Evidence of microplastics in remote alpine lakes of the eLTER network

Microplastic pollution is increasingly recognized as a global environmental issue, but its presence and sources in remote high-altitude freshwater ecosystems remain poorly understood. Here, we provide the first evidence of microplastics in alpine lakes of the European Long-Term Ecological Research network (eLTER), focusing on two lakes—Paione Superiore and Paione Inferiore—and their outlet in the Western Alps. Despite close proximity within a cascading lake system, the sites differ in accessibility and potential anthropogenic pressure. We conducted a preliminary assessment of microplastics (100 μm–5 mm) in surface waters using standardized collection and spectroscopic identification techniques. Microplastics were detected at all sites, with increasing abundance and particle size from the upper lake to the outlet. Fibers were the dominant morphotype, with black and blue fibers prevalent in the upper lake, and clear fibers in the lower lake and outlet. Polyethylene terephthalate and polyester were the most frequently identified polymers. The observed distribution patterns suggest a dual origin: long-range atmospheric transport and local recreational activities such as hiking, picnicking, and fishing. These findings reinforce growing evidence that high-altitude lakes are exposed to microplastic pollution and highlight the need of incorporating these sensitive ecosystems in environmental monitoring programs. We recommend expanding microplastic surveillance within long-term ecological networks and integrating this emerging pollutant into environmental frameworks addressing transboundary air pollution, ecosystem health, and conservation planning.