Spatial-temporal distribution and polymer characterization of microplastics in surface waters of Lake Singkarak (Solok Region, Indonesia): A baseline study

Microplastics (MPs) are emerging pollutants of global concern, yet their distribution in tropical freshwater ecosystems remains poorly understood. This study presents the first comprehensive assessment of MP occurrence in the surface waters of Lake Singkarak, a nationally strategic ecosystem and habitat for endemic fish species. Surface water samples were collected from five monitoring stations (S1–S5) during both rainy and dry seasons. MPs were widely distributed across all stations, with average concentrations ranging from 250 to 1200 particles L⁻¹ , and abundance was generally higher during the rainy season, particularly at sites influenced by domestic activities, aquaculture, and agriculture. Station S2 (Muaro Paninggahan) exhibited the highest seasonal increase (≈1000 %), while stations with minimal anthropogenic influence (S4 and S5) showed comparatively smaller variations (28–67 %). Fragments dominated MP morphology, and polyamide (PA) and polyethylene terephthalate (PET) were the most frequently detected polymers, suggesting significant contributions from domestic waste, aquaculture operations, and agricultural runoff. Although spatiotemporal variations were apparent, statistical analyses indicated no significant seasonal differences (p > 0.05), highlighting the influence of localized environmental factors, such as hydrodynamics and human activity, on MP distribution. These findings underscore the urgent need for targeted pollution control, improved waste management, and long-term monitoring to safeguard the ecological integrity and socio-economic value of Lake Singkarak.