Environmental factors affecting the production of peptide toxins in floating scums of the cyanobacterium Microcystis aeruginosa in a hypertrophic African reservoir

The toxin content of buoyant scums of Microcystis aeruginosa was quantitatively determined and related to various environmental factors, using samples collected during a 2.5 year period at the hypertrophic Hartbeespoort reservoir, South Africa. Six cyclic heptapeptide toxins were separated using reversed-phase high-pressure liquid chromatography. Their levels were too low to be detected during the winter, but reached maximal concentrations during the summer. Combined concentrations of 4 of the toxins were strongly positively correlated to primary production per unit of chlorophyll a, solar radiation, surface water temperature, pH and oxygen saturation. There was a weak negative correlation with surface chlorophyll a, and orthophosphate concentrations. There are 45 references.