Water Quality Dynamics in Cyanobacterial Control in Brazilian Cerrado Reservoir

Understanding cyanobacterial dominance in tropical reservoirs is crucial for water management. This study investigated water quality dynamics in the João Leite Reservoir, Brazilian Cerrado, using 30 months of monitoring data from five sites. Physical, chemical, and biological parameters, including fluorometric chlorophyll-a and phycocyanin, were analysed alongside the Trophic State Index (TSI) using multivariate statistics (PCA, CCA). Results showed temporal variations exceeded spatial differences. Cyanobacteria were dominant despite generally low nutrient levels and an oligotrophic TSI classification. Principal Component Analysis identified temperature as strongly associated with cyanobacterial density. However, Canonical Correspondence Analysis and correlastions revealed limited direct statistical influence of measured physicochemical parameters, including nutrients, on cyanobacterial abundance. Findings suggest that in this warm, tropical system, high temperatures combined with stable hydrodynamics due to long hydraulic retention (>180 days) likely facilitate cyanobacterial success, overriding direct nutrient limitation.