The effect of tourism on microplastic pollution amount in Baltic Sea Region lakes

Lakes in Baltic Sea Region are relatively little studied regarding microplastics pollution, simultaneously those lakes experience varying pressure of tourism related activities in the catchment area. Hence, lakes may serve as intermediary containers and accumulation point for microplastic particles. In this study we measured microplastic pollution levels in water surface and sediments from 10 lakes in Latvia, Lithuania and Poland. Manta net (300 µm) and a Kayak gravity corer were used to collect 90 surface water and 16 sediment samples. Sampling was done in Spring, Summer and Autumn in 2023. Purified samples were analyzed visually under a microscope in order to determine size, shape and colour of particles. Polymer type of microplastic particles was determined by ATR-FTIR. Microplastics were found in all lake samples. Concentrations of microplastics in surface water varied: in Latvia 0.77 – 4.30 particles/m3, in Lithuania 0.95 – 38.53 particles/m3 and in Poland 0,56 – 18.65 particles/m3. Sediments contained microplastic particles per dry mass gram unit in concentrations of 0.17 – 7.87, 0.19 – 13.48, 0.17 – 3.07 in lakes of Latvia, Lithuania and Poland, respectively. With exception of lakes Mastis and Lukstas in Lithuania, where the highest particle concentrations were found in Summer (19.26 particles/m3) and Autumn (2.81 particles/m3), accordingly, in other lakes the highest microplastic loads in surface waters were observed in Spring. Comparing lakes with high and low tourism intensity, it turned out that intensively used lakes showed on average 0.9 – 6.8 times more microplastic contamination than lakes less affected by tourism. Thus, we conclude that tourism negatively impacts microplastic pollution levels in lakes, however other sources of pollution cannot be excluded. The study was funded by Interreg Baltic Sea Region project Lakes Connect. Also see: https://micro2024.sciencesconf.org/555346/document