This study investigated the role of Cladocera species based on subfossil assemblages in Vekeri Lake, Hungary. The study of this aquatic ecosystem is pivotal to understanding the dynamics of freshwater environments and their responses to environmental changes. The primary objective of this study is to unravel the ecological significance of Cladocera species in Vekeri Lake. By examining subfossil assemblages preserved in the sediment core, we aim to identify Cladocera taxa present in different sediment layers. We look forward to assessing their abundance and diversity across time and investigate how Cladocera respond to the water level dluctuations during drying periods. We too aim to explore any potential implications for the lake’s limnological conditions. Through this interdisciplinary approach integrating hydrobiology, paleolimnology and climate science, this thesis aims to advance knowledge of how Cladocera species can serve as indicatior of ecological change in lakes facing drying seasons. Such insights are crucial for effective management and conservation of freshwater resources amidst a changing climate.