Two-year moving aeration controls cyanobacterial blooms in an extremely eutrophic shallow pond: Variation in phytoplankton community and Microcystis colony size

Artificial mixing is considered as one of the most effective methods for controlling cyanobacterial blooms. However, the success rate of this method is still very low, and whether it could be successfully applied to shallow waters remains unclear. In the current study, a self-designed moving aeration device was employed in an extremely eutrophic shallow pond with water depth of 1.5 m. A similar pond without aeration was set as the control. The experiment was performed over two years (2019-2020). There were no significant differences in the mean values of all water quality parameters (except for ammonia concentration) between the two ponds. Nevertheless, the occurrence of blooms was eliminated in the treated pond in the second year, while cyanobacterial blooms still occurred frequently in the control pond. In the second year of the experiment, Cyanobacteria was the dominant phytoplankton phylum in the control pond, comprising up to 68% of the total community. However, in the treated pond, the maximum proportion of Cyanobacteria was just 30%, while the proportions of Bacillariophyta and Chlorophyta reached approximately 80%. Microcystis was the dominant genus in the control pond, while Scenedesmus and Pediastrum became dominant in the treated pond in the second year. Microcystis colony size decreased substantially in the treated pond in the second year. The results suggest that moving aeration is an environmentally friendly method of controlling cyanobacterial blooms in shallow ponds and lakes. The aeration could disaggregate Microcystis colonies and shift the phytoplankton community from Cyanobacteria to Chlorophyta and Bacillariophyta.

Automated summary

Artificial mixing is considered as an effective method for controlling cyanobacterial blooms, but its successful application in shallow waters remains unclear. The study showed that a self-designed moving aeration device successfully eliminated blooms in the treated pond, whereas the control pond still experienced frequent cyanobacterial blooms. The aeration method could shift the phytoplankton community from Cyanobacteria to Chlorophyta and Bacillariophyta, suggesting its environmentally friendly potential for bloom control in shallow ponds and lakes.