Effects of Rainfall in Kunming on the Growth and Alkaline Phosphatase Activity of the Cyanobacterium Microcystis aeruginosa

The effects of rainwater on freshwater ecosystems have received increasing attention worldwide. Alkaline phosphatase activity (APA) affects the biochemical cycles of phosphorus in the water, thereby affecting the proliferation and outbreak of cyanobacteria blooms. However, it is still unclear whether the complex composition of rainwater has a significant effect on the alkaline phosphatase activity. In this study, the effects of rainfall on Microcystis aeruginosa in Kunming were evaluated based upon changes in alkaline phosphatase activity, algal growth, and chlorophyll a. The results showed that the addition of rainwater brought about different changes in alkaline phosphatase activity, algal growth, and chlorophyll a. The general trend showed that a certain amount of rainwater (equivalent to light, moderate rain, and heavy levels) had a positive effect on the alkaline phosphatase activity, algal growth, and chlorophyll a in the cultivation system. Therefore, the following preliminary inference can be drawn: in the Kunming area, a certain amount of rainwater may promote the growth of blue-green algae, exacerbating an outbreak of cyanobacteria blooms.