Evaluation of a Peroxide-Based Algaecide for Cyanobacteria Control: A Mesocosm Trial in Lake Okeechobee, FL, USA

Kaytee L Pokrzywinski,Kaitlin Volk,Erika M Van Goethem,Brianna M Fernando,Haywood Dail Laughinghouse,Kurt D Getsinger,Christopher R Grasso,Benjamen P Sperry,West M Bishop,Mark Heilman,David E Berthold

doi:10.3390/w14020169

Abstract

A 72 h small-scale trial was conducted in enclosed mesocosms in the Lake Okeechobee waterway to evaluate the effectiveness of a USEPA-registered peroxide-based algaecide (formulated as sodium carbonate peroxyhydrate) for controlling a natural cyanobacteria population. Mesocosms were initially subjected to either no algaecide or the maximum label rate of 10 mg H2O2·L−1. A subset of mesocosms were then subjected to a sequential application of 5 mg H2O2·L−1 at 48 h after initial treatment. Following application, peroxide concentrations rapidly decreased and were undetectable by 48 h. At 24 h after treatment, significant decreases in all biomass indicators were observed (compared to untreated mesocosms), including extracted chlorophyll a, microscopic counts (total phytoplankton and total cyanobacteria), and cyanobacteria-specific 16S rRNA gene copies by over 71%. Although peroxide treatment reduced cyanobacteria biomass, there was no change in overall community structure and the remaining population was still dominated by cyanobacteria (>90%). After 48 h exposure, some biomass recovered in single application mesocosms resulting in only a 32–45% reduction in biomass. Repeated peroxide dosing resulted in the greatest efficacy, which had a sustained (60–91%) decrease in all biomass indicators for the entire study. While a single application of the peroxide was effective in the first 24 h, a sequential treatment is likely necessary to sustain efficacy when using this approach to manage cyanobacteria in the field. Results of this study support that this peroxide-based algaecide is a strong candidate to continue with scalable field trials to assess its potential future utility for operational management programs in the Lake Okeechobee waterway.

Highlights

Increased nutrient loading, in freshwater systems, has been linked with the emergence of dense cyanobacteria harmful algal blooms that are known to have severe negative impacts on ecosystem services [1]
The targeted use of US Environmental Protection Agency (EPA)registered, peroxide-based algaecides have a high potential for immediate implementation
A USEPA-registered peroxide-based algaecide was used to control a natural cyanobacteria bloom in enclosed mesocosms in the Lake Okeechobee waterway to evaluate its potential future use in this system. This product caused a significant decline in cyanobacteria biomass as determined by chlorophyll a, cell counts, and 16S rRNA cyanobacteria gene copies

Summary

Introduction

In freshwater systems, has been linked with the emergence of dense cyanobacteria harmful algal blooms (cyanoHABs) that are known to have severe negative impacts on ecosystem services [1]. Water-use dynamics (e.g., dynamic rainfall, residence time, etc.), cyanoHAB intensity, duration, and associated toxicity are predicted to increase [4,5,6,7]. Both public awareness and rising human and ecological health concerns over cyanoHABs will likely prompt the necessity for large-scale mitigation measures [8,9,10]. While long-term management strategies typically focus on reducing nutrient loading and land-use patterns, short-term strategies, such as algaecide applications, can provide immediate relief from devastating bloom events [11,12,13,14,15]. The targeted use of US Environmental Protection Agency (EPA)registered, peroxide-based algaecides have a high potential for immediate implementation

Objectives

Methods

Results

Conclusion