Comparative assessment of algaecide performance on freshwater phytoplankton: Understanding differential sensitivities to frame cyanobacteria management

Authors

Malihe Mehdizadeh Allaf, Kevin J. Erratt, Hassan Peerhossaini

Cyanobacterial bloom represent a growing threat to global water security. With fast proliferation, they raise great concern due to potential health and socioeconomic concerns. Algaecides are commonly employed as a mitigative measure to suppress and manage cyanobacteria. However, recent research on algaecides has a limited phycological focus, concentrated predominately on cyanobacteria and chlorophytes. Without considering phycological diversity, generalizations crafted from these algaecide comparisons present a biased perpective. To limit the collateral impacts of algaecide interventions on phytoplankton communities it is critical to understand differential phycological sensitivities for establishing optimal dosage and tolerance thresholds. This research attempts to fill this knowledge gap and provide effective guidelines to frame cyanobacterial management. We investigate the effect of two common algaecides, copper sulfate (CuSO₄) and hydrogen peroxide (H₂O₂), on four major phycological divisions (chlorophytes, cyanobacteria, diatoms, and mixotrophs). All phycological divisions exhibited greater sensitivity to copper sulfate, except chlorophytes. Mixotrophs and cyanobacteria displayed the highest sensitivity to both algaecides with the highest to lowest sensitivity being observed as follows: mixotrophs, cyanobacteria, diatoms, and chlorophytes. Our results suggest that H₂O₂ represents a comparable alternative to CuSO₄ for cyanobacterial control. However, some eukaryotic divisions such as mixotrophs and diatoms mirrored cyanobacteria sensitivity, challenging the assumption that H₂O₂ is a selective cyanocide. Our findings suggest that optimizing algaecide treatments to suppress cyanobacteria while minimizing potential adverse effects on other phycological members is unattainable. An apparent trade-off between effective cyanobacterial management and conserving non-targeted phycological divisions is expected and should be a prime consideration of lake management.

Differential Effect of Hydrogen Peroxide οn Toxic Cyanobacteria of Hypertrophic Mediterranean Waterbodies

Authors

Theodoti Papadimitriou, Matina Katsiapi, Natassa Stefanidou, Aikaterini Paxinou, Vasiliki Poulimenakou, Chrysi S. Laspidou, Maria Moustaka-Gouni and Konstantinos A. Kormas

Cyanobacterial blooms have been known since ancient times; however, they are currently increasing globally. Human and ecological health risks posed by harmful cyanobacterial blooms have been recorded around the world. These risks are mainly associated with their ability to affect the ecosystem chain by different mechanisms like the production of cyanotoxins, especially microcystins. Their expansion and their harmful effects have led many researchers to seek techniques and strategies to control them. Among them, hydrogen peroxide could be a promising tool against cyanobacteria and cyanotoxins and it is well-established as an environmentally friendly oxidizing agent because of its rapid decomposition into oxygen and water. The aim of the present study was to evaluate the effect of hydrogen peroxide on phytoplankton from two hypertrophic waterbodies in Greece. The effect of hydrogen peroxide on concentration of microcystins found in the waterbodies was also studied. Treatment with 4 mg/L hydrogen peroxide was applied to water samples originated from the waterbodies and Cyanobacterial composition and biomass, phycocyanin, chlorophyll-a, and intra-cellular and total microcystin concentrations were studied. Cyanobacterial biomass and phycocyanin was reduced significantly after the application of 4 mg/L hydrogen peroxide in water treatment experiments while chlorophytes and extra-cellular microcystin concentrations were increased. Raphidiopsis (Cylindrospermopsis) raciborskii was the most affected cyanobacterial species after treatment of the water of the Karla Reservoir in comparison to Aphanizomenon favaloroi, Planktolyngbya limnetica, and Chroococcus sp. Furthermore, Microcystis aeruginosa was more resistant to the treatment of Pamvotis lake water in comparison with Microcystis wesenbergii and Microcystis panniformis. Our study showed that hydrogen peroxide differentially impacts the members of the phytoplankton community, affecting, thus, its overall efficacy. Different effects of hydrogen peroxide treatment were observed among cyanobacerial genera as well as among cyanobacterial species of the same genus. Different effects could be the result of the different resistance mechanisms of each genus or species to hydrogen peroxide. Hydrogen peroxide could be used as a treatment for the mitigation of cyanobacterial blooms in a waterbody; however, the biotic and abiotic characteristics of the waterbody should be considered.

The Application of Potassium Permanganate to Treat Cyanobacteria-Laden Water: a Review

Authors

Kayla Piezer, Lei Li, Youchul Jeon, Anusha Kadudula, Youngwoo Seo

Climate change and eutrophication provide favorable conditions for cyanobacterial growth which can lead to harmful algal blooms (HABs). HABs pose a threat to society due to the release of algal metabolites. Water utilities are challenged with treating cyanobacteria-laden water to effectively eliminate cyanotoxins while avoiding the negative impacts of taste and odor causing compounds, disinfection byproduct (DBP) formation, and increased organic matter loading caused by HABs. Historically, potassium permanganate (KMnO₄) has been used for various applications in water treatment due to its affordability and easy implementation, but more recently, KMnO₄ gained attention for its potential application to treat cyanobacterial cells. Accordingly, this review aims to summarize the current understanding of the application of KMnO₄ as a pre-oxidant for the treatment of HAB impacted water. In this review, we discussed the impacts of KMnO₄ on cyanobacterial cell and associated cyanotoxin removal, altering DBP formation, and reducing production of taste and odor causing compounds to highlight the potential application of KMnO₄ for HAB treatment. Additionally, we summarized the adverse effects of using KMnO₄, gave recommendations to minimize those impacts, and identified future research needs from multiple perspectives. Overall, this review provides a comprehensive current understanding, future directions and insights into the application of KMnO₄ to address HABs related issues.

Novel Algicides against Bloom-Forming Cyanobacteria from Allelochemicals: Design, Synthesis, Bioassay, and 3D-QSAR Study

Authors

Yin Luo,Yushun Yang, Wenguang Hou, and Jie Fu

Cyanobacteria bloom caused by water eutrophication has threatened human health and become a global environmental problem. To develop green algicides with strong specificity and high efficiency, three series of ester and amide derivatives from parent allelochemicals of caffeic acid (CA), cinnamic acid (CIA), and 3-hydroxyl-2-naphthoic acid (HNA) were designed and synthesized. Their inhibitory effects on the growth of five harmful cyanobacterial species, Microcystis aeruginosa (M. aeruginosa), Microcystis wesenbergii (M. wesenbergii), Microcystis flos-aquae (M. flos-aquae), Aphanizomenon flos-aquae (Ap. flos-aquae), and Anabaena flos-aquae (An. flos-aquae), were evaluated. The results revealed that CIA esters synthesized by cinnamic acid and fatty alcohols showed the best inhibition effect, with EC₅₀ values ranging from 0.63 to >100 µM. Moreover, some CIA esters exhibited a good selectivity in inhibiting cyanobacteria. For example, the inhibitory activity of naphthalen-2-yl cinnamate was much stronger on Ap. flos-aquae (EC₅₀ = 0.63 µM) than other species (EC₅₀ > 10 µM). Three-dimensional quantitative structure–activity relationship (3D-QSAR) analysis was performed and the results showed that the steric hindrance of the compounds influenced the algicidal activity. Further mechanism study found that the inhibition of CIA esters on the growth of M. aeruginosa might be related to the accumulation of malondialdehyde (MDA).

Nitrite-responsive hydrogel for long-term and smart control of cyanobacteria bloom

Authors

Jialiang Xiong, Ruoxiao Xie, Huiying Zhang, Jianyi Gao, Jiaping Wang, Qionglin Liang

Frequent cyanobacteria bloom has caused serious environmental consequences and economic loss, especially in aquaculture. Direct algaecide addition, the most commonly used method, suffered from the poor control and overdose of algaecide. In this manuscript, we designed a smart nitrite-responsive hydrogel (DHPG) loading algaecide (BZK@DHPG) based on selective crosslinker: a kind of dihydropyridine derivatives termed DHPL. The network of the polymer could be decomposed by the nitrite-induced cleavage of DHPL. Compared to the traditional method, BZK@DHPG can adjust releasing speed according to the concentration of NO₂⁻, the marker of cyanobacteria bloom level, and elongate the releasing time. Furthermore, BZK@DHPG could shift the effective dose of algaecide much ahead of the safety threshold, thus reducing deterioration of water quality caused by the overdose of algaecide.

The Efficacy of Hydrogen Peroxide in Mitigating Cyanobacterial Blooms and Altering Microbial Communities across Four Lakes in NY, USA

Authors

Mark W. Lusty and Christopher J. Gobler

Hydrogen peroxide (H₂O₂) has been proposed as an agent to mitigate toxic cyanobacterial blooms due to the heightened sensitivity of cyanobacteria to reactive oxygen species relative to eukaryotic organisms. Here, experiments were conducted using water from four diverse, eutrophic lake ecosystems to study the effects of H₂O₂ on cyanobacteria and non-target members of the microbial community. H₂O₂ was administered at 4 µg L⁻¹ and a combination of fluorometry, microscopy, flow cytometry, and high throughput DNA sequencing were used to quantify the effects on eukaryotic and prokaryotic plankton communities. The addition of H₂O₂ resulted in a significant reduction in cyanobacteria levels in nearly all experiments (10 of 11), reducing their relative abundance from, on average, 85% to 29% of the total phytoplankton community with Planktothrix being highly sensitive, Microcystis being moderately sensitive, and Cylindrospermopsis being most resistant. Concurrently, eukaryotic algal levels increased in 75% of experiments. The bacterial phyla Actinobacteria, cyanobacteria, Planctomycetes, and Verrucomicrobia were most negatively impacted by H₂O₂, with Actinobacteria being the most sensitive. The ability of H₂O₂ to reduce, but not fully eliminate, cyanobacteria from the eutrophic water bodies studied here suggests it may not be an ideal mitigation approach in high biomass ecosystems.

Influence of Environmental Factors on the Production of MIB and Geosmin Metabolites by Bacteria in a Eutrophic Reservoir

Authors

Nicolas A. Clercin, Gregory K. Druschel

Occurrences of odorous bacterial metabolites, 2‐methylisoborneol (MIB) and geosmin (GSM), in drinking water supply reservoirs are considered as a nuisance by the water industry and a source of complaints from customers. In Eagle Creek Reservoir, routine monitoring programs of MIB and GSM highlight intense odorous outbreaks during the spring season when high inflow discharges occur. Cyanobacteria have always been assumed to be source of these metabolites even if no known producers are present in raw water. A copper‐based algaecide is often used to terminate the metabolite production and the algal growth in the reservoir. The current study was designed to investigate and identify other biological sources involved in the biosynthesis of MIB and GSM metabolites as well as environmental factors that could be important triggers for the growth of bacterial producers. The community structure of the bacterioplankton was determined using a 16S rRNA gene sequencing technique, which showed that not only Cyanobacteria but Actinobacteria also were involved in the reservoir internal production. Planktothrix species was identified as the main source of GSM (p < 0.001) while Streptomyces (Actinobacteria) was very likely responsible of MIB (p < 0.01). Application of an algaecide disrupted GSM and the growth of Planktothrix but was less effective against MIB and Streptomyces. Statistical analyses revealed that MIB‐ and GSM‐causing bacteria were found abundant when the water was enriched with nitrogen, temperature cooler, and the water column mixed.

Hydrogen peroxide treatment promotes chlorophytes over toxic cyanobacteria in a hyper-eutrophic aquaculture pond

Authors

Zhen Yang, Riley P. Buley, Edna G. Fernandez-Figueroa, Mario U. G. Barros, Soorya Rajendran, Alan E. Wilson

Controlling blooms of toxigenic phytoplankton, including cyanobacteria, is a high priority for managers of aquatic systems that are used for drinking water, recreation, and aquaculture production. Although a variety of treatment approaches exist, hydrogen peroxide (H2O2) has the potential to be an effective and ecofriendly algaecide given that this compound may select against cyanobacteria while not producing harmful residues. To broadly evaluate the effectiveness of H2O2 on toxigenic phytoplankton, we tested multiple concentrations of H2O2 on (1) four cyanobacterial cultures, including filamentous Anabaena, Cylindrospermopsis, and Planktothrix, and unicellular Microcystis, in a 5-day laboratory experiment and (2) a dense cyanobacterial bloom in a 7-day field experiment conducted in a nutrient-rich aquaculture pond. In the laboratory experiment, half-maximal effective concentrations (EC50) were similar for Anabaena, Cylindrospermopsis, and Planktothrix (average EC50 = 0.41 mg L−1) but were ∼10x lower than observed for Microcystis (EC50 = 5.06 mg L−1). Results from a field experiment in an aquaculture pond showed that ≥1.3 and ≥ 6.7 mg L−1 of H2O2 effectively eliminated Planktothrix and Microcystis, respectively. Moreover, 6.7 mg L−1 of H2O2 reduced microcystin and enhanced phytoplankton diversity, while causing relatively small negative effects on zooplankton abundance. In contrast, 20 mg L−1 of H2O2 showed the greatest negative effect on zooplankton. Our results demonstrate that H2O2 can be an effective, rapid algaecide for controlling toxigenic cyanobacteria when properly dosed.