Green Algae Indirectly Threatens Water Quality

By: Melissa Villarreal 

The figure shows the relationship of the population density of Chlorella (green algae) with Microcystis (cyanobacteria) under different concentrations of hydrogen peroxide. A higher density of green algae protects cyanobacteria more effectively. Figure taken from Weenink et al. 2021.

Protecting our ever-diminishing drinking water and fresh body water is crucial for our growing population. A significant threat to water quality are cyanobacteria, and finding methods to combat them is essential. A study by Weenink and colleagues (2021) mentioned that cyanobacteria are responsible for toxic blooms, which threaten the water quality of freshwater lakes and reservoirs. This has a significant impact on the safety of drinking water, recreation, and irrigation water. Because cyanobacteria are very sensitive to hydrogen peroxide, this is a standard treatment used to diminish their presence and combat toxic blooms. Low concentrations of hydrogen peroxide are enough to control cyanobacteria while protecting the ecosystem of the water source. However, green algae, which is commonly found in freshwater, efficiently degrades hydrogen peroxide. Thus, green algae indirectly protect the cyanobacteria from the hydrogen peroxide, making the treatment ineffective. As shown in the figure, cyanobacteria can survive in high levels of hydrogen peroxide in the presence of green algae. So, the higher the population of green algae, the higher rates of survival of cyanobacteria. Unfortunately, using too high concentration of hydrogen peroxide to counteract the green algae can have a negative effect on the environment and ecosystem. Therefore, it is vital to find methods to effectively combat cyanobacteria to protect our water sources while preserving the ecosystem. 

Original Article: 

Weenink, E.F.J., Matthijs, H.C.P., Schuurmans, J.M., Piel, T., Herk, M.J., Sigon, C.A.M., et al. (2021) Interspecific protection against oxidative stress: green algae protect harmful cyanobacteria against hydrogen peroxide. Environ Microbiol 23: 2404–2419.