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Toxins
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Harmful Algal Blooms in Waters: Characterization, Monitoring and Management
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Harmful Algal Blooms in Waters: Characterization, Monitoring and Management

A special issue of Toxins (ISSN 2072-6651). This special issue belongs to the section "Marine and Freshwater Toxins".

Deadline for manuscript submissions: 30 September 2025 | Viewed by 8931

Special Issue Editor

Dr. Audrey Roy-Lachapelle

E-Mail Website
Guest Editor
Aquatic Contaminants Research Division, Environment and Climate Change Canada, Montreal, QC H2Y 2E7, Canada
Interests: cyanobacteria; cyanotoxins; eutrophication; environmental contaminants and fate; mixtures effects; mass spectrometry
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The rising prevalence of harmful algal blooms (HABs) poses significant threats to environmental and public health. These blooms, fueled by nutrient input and climate change, contribute to water quality degradation, and the cyanotoxins produced by certain cyanobacteria can contaminate water sources. HABs are therefore jeopardizing aquatic ecosystems, for instance, by causing fish kills and adversely affecting human health when consumed or during recreational activities. The diversity of cyanobacterial species and their variable toxin production under different circumstances poses a multifaceted challenge. The diversity of cyanotoxins, their extensive structural variability and the lack of knowledge about their environmental fate highlights the need for accurate detection and characterization methods. The unpredictability of cyanotoxin occurrence necessitates the continuous monitoring and adaptability of response strategies for water management. This Special Issue invites research articles and reviews that explore original methodologies for characterizing toxic cyanobacteria, cyanotoxins and secondary metabolites, as well as studying their diversity and environmental fate for improved monitoring strategies. Studies on predictive models for the occurrence of cyanobacteria and the production of cyanotoxins, along with the exploration of effective water treatment methodologies and the study of residual by-product toxicity for better management are also welcome in this Special Issue.

Dr. Audrey Roy-Lachapelle
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a double-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Toxins is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • harmful algal blooms
  • cyanobacteria
  • cyanotoxins
  • toxin production
  • monitoring
  • structural characterization
  • environmental fate
  • disinfection by-product
  • water management

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Published Papers (6 papers)

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Research

20 pages, 2960 KiB  
Article
Effectiveness of Kaolinite with and Without Polyaluminum Chloride (PAC) in Removing Toxic Alexandrium minutum
by Cherono Sheilah Kwambai, Houda Ennaceri, Alan J. Lymbery, Damian W. Laird, Jeff Cosgrove and Navid Reza Moheimani
Toxins 2025, 17(8), 395; https://doi.org/10.3390/toxins17080395 - 6 Aug 2025
Viewed by 472
Abstract
Alexandrium spp. blooms and paralytic shellfish poisoning pose serious economic threats to coastal communities and aquaculture. This study evaluated the removal efficiency of two Alexandrium minutum strains using natural kaolinite clay (KNAC) and kaolinite with polyaluminum chloride (KPAC) at three concentrations (0.1, 0.25, [...] Read more.
Alexandrium spp. blooms and paralytic shellfish poisoning pose serious economic threats to coastal communities and aquaculture. This study evaluated the removal efficiency of two Alexandrium minutum strains using natural kaolinite clay (KNAC) and kaolinite with polyaluminum chloride (KPAC) at three concentrations (0.1, 0.25, and 0.3 g L−1), two pH levels (7 and 8), and two cell densities (1.0 and 2.0 × 107 cells L−1) in seawater. PAC significantly enhanced removal, achieving up to 100% efficiency within two hours. Zeta potential analysis showed that PAC imparted positive surface charges to the clay, promoting electrostatic interactions with negatively charged algal cells and enhancing flocculation through Van der Waals attractions. In addition, the study conducted a cost estimate analysis and found that treating one hectare at 0.1 g L−1 would cost approximately USD 31.75. The low KPAC application rate also suggests minimal environmental impact on benthic habitats. Full article
(This article belongs to the Special Issue Harmful Algal Blooms in Waters: Characterization, Monitoring and Management)
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27 pages, 11944 KiB  
Article
Heatwave-Induced Thermal Stratification Shaping Microbial-Algal Communities Under Different Climate Scenarios as Revealed by Long-Read Sequencing and Imaging Flow Cytometry
by Ayagoz Meirkhanova, Adina Zhumakhanova, Polina Len, Christian Schoenbach, Eti Ester Levi, Erik Jeppesen, Thomas A. Davidson and Natasha S. Barteneva
Toxins 2025, 17(8), 370; https://doi.org/10.3390/toxins17080370 - 27 Jul 2025
Viewed by 510
Abstract
The effect of periodical heatwaves and related thermal stratification in freshwater aquatic ecosystems has been a hot research issue. A large dataset of samples was generated from samples exposed to temporary thermal stratification in mesocosms mimicking shallow eutrophic freshwater lakes. Temperature regimes were [...] Read more.
The effect of periodical heatwaves and related thermal stratification in freshwater aquatic ecosystems has been a hot research issue. A large dataset of samples was generated from samples exposed to temporary thermal stratification in mesocosms mimicking shallow eutrophic freshwater lakes. Temperature regimes were based on IPCC climate warming scenarios, enabling simulation of future warming conditions. Surface oxygen levels reached 19.37 mg/L, while bottom layers dropped to 0.07 mg/L during stratification. Analysis by FlowCAM revealed dominance of Cyanobacteria under ambient conditions (up to 99.2%), while Cryptophyta (up to 98.9%) and Chlorophyta (up to 99.9%) were predominant in the A2 and A2+50% climate scenarios, respectively. We identified temperature changes and shifts in nutrient concentrations, particularly phosphate, as critical factors in microbial community composition. Furthermore, five distinct Microcystis morphospecies identified by FlowCAM-based analysis were associated with different microbial clusters. The combined use of imaging flow cytometry, which differentiates phytoplankton based on morphological parameters, and nanopore long-read sequencing analysis has shed light into the dynamics of microbial communities associated with different Microcystis morphospecies. In our observations, a peak of algicidal bacteria abundance often coincides with or is followed by a decline in the Cyanobacteria. These findings highlight the importance of species-level classification in the analysis of complex ecosystem interactions and the dynamics of algal blooms in freshwater bodies in response to anthropogenic effects and climate change. Full article
(This article belongs to the Special Issue Harmful Algal Blooms in Waters: Characterization, Monitoring and Management)
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22 pages, 629 KiB  
Article
Investigation into Paralytic Shellfish Toxins and Microcystins in Seabirds from Portugal
by Lucía Soliño, Andrew D. Turner, Begoña Ben-Gigirey, Ryan P. Alexander, Karl J. Dean, Robert G. Hatfield, Benjamin H. Maskrey and María V. Mena Casero
Toxins 2025, 17(3), 135; https://doi.org/10.3390/toxins17030135 - 13 Mar 2025
Cited by 1 | Viewed by 939
Abstract
Microalgae form the basis of marine food webs, essential in sustaining top predators including seabirds. However, certain species of microalgae synthesize biotoxins, which can accumulate in shellfish and fish and may cause harm to marine animals feeding on them. Toxins produced by dinoflagellates [...] Read more.
Microalgae form the basis of marine food webs, essential in sustaining top predators including seabirds. However, certain species of microalgae synthesize biotoxins, which can accumulate in shellfish and fish and may cause harm to marine animals feeding on them. Toxins produced by dinoflagellates have been previously observed to be poisonous to seabirds. Also, in freshwater and brackish habitats, cyanobacteria have caused bird mortality events. In this work, we analyze the prevalence of six families of biotoxins (paralytic shellfish toxins (PSTs), microcystins (MCs), anatoxins, amnesic shellfish toxins (ASTs), cylindrospermopsin, and tetrodotoxins (TTXs)) in 340 samples from 193 wild birds admitted to a wildlife rehabilitation centre in south Portugal. Furthermore, we consider the clinical picture and signs of 17 birds that presented quantifiable levels of biotoxins in their tissues. The relationship between toxin burdens and the symptomatology observed, as well as possible biotoxin sources, are discussed. Based on previously published research data, we conclude that, in these birds, the biotoxins are unlikely to be the only cause of death but might contribute to some extent to a reduction in birds’ fitness. Full article
(This article belongs to the Special Issue Harmful Algal Blooms in Waters: Characterization, Monitoring and Management)
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14 pages, 3850 KiB  
Article
Cobalt-Doped Carbon Nitride for Efficient Removal of Microcystis aeruginosa via Peroxymonosulfate Activation
by Wen Yan, Chuqiao Li, Yunjuan Meng, Yao Yue, Teer Wen, Jiafeng Ding and Hangjun Zhang
Toxins 2024, 16(11), 455; https://doi.org/10.3390/toxins16110455 - 24 Oct 2024
Cited by 1 | Viewed by 1584
Abstract
Heterogeneous persulfate activation is an advanced technology for treating harmful algae in drinking water sources, while it remains a significant hurdle in the efficient management of cyanobacterial blooms. In this study, super-dispersed cobalt-doped carbon nitride (2CoCN) was prepared to activate peroxymonosulfate (PMS) for [...] Read more.
Heterogeneous persulfate activation is an advanced technology for treating harmful algae in drinking water sources, while it remains a significant hurdle in the efficient management of cyanobacterial blooms. In this study, super-dispersed cobalt-doped carbon nitride (2CoCN) was prepared to activate peroxymonosulfate (PMS) for simultaneous Microcystis aeruginosa inhibition and microcystin (MC-LR) degradation. When the initial PMS and 2CoCN concentrations were 0.3 g/L and 0.4 g/L, respectively, the efficiency of algal cell removal reached 97% in 15 min, and the degradation of MC-LR reached 96%. Analyses by SEM, TEM, and EEM spectra revealed that the reaction led to changes in algal cell morphology, damage to the cell membrane and cell wall, and the diffusion of thylakoid membranes and liposomes. The activities of antioxidant enzymes (superoxide dismutase and catalase) and antioxidants (glutathione) in algal cells generally increased, and the content of malondialdehyde increased, indicating severe damage to the cell membrane. Radical capture experiments confirmed that singlet oxygen (1O₂) was the key species destroying algal cells in the 2CoCN/PMS system. The 2CoCN/PMS system was effective in removing M. aeruginosa within a wide pH range (3–9), and 2CoCN had good reusability. Additionally, three degradation products of MC-LR were identified by LC–MS/MS analysis, and a possible mechanism for the inactivation of M. aeruginosa and the degradation of MC-LR was proposed. In conclusion, this study pioneered the 2CoCN/PMS system for inhibiting M. aeruginosa and degrading microcystin, aiming to advance water purification and algae removal technology. Full article
(This article belongs to the Special Issue Harmful Algal Blooms in Waters: Characterization, Monitoring and Management)
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13 pages, 5581 KiB  
Article
Microbial Community Response to Granular Peroxide-Based Algaecide Treatment of a Cyanobacterial Harmful Algal Bloom in Lake Okeechobee, Florida (USA)
by Forrest W. Lefler, Maximiliano Barbosa, David E. Berthold, Rory Roten, West M. Bishop and H. Dail Laughinghouse IV
Toxins 2024, 16(5), 206; https://doi.org/10.3390/toxins16050206 - 26 Apr 2024
Cited by 1 | Viewed by 2309
Abstract
Cyanobacterial harmful algal blooms (cyanoHABs) occur in fresh water globally. These can degrade water quality and produce toxins, resulting in ecological and economic damages. Thus, short-term management methods (i.e., algaecides) are necessary to rapidly mitigate the negative impacts of cyanoHABs. In this study, [...] Read more.
Cyanobacterial harmful algal blooms (cyanoHABs) occur in fresh water globally. These can degrade water quality and produce toxins, resulting in ecological and economic damages. Thus, short-term management methods (i.e., algaecides) are necessary to rapidly mitigate the negative impacts of cyanoHABs. In this study, we assess the efficacy of a hydrogen peroxide-based algaecide (PAK® 27) on a Microcystis dominated bloom which occurred within the Pahokee Marina on Lake Okeechobee, Florida, USA. We observed a significant reduction in chlorophyll a (96.81%), phycocyanin (93.17%), and Microcystis cell counts (99.92%), and a substantial reduction in microcystins (86.7%) 48 h after treatment (HAT). Additionally, there was a significant shift in bacterial community structure 48 HAT, which coincided with an increase in the relative abundance of photosynthetic protists. These results indicate that hydrogen peroxide-based algaecides are an effective treatment method for cyanoHAB control and highlight their effects on non-target microorganisms (i.e., bacteria and protists). Full article
(This article belongs to the Special Issue Harmful Algal Blooms in Waters: Characterization, Monitoring and Management)
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16 pages, 4157 KiB  
Article
Microbial Diversity Impacts Non-Protein Amino Acid Production in Cyanobacterial Bloom Cultures Collected from Lake Winnipeg
by Stephanie L. Bishop, Julia T. Solonenka, Ryland T. Giebelhaus, David T. R. Bakker, Isaac T. S. Li and Susan J. Murch
Toxins 2024, 16(4), 169; https://doi.org/10.3390/toxins16040169 - 26 Mar 2024
Viewed by 2133
Abstract
Lake Winnipeg in Manitoba, Canada is heavily impacted by harmful algal blooms that contain non-protein amino acids (NPAAs) produced by cyanobacteria: N-(2-aminoethyl)glycine (AEG), β-aminomethyl-L-alanine (BAMA), β-N-methylamino-L-alanine (BMAA), and 2,4-diaminobutyric acid (DAB). Our objective was to investigate the impact of microbial [...] Read more.
Lake Winnipeg in Manitoba, Canada is heavily impacted by harmful algal blooms that contain non-protein amino acids (NPAAs) produced by cyanobacteria: N-(2-aminoethyl)glycine (AEG), β-aminomethyl-L-alanine (BAMA), β-N-methylamino-L-alanine (BMAA), and 2,4-diaminobutyric acid (DAB). Our objective was to investigate the impact of microbial diversity on NPAA production by cyanobacteria using semi-purified crude cyanobacterial cultures established from field samples collected by the Lake Winnipeg Research Consortium between 2016 and 2021. NPAAs were detected and quantified by ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) using validated analytical methods, while Shannon and Simpson alpha diversity scores were determined from 16S rRNA metagenomic sequences. Alpha diversity in isolate cultures was significantly decreased compared to crude cyanobacterial cultures (p < 0.001), indicating successful semi-purification. BMAA and AEG concentrations were higher in crude compared to isolate cultures (p < 0.0001), and AEG concentrations were correlated to the alpha diversity in cultures (r = 0.554; p < 0.0001). BAMA concentrations were increased in isolate cultures (p < 0.05), while DAB concentrations were similar in crude and isolate cultures. These results demonstrate that microbial community complexity impacts NPAA production by cyanobacteria and related organisms. Full article
(This article belongs to the Special Issue Harmful Algal Blooms in Waters: Characterization, Monitoring and Management)
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