The dynamics of the water bloom-forming Microcystis aeruginosa and its relationship with biotic and abiotic factors in Lake Taihu, China

The dynamics of the bloom-forming cyanobacterium Microcystis aeruginosa (MA), total bacteria (TB), and the algicidal bacterium Pseudomonas aeruginosa R219 (PaR) in a eutrophic lake was followed from December 2007 to November 2008 by measuring the copy numbers of 16s rRNA genes (CNrG) of each species using a real-time fluorescence quantitative PCR (FQ-PCR) technique. The highest CNrG of MA was observed in July (3.4 × 105 copies mL−1), while those of TB and PaR peaked in May (2.1 × 106 copies mL−1) and August (3.2 × 104 copies mL−1), respectively. A significant relationship was found between the CNrG of MA and biological factors such as the CNrG of PaR, TB, and the ratio of PaR to TB, as well as environmental factors including dissolved nitrogen (DN) and surface water temperature (T) (r2 = 0.955, p < 0.001), suggesting that the dynamics of the algicidal bacterium PaR and TB, particularly the ratio of PaR to TB, may regulate the abundance of M. aeruginosa. Thus, we suggest that the algicidal bacterium PaR together with T and DN might play important roles in MA bloom formation and outbreaks in freshwater environments.