Baltic Sea. The content of microplastics varied with water depth, with fibers being the most common type. The distributions of fibers, fragments, and films differed significantly from different types of bottom sediments. An erosion/transition/accumulation pattern for fibers in the Baltic Sea was outlined. The distribution principles of other microplastics remain uncertain.