Microplastic pollution and ecotoxicological risk in high-altitude glacial lakes of Durmitor, Montenegro

Microplastics (MPs) are increasingly recognized as widespread contaminants in aquatic environments, including remote freshwater systems, where their presence is linked to waste generation and transport pathways. This study examined the occurrence, spatial-temporal distribution, polymer composition, and ecological risks of MPs in surface sediments from Black Lake and Devil Lake, two high-altitude glacial lakes in Durmitor National Park, Montenegro. Sediment samples were collected across three seasons and analyzed using standardized methods, including density separation, visual identification, and polymer characterization. MPs abundance averaged 5.1 ± 1.4 items per 100 g of dry sediment in Black Lake and 3.8 ± 0.5 items per 100 g in Devil Lake. Fibers and fragments were dominant morphotypes, with particles sized 1-3 mm prevailing. Blue particles were most frequent. Five polymer types were identified, with polyethylene as the dominant polymer. Pollution load index values indicated moderate contamination, while polymer hazard and ecological risk indices suggested high to very high environmental risk. The presence of MPs in protected, high-altitude glacial lakes highlights their vulnerability to diffuse pollution sources, including tourism and long-range transport. The findings provide baseline data for alpine freshwater environments and underline the importance of integrating MPs pollution into waste management and environmental protection strategies.