2 Apr 2025

Bacterial Remediation of Microsystin-HAB Toxins Utilizing Microcystinase (MlrA)

Abstract: Microcystins are a class of hepatotoxins produced by some harmful algal bloom–associated cyanobacteria and are the most reported tox-ins in freshwaters. Their cyclic structure makes them resistant to conventional methods used in water treatment operations (boiling, chlorination, and UV treatment). Some bacteria can naturally degrade microcystins via the mlrABCD cluster, a pathway initiated by the primary enzyme microcystinase (MlrA). MlrA linearizes the cyclic microcystin, greatly reducing its toxicity. Protein fusion was employed to produce a recombinant MlrA enzyme fused to maltose-binding protein ([MBP] MBP-MlrA) and to evaluate long-term enzymatic stabilization and reconstitution for future applications. MBP-MlrA degraded cyclic microcystin in vitro and demonstrated stability across a range of biological pHs. At a concentration of 0.61 ng/µl in buffer, MBP-MlrA achieved and maintained an average degradation rate of approximately 101.95 µM/h/ng of protein across fifteen freeze/thaw cycles. Stability assays demonstrated that enzyme activity was preserved over 5 months at −20°C. Results also demonstrated the effectiveness of MBP-MlrA to linearize microcystin upwards of 55.59 µM/h/ng of protein at the bench scale in both buffer and various freshwater matrices. The presence of the linear metabolite is of concern regarding intermediate toxicity, and future studies to incorporate the MlrB peptidase are discussed.

8 May 2024

Management Strategy for Overwintering Cyanobacteria in Sediments Contributing to Harmful Algal Blooms (HABs)

Purpose: Cyanobacteria that cause harmful algal blooms (HABs) can overwinter in sediments as resting cells (akinetes or vegetative colonies) and contribute to seasonal bloom resurgences. However, to date there has been limited focus on management tactics specifically targeting the control of cyanobacterial sources from sediments. Targeting resting cells in sediments for preventative management may provide a viable approach to delay onset and mitigate blooms (Calomeni et al. 2022). However, there are limited resources for this novel strategy. Given the growing global impact of HABs, there is a need to develop management strategies focused on sediments as a potential source and contributor to HABs. Therefore, the objective of this report is to provide a management strategy in terms of approaches, information, and case study examples for managing overwintering cyanobacteria in sediments with the goal of mitigating seasonal HAB occurrences.

6 Feb 2024

USACE Freshwater Harmful Algal Bloom Research and Development Initiative

Abstract: Harmful Algal Blooms (HABs) represent a significant and costly threat to our nation’s economy and natural resources. This report outlines the US Army Corps of Engineers, Engineer Research and Development Center’s (USACE-ERDC’s) approach to deliver scalable technologies for prevention, early detection, and management of HABs to reduce HAB event frequency, severity, and duration.

10 Oct 2023

A Review of Algal Phytoremediation Potential to Sequester Nutrients from Eutrophic Surface Water

Abstract: Harmful algal blooms (HABs) and coastal hypoxic zones are evidence of cultural nutrient enrichment affecting public health and water supplies, aquatic ecosystem health, and economic well-being in the United States. Recognition of the far-reaching impacts of Midwest agriculture has led to establishing nutrient reduction objectives for surface waters feeding the Gulf of Mexico, Lake Erie, and many smaller water bodies. Municipal nutrient enrichment impacts have been addressed by increasing levels of sewage treatment and waste management through the Clean Water Act era, but HABs rebounded in the 1990s because of non-point source nutrient enrichment. HAB control and treatment includes watershed and waterbody treatments to reduce loading and address outbreaks. Systems to remove nutrients from impaired waters are expensive to build and operate. This review of algal production systems summarizes emerging algal water treatment technologies and considers their potential to effectively sequester nutrients and atmospheric carbon from hundreds of eutrophic reservoirs and DoD wastewater treatment facilities while producing useful biomass feedstock using solar energy. Algal water treatment systems including open ponds, photobioreactors, and algal turf scrubbers® can be used to grow biomass for biofuel, wastewater treatment, and commercial products. This review recommends continuing research on surface water nutrient reduction potential with algal turf scrubber productivity pilot studies, preliminary site design, and biomass utilization investigations.

15 Aug 2022

Identification and Preventative Treatment of Overwintering Cyanobacteria in Sediments: A Literature Review

Abstract: Freshwaters can experience growths of toxin-producing cyanobacteria or harmful algal blooms (HABs). HAB-producing cyanobacteria can develop akinetes, which are thick-enveloped quiescent cells akin to seeds in vascular plants or quiescent colonies that overwinter in sediment. Overwintering cells produce viable “seed beds” for HAB resurgences and preventative treatments may diminish HAB intensity. The purpose of this literature review was to identify (1) environmental factors triggering germination and growth of overwintering cells, (2) sampling, identification, and enumeration methods, and (3) feasibility of preventative algaecide treatments. Conditions triggering akinete germination (light ≥0.5 µmol m-2s-1, temperature 22-27℃) differ from conditions triggering overwintering Microcystis growth (temperature 15-30℃, nutrients, mixing). Corers or dredges are used to collect surficial (0-2 cm) sediment layers containing overwintering cells. Identification and enumeration via microscopy are aided by dilution, sieving, or density separation of sediment. Grow-out studies simulate environmental conditions triggering cell growth and provide evidence of overwintering cell viability. Lines of evidence supporting algaecide efficacy for preventative treatments include (1) field studies demonstrating scalability and efficacy of algaecides against benthic algae, (2) data suggesting similar sensitivities of overwintering and planktonic Microcystis cells to a peroxide algaecide, and (3) a mesocosm study demonstrating a decrease in HAB severity following preventative treatments. This review informs data needs, monitoring techniques, and potential efficacy of algaecides for preventative treatments of overwintering cells.

18 Apr 2022

Sustainable Harmful Algal Bloom Mitigation by 3D Printed Photocatalytic Oxidation Devices (3D-PODs)

Abstract: The impacts of Harmful Algal Blooms (HAB), often caused by cyanobacteria (Figure 1), on water resources are increasing. Innovative solutions for treatment of HABs and their associated toxins are needed to mitigate these impacts and decrease risks without introducing persistent legacy contaminants that cause collateral ecosystem impacts. This technical note (TN) identifies novel opportunities enabled by Additive Manufacturing (AM), or 3D printing, to produce high surface area advanced material composites to rapidly prototype sustainable environmental solutions for aquatic nuisance species control. This innovative research explores deployment of 3D-printable polymer composite structures containing nano-scale photocatalysts for targeted open water treatment of HABs that are customizable to the site-of-concern and also retrievable, reusable, and sustainable. The approach developed to control cyanobacteria HAB events has the potential to augment or replace broadcast, non-specific chemical controls that otherwise put non-target species and ecological resources at long-term risk. It can also augment existing UV-treatment HAB treatment control measures. The expected research outcome is a novel, effective, and sustainable HAB management tool for the US Army Corps of Engineers (USACE) and resource managers to deploy in their HAB rapid response programs. The research will provide a framework for scale-up into other manufacturing methods (e.g., injection molding) to produce the devices in bulk (quickly and efficiently). Research for this project title “Mitigation of Harmful Algal Bloom Toxins using 3D Printed Photocatalytic Materials (FY21-23)” was sponsored by the US Army Engineer Research Development Center’s (ERDC) Aquatic Nuisance Species Research Program (ANSRP).

13 Oct 2021

Optimizing the Harmful Algal Bloom Interception, Treatment, and Transformation System (HABITATS)

Abstract: Harmful algal blooms (HABs) continue to affect lakes and waterways across the nation, often resulting in environmental and economic damage at regional scales. The US Army Engineer Research and Development Center (ERDC) and collaborators have continued research on the Harmful Algal Bloom Interception, Treatment, and Transformation System (HABITATS) project to develop a rapidly deployable and scalable system for mitigating large HABs. The second year of the project focused on optimization research, including (1) development of a new organic flocculant formulation for neutralization and flotation of algal cells; (2) testing and initial optimization of a new, high-throughput biomass dewatering system with low power requirements; (3) development, design, assembly, and initial testing of the first shipboard HABITATS prototype; (4) execution of two field pilot studies of interception and treatment systems in coordination with the Florida Department of Environmental Protection and New York State Department of Environmental Conservation; (5) conversion of algal biomass into biocrude fuel at pilot scale with a 33% increase in yield compared to the previous bench scale continuous-flow reactor studies; and (6) refinement of a scalability analysis and optimization model to guide the future development of full-scale prototypes.

24 Aug 2021

Aligning research and monitoring priorities for benthic cyanobacteria and cyanotoxins : a workshop summary

Abstract: In 2018, the US Army Engineer Research and Development Center partnered with the US Army Corps of Engineers–Buffalo District, the US Environmental Protection Agency, Bowling Green State University, and the Cawthron Institute to host a workshop focused on benthic and sediment-associated cyanobacteria and cyanotoxins, particularly in the context of harmful algal blooms (HAB). Technical sessions on the ecology of benthic cyanobacteria in lakes and rivers; monitoring of cyanobacteria and cyanotoxins; detection of benthic and sediment-bound cyanotoxins; and the fate, transport, and health risks of cyanobacteria and their associated toxins were presented. Research summaries included the buoyancy and dispersal of benthic freshwater cyanobacteria mats, the fate and quantification of cyanotoxins in lake sediments, and spatial and temporal variation of toxins in streams. In addition, summaries of remote sensing methods, omic techniques, and field sampling techniques were presented. Critical research gaps identified from this workshop include (1) ecology of benthic cyanobacteria, (2) identity, fate, transport, and risk of cyanotoxins produced by benthic cyanobacteria, (3) standardized sampling and analysis protocols, and (4) increased technical cooperation between government, academia, industry, nonprofit organizations, and other stakeholders. Conclusions from this workshop can inform monitoring and management efforts for benthic cyanobacteria and their associated toxins.

30 Jul 2021

Cyanobacteria Harmful Algal Blooms (HABs) and US Army Engineer Research and Development Center (ERDC): Research and Services

Abstract: This factsheet details the research and services available from the US Army Engineer Research and Development Center–Environmental Laboratory’s Harmful Algal Blooms team.

19 Oct 2020

Corps announces approval of a planned deviation from Lake O Regulation Schedule to reduce risk from Harmful Algal Blooms

The U.S. Army Corps of Engineers Jacksonville District, announces the approval of a planned deviation from the water control plan for Lake Okeechobee and the Everglades Agricultural Area, also known as the Lake Okeechobee Regulation Schedule (LORS 2008), in order to reduce risk from Harmful Algal Blooms.