Abstract: Phosphorus stress of phytoplankton was determined by analysis of alkaline phosphatase activity during spring （April to May） in 2016 in river-lake and adjacent water system of Qionghai lake, including 6 major rivers, estuary and adjacent water around Qionghai lake. The result showed that there were obvious spatial heterogeneity in chlorophyll concentration and alkaline phosphatase activity of phytoplankton of the river-lake system of Qionghai in spring, indicating that different rivers and regions shows different phosphorus stress. Among all the study sites, the phosphorus stress was the highest in the Guanba river, and followed by estuary of Guanba river, estuary of Qing river and adjacent water of E’zhang river, while the adjacent water of Qing river showed the lowest phosphorus stress.

Key words: phosphorus stress, environmental factor, alkaline phosphatase activity, chlorophyll, river-lake and adjacent waters systems of Qionghai lake