Seasonal Dynamics and Ecological Health of Ullal Lake in Bengaluru North, Karnataka, India Introspected through Limnological Perspective and Physiological Response Assessment on Zebrafish (Danio rerio)

Aim: Bangalore City in Karnataka is known for its serene environment, landscapes, and IT development. The continuous inflow of people from various states and increased anthropogenic activities have caused stress to lake ecosystems and influenced the seasons. Therefore, the present research investigates the seasonal and spatial variations in the limnological factors of Ullal Lake in Bangalore North to identify environmental stressors and assess its ecological health. Materials and Methods: Composite water samples were collected from three sampling stations: an open surface, a deposit, and an inlet. These samples were analyzed for physicochemical factors, including pH, temperature, conductivity, humidity, turbidity, dissolved oxygen, biochemical oxygen demand, chemical oxygen demand, hardness, alkalinity, and the most probable number. Seasonal patterns and developmental stages in Danio rerio were also examined to evaluate the environmental stress. Results: Significant fluctuations were observed in the physical parameters. Oxygen-dependent variables also varied, including, hardness, alkalinity, and microbial load. Seasonal patterns showed that environmental factors like temperature, humidity, and biological activity influenced water quality. Specifically, pH and conductivity were most influenced during spring, while autumn significantly affected dissolved oxygen and microbial load. Summer exhibited elevated alkalinity and turbidity. Developmental stages in Danio rerio were unaffected in the open surface and inlet stations, but decreased heart rate indicated environmental stress at the deposit and inlet stations. Conclusion: The open surface station demonstrated superior water quality compared to the other two stations. The study highlights the importance of seasonal dynamics in influencing limnological parameters and the ecological health of Ullal Lake. It recommends addressing seasonal variations, continuous monitoring, and the implementation of sustainable management practices for the conservation and sustainability of these wetlands.