Controlling of cyanobacteria bloom during bottleneck stages of algal cycling in shallow Lake Taihu (China)

To suppress the occurrence of phytoplankton blooms dominated by cyanobacteria, control measures were implemented during the bottleneck stages of algal succession, overwintering and pre-recruitment, using a combination of chemical and biological algicides. First, water and sediment samples were incubated in the laboratory to determine the threshold temperature for cyanobacteria recruitment. Second, the functional characteristics of candidate algicides were screened. Third, an in situ pilot experiment was conducted to test the feasibility of this method. Our results indicated that (1) the recruitment of cyanophytes was initiated at 15 degrees C, (2) H2O2 and rice straw were the optimum algicides and their optimal concentrations were 10mg/L and 1g/L, respectively, and (3) following the combined application of H2O2 and rice straw during overwintering and pre-recruitment, the biomass of cyanobacteria decreased by 27.1% during recruitment and by 53.2% during the first algal bloom. These results suggested that the combined application of H2O2 and rice straw, during the bottleneck stages of algal cycling, suppressed the recruitment of cyanobacteria and decreased the magnitude of algal blooms, thus offering a promising choice for prevention of cyanobacterial blooms.