Abstract: This is the first report of the algal toxins of water bloom in Guanting Reservoir of Beijing. The algal compositions and one family of their toxins-microcystins were investigated. The dominant species in the blooms found in September of 2003 were Microcystis, whose ratio to the number of total algal cells reach 97.2%. The specific species of the microcystis in the bloom included microcystis aeruginosa(52.7%), microcystis wesenbergii(36.2%) and Microcystis pseudofilamentasa(8.3%). The qualitative analysis by HPLC shows that at least five microcystins were contained in the scum of the blooms. The major microcystins were microcystin-RR and microcystin-LR. The quantitative analysis by HPLC indicates that the blooms contained microcystin-RR 1.69 mg/g and microcystin-LR 1.44 mg/g dried sample. The other three microcystins would be studied later.

Key words: Guanting reservoir, Microcysitin aeruginosa, Microcystins, Microcystins-RR, Microcystin-LR