Microbial community analysis for evaluating water quality improvement in reservoirs installed with destratification system

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Seasonal change of microbial community including bacteria and algae in Tsukui Lake, where destratification system was installed, was investigated by denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR). In order to express graphically the seasonal change of the community based on the dissimilarity index, multi-dimensional scaling (MDS) was applied. The MDS map revealed a cyclic change of the community and a distinctive divergence from the path during a sudden algal bloom after a heavy storm. Since the divergence disappeared in an analysis excluding cyanobacteria, the major part of the community might be independent of the sudden algal bloom. Dissimilarity of microbial communities was much lower among three different sampling sites than among the sampling months.Excitation emission matrix spectroscopy (EEMS) and PCR-DGGE were applied to elucidate the relationship between production of dissolved organic matter (DOM) and bacterial community change during the l … More ysis of algal bloom followed by their degradation in a batch incubation test. The lysis of the algal bloom collected from Tsukui Lake was indicated by rapid increases of dissolved organic carbon and UV absorbance at 260 nm within five days In accordance with the lysis, several fluorescence peaks derived from humic- and protein-like substances appeared in the EEM. Phylogenetic analysis of the major DGGE bands showed that bacteria closely related to y-Proteobacteria, CFB group and a-Proteobacteria probably played important roles in the lysis and degradation of algal bloom.The phenomena of algal lysis and DOM formation were investigated also in laboratory. Pure culture of Microcystis aeruginosa was inoculated into sterilized and non-sterilized Tsukui lake water. The existence of eubacteria differed the DOM formation after the algal lysis. The fluorescence derived from humic-like substances increased and subsequently decreased in the non-sterilized lake water, while such a variation was not observed in the sterilized water. Less