Studies On Primary Productivity Of Khajikotnoor Reservoir, Kalaburagi, Karnataka

Abstract

The present study assessed variation in primary productivity with respect to the alkalinity of Khajikotnoor Reservoir, an important freshwater body in Kalaburagi District, Karnataka State, India, providing irrigation water as well as supplying fish and domestic water. From January 2023 through December 2023 GPP, NPP, and CR were quantified by the light-dark bottle method at five independent sampling sites. GPP peaked during pre-monsoon period (1.12 gC/m³/hr), which was attributed to temperature and nutrient conditions, and NPP was highest in the post-monsoon season (0.58 gC/m³/hr), manifesting for effective energy use. During pre-monsoon, CR was high (0.68 gC/m³/hr), indicating vigorous metabolic activity. Lowest productivity values were observed in monsoon season (GPP: 0.48 gC/m³/h, NPP: 026 gC/m³/h, CR: 0.19 gC/m³/h) which might be due to turbidity and dilution effects of rain-fall. Spatial variation suggested that productivity was greater in the littoral zones (0.89 gC/m³/hr) than in deeper pelagic areas. The mesotrophic to eutrophic condition of the reservoir highlights the importance of having a proper managing plan for its ecological equilibrium conservation. These results provide important information for the sustainable fisheries, water quality controls and conservation in this area.