Spatiotemporal variability of microplastics in Muskoka-Haliburton headwater lakes, Ontario, Canada

Microplastics (mp) are a growing environmental concern due to their ubiquity in terrestrial and aquatic environments. Nonetheless, there is limited knowledge on their abundance in lakes in rural areas. In this study, we surveyed 14 headwater lakes in Muskoka-Haliburton, Ontario, to assess the spatial and temporal variability of microplastics. The average microplastic concentration across the study lakes was 1.78 mp/L during May–June 2019, with limited spatial variability (coefficient of variation = 22%). Further, microplastic abundance was weakly correlated with lake area (rs: 0.469), the number of shoreline residences (rs: 0.399), and watershed area (rs: 0.350), suggesting that diffusive inputs, such as atmospheric deposition, were the dominant source of microplastics to the study lakes. In contrast, microplastics showed a distinct temporal (seasonal) variability, as the average concentration in August 2019 (0.91 mp/L) was significantly lower ( p