Biodegradation of microcystis and microcystins by indigenous nanoflagellates on biofilm in a practical treatment facility.

The potential for degradation of Microcystis and microcystins by organisms in biofilm in a practical biological treatment facility combined with conventional treatment processes was examined. Viable cells of Microcystis viridis, which produced microcystin LR, RR and YR, were degraded in 6 to 10 days by the addition of biofilm collected in early summer, mid-summer and autumn. Monas sp. grew remarkably well compared with other organisms in the samples of all seasons. Therefore, we conclude that Monas sp. was indigenous animals in the biological treatment facility and was able to degrade Microcystis cells. Some previous studies reported the predation of Microcystis cells by Monas guttula in pure culture conditions (monoxenic culture). We clarified that Monas sp. can grow and prey on Microcystis cells even in mixed culture including many kinds of other organisms in biofilm in a practical treatment facility. Also, intracellular microcystin LR, RR and YR in Microcystis cells could be degraded simultaneously with high reduction of Microcystis cells by organisms in biofilm.