CHARACTERISTICS OF CYANOBACTERIA BLOOM GRADING AND ITS TEMPORAL AND SPATIAL VARIATION IN TAIHU LAKE

Using MODIS satellite images and Chlorophyll-a concentration data and adopting cyanobacteria bloom evaluation method,this paper studied different type of cyanobacteria bloom from 2004 to 2008 in Taihu Lake,and explored the characteristics of cyanobacteria bloom and its spatial and temporal variation,which provided pre-prevention and early warning for cyanobacteria bloom.The results showed that from 2004 to 2008,there were 414 cyanobacteria bloom incidents,and small scale cyanobacteria bloom occured 333 times,which occupied 80.43% of the cyanobacteria bloom incidents.As the grade of the cyanobacteria bloom increased,the number reduced.In the space,cyanobacteria bloom occurred mainly in the northern and western regions.And the distribution of the cyanobacteria bloom grade from high to low was mainly accord with the direction from northwest to southeast.Among the annual change,the number of cyanobacteria bloom gradually increased.The year in which large-scale cyanobacteria bloom happened and the cyanobacteria bloom occurred frequently was concentrated on 2006 and 2007.The number of cyanobacteria bloom increased from April to August,and decreased from August to November.The cyanobacteria bloom concentrated in May and from July to October,especially from August to October.