A Field Study to Investigate Environmental Factors that Could Effect Microcystin Synthesis of a Microcystis Population in the Bautzen Reservoir

Abstract Toxicity of Microcystis blooms to warm‐blooded animals generated by microcystins has bew reported world wide. The ecological relevance of microcystin production for cyanobacteria remains unknown. The microcystin concentration in Microcystis blooms occurring in the Bautzen reservoir Was investigated. The microcystin content of samples were determined by HPLC and ranged from undetectabel to 14.7 μg mg −1 . Various chemical and physical parameters were monitored at the same time as Microcystis sampling, however, there was no correlation between these parameters and microcystin dynamics. The spatial distribution of microcystin in the Microcystis population was investigated once and showed no difference between samples taken at five stations. The microcystin concentration in ihc cell free water from the reservoir was below the detection threshold (< 1 μg L −1 ). Size dependent Fractions of the Microcystis population analyzed for microcystin concentration correlated with colony sim. In the small fraction (>30 <66 μm) microcystin was not detected. In the medium fraction (> 6 h < 100μm) lower microcystin concentrations were detected than in large fraction (>100μm) in which the highest microcystin concentrations were found.