Seasonal Variability of Chlorophyll in Lake Cuitzeo, México with Hyperspectral EnMAP Data

Abstract. Lake Cuitzeo, Mexico’s second-largest freshwater lake, is a highly eutrophic system with spatial and seasonal variability. Monitoring chlorophyll-a, a key indicator of phytoplankton biomass and trophic status, is essential for understanding its ecological dynamics and supporting surrounding communities reliant on the lake’s resources. This study employed hyperspectral EnMAP imagery acquired during the dry (April 2025) and wet (August 2025) seasons to assess chlorophyll-a distribution. Water pixels were delineated using the Modified Normalized Difference Water Index (MNDWI), while chlorophyll-a concentrations were estimated with the Normalized Difference Chlorophyll Index (NDCI), which is particularly effective in optically complex inland waters. Two in-situ chlorophyll-a measurements collected during the dry season were used for qualitative consistency verification. Although a two-sample t-test indicated no statistically significant difference in mean NDCI between seasons (t = 1.27, p = 0.204), spatial analysis revealed marked heterogeneity. Elevated NDCI values during the wet season were concentrated in the central–western basin, whereas higher dry-season values were observed along shallow eastern shorelines. These results underscore the value of high-resolution, spatially explicit monitoring for detecting localized eutrophication and guiding management strategies aimed at preserving the ecological and socio-economic functions of Lake Cuitzeo.