Managing and Preventing Harmful Algal Blooms (HABs): Do We Know Enough?

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

Deadline for manuscript submissions: closed (30 September 2023) | Viewed by 8333

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Brain Chemistry Labs, Institute for Ethnomedicine, Box 3464, Jackson, WY 83001, USA
Interests: cyanobacteria; cyanotoxins; analysis; toxicology; exposure routes
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Special Issue Information

Dear Colleagues,

Marine and freshwaters are frequently populated with harmful cyanobacterial or algal blooms that can result in closures of waterbodies, fisheries, and recreational areas with resulting significant impacts, including economic effects from produce loss (e.g., fish and shellfish) and negative effects on tourism, as well as to closures of water treatment plants. Studying such blooms for many years has advanced our understanding of the risks associated with exposure to these organisms and the toxins they produce, including a greater understanding of the health risks associated with long-term exposure to these compounds. However, many uncertainties and gaps may still remain. This Special Issue aims to ask the question of whether we know enough regarding harmful cyanobacterial and algal blooms and what further fundamental and applied research is required. Such issues may apply to detection, monitoring, health risks, and treatment and mitigation solutions for blooms and toxins, as examples. Therefore, this Special Issue solicits manuscripts concerning all aspects of detection, risk assessment, and the management and prevention of harmful cyanobacterial and algal blooms as well as novel and innovative practical solutions to fill current gaps in knowledge and science.

Dr. James S. Metcalf
Guest Editor

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Keywords

  • knowledge gaps
  • mitigation
  • risk assessment and management
  • analysis
  • health risks
  • future research questions

Published Papers (4 papers)

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Research

11 pages, 2949 KiB  
Article
Cyanotoxin Analysis of Air Samples from the Great Salt Lake
by James S. Metcalf, Sandra Anne Banack and Paul Alan Cox
Toxins 2023, 15(11), 659; https://doi.org/10.3390/toxins15110659 - 15 Nov 2023
Viewed by 3029
Abstract
The Great Salt Lake in Utah is the largest saline lake in the Western hemisphere and one of the largest terminal lakes in the world. Situated at the eastern edge of the Great Basin, it is a remnant of the freshwater Lake Bonneville [...] Read more.
The Great Salt Lake in Utah is the largest saline lake in the Western hemisphere and one of the largest terminal lakes in the world. Situated at the eastern edge of the Great Basin, it is a remnant of the freshwater Lake Bonneville whose water level precipitously lowered about 12,000 years ago due to a natural break in Red Rock pass to the north. It contains a diverse assemblage of cyanobacteria which vary spatially dependent on salinity. In 1984, the waters of the Great Salt Lake occupied 8500 km2. Nearly four decades later, the waters occupy 2500 km2—a reduction in surface area of 71%. With predominantly westerly winds, there is a potential for the adjacent metropolitan residents to the east to be exposed to airborne cyanobacteria- and cyanotoxin-containing dust. During the summer and fall months of 2022, air and dried sediment samples were collected and assessed for the presence of BMAA which has been identified as a risk factor for ALS. Collection of air samples equivalent to a person breathing for 1 h resulted in BMAA and isomers being found in some air samples, along with their presence in exposed lakebed samples. There was no clear relationship between the presence of these toxins in airborne and adjacent lakebed samples, suggesting that airborne toxins may originate from diffuse rather than point sources. These findings confirm that continued low water levels in the Great Salt Lake may constitute an increasing health hazard for the 2.5 million inhabitants of communities along the Wasatch Front. Full article
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15 pages, 1660 KiB  
Article
A Sub-Acute Dosing Study of Saxitoxin and Tetrodotoxin Mixtures in Mice Suggests That the Current Paralytic Shellfish Toxin Regulatory Limit Is Fit for Purpose
by Sarah C. Finch, Nicola G. Webb, Michael J. Boundy, D. Tim Harwood, John S. Munday, Jan M. Sprosen, Chanatda Somchit and Ric B. Broadhurst
Toxins 2023, 15(7), 437; https://doi.org/10.3390/toxins15070437 - 03 Jul 2023
Cited by 2 | Viewed by 1610
Abstract
Paralytic shellfish poisoning is a worldwide problem induced by shellfish contaminated with paralytic shellfish toxins. To protect human health, a regulatory limit for these toxins in shellfish flesh has been adopted by many countries. In a recent study, mice were dosed with saxitoxin [...] Read more.
Paralytic shellfish poisoning is a worldwide problem induced by shellfish contaminated with paralytic shellfish toxins. To protect human health, a regulatory limit for these toxins in shellfish flesh has been adopted by many countries. In a recent study, mice were dosed with saxitoxin and tetrodotoxin mixtures daily for 28 days showing toxicity at low concentrations, which appeared to be at odds with other work. To further investigate this reported toxicity, we dosed groups of mice with saxitoxin and tetrodotoxin mixtures daily for 21 days. In contrast to the previous study, no effects on mouse bodyweight, food consumption, heart rate, blood pressure, grip strength, blood chemistry or hematology were observed. Furthermore, no histological findings were associated with dosing in this trial. The dose rates in this study were 2.6, 3.8 and 4.9 times greater, respectively, than the highest dose of the previous study. As rapid mortality in three out of five mice was observed in the previous study, the deaths are likely to be due to the methodology used rather than the shellfish toxins. To convert animal data to that used in a human risk assessment, a 100-fold safety factor is required. After applying this safety factor, the dose rates used in the current study were 3.5, 5.0 and 6.5 times greater, respectively, than the acute reference dose for each toxin type set by the European Union. Furthermore, it has previously been proposed that tetrodotoxin be included in the paralytic shellfish poisoning suite of toxins. If this were done, the highest dose rate used in this study would be 13 times the acute reference dose. This study suggests that the previous 28-day trial was flawed and that the current paralytic shellfish toxin regulatory limit is fit for purpose. An additional study, feeding mice a diet laced with the test compounds at higher concentrations than those of the current experiment, would be required to comment on whether the current paralytic shellfish toxin regulatory limit should be modified. Full article
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11 pages, 556 KiB  
Article
The Effect of Experimental Protocol on the Toxicity of Saxitoxin in Mice
by Sarah C. Finch, Michael J. Boundy, Nicola G. Webb and D. Tim Harwood
Toxins 2023, 15(4), 290; https://doi.org/10.3390/toxins15040290 - 17 Apr 2023
Cited by 5 | Viewed by 1551
Abstract
Regulatory limits for toxins in shellfish are required to ensure the health of consumers. However, these limits also impact the profitability of shellfish industries making it critical that they are fit for purpose. Since human toxicity data is rarely available, the setting of [...] Read more.
Regulatory limits for toxins in shellfish are required to ensure the health of consumers. However, these limits also impact the profitability of shellfish industries making it critical that they are fit for purpose. Since human toxicity data is rarely available, the setting of regulatory limits is dependent on animal data which can then be extrapolated for use in the assessment of human risk. The dependence on animal data to keep humans safe means that it is critical that the toxicity data used is robust and of high quality. Worldwide, the protocols used in toxicity testing are varied, making it hard to compare results and adding confusion over which results better reflect the true toxicity. In this study, we look at the effect of mouse gender, i.p. dose volume, mouse body weight and feeding protocols (both acute and sub-acute) on the toxicity of saxitoxin. This allowed the effect of different variables used in toxicity testing to be understood and showed that the feeding protocol used in both acute and sub-acute studies greatly influenced the toxicity of saxitoxin in mice. Therefore, the adoption of a standard protocol for the testing of shellfish toxins is recommended. Full article
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24 pages, 4210 KiB  
Article
Progress on the Link between Nutrient Availability and Toxin Production by Ostreopsis cf. ovata: Field and Laboratory Experiments
by Noemí Inmaculada Medina-Pérez, Elena Cerdán-García, Francesc Rubió, Laia Viure, Marta Estrada, Encarnación Moyano and Elisa Berdalet
Toxins 2023, 15(3), 188; https://doi.org/10.3390/toxins15030188 - 02 Mar 2023
Cited by 2 | Viewed by 1660
Abstract
This study aimed to improve the understanding of the nutrient modulation of Ostreopsis cf. ovata toxin content. During the 2018 natural bloom in the NW Mediterranean, the total toxin content (up to ca. 57.6 ± 7.0 pg toxin cell−1) varied markedly. [...] Read more.
This study aimed to improve the understanding of the nutrient modulation of Ostreopsis cf. ovata toxin content. During the 2018 natural bloom in the NW Mediterranean, the total toxin content (up to ca. 57.6 ± 7.0 pg toxin cell−1) varied markedly. The highest values often coincided with elevated O. cf. ovata cell abundance and with low inorganic nutrient concentrations. The first culture experiment with a strain isolated from that bloom showed that cell toxin content was higher in the stationary than in the exponential phase of the cultures; phosphate- and nitrate-deficient cells exhibited similar cell toxin variability patterns. The second experiment with different conditions of nitrogen concentration and source (nitrate, urea, ammonium, and fertilizer) presented the highest cellular toxin content in the high-nitrogen cultures; among these, urea induced a significantly lower cellular toxin content than the other nutrient sources. Under both high- and low-nitrogen concentrations, cell toxin content was also higher in the stationary than in the exponential phase. The toxin profile of the field and cultured cells included ovatoxin (OVTX) analogues -a to -g and isobaric PLTX (isoPLTX). OVTX-a and -b were dominant while OVTX-f, -g, and isoPLTX contributed less than 1-2%. Overall, the data suggest that although nutrients determine the intensity of the O. cf. ovata bloom, the relationship of major nutrient concentrations, sources and stoichiometry with cellular toxin production is not straightforward. Full article
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