Abstract: In the context of global warming, increasing human activities have significantly altered the ecological evolution of lakes. To understand the relationships between watershed processes and the ecological environment of Lugu Lake, we measured the weathering rate of carbonate rocks under different vegetation types in the watershed, and investigated seasonal dynamics of water quality and diatom communities in 2019. The weathering rate of carbonate rocks was significantly different between habitats with different vegetation types, which was higher under natural vegetation (forest land, shrub, grassland, etc.) than that under humandisturbed land (farmland). Catchment weathering and terrestrial input exerted significant effects on seasonal variations of dissolved inorganic carbon concentration in water column. Three factors (nutrient concentrations, water temperature, and silicate concentration) shaped the seasonal variations of diatom communities, which were dominated by nitrophilous taxa through the whole year and by small-sized species (Cyclotella ocellata) in summer. Our results indicate that there is a strong coupling between catchment processes and lake environments, and highlight the dependence of lake protection and effective management on the rational planning and exploitation of lake catchment.

Key words: land use type, karst, lake carbon cycling, diatom