Distribution of the Harmful Bloom-Forming Cyanobacterium, Microcystis aeruginosa, in 88 Freshwater Environments across Japan

摘要

Microcystis aeruginosa was quantitatively surveyed in 88 freshwater environments across Japan within 3? ?weeks in 2011. In order to clarify the distribution pattern of M. aeruginosa at the intra-species level, three major genotypes, which were defined by 16S–23S rRNA inter-transcribed-spacer (ITS) regions, were selectively detected using quantitative real-time PCR assays. Of the 68 sites at which the Microcystis intergenic-spacer region of the phycocyanin (IGS-PC) gene was detected, the M. aeruginosa morphotype-related genotype (MG1) dominated in 41 sites, followed by the non-toxic M. wesenbergii -related genotype (MG3). A correlation analysis showed that total nitrogen and phosphate positively correlated with the abundance of IGS-PC, which positively correlated with microcystin synthetase gene abundance. A redundancy analysis of genotype compositions showed that pH positively correlated with the dominance of MG3 and negatively correlated with MG1, i.e. , both toxic and non-toxic genotypes. Our survey of Microcystis populations over a wide area revealed that MG1 is a dominant genotype in Japan.