Data on microplastic contamination of the Baltic Sea bottom sediment samples in 2015-2016.

The contamination by microplastics particles (MPs, 0.2-5 mm) in bottom sediments of the Baltic Sea is quantified. In total, 53 sediment samples were obtained in 8 cruises of research vessels in July-October 2015 and March-December 2016. The depths from 3 to 215 m in the Gotland, Gdansk, and Bornholm Basins are covered. Primary data is provided, along with exhaustive information on sampling dates and coordinates, depths, sampling methods, extracting procedures, control measures, detection techniques, and verification by µ-Raman spectroscopy. Number of pieces per kg dry weight is determined separately for fibres, films, and fragments. Distributions by size, plastic colour, and plastic type are presented. Modified NOAA method and µ-Raman spectroscopy were applied to obtain the data, thus they can be used for comparative analyses.