Diversity and dynamics of microcystin—Producing cyanobacteria in China's third largest lake, Lake Taihu

Microcystins (MC), the most prevalent group of harmful cyanobacterial hepatotoxins, are primarily produced by strains of cyanobacteria in Microcystis, Anabaena and Planktothrix. Lake Taihu, which is the third largest freshwater lake in China, is a hypertrophic shallow lake in eastern China that has experienced lake-wide cyanobacterial blooms annually during the last few decades. In this study, PCR-DGGE was used to evaluate the diversity of potential MC-producing cyanobacteria and real-time PCR was used to analyze the dynamics of this population based on the presence of the mcy gene in samples collected during a year long study. The results revealed that all MC-producing genotypes detected belonged to the genus Microcystis. In addition, the MC-producing genotype communities were more diverse during the bloom season than the non-bloom season, and the diversity in the late bloom period was lower than the diversity in the early bloom period. Furthermore, the abundance of MC-producing genotypes increased dramatically during the bloom development period, reaching its peak in late summer (September). The results also suggested that the highest mcy gene concentration lagged behind the highest MC concentration, and the potential MC-producing cyanobacterial community shift lagged behind the development of blooms.