Remote Sensing of Atmospheric Methane (XCH4) Concentrations over Lake Ecosystems: Seasonal Dynamics and Environmental Drivers in Eğirdir and Burdur Lakes of Türkiye

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Abstract
As lakes contribute significant amounts of methane (CH4) to the atmosphere, they account for a significant share of the global greenhouse gases (GHGs) budget. Since lakes are ecosystems where physical and biological processes influencing CH4 formation are concentrated, the study focuses on atmospheric CH4 column concentrations over lake areas. This study aims to analyze the temporal variation in atmospheric CH4 column concentrations (XCH4) over Lake Eğirdir and Lake Burdur in Türkiye in 2023 and 2025 as well as the relationship between XCH4 and environmental parameters such as Water Surface Temperature (WST), Normalized Difference Chlorophyll Index (NDCI), and Floating Algae Index (FAI). The temporal variability of XCH4 observed over both lakes showed statistically significant positive correlations with lake-area-averaged WST, NDCI, and FAI (Pearson r = 0.49–0.65, p < 0.01). This outcome indicates consistent temporal patterns between XCH4 and environmental conditions at the lake scale. Furthermore, time-series graphs show that monthly average XCH4 values in both lakes reached their highest levels during the summer and autumn months. During these periods, XCH4 concentrations exceeded 1860 ppb in Lake Eğirdir and 1900 ppb in Lake Burdur. The areas of land use/land cover (LULC) classes surrounding the lakes were evaluated together with XCH4, and relatively higher XCH4 values were observed over agricultural areas, which constitute the dominant class in the basins of both lakes. The distribution of XCH4 throughout the lake depth showed higher values in the shallow and mid-depth zones and lower values in the deeper areas beyond 20 m, indicating that the distribution of XCH4 varies throughout lake depth. The results obtained underline the importance of remote sensing data in monitoring XCH4 in lake ecosystems.

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