Although our understanding of HABs is still far from complete, the severity of their impacts precludes waiting for that knowledge before pursuing methods and technologies to, at least in part, prevent, control, and/or mitigate HABs and their impacts. PCM approaches can be based on tools that either physically remove algae, biophysically precipitate the algae out of the water column, chemically kill the algae, inhibit toxin(s) synthesis, prevent toxin(s) release, or remove/degrade toxin(s) from affected waters. The private sector, academia and the federal government have been working on developing and vetting strategies using algaecides, nanobubbles, ozonation, UV-light, flocculants, adsorption, bioremediation, etc. However, questions remain about how effective these methods can be at scale depending on the type of algae and the intensity with which many of the worst HABs occur. While there are now many products in the development stage there are paucity of solutions available on the market. Therefore, in this session, we will showcase research that demonstrates technical advances in the development of PCM methodologies and assessments of their effectiveness, with particular emphasis on the feasibility/scalability of these technologies for real-world applications and transitioning these to practitioners.
Lead Organizer: Felix Martinez, NOAA (felix.martinez@noaa.gov)
Co-organizers:
Jason Huntley, University of Toledo (jason.huntley@utoledo.edu)
Mandy Michalsen, USACE (Mandy.M.Michalsen@usace.army.mil)
Allen Place, University of Maryland Center for Environmental Science (place@umces.edu)
Kaytee Pokrzywinski, NOAA (kaytee.pokrzywinski@noaa.gov)
Presentations
09:00 AM
Mitigation of HABs in Mantua Reservoir, Utah using Floating, Time-released, Peroxide-based Algaecide Lake Guard Oxy (8422)
Primary Presenter: Jessica Frost, BlueGreen Water US Technologies (jessica.frost@bluegreenwatertech.com)
Mantua Reservoir is highly productive, creating problems that include HABs, low DO, and high pH. As of 08/7/23, local water authorities issued a health advisory warning due to elevated cyanotoxin levels, rendering the water unsuitable for recreational activities and consumption. Historic documented deaths of fish and dogs were due to Mantua Reservoir’s cyanotoxin levels. BlueGreen Water Technologies used its Lake Guard Technology for assessment, monitoring, and treatment. Lake Guard Oxy algaecide is formulated with a proprietary coating that enables the product to float and slowly time-release into the water column its active ingredient, sodium percarbonate, that converts to hydrogen peroxide when mixed with water, which induces oxidative stress on cyanobacteria. Results from using an UAV to capture live images before and after the mitigation treatment showed a marked improvement in water clarity and a notable reduction of the HAB. Secchi disk depth increased from 0.35m prior to treatment to 2.33m after treatment. Results of toxin analyses showed a significant decrease in Microcystin levels to below the state’s threshold for a public warning advisory. Results of biodiversity showed a discernible rise in the average daily Shannon Diversity of phytoplankton cells from 1.18 to 1.43 and means a 20.7% increase in the overall biodiversity. Results from the in-situ dry biomass measurements ranged from 0.25 to 0.34 g/L, with a mean value of 0.28 g/L. These results indicated a uniform biomass distribution both vertically and horizontally.
09:15 AM
Using Bacteria to Degrade Microcystin Toxins (8448)
Primary Presenter: Jason Huntley, University of Toledo College of Medicine and Life Sciences (jason.huntley@utoledo.edu)
Lake Erie harmful algal blooms (HABs) are dominated by microcystin (MC) toxin-producing cyanobacteria, including Microcystis species. Of over 300 MC variants, Lake Erie HABs primarily release MC-LR, a cyclic and highly-stable heptapeptide which is a potent toxin to the liver and other organs. Given concerns over human health and the high costs of water treatment, there is great interest in developing new methods to remove MC from contaminated waters. We hypothesized that naturally-occurring Lake Erie bacteria have adapted to use MC-LR as an energy source. As such, our lab isolated and characterized over 60 MC-degrading bacterial isolates that, when grown in various combinations, degraded MC-LR into non-toxic fragments. In recent experiments, we have tested MC-LR degradation by less-complex groups of bacterial isolates (e.g., groups of 5, 4, 3, or 2 bacterial isolates) and have assessed bacterial member composition over time to correlate bacterial abundance with MC-LR degradation. Liquid chromatography coupled to mass spectrometry (LC-MS) analysis of these cultures has confirmed MC-LR degradation by these less complex groups and identified several novel breakdown products, including previously unreported linear, tetrapeptide and tripeptide fragments, highlighting that our MC-degrading bacteria encode unique enzymes to degrade MC-LR. Finally, in proof of principle experiments, we have demonstrated robust MC-LR degradation in biologically-active water filters (i.e.,biofilters), providing strong evidence that our bacteria could be used to treat drinking water.
09:30 AM
ASSESSMENT OF A PEROXIDE-BASED ALGAECIDE PRODUCT FOR CONTROL OF CYANOBACTERIA IN LAKE OKEECHOBEE: A MESOCOSM STUDY (8314)
Primary Presenter: David Berthold, University of Florida (dberthold@ufl.edu)
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.
09:45 AM
Evaluation of Nanobubble Ozone Technology (NBOT) for Cyanobacterial Harmful Algal Bloom Control (8426)
Primary Presenter: Dail Laughinghouse, University of Florida (hlaughinghouse@ufl.edu)
Effective Cyanobacterial Harmful Algal Bloom (cyanoHAB) control strategies are needed to address recreational and drinking water impacts. Nanobubble ozone technology (NBOT) is an emerging control method, but cyanoHAB efficacy studies are limited. Lab and mesocosm NBOT experiments, and full-scale field NBOT treatment trials were conducted June 2021 through October 2023. Lab studies evaluated nanobubble size distribution, density, lifetime, aqueous ozone and hydroxyl radical production, and impact of organic matter on dose response. Lab studies confirmed production of high densities of nanobubbles and the total hydroxyl radical production from nanobubble collapse alone (no ozone) was insufficient for the oxidation demand for most treatments. These results indicate that nanobubble technology without ozone gas, claiming to work through the action of hydroxyl radical production, is not a suitable treatment. Mesocosm studies compared efficacy of NBOT to traditional algaecide treatments and evaluated impacts to non-target organisms. Algaecides decreased the zooplankton community while the lower dose NBOT treatment increased the abundance of zooplankton and the higher dose NBOT treatment had only minor negative impacts. In mesocosms, NBOT treatment reduced cyanoHABs at all doses. Multi-month NBOT trials were conducted at Lake Sylvan and Grand Lake Saint Mary’s West Beach. At Lake Sylvan, following increased NBOT dose, cyanobacteria concentrations decreased, the community shifted, and recreational advisories were avoided. Cyanobacteria and toxin concentrations were higher during the Grand Lake Saint Mary’s beach NBOT trial and treatment effects were localized and minimal, which could be due to scale, bloom intensity and/oe application rate.
10:00 AM
Field use of ultrasound for management of algal blooms: evaluation of sound pressure and water quality (8125)
Primary Presenter: Linda Weavers, The Ohio State University (weavers.1@osu.edu)
Ultrasound is an emerging technology to manage cyanobacteria harmful algal blooms (cHABs). It involves ultrasonic transducers placed in reservoirs that emit ultrasound throughout the cHAB season. Various mechanisms have been proposed, including targeting gas vesicles that regulate algal buoyancy, potentially collapsing them or inducing cavitation. Despite laboratory findings, field operation effects remain unclear. This study characterized ultrasound signals and water quality in lakes and reservoirs with ultrasound deployed to understand field operation. Field data from five sites were analyzed. The ultrasound signal attenuated with distance with attenuation coefficients about ten times greater than pure water. Attenuation was consistent across sites and minimal variation with environmental factors were observed. Spatially, no significant water quality differences were observed in reservoirs with ultrasound, but variations across connected reservoirs indicated the potential influence of detention time. Field evaluation suggested that known mechanisms such as cavitation and gas vesicle collapse are unlikely to affect cHABs at measured sound pressures and frequencies. Water quality paired with ultrasound did not show significant differences compared to control reservoirs.
SS11A - Facing the Gauntlet: Understanding the How, When and Where of HAB Prevention, Control, and Mitigation (PCM)
Description
Time: 9:00 AM
Date: 3/6/2024
Room: Lecture Hall