The species diversity of cyanobacteria in Beijing 53 waters of five major river systems was studied during May and September, 2016-2018. The results showed that 63 species of the genus cyanobacteria belonged to 4 orders, 4 families, 22 genera were found, and the dominant species (IRI) was Chroococcus minor, Lyngbyalimnetica, Aphanizomenon flos-aquae, Phormidium tenue, Arthrospira platensis, Oscillatoria tenuis, Microcystis aeruginosa, and Microcystis flos-aquae. By combining the results of CCA analysis of the dominant species in all waters in Beijing, most of the dominant species are positively correlated with active phosphorus, chlorophyll a, temperature, dissolved oxygen, total alkalinity, total hardness and pH, and TN, TP was negatively correlated with the characteristics of cyanobacteria, and active phosphorus is an important factor limiting the growth of cyanobacteria. The mean density of cyanobacteria in each waters was 1.32×106 ind/L, the mean biomass was 0.003 2 mg/L, and the diversity index was 0.45 in average. The density and biomass of most waters in 2018 decreased as compared with those of in 2017, and the diversity index increased, indicating that Beijing water environment management has improved, but it still needs continuing to strengthen the governance and improvement. |