Cyanobacterial bloom in Xiangxi Bay,Three Gorges Reservoir

A cyanobacteria bloom was observed in Xiangxi Bay of Three Gorges Reservoir in summer of 2010.Based on field data collected from 19 July to 30 August 2010,this paper descripted the cyanobacteria bloom process and analyzed the influence factors.The bloom lasting for about 25 days,broke out on 23 July,and ended on 16 August,cell density summit reached 108.03 106cell/L.The dominant species was Anabaena,and the major reasons were the suspension and nitrogen fixation mechanism,along with the capacity to produce microcystin to inhibit the growth of other algal.Specific stratification model of water and adequate nutrients were necessary to the cyanobacteria bloom,and nitrate might be the major nitrogen source.Under the conditions of undisturbed water situation and adequate nutrients,the proliferation rate of cyanobacteria might be accelerated gradually with increasing water temperature and lowering Zmix/Zeu.Especially when Zmix/Zeuwas less than 0.5,it was more favorable to cyanobacteria growth.