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

Tim Piel,Maria J Van Herk,Gerard Muyzer,Jef Huisman,Petra M Visser,Corina P D Brussaard,Giovanni Sandrini,Pieter C Slot

doi:10.3390/microorganisms9071495

Abstract

Applying low concentrations of hydrogen peroxide (H2O2) to lakes is an emerging method to mitigate harmful cyanobacterial blooms. While cyanobacteria are very sensitive to H2O2, little is known about the impacts of these H2O2 treatments on other members of the microbial community. In this study, we investigated changes in microbial community composition during two lake treatments with low H2O2 concentrations (target: 2.5 mg L−1) and in two series of controlled lake incubations. The results show that the H2O2 treatments effectively suppressed the dominant cyanobacteria Aphanizomenon klebahnii, Dolichospermum sp. and, to a lesser extent, Planktothrix agardhii. 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., Rheinheimera) strongly increased in relative abundance during the first 24 h after H2O2 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 H2O2 to suppress cyanobacterial blooms provides a short-term pulse disturbance but is not detrimental to lake microbial communities and their ecosystem functioning.

Highlights

The widespread increase of harmful cyanobacterial blooms around the globe has been linked to eutrophication and climate change [9,10,11,12]
The results of this study confirm that low concentrations of H2 O2 can effectively suppress cyanobacterial blooms
A fast decline of cyanobacterial blooms has been observed in two previous H2 O2 treatments of lakes dominated by Planktothrix agardhii [43] and Aphanizomenon flos-aquae [25]

Summary

Introduction

Harmful cyanobacterial blooms often occur in eutrophic freshwater ecosystems, causing degradation of water quality and possibly ecological and economic disruption [1,2,3,4]. Many bloom-forming cyanobacteria can produce toxins which harm animals such as fish, birds and mammals, including humans, either directly after ingestion of contaminated water or indirectly via the food chain [5,6,7,8]. The widespread increase of harmful cyanobacterial blooms around the globe has been linked to eutrophication and climate change [9,10,11,12]. The most effective and most preferred long-term method to reduce cyanobacterial blooms is reduction of nutrient inputs into the water body [13,14].

Methods

Results

Discussion

Conclusion