Drivers of cyanobacterial blooms in lakes and reservoirs in Jinan City, China

Abstract

Cyanobacterial blooms are a serious issue and frequently occur in lakes and reservoirs. Understanding how topography and human activities affect cyanobacterial dominance and blooms can greatly enhance the success of restoration projects to reduce blooms. Therefore, in this study the dominant species of cyanobacteria were determined by calculating the break point of the cumulative dominance curve for multiple sites in Jinan, China. In addition, the key drivers affecting the dominant cyanobacteria species were identified by canonical correspondence analysis and correlations between topography, human activities and the key drivers of the dominant cyanobacteria were investigated using random forests analysis. Merismopedia glauca, Merismopedia tenuissima, Microcystis aeruginosa, Oscillatoria tenuis, Phormidium tenus and Raphidiopsis sinensia were determined to be the dominant species. The key drivers of cyanobacterial bloom development were total phosphorus (TP), ammonium nitrogen (NH3-N), water temperature and total hardness. Topography and human activities were highly correlated with the key driving factors. The higher the altitude, the greater the effect of water temperature on the cyanobacteria community. In the area where sewage irrigation was present and a large amount of chemical fertiliser was used, total hardness had a greater effect on the cyanobacteria community. In areas where the population was more concentrated, TP and NH3-N had greater effects on the cyanobacteria community.