This thesis investigates the ecological history and rehabilitation potential of Lake Vekeri by analyzing Cladocera subfossils preserved in sediment cores. Through species-level identification and abundance counts across sediment depths, the study reconstructs past environmental conditions and reveals clear shifts between pelagic and littoral taxa. The results indicate phases of eutrophication, reduced water transparency, and habitat degradation, reflected by the dominance of Bosmina species and the decline of macrophyte-associated taxa. Diversity indices support these findings by showing fluctuations consistent with hydrological changes and human impacts on the lake. Overall, the research demonstrates that Cladocera subfossils are effective bioindicators and provides valuable insights for future lake rehabilitation and management strategies.