Dataset on microplastic concentrations, characteristics, and chemical composition in the marine surface waters of Latvia - the Eastern Gotland basin and the Gulf of Riga.

The dataset provides information on spectroscopically verified microplastics, both particles and fibers, from 44 marine surface water samples of two Baltic Sea sub-basins - the semi-enclosed Gulf of Riga and the Eastern Gotland Basin. Sampling was performed by using Manta trawl with a mesh size of 300 µm. Thereafter, the organic material was digested with sodium hydroxide, hydrogen peroxide and enzymes. Samples were filtered on glass fiber filters and analyzed visually, registering the shape, size, and color of each item. Where feasible, the polymer type was determined using Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy method. The number of plastic particles per m of filtered water was determined. The data presented in this article may be useful for further research on microplastic pollution, meta-analysis and calculation of microplastic flow. Interpretation and analysis of total acquired data on micro debris and microplastics are reported in the article "Occurrence and spatial distribution of microplastics in the surface waters of the Baltic Sea and the Gulf of Riga".