Cyanobacterial blooms are intensifying global ecological hazards. The fine structure and dynamics of bloom community are critical to understanding bloom development but little understood. Here, the questions whether dominant bloomers have high diversity and whether dominant OTUs (operational taxonomical units) compete with one another were addressed. 16S rRNA gene amplicons from an annual bloom at five locations in Harsha Lake (Ohio, USA) showed cyanobacteria were the dominant phylum, and co-existing major bacterial phyla included Proteobacteria, Bacteroidetes, Actinoacteria, and Verrucomicrobia. On the genus level, the initial dominance by Dolichospermum in June yielded to Planktothrix in July, which were replaced by Microcystis and Cylindrospermopsis in August throughout the bloom. Based on the number of verified unique OTUs (a within-genus biodiversity metric), dominant genera tended to have high within-genus diversity. For example, Dolichospermum had 57 unique OTUs, Planktothrix had 36, Microcystis had 12, and Cylindrospermopsis had 4 unique OTUs. Interestingly, these different OTUs showed different dynamics and association with other OTUs. First, no between-OTU competitions were observed during the bloom cycle, and dominant OTUs were abundant throughout the bloom. Such biodiversity of OTUs and their dynamics were verified in Microcystis aeruginosa with two microcystin synthetase genes (mcyA and mcyG): the relative abundance of both genes varied during the bloom based on quantitative PCR. Two Dolichospermum circinale OTUs and one P. rubescens OTU were most abundant and persistently present throughout the entire bloom. Second, these OTUs differed in the OTUs they were associated with. Third, these OTUs tended to have different levels of association with the environmental factors, even they belonged to the same genera. These findings suggest the structure and dynamics of a cyanobacterial bloom community is complex, with only few OTUs dominating the bloom. Thus, high-resolution molecular characterization will be necessary to understand bloom development.

蓝藻水华正在加剧全球生态危害。开花群落的精细结构和动力学对于理解开花发育至关重要，但鲜为人知。这里，主要的开花者是否具有较高的多样性以及主要的OTU（业务分类单位）是否相互竞争的问题得到了解决。来自Harsha Lake（美国俄亥俄州）五个地点的一年生花粉的16S rRNA基因扩增子显示，蓝细菌是优势菌门，并存的主要细菌菌门包括变形杆菌，拟杆菌，放线菌和疣状微生物。在属水平上，6月份Dolichospermum的最初优势在7月份降到了Planktothrix，被Microcystis和Microcystis取代。八月的圆柱状整个开花。根据已验证的唯一OTU（属内生物多样性指标）的数量，优势属往往具有较高的属内多样性。例如，Dolichospermum有57个唯一的OTU，Planktothrix有36个，微囊藻有12个，Cylindrospermopsis有4个唯一的OTU。有趣的是，这些不同的OTU显示出不同的动态以及与其他OTU的关联。首先，在开花周期中未观察到OTU之间的竞争，并且整个开花过程中占主导地位的OTU都很丰富。OTUs的这种生物多样性及其动态在铜绿微囊藻中带有两个微囊藻毒素合成酶基因（mcyA）进行了验证。和mcyG）：基于定量PCR，这两个基因的相对丰度在盛开期间会发生变化。在整个开花期间，两个圆环杜鹃（Olichospermum circinale） OTU和一个红杨假单胞菌（P. rubescens） OTU最丰富，并持续存在。其次，这些OTU与其关联的OTU不同。第三，这些OTU与环境因素的关联程度往往不同，即使它们属于同一属。这些发现表明，蓝藻水华群落的结构和动力学很复杂，只有很少的OTU主导水华。因此，高分辨率分子表征对于理解水华发展将是必要的。