Seasonal Dynamics of Physico – Chemical Parameters and Zooplankton Community Structure in Gobbur Reservoir, Afzalpur, Kalaburagi District, Karnataka

Assessing water quality through physico-chemical analysis is crucial for evaluating its suitability for residential, agricultural, and drinking activities, whereas zooplankton diversity illustrates bioindicators of ecosystem health. This research study examines seasonal changes of physico-chemical parameters and zooplankton communities in Gobbur Reservoir, Afzalpur, Kalaburagi District, Karnataka, covering the period from January 2024 to December 2024. Notable physico-chemical parameters also included the measurement of atmospheric temperature, water temperature, pH, oxygen (DO), free carbon dioxide, total dissolved solids (TDS), chloride, calcium, magnesium, and phosphate, as well as sulphate. The diversity of zooplankton included five groups: Protozoa, Rotifera, Cladocera, Copepoda, and Ostracoda. Findings demonstrated seasonal patterns influenced by climate conditions, with increased summer temperatures, pH and DO relating strongly with zooplankton numbers, especially Rotifera which constituted 35.64% of the total. Pearson correlation analysis showed strong and significant positive correlations between total zooplankton density and water temperature (r=0.86, p=0.0003), pH (r=0.88, p=0.0002), DO (r=0.83, p=0.0009), TDS (r=0.72, p=0.0083), total alkalinity (r=0.76, p=0.0044), as well as total hardness (r=0.74, p=0.0064). All physico-chemical parameters were compliant, signifying water was safe for consumption after treatment and safe for irrigation. Summer showed the greatest diversity of zooplankton while post-monsoon showed the least, which indicates seasonal shifts in environmental conditions. This comprehensive assessment sheds light on the ecological equilibrium of the reservoir.