Microplastic pollution of the Vistula Lagoon and Baltic Sea: A comparison study

Environmental contamination by microplastics (MPs) is reported in a wide range of aquatic habitats worldwide. Semi-enclosed seas, such as the Baltic Sea, have been identified as among the more polluted marine environments, with relatively high concentrations of MPs in water and sediments. We investigated MP concentrations in the surface waters of the Vistula Lagoon and compared them with those in the Bay of Gdańsk in the Baltic Sea. Water samples were collected using a plankton net with a 20 μm mesh size. MPs were identified and enumerated using a Keyence VHX 7000 digital microscope and analyzed by Raman spectroscopy with an Alpha300M+ confocal microscope. Polyethylene was the dominant polymer type, followed by PET. The concentration of microplastic contamination was higher in the Vistula Lagoon (1389 particles/m³) compared to the Gulf of Gdańsk (1244 particles/m³), indicating a greater accumulation of microplastic particles in the semi-enclosed lagoon environment. The dominant type of microplastic detected was fibers, constituting 73% in the Vistula Lagoon and 82% in the Gulf of Gdańsk, respectively. We documented the presence of significantly longer microplastic fibers in the Vistula Lagoon water compared to those identified in the Baltic Sea. Microplastic was detected in all samples, with 112 particles from Krynica Morska (Gulf of Gdańsk) and 125 particles from Kąty Rybackie (Vistula Lagoon). To our knowledge, this is the first documented observation of such a disparity between lagoon and sea waters. • Microplastic pollution assessed in the Vistula Lagoon and the Baltic Sea. • Dominance of polyethylene and PET microfibers identified in samples. • Significant size variation in microplastic fibers between lagoon and sea. • First documentation of longer fibers in lagoon waters compared to the sea. • Study establishes a baseline for microplastic contamination in the region