Study on Relationship between Cyanobacteria Blooms and Chemical Biological Factors in a Shallow Temperate Zone Lake

A 4-month data set was used to investigate historical changes between the number of the Cyanobacteria and concentrations of total nitrogen (TN), total phosphorus (TP), TN:TP, chemical oxygen dawdling (COD), NO₃, pH and Chl-a in a shallow temperate zone lake (Guishui Lake, Beijing, China). The aim was to evaluate changes in the risk of Cyanobacteria blooms, which have occurred several times in the lake every year. Observe that high ratios of total TN:TP (> 20), and low concentration of TP (<0.3 mg/L) may suppress the growth of the Cyanobacteria in the lake. Two thresholds that P = 0.6 mg/L and NO₃ = 1.0 mg/L have been found to be related to the Cyanobacteria blooms in the lake. Based on the data collected at six water quality monitoring sites in the Lake, a nonlinear regression formula on growth of blue algae cells is established via ratio TN:TP and the concentrations of COD, NO₃, pH and Chl-a. The calculated results on the number of the Cyanobacteria cells via the nonlinear regression formulas are good in agreement with the monitoring data of the six water quality monitoring sites.