Inhibition of CO2 Fixation as a Potential Target for the Control of Freshwater Cyanobacterial Harmful Algal Blooms

Global warming and climate change have created various problems, one of which is the increase in harmful algal blooms (HABs) in freshwater systems. Annually, numerous freshwater bodies experience cyanobacterial HABs, which pose significant ecological and public health risks. In this study, we investigated a novel strategy for controlling cyanobacteria by inhibiting CO₂ fixation using glycolaldehyde (GLA) as a nonoxidative algicide. After treatment of Microcystis aeruginosa (M. aeruginosa), a model cyanobacterium, with various doses of GLA, changes in cell number and biomass were observed, along with alterations in the photochemical efficiency of Photosystem II and electron transfer processes in M. aeruginosa, as measured through chlorophyll a fluorescence transients. Treatment with GLA concentrations of 2.5 mM and above completely suppressed the growth and photosynthesis of the M. aeruginosa cells. However, the use of 0.5 mM GLA led to a hormetic effect in M. aeruginosa. When GLA was tested on cyanobacteria-laden water samples collected from a lake, primarily consisting of colonial M. aeruginosa cells, the obtained results indicated that GLA is equally effective against them. These results suggest that GLA could potentially control both M. aeruginosa and other phytoplankton. Our findings led us to consider target-specific approaches for the control and mitigation of cyanobacterial HABs.