In order to understand the seasonal variation characteristics and trend of water quality parameters in Lake Yangzong, water temperature, dissolved oxygen (DO), pH, conductivity, chlorophyll-a and phycocyanin were monitored from 2013 to 2106 in different seasons. In these parameters, the phycocyanin mainly exists in the cyanobacteria, while Chlorophyll-a is found in all algae. So, the ratio of phycocyanin and chlorophyll-a can be used to represent the relative amount of cyanobacteria in water.

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... asonal variation characteristics of water quality parameters and cyanophyte relative quantity index (CRQI) showed that: Lake Yangzong belongs to warm monomictic lakes, the minimum water temperature is higher than 4˚C, thermal stratification phenomenon was observed in spring, summer and autumn, and the water mixed in winter; thermal stratification and mixture had influences on vertical distribution of other water quality parameters, variation trends of all parameters are basically consistent; Cyanophyte Relative Quantity Index (CRQI) in spring, summer and autumn is higher than winter, and increased in April 2016, which was higher than that in April 2015. In particular, there is a sharp increase in the southern region of the lake, where rivers brought a lot of sewage. This indicates that human activities have contributed to the deterioration of water quality.