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
A NOVEL IMMOBILIZED ALGICIDAL BACTERIA (DINOSHIELD) FOR CONTROLLING HARMFUL DINOFLAGELLATES: TRANSITIONING RESEARCH TO THE FIELD (8238)
Primary Presenter: Kaytee Pokrzywinski, National Oceanic and Atmospheric Administration National Centers for Coastal Ocean Science (kaytee.pokrzywinski@noaa.gov)
Karenia brevis presents a major human health and economic threat to coastal communities in the Gulf of Mexico. Previous research identified an algicidal bacteria, Shewanella sp. IRI-160, having algicidal activity against dinoflagellates, including K. brevis, while having no negative impacts on other phytoplankton tested. Previous research indicated that this bacterium secretes water-soluble algicidal compounds to control the growth of dinoflagellates without the requirement of direct bacteria-algae contact. However, high-dose repeated application of the bacteria or algicidal filtrate may raise concerns about biosafety. Recent research demonstrated the algicidal activity of Shewanella sp. and the algicidal filtrate in retrievable alginate hydrogels (designated as “DinoSHIELDs”) as an effective alternative to direct application of the bacteria or product. Furthermore, at concentrations required to kill K. brevis, DinoSHIELDs were recently demonstrated in in situ mesocosms (2900 L) to have a negligible effect on the microbial community with respect to non-target species. Current research is focused on scaling-up production to conduct a field demonstration on the west coast of Florida, USA. The study will use both turbidity and bubble curtains to confine the trial in the native environment. The overall goal of the field study is to optimize the delivery of the algicide from DinoSHIELDs containing either the immobilized Shewanella sp. IRI-160 or cell-free algicidal product and demonstrate the utility of this technology for continuous red-tide management in the Gulf.
09:15 AM
SAFE AND SUSTAINABLE HAB AND MICROPOLLUTANT CONTROL BY ULTRADILUTE TAML/PEROXIDE (8187)
Primary Presenter: Terrence Collins, Carnegie Mellon University (tc1u@andrew.cmu.edu)
TAML catalysts are bioinspired, miniaturized replicas of peroxidase enzymes where a latest generation composition, NT7® (1.4–16.8 ppb) with hydrogen peroxide (1–10.2 ppm), has achieved transformative technical performances in removing micropollutants (MPs) from multiple waters: lab, river, and lake waters and urban wastewater. Harmful algal blooms (HABs) pose a significant threat to contemporary ecosystems and water security, necessitating the development of efficient, low-cost, easy-to-deploy, safe and sustainable control technologies. Thus, we have studied if the striking NT7®/peroxide effectiveness against MPs is transferable to HABs. Here, we introduce results signaling a potentially practical solution for control of Karenia brevis blooms (red tides). The effective removal of K. brevis and brevetoxins in seawater has been achieved in NT7®/peroxide test experiments in the early stages of a HAB-CTI supported project. Specifically, K. brevis (1 million cells/L) could be completely killed by NT7® (560 ppb) with H2O2 (1.7 ppm) within 4 hours, while the concentration of detected brevetoxins released by K. brevis (BTX-1, BTX-2, BTX-3, and BTX-B5) were decreased cumulatively by about 75% in 72 hours. In contrast, H2O2 (1.7 ppm) alone exhibited no impact on K. brevis or its associated brevetoxins. Concentration optimization, mesocosm and ecotoxicology studies are components of the evolving project. In earlier scoping studies in the cHAB area, NT7® (56 ppb) with H2O2 (340 ppm) removed to non-detectable from lab water within 3 min the cyanobacterial toxin and micropollutant, microcystin-LR (12 ppm).
09:30 AM
The targeted destruction of Karenia brevis through algaecide integration in flocculation and sinking technologies. (8025)
Primary Presenter: Vijay John, Tulane University (vj@tulane.edu)
Harmful Algal blooms (HABs) of the dinoflagellate Karenia brevis pose a serious threat to the marine and coastal ecosystem. These HAB species synthesize polyether brevotoxins released upon secretion and cell lysis causing significant mortality in marine life. The severe environmental concern necessitates the development of environmentally safe mitigation methods. We address the targeted and rapid destruction of Karenia brevis using the algaecide, calcium peroxide, in tandem with the flocculation and sinking of the algal species. The incorporation of the algaecide within the floc as granules or affixed to the surface of tubular clays serves to rapidly kill K. brevis minimizing escape from the floc and reentry to the water column. Calcium peroxide reacts with water to form the water-insoluble calcium hydroxide gradually releasing hydrogen peroxide which permeates cell membranes and reacts with intracellular iron to generate hydroxyl radicals toxic to the cell. Additionally, calcium peroxide also serves as a ballast. Pulse amplitude modulated fluorometry results indicate that dose levels as low as 30 mg/L are effective in suppressing photosynthesis destroying cell viability in 3-6 hours. Toxin analysis indicates a significant reduction of toxin levels attributed to Fenton processes. Thus, the proposed technology leads to an inexpensive and scalable technology to mitigate harmful algal blooms of K. brevis. The environmentally benign aspect of calcium peroxide is further substantiated by its eventual conversion to calcium carbonate upon exposure to carbon dioxide.
09:45 AM
FLOCCULATION AND SEDIMENTATION FOR CONTROL OF FLORIDA RED TIDE AND OTHER HARMFUL ALGAL BLOOMS (8384)
Primary Presenter: Vincent Lovko, Mote Marine Laboratory (vlovko@mote.org)
The worldwide proliferation of HABs in aquatic systems results in severe environmental, economic, and human health effects. These impacts emphasize the need for effective strategies to reduce the effects of HABs on coastal resources and communities, while causing minimal environmental impact. Strategies for flocculation and sedimentation of cells are at the forefront of HAB control technologies, with regular application in marine and freshwater systems in some parts of the world. This technology is achieved using combinations of clays, polymers, coagulants and other materials, sometimes with other chemicals acting as algaecides or contributing to toxin breakdown. Through multiple projects, we have examined the efficacy of several compounds, including mineral clays, polyaluminum chloride (PAC), activated carbon, calcium peroxide (CaO2) and polyphenolic compounds, individually and in combination, for the destruction and removal of Karenia brevis cells and toxins. PAC-modified kaolinite clay rapidly removed cells from the water column (>90% in ≤6hrs at clay loadings ≥0.3g/L), although cells remained viable in floc for >48hrs and toxin removal was ≤50%. The addition of 5% curcumin with clay resulted in 100% cell death within 6hrs. PAC without clay but with 150mg/L CaO2 resulted in 100% cell death within 2hrs. 0.5g L-1 activated carbon with luteolin resulted in ~90% cell removal at 24hrs and >97% removal within 72hrs. This presentation will overview these studies, summarize results and consider the feasibility of applying these approaches as bloom control strategies.
10:00 AM
Evaluating microcystin detection models for lakes in a nutrient-rich landscape applied under varying climate conditions (8230)
Primary Presenter: Jonathan Walter, University of California Davis (waltjo04@gmail.com)
Algal blooms can threaten human health if toxins such as microcystin are produced by cyanobacteria. Regularly monitoring microcystin concentrations in recreational waters is a tool for protecting public health; however, monitoring cyanotoxins is resource- and time-intensive. Statistical models that identify waterbodies likely to produce toxins can help guide monitoring efforts, but variability in bloom severity and toxin production among lakes and years makes prediction challenging. We evaluated the skill of a statistical classification model developed from water quality surveys in one season with low temporal replication but broad spatial coverage to predict if microcystin is likely to be detected in a lake in subsequent years. We used summertime monitoring data from 132 lakes in Iowa (USA) sampled between 2017-2021 to build and evaluate a predictive model of microcystin detection as a function of lake physical and chemical attributes, watershed characteristics, zooplankton abundance, and weather. The model built from 2017 data identified pH, total nutrient concentrations, and ecogeographic variables as the best predictors of microcystin detection in this population of lakes. We then applied the 2017 classification model to data collected in subsequent years and found that model skill declined but remained effective at predicting microcystin detection (area under the curve, AUC ≥ 0.7). We also assessed if classification skill could be improved by assimilating the previous years’ monitoring data into the model, but model skill was only minimally enhanced. Overall, the classification model remained reliable under varying climatic conditions. Finally, we tested if early season observations could be combined with a trained model to provide early warning for late summer toxin detection, but model skill was low in all years and below the AUC threshold for two years. The results of these modeling exercises support the application of correlative analyses built on single-season sampling data to decision-making for resource allocation, but similar investigations are needed in other regions to build further evidence for this approach.
10:15 AM
USING WATER LEVEL MANAGEMENT TO REDUCE CYANOBACTERIAL BLOOM TOXICITY IN A NORTHERN LAKE (7772)
Primary Presenter: James Larson, U.S. Geological Survey (jlarson1@alumni.nd.edu)
Lake water level (WL) fluctuations are an important factor driving variation in many ecosystem processes. Relative to permanently inundated sediments in deeper waters, nearshore sediments that are periodically exposed and re-inundated develop distinct physicochemical characteristics, which we hypothesize alters nitrogen (N) and phosphorus (P) flux from sediments and influences nearshore harmful algal blooms (HABS). To test this hypothesis we studied Lake Kabetogama (MN, USA), a northern lake where WLs are managed for multiple purposes and that experiences HABs in nearshore areas. Using intact sediment core experiments, we found that greater WL fluctuations were associated with increases in organic N and P flux from sediments into the water column. Concurrent experiments on naturally occurring HABs indicate N limitation, and additions of ammonium (but not nitrate) caused decreases in the expression of a cyanotoxin gene (mcyE). The supply of organic N or P is probably only important for cyanobacteria when more labile forms are depleted, which appeared to be the case for N in our phytoplankton experiment. Possibly, increases in available organic N would prolong the persistence of cyanobacteria blooms, which in our study produced mcyE RNA when N limited. Using our data to parameterize structural equation models, we predict that, all other things being equal, WL management regimes with greater annual WL fluctuation would result in more N and P supply to the nearshore zone.
SS11B - Facing the Gauntlet: Understanding the How, When and Where of HAB Prevention, Control, and Mitigation (PCM)
Description
Time: 9:00 AM
Date: 4/6/2024
Room: Lecture Hall