ASSESSMENT OF A PEROXIDE-BASED ALGAECIDE PRODUCT FOR CONTROL OF CYANOBACTERIA IN LAKE OKEECHOBEE: A MESOCOSM STUDY

To evaluate the effectiveness of a USEPA-registered peroxide-based algaecide for controlling cyanobacteria in the Lake Okeechobee waterways, a three-day small-scale field study was conducted in the summer of 2019 in enclosed in situ mesocosms. Mesocosms with natural cyanobacterial populations were deployed with either no algaecide or maximum label rate of 10 mg H₂O₂·L⁻¹. A subset of algaecide treated mesocosms were subjected to a sequential application of 5 mg H₂O₂·L⁻¹ at 48 h after initial treatment. Following applications, peroxide concentrations rapidly decreased and were non-detectable by 48 h. 24 h after treatment, significant decreases were observed in all biomass indicators compared to untreated mesocosms, including extracted chlorophyll a, cell counts (total phytoplankton and total cyanobacteria), and cyanobacteria-specific 16S rRNA gene copies. Although peroxide treatment reduced cyanobacteria biomass, overall community structure remained unchanged, and the population still dominated by cyanobacteria 72 h after treatment. By 48 h exposure, some biomass recovered in single application mesocosms while repeated peroxide dosing resulted in the greatest efficacy, with sustained decrease in all biomass indicators for the 72 h study, which suggests that sequential treatment is necessary to sustain efficacy to manage cyanobacteria in the field. Results support the evaluation of peroxide-based algaecides for rapid short-term relief from cyanobacterial harmful algal blooms in field trials to assess its future utility for management programs in the Lake Okeechobee waterway.

Primary Presenter: David Berthold, University of Florida (dberthold@ufl.edu)

Authors:

Kaytee Pokrzywinski, National Oceanic and Atmospheric Administration, National Centers for Coastal Ocean Science  (kaytee.pokrzywinski@noaa.gov)

West Bishop, SePRO Research and Technology Campus  (westb@sepro.com)

Christopher Grasso, Illumina, Inc.  (cgrasso@illumina.com)

Brianna Fernando, Environmental Laboratory, US Army Engineer Research and Development Center  (Brianna.M.Fernando@erdc.dren.mil)

David Berthold, Fort Lauderdale Research and Education Center, University of Florida and Oak Ridge Institute for Science and Education,  (dberthold@ufl.edu)

Benjamin Sperry, Center for Aquatic and Invasive Plants, University of Florida,  (bpsperry@ufl.edu)

Forrest Lefler, Fort Lauderdale Research and Education Center  (flefler@ufl.edu)

Dail Laughinghouse IV, Fort Lauderdale Research and Education Center, University of Florida  (hlaughinghouse@ufl.edu)

Mark Heilman, SePRO Research and Technology Campus  (MarkH@sepro.com)

Kurt Getsinger, Environmental Laboratory, US Army Engineer Research and Development Center  (Kurt.D.Getsinger@usace.army.mil)