Influence of Seasonal Environmental Factors on Physico-Chemical Parameters and Zooplankton Diversity in Gobbur Reservoir, Afzalpur, Kalaburagi District, Karnataka

Abstract

Evaluating water quality via physico-chemical parameters is essential for determining suitability for domestic, agricultural and potable uses, while zooplankton diversity serves as a key bioindicator of aquatic ecosystem integrity. This study investigates seasonal variations in physico-chemical parameters and zooplankton communities in Gobbur Reservoir, Afzalpur, Kalaburagi District, Karnataka, spanning January 2023 to December 2023. Key physico-chemical metrics included air temperature, water temperature, pH, dissolved oxygen (DO), free carbon dioxide, total dissolved solids (TDS), chloride, calcium, magnesium, phosphate, sulphate, total alkalinity and total hardness. Zooplankton diversity encompassed four major groups:  Rotifera, Cladocera, Copepoda, and Ostracoda. Results revealed climate-driven seasonal patterns, with elevated temperatures in summer correlating strongly with pH and DO, influencing zooplankton abundance—particularly Rotifera, which accounted for 36.2% of the total. Pearson correlation analysis indicated significant positive relationships between total zooplankton density and water temperature (r=0.85, p=0.0004), pH (r=0.87, p=0.0003), DO (r=0.82, p=0.0010), TDS (r=0.71, p=0.0090), total alkalinity (r=0.75, p=0.0050), and total hardness (r=0.73, p=0.0070). All physico-chemical parameters met standards, confirming the water's safety for treated consumption and irrigation. Highest zooplankton diversity occurred in summer, with the lowest in post-monsoon, highlighting environmental variability. This analysis provides insights into the reservoir's ecological stability and informs management strategies.