Release and Degradation of Microcystins during the Batch Culture of Microcystis aeruginosa and Grazing with and without Microanimals.

The production and release of microcystins during the batch culture of Microcystis aeruginosa LERL 031 which was isolated from Korean freshwater were investigated. Total amounts of two major toxins (microcystin-RR and -LR) did not decrease at the death phase of the culture while chlorophyll-a concentration decreased. The ratio of two major intracellular microcystin amounts of the cyanobacteria was changed depending on the growth phase.The grazing effects on Microcystis biomass and microcystins by micrometazoa and protozoan which were isolated from biofilm oxidation reactor were examined. Among three microanimals Monas guttula was turned out to be the most effective grazer of M. aeruginosa LERL-031. In the condition of coexistence of Aeolosoma hemprichi, Philodina erythrophthalma, Monas guttula in the cyano-bacterial as grazer, chlorophyll-a concentration decreased by 73% of initial concentration after 31 days. In the condition of no addition of microanimals, intracellular microcystins were released to surrounding water during the lysis of cells but not degraded.