5. The Distribution and Molecular Identification of the Microcystis aeruginosa in Yuqiao Reservoir

Yuqiao reservoir, the only drinking water source of Tianjin in the downstream of Luan river basin, has occurrence of water bloom, at a small scale, annually. Hence the research in Microcystis distribution spatially and temporally has been conducted. In this study, we focus on Microcystis aeruginosa, which is one of the most contributing causes of the bloom. Samples are collected from seven sites in July and October 2012 and molecular techniques conducted to identify the selected clone from the samples by 16S rDNA sequencing. According to the results, M. aeruginosa has grown vigorously in July with the average biomass of 1.59 ± 0.39 mg/L and the cell density of 3191.25 ± 768.04 × 10⁴/L. The maximum value occurs in the site of the northern reservoir (the average biomass and the cell density were 1.37 ± 1.07 mg/L and 2723.33 ± 2131.13 × 10⁴/L respectively). By analyzing the sequencing results and comparing with the morphological characters, the accuracy of molecular identification based on the 16S rDNA region is confirmed. From the BLAST alignments in NCBI, we find that the homology of 30 clones of M. aeruginosa is between 97 and 99 %; A+T (56.6 %), which is higher than C+G (43.4 %). The samples almost match the same branch of phylogenetic tree.