Relationships between chlorophyll a and environmental factors of the main stream of the Qiantang River in Hangzhou

The investigations at ten stations were carried out in Qiangtan River from January 2006 to December 200. The spatio-temporal distribution of chlorophyll a and the relationships with environmental factors were studied according to the results of investigations. The results showed that there were obvious temporal differences in chlorophyll a, but not spatial differences. The concentrations of chlorophyll a were high in summer and autumn and low in winter and spring. There was significant positive correlation between chlorophyll a content and temperature. The correlation coefficients between chlorophyll a content and transparency varied in different ranges. The correlation coefficients between chlorophyll a content and TN、TP varied in different river sections. TN and TP concentrations were high enough to meet the needs of algal growth. Low N/P (8 to 30) showed that nitrogen and phosphorus may not be limiting factors for the growth of algae in the Qiangtan River.