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Microplastics in Two Tropical Andean Lakes: Contrasting Human-Impacted and Minimally Disturbed Watersheds
Summary
Researchers compared microplastic contamination in two Andean lakes in Ecuador at different altitudes and with contrasting levels of human activity. They found that the lake influenced by agricultural and urban land use had higher contamination than the protected high-altitude lake, though both contained microplastics. The study helps clarify how different pollution sources and transport pathways contribute to microplastic presence in remote tropical freshwater systems.
Microplastics (MPs) are emerging contaminants in freshwater systems, yet their sources and transport pathways in tropical high-altitude lakes remain poorly understood. This study quantified and characterized MPs in two Andean lakes in Ecuador with contrasting watershed conditions: San Pablo (2672 m a.s.l.), influenced by agricultural and urban land use, and Caricocha (3724 m a.s.l.), a protected high-Andean lake. Sixteen samples per lake were collected during four field campaigns. MPs were identified using visual and morphological criteria, and classified by shape, color, and size. MP concentrations were higher in San Pablo (238 ± 32 MP m−3, mean ± SD) than in Caricocha (32 ± 10 MP m−3). Fibers dominated (87.3%), followed by fragments, while microspheres were detected only in Caricocha. MP concentrations showed positive correlations with urban-agricultural land use (ρ = 0.87, p < 0.0001) and negative correlations with natural vegetation cover (ρ = −0.87, p < 0.0001). Principal Component Analysis linked fiber abundance and small size classes (<500 µm) and anthropogenic land use, consistent with surface runoff and wastewater-associated pathways. In contrast, MPs in the protected lake may originate from long-range atmospheric deposition. These results indicate that watershed configuration and protection status shape MP inputs in high-Andean lakes.