Resilience of Microbial Communities after Hydrogen Peroxide Treatment of a Eutrophic Lake to Suppress Harmful Cyanobacterial Blooms.

Applying low concentrations of hydrogen peroxide (HO) to lakes is an emerging method to mitigate harmful cyanobacterial blooms. While cyanobacteria are very sensitive to HO, little is known about the impacts of these HO treatments on other members of the microbial community. In this study, we investigated changes in microbial community composition during two lake treatments with low HO concentrations (target: 2.5 mg L) and in two series of controlled lake incubations. The results show that the HO treatments effectively suppressed the dominant cyanobacteria , sp. and, to a lesser extent, . Microbial community analysis revealed that several Proteobacteria (e.g., Alteromonadales, Pseudomonadales, Rhodobacterales) profited from the treatments, whereas some bacterial taxa declined (e.g., Verrucomicrobia). In particular, the taxa known to be resistant to oxidative stress (e.g., ) strongly increased in relative abundance during the first 24 h after HO addition, but subsequently declined again. Alpha and beta diversity showed a temporary decline but recovered within a few days, demonstrating resilience of the microbial community. The predicted functionality of the microbial community revealed a temporary increase of anti-ROS defenses and glycoside hydrolases but otherwise remained stable throughout the treatments. We conclude that the use of low concentrations of HO to suppress cyanobacterial blooms provides a short-term pulse disturbance but is not detrimental to lake microbial communities and their ecosystem functioning.