Micro- and mesoplastic pollution along the beaches in the open Baltic Sea and Gulf of Riga

We present a comprehensive assessment of micro- and mesoplastic pollution along 24 beaches of the Latvian coastline (Northern Europe, Baltic states) establishing a baseline for pollution distribution in the Baltic Sea Region. A detailed analysis of sand granulometry, hydrodynamic variables (waves and currents) and tourism intensity allowed us to understand better factors that drive plastic pollution distribution along beaches. Over 250 volunteers participated in the sample collection highlighting the importance of citizen science as a tool to support data collection. Our findings reveal a lower concentration of micro- and mesoplastic particles in the semi-closed Gulf of Riga (0.10 particles/kg dry sand) compared to the open Baltic Sea (0.16 particles/kg dry sand). The microplastic size fraction (1-5 mm) showed a distinct cluster with higher concentrations and fiber abundance in coarser beach sands of the open Baltic Sea and eastern Gulf of Riga. We emphasize hydrodynamics as a key factor in the distribution and accumulation of microplastics, while impacts are predominantly of local scale and vary considerably across existing studies. No clear pattern of recreational activities on plastic distribution was identified. Studies elaborating on aspects like sampling season, wave energy, wind, currents, sand granulometric properties, and pollution sources are encouraged to enhance result interpretation and move towards more comparable micro-litter case studies. Reference: Dimante-Deimantovica I, Bebrite A, Skudra M, Retike I, Vika M, Bike J, Barone M, Prokopovica A, Svipsta S and Aigars J (2023) The baseline for micro- and mesoplastic pollution in open Baltic Sea and Gulf of Riga beach. Front. Mar. Sci. https://www.frontiersin.org/articles/10.3389/fmars.2023.1251068/full This work was supported by voluntary donations from the student sorority Selga, the European Regional Development Fund post-doctoral projects No.1.1.1.2/VIAA/2/18/359 and No.1.1.1.2/VIAA/4/20/733, ESF Project No. 8.2.2.0/20/I/003 Strengthening of Professional Competence of Daugavpils University Academic Personnel of Strategic Specialization Branches 3rd Call, and the European Economic Area (EEA) Financial Mechanism 20142021 Baltic Research Programme (grant EMP480).