Effects of Algae on the Formation of Black Blooms and Bacterial Community Structure Changes in Sediments and Black Floats

Black bloom is a phenomenon of serious deterioration in shallow-water ecosystems worldwide. This study investigated the effects of algae on the formation of black blooms and the changes of bacterial community using nearly in-situ cores for a 40-day indoor simulation. We designed experiments with different combinations of water (W), sediments-water (SW), and sediments-water-algae (SWA), and made a comparative analysis of bacterial communities in sediments and black floats. The results demonstrated that the severity of black blooms was considerably affected by the presence of cyanobacteria. The concentration of total nitrates (TN) and NH 4 + -N in the SWA group increased to 25.1 mg/L and 22.5 mg/L (4.05 and 5.4 times of their initial concentrations), respectively. The abundance of microorganisms in the sediments was significantly higher than that of the black floats. The dominant species in both sediments were Proteobacteria and Chloroflexi , whose total proportion exceeded 50%. The addition of algae did not change the dominant community of the sediments. In black floats, the dominant species of the SW group were Proteobacteria (39%) and Actinobacteria (16%), and these of the SWA group were Proteobacteria (38%) and Cyanobacteria (35%). It is obvious that the dominant species in black floats changed significantly. Cyanobacteria increased remarkably in black floats in the group of algae additions. The possible reason may be that the Actinobacteria was suppressed by Cyanobacteria . Therefore, the addition of algae has a significant promoting effect on black blooms and significantly affects the microbial community structure of black floats