Microcystin in cyanobacterial blooms in a Chilean lake

Cyanobacterial blooms dominated by Microcystis sp. occurred in lake Rocuant ("marisma", near Concepcion/ Chile) in February 1995 and 1996. In the bloom samples collected in both years the hepatotoxin microcystin was detected by RP-HPLC in bath samples and in the sample of 1995 also by a toxicity assay using primary rat hepatocytes. In the bloom of 1995, the microcystin content of the dry bloom biomass was determined to be 130 mu g/g on the basis of the RP-HPLC peak area and 800 mu g/g on the basis of the rat hepatotoxicity assay, respectively. In the bloom of 1996, RP-HPLC analysis revealed a microcystin content of 8.13 mu g/g bloom material dry weight. In this year no hepatotoxicity Mras measured using a concentration range up to 0.8 mg (d. w.) of bloom material per mi in the rat hepatotoxicity assay. This is the first report on the detection of microcystins in Chilean water bodies.