The investigations oil chlorophyll a of the water body,total nitrogen,total phosphorus and other environmental factors were carried out at 14 sampling sites of Xiangxi Bay of Three Gorges Reservoir from March to April 2005. We have also analyzed tile spatial and temporal variation of chlorophyll a and its relationship with environmental factors.Chlorophyll a was extracted and measured according to procedures of UNESCO's spectrometer methods under 750nm, 665nm, 645nm and 630nm wavelengths. Dissolved oxygen and nutrient data were Supplied by the chemical working group of the research project. The result showed that from I lie upper reaches to the lower reaches of the Xiangxi Bay, there was evident horizontal variation of chlorophyll a concentrations in the water Column One bloom event occured at March 17th at a very large scale. Then bloom went forward from the lower reaches to the upper reaches along with the time in April. In detail, bloom event occurred at April 11th tit the sampling sits of group 1, then about five days later it occurred at the sampling sits of group H. Bloom event Occurred at the sampling sits of group III between April 1601 and April 22th,, while it occurred at April 22th at the sampling sits of group IV.Obviously, ecological factors, including total nitro, en, total phosphorus, water temperature, transparency and dissolved oxygen,bad significant impact oil the concentrations of chlorophyll a directly and indirectly. Generally speaking, total phosphorus increased from the lower reaches to the tipper reaches of the Xiangxi Bay, while total nitrogen decreased first I then increased. The result obtained showed that oil the one hand total phosphorus and total nitrogen were enough for the growth of phytoplankton, on the other hand the ratio of total nitrogen to total phosphorus was very low, which ranged front 0.57 to 21.14. The relationship between chlorophyll a and total nitrogen, total phosphorus was negative to some extent. The correlation coefficent between chlorophyll a and total nitrogen was higher than that between chlorophyll a and total phosphorus. Considering the distribution of the nutrients and their correlation with the chlorophyll a, total nitrogen was possibly the main limited factor of phytoplankton growth, while total phosphorus. was not the main limited factor of phytoplankton growth. The relationship between chlorophyll a and transparency was a curve of anti-hyperbola. This result was similar to the research result of the Japan and North America's experts. The relationship between chlorophyll a and dissolved oxygen was positive. It was due to the increase of oxygen which was released during photosynthesis.
Han Xin-Qin; Ye Lin; Xu Yao-Yang; Cai Qing-Hua (email@example.com).Analysis of the spatial and temporal changes of chlorophyll a concentration in Xiangxi Bay in spring and its impact factors,Acta Hydrobiologica Sinica,2006,30(1):89-94