Effects of suspended solids on cyanobacterial bloom formation under different wind fields.

Abstract

Wind waves and suspended solids (SS) generated by the resuspension of sediments are ubiquitous characteristics of lake ecosystems. However, their effects on phytoplankton remain poorly elucidated in shallow eutrophic lakes. Laboratory experiments were carried out to investigate the responses of Microcystis aeruginosa to SS under static (wind speed of 0m/s) and breeze (wind speed of 3m/s) conditions. Results showed that 50mg/L SS can promote the growth of M. aeruginosa, accelerate the formation of colonies, and increase the floating rate under no-wind conditions. Comparing with static environment, breeze can significantly increase the growth rate of M. aeruginosa and benefit the formation of larger colonies of algae cells. Driven by wind and SS, the buoyancy of the cyanobacteria community in different experimental groups was obviously different. The specific performance was that low SS concentration and breeze were in favor of the floating of cyanobacteria, while high SS concentration went against the floating of algal cells. As a conclusion, wind speed of 3m/s and 20-50mg/L SS have a synergistic effect on the formation of cyanobacterial blooms. This study can provide an improved current understanding of bloom formation and turbidity management strategies in shallow eutrophic lakes.