Influence of phragmites density, algal concentration and water velocity on cyanobacterial bloom dynamics

Algal concentration and water velocity had a greater impact on water quality than <i>Phragmites</i> density. Employing 16S rRNA gene sequencing technology, we discovered that bacterial α-diversity was significantly affected by <i>phragmites</i> density, water velocity, and time (<i>P</i> < 0.01), whereas bacterial β-diversity was significantly influenced by algal concentration and time (<i>P</i> < 0.001). The bacterial community structure was significantly impacted by <i>phragmites</i> density, water velocity, algal concentration, and time (<i>P</i> < 0.001). During the degradation of cyanobacterial blooms, the most abundant bacteria were Proteobacteria (36.8%), Bacteroidetes (20.4%), Cyanobacteria (19.1%), and Actinobacteria (10.3%). Algal density had a stronger influence on bacterial community structure than <i>Phragmites</i> density or water velocity. Orthogonal test results indicated that high algal concentration, coupled with reduced <i>Phragmites</i> density and increased water velocity, rapidly decreased nitrogen, phosphorus concentrations, and bacterial diversity. These findings deepen our understanding of <i>Phragmites</i> wetland effects on cyanobacterial blooms, offering insights for water ecological conservation and resource management in cyanobacteria-affected lakes.