Cyanobacteria composition and microcystins distribution of Wanfeng Reservoir and Baihua Reservoir on Guizhou Plateau

Aim: To understand the cyanobacteria composition and microcystins distribution of reservoirs in Guizhou Plateau,Wan-feng Reservoir and Baihua Reservoir were chosen to be investigated in October 2009.Results: The dominant phytoplankton species was cyanobacteria in Wanfeng Resevoir in which Cylindrospermopsis sp.took preponderance absolutely.The phytoplankton abun-dance ranged between 13.05×104 cells·L-1 and 55.80×104 cells·L-1 with cyanobacteria taking up to 82.55% in total.Mycrocystins-RR was detected in 3 sampling sites(Daba,Yeyatan and Gebu) while not in the other 3 sites(Baai,Badazhang and Jiulibao),and the concentration of mycrocystins reached above the limitation in 1 site(Gebu) according to Chinese standard.In Baihua Reservoir,the dominant species were mainly composed of cyanobacteria,chlorophyta and bacillariophyta.Pseudanabaena limnetica.dominated cyanobacteria.The phytoplankton abundance varied from 6.16×104 cells·L-1 to 65.00×104 cells·L-1 with cyanobacteria accounting for 33.25% in total.None of the 3 sampling sites(Daba,Yanjiaozhai and Matou) found Mycrocystins.The reason for the differences between Wanfeng Reservoir and Baihua Reservoir in cyanobacteria composition and microcystins distribution is possibly that dif-ferent nutrients level of nitrogen and phosphorus caused distinction of phytoplankton community structure,and then resulted in the diversity of microcystins distribution.