Extreme weather events caused by climate change have a significant impact on the lake ecosystems. While many researchers believe that heatwaves and droughts may enhance algal bloom, heatwaves and droughts reduced algal blooms in Lake Chaohu during the spring and summer of 2022. To investigate the mechanism behind this phenomenon, on-site sampling and online monitoring were conducted in Lake Chaohu from 2019 to 2022. The results showed that non-algal turbidity played a critical role in temporarily inhibiting algal blooms. The water level in spring and summer of the drought year was 1.2 m lower than that in conventional years, resulting in the area of shoals where resuspension could occur being nearly 4 times larger than in conventional years. Strong resuspension caused turbidity in spring and summer to be more than double that of conventional years, sharply reducing gross primary productivity by 39 %, which led to lower chlorophyll a concentration than in conventional years. These results indicate that drought does not necessarily exacerbate algal blooms, and changes in shoal area due to water level fluctuations are a key factor affecting algal blooms in shallow lakes prone to resuspension. Furthermore, these results suggest lake managers can control algal blooms by adjusting water level to increase turbidity during or before algal bloom seasons.
{"title":"Light limitation during a compound drought and heat event inhibited algal blooms in a nutrient-rich shallow lake","authors":"Tianhao Wu , Rui Gao , Xiaoxian Tang , Zhaosheng Chu , Bibi Ye , Zhen Yuan","doi":"10.1016/j.hal.2024.102796","DOIUrl":"10.1016/j.hal.2024.102796","url":null,"abstract":"<div><div>Extreme weather events caused by climate change have a significant impact on the lake ecosystems. While many researchers believe that heatwaves and droughts may enhance algal bloom, heatwaves and droughts reduced algal blooms in Lake Chaohu during the spring and summer of 2022. To investigate the mechanism behind this phenomenon, on-site sampling and online monitoring were conducted in Lake Chaohu from 2019 to 2022. The results showed that non-algal turbidity played a critical role in temporarily inhibiting algal blooms. The water level in spring and summer of the drought year was 1.2 m lower than that in conventional years, resulting in the area of shoals where resuspension could occur being nearly 4 times larger than in conventional years. Strong resuspension caused turbidity in spring and summer to be more than double that of conventional years, sharply reducing gross primary productivity by 39 %, which led to lower chlorophyll <em>a</em> concentration than in conventional years. These results indicate that drought does not necessarily exacerbate algal blooms, and changes in shoal area due to water level fluctuations are a key factor affecting algal blooms in shallow lakes prone to resuspension. Furthermore, these results suggest lake managers can control algal blooms by adjusting water level to increase turbidity during or before algal bloom seasons.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102796"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.hal.2024.102785
Maša Jablonska , Tina Eleršek
Anatoxins (ATX) are globally occurring toxins produced by some species of cyanobacteria in aquatic habitats. They can cause acute poisoning in animals, leading to muscle paralysis and respiratory failure, and might also pose a long-term health risk to humans. Thanks to advances in molecular methods and genomic knowledge, it is now possible to rapidly detect and quantify the genes associated with cyanotoxin production for most major groups of cyanotoxins except ATX. The aim of this study was to develop and validate a new quantitative PCR (qPCR) assay for general detection of all potential ATX producers in the environment. After specificity testing in silico and in vitro with 16 cyanobacterial strains (endpoint PCR, amplicon sequencing and qPCR), two assays targeting the anaC gene were thoroughly validated for linearity, amplification efficiency, sensitivity, dynamic range, inter-assay and intra-assay variability, and the influence of background DNA. The assays were then applied to 144 environmental samples of plankton and biofilm from lakes and rivers whose ATX content had previously been measured by liquid chromatography with tandem mass spectrometry (LC-MS/MS). Amplification efficiency of the two designed assays was between 94 % and 103 %, and the limits of quantification and detection were up to, but mostly below, 322 and 32 cells/mL, respectively. Both assays showed better or equal specificity in cyanobacterial cultures than currently available PCR assays and were able to predict the presence of ATX detected by LC-MS/MS in most environmental samples (83 % in plankton and 52–62 % in biofilm). A higher number of discrepancies between qPCR and LC-MS/MS results in biofilm than in plankton samples indicates limited knowledge and sparse genomic data on benthic cyanobacteria. These assays are the first published general qPCR assays targeting all ATX producers and could provide water managers with a rapid and cost-effective risk assessment to better protect human and animal health.
{"title":"A new quantitative PCR assay for detection of potentially anatoxin-producing cyanobacteria","authors":"Maša Jablonska , Tina Eleršek","doi":"10.1016/j.hal.2024.102785","DOIUrl":"10.1016/j.hal.2024.102785","url":null,"abstract":"<div><div>Anatoxins (ATX) are globally occurring toxins produced by some species of cyanobacteria in aquatic habitats. They can cause acute poisoning in animals, leading to muscle paralysis and respiratory failure, and might also pose a long-term health risk to humans. Thanks to advances in molecular methods and genomic knowledge, it is now possible to rapidly detect and quantify the genes associated with cyanotoxin production for most major groups of cyanotoxins except ATX. The aim of this study was to develop and validate a new quantitative PCR (qPCR) assay for general detection of all potential ATX producers in the environment. After specificity testing in silico and in vitro with 16 cyanobacterial strains (endpoint PCR, amplicon sequencing and qPCR), two assays targeting the <em>anaC</em> gene were thoroughly validated for linearity, amplification efficiency, sensitivity, dynamic range, inter-assay and intra-assay variability, and the influence of background DNA. The assays were then applied to 144 environmental samples of plankton and biofilm from lakes and rivers whose ATX content had previously been measured by liquid chromatography with tandem mass spectrometry (LC-MS/MS). Amplification efficiency of the two designed assays was between 94 % and 103 %, and the limits of quantification and detection were up to, but mostly below, 322 and 32 cells/mL, respectively. Both assays showed better or equal specificity in cyanobacterial cultures than currently available PCR assays and were able to predict the presence of ATX detected by LC-MS/MS in most environmental samples (83 % in plankton and 52–62 % in biofilm). A higher number of discrepancies between qPCR and LC-MS/MS results in biofilm than in plankton samples indicates limited knowledge and sparse genomic data on benthic cyanobacteria. These assays are the first published general qPCR assays targeting all ATX producers and could provide water managers with a rapid and cost-effective risk assessment to better protect human and animal health.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102785"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.hal.2024.102781
Tim M. Szewczyk, Dmitry Aleynik, Keith Davidson
Harmful algal blooms pose a significant threat to marine ecosystems, aquaculture industries, and human health. To mitigate these risks, agencies around the globe perform regular monitoring and operate early warning systems based on expected risk levels. However, bloom dynamics can be influenced by a large range of physical and biological factors, leading to high uncertainty in predictions of future blooms. Here, we explore the effectiveness of ensemble models for forecasting risk of algal blooms and associated toxins in Scotland, employing a diverse set of candidate models, including tree-based approaches, neural networks, and hierarchical Bayesian regression. These models predicted the probability that algal densities or biotoxin concentrations would exceed a threshold (either ‘amber’ status in the traffic light guidance system, or ‘detection’) in the next week using publicly available environmental products combined with regulatory monitoring data from dozens of locations in Scotland (2015–2022; Alexandrium spp., Dinophysis spp., Karenia mikimotoi, Pseudo-nitzschia spp. [+ delicatissima, serriata groups], domoic acid (DA), okadaic acid / dinophysistoxins / pectenotoxins (DSTs), paralytic shellfish toxins (PSTs)). The forecasted probabilities from the candidate models were used as inputs for a stacking ensemble model. Compared to individual candidate and null models, the ensemble models consistently improved forecasting performance across two years of withheld out-of-sample validation data, as assessed by five distinct performance metrics (ensemble skill scores among metrics and targets: mean = 0.499, middle 95 % = 0.214–0.900; skill score give improvement over the null model, with 1 indicating perfect performance). Performance varied by monitoring target, with best forecasts for DSTs (mean ensemble skill: 0.747) and poorest for K. mikimotoi (mean ensemble skill: 0.334). Autoregressive terms and regional spatiotemporal patterns emerged as the most informative predictors, with effects of environmental conditions contingent on the algal density or toxin concentration. Our results demonstrate the clear advantage of the ensemble approach. The operational implementation of these models provides probabilistic forecasts to enhance Scotland's monitoring program and early warning system. Ensemble modelling leverages the combined strengths of the wide array of modern techniques available, offering a promising path toward improved forecasts.
{"title":"Ensemble models improve near-term forecasts of harmful algal bloom and biotoxin risk","authors":"Tim M. Szewczyk, Dmitry Aleynik, Keith Davidson","doi":"10.1016/j.hal.2024.102781","DOIUrl":"10.1016/j.hal.2024.102781","url":null,"abstract":"<div><div>Harmful algal blooms pose a significant threat to marine ecosystems, aquaculture industries, and human health. To mitigate these risks, agencies around the globe perform regular monitoring and operate early warning systems based on expected risk levels. However, bloom dynamics can be influenced by a large range of physical and biological factors, leading to high uncertainty in predictions of future blooms. Here, we explore the effectiveness of ensemble models for forecasting risk of algal blooms and associated toxins in Scotland, employing a diverse set of candidate models, including tree-based approaches, neural networks, and hierarchical Bayesian regression. These models predicted the probability that algal densities or biotoxin concentrations would exceed a threshold (either ‘amber’ status in the traffic light guidance system, or ‘detection’) in the next week using publicly available environmental products combined with regulatory monitoring data from dozens of locations in Scotland (2015–2022; <em>Alexandrium spp</em>., <em>Dinophysis spp</em>., <em>Karenia mikimotoi, Pseudo-nitzschia spp</em>. [<em>+ delicatissima, serriata</em> groups], domoic acid (DA), okadaic acid / dinophysistoxins / pectenotoxins (DSTs), paralytic shellfish toxins (PSTs)). The forecasted probabilities from the candidate models were used as inputs for a stacking ensemble model. Compared to individual candidate and null models, the ensemble models consistently improved forecasting performance across two years of withheld out-of-sample validation data, as assessed by five distinct performance metrics (ensemble skill scores among metrics and targets: mean = 0.499, middle 95 % = 0.214–0.900; skill score give improvement over the null model, with 1 indicating perfect performance). Performance varied by monitoring target, with best forecasts for DSTs (mean ensemble skill: 0.747) and poorest for <em>K. mikimotoi</em> (mean ensemble skill: 0.334). Autoregressive terms and regional spatiotemporal patterns emerged as the most informative predictors, with effects of environmental conditions contingent on the algal density or toxin concentration. Our results demonstrate the clear advantage of the ensemble approach. The operational implementation of these models provides probabilistic forecasts to enhance Scotland's monitoring program and early warning system. Ensemble modelling leverages the combined strengths of the wide array of modern techniques available, offering a promising path toward improved forecasts.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102781"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.hal.2024.102795
Nur Syazwani Kassim , Li Keat Lee , Kieng Soon Hii , Nur Fatihah Mohd Azmi , Siti Nursyuhada Baharudin , Minlu Liu , Haifeng Gu , Po Teen Lim , Chui Pin Leaw
Harmful algal blooms in the benthic system (BHAB) are a major environmental problem that has increased worldwide in the context of global climate change. While systematic cell-based BHAB monitoring for risk assessment and early warning systems have been recommended, implementation of a standardized sampling method is challenging owing to the benthic nature of these harmful microalgal taxa. This study investigated the molecular diversity of benthic harmful dinoflagellates in tropical reefs of Perhentian Islands, Malaysia, using artificial substrate (AS) and sampling natural substrates (NS), combined with environmental DNA (eDNA) analysis and high-throughput amplicon sequencing targeting the small subunit (SSU) and large subunit (LSU) rDNA markers. Our results revealed that the AS method effectively captured a representative subset of the benthic dinoflagellate community, with significant taxonomic overlap between AS and NS. Both markers enabled high-resolution detection of BHAB taxa, particularly of Gambierdiscus and Ostreopsis, which are challenging to identify by light microscopy. The LSU rDNA marker provided finer taxonomic resolution, capturing a broader range of dinoflagellate species. The molecular approach consistently aligned with cell quantification data, supporting AS and DNA metabarcoding as robust methods for BHAB monitoring. The findings highlight the potential of these methods for early detection, especially areas susceptible for ciguatera and BHAB-related poisoning, offering a systematic approach for routine cell-based monitoring.
{"title":"Molecular diversity of benthic harmful dinoflagellates on a tropical reef: Comparing natural and artificial substrate sampling methods using DNA metabarcoding and morphological analysis","authors":"Nur Syazwani Kassim , Li Keat Lee , Kieng Soon Hii , Nur Fatihah Mohd Azmi , Siti Nursyuhada Baharudin , Minlu Liu , Haifeng Gu , Po Teen Lim , Chui Pin Leaw","doi":"10.1016/j.hal.2024.102795","DOIUrl":"10.1016/j.hal.2024.102795","url":null,"abstract":"<div><div>Harmful algal blooms in the benthic system (BHAB) are a major environmental problem that has increased worldwide in the context of global climate change. While systematic cell-based BHAB monitoring for risk assessment and early warning systems have been recommended, implementation of a standardized sampling method is challenging owing to the benthic nature of these harmful microalgal taxa. This study investigated the molecular diversity of benthic harmful dinoflagellates in tropical reefs of Perhentian Islands, Malaysia, using artificial substrate (AS) and sampling natural substrates (NS), combined with environmental DNA (eDNA) analysis and high-throughput amplicon sequencing targeting the small subunit (SSU) and large subunit (LSU) rDNA markers. Our results revealed that the AS method effectively captured a representative subset of the benthic dinoflagellate community, with significant taxonomic overlap between AS and NS. Both markers enabled high-resolution detection of BHAB taxa, particularly of <em>Gambierdiscus</em> and <em>Ostreopsis</em>, which are challenging to identify by light microscopy. The LSU rDNA marker provided finer taxonomic resolution, capturing a broader range of dinoflagellate species. The molecular approach consistently aligned with cell quantification data, supporting AS and DNA metabarcoding as robust methods for BHAB monitoring. The findings highlight the potential of these methods for early detection, especially areas susceptible for ciguatera and BHAB-related poisoning, offering a systematic approach for routine cell-based monitoring.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102795"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.hal.2025.102800
Saranya Anantapantula , Susanne Wittenzeller , Matthew F. Gladfelter , Suzanne E. Tenison , Hannah Zinnert , Angelea P. Belfiore , Alan E. Wilson
Excess nutrient loading often promotes harmful algal blooms. Despite many past studies, few algal bloom control methods show clear, long-term improvements in water quality. For example, chemical treatments are often used to control algal blooms because they can cause large, rapid declines in algal abundance. However, these effects are often transient requiring future treatments that increase costs and risks to water quality. Moreover, empirical tests of repeated applications or combinations of different treatments are rare, even with their common use across industries, like aquaculture and drinking water. To rigorously test the effects of single or combined treatments on water quality in a eutrophic aquaculture pond, copper sulfate pentahydrate (henceforth called copper) and Phoslock were used independently (full dose) or combined (each at half dose) in a 56-day field experiment conducted in a hypereutrophic aquaculture pond. The two copper-containing treatments caused rapid declines (-83%) in algal abundance the day after treatment followed by very large (2,617%) increases after another five days. In contrast, zooplankton were reduced by 43% in the copper treatment but minimally affected (+1%) by the combined treatment the day after application. To further show that copper treatment is the mechanism responsible for the negative effects on zooplankton and phytoplankton, half of the mesocosms for all four treatments were treated with a full dose of copper on day 13 and similar effects on phytoplankton were observed as when copper was initially applied. The combined treatment was more effective at controlling phytoplankton than the copper only treatment, in part, because of lesser negative effects on zooplankton. Overall, this experiment further highlights the long-term, negative effects that chemical treatments, like copper, have on non-target taxa, such as beneficial zooplankton, which limits their potential for ecological and sustainable control of harmful algal blooms.
{"title":"Copper sulfate treatment harms zooplankton and ultimately promotes algal blooms: A field mesocosm experiment","authors":"Saranya Anantapantula , Susanne Wittenzeller , Matthew F. Gladfelter , Suzanne E. Tenison , Hannah Zinnert , Angelea P. Belfiore , Alan E. Wilson","doi":"10.1016/j.hal.2025.102800","DOIUrl":"10.1016/j.hal.2025.102800","url":null,"abstract":"<div><div>Excess nutrient loading often promotes harmful algal blooms. Despite many past studies, few algal bloom control methods show clear, long-term improvements in water quality. For example, chemical treatments are often used to control algal blooms because they can cause large, rapid declines in algal abundance. However, these effects are often transient requiring future treatments that increase costs and risks to water quality. Moreover, empirical tests of repeated applications or combinations of different treatments are rare, even with their common use across industries, like aquaculture and drinking water. To rigorously test the effects of single or combined treatments on water quality in a eutrophic aquaculture pond, copper sulfate pentahydrate (henceforth called copper) and Phoslock were used independently (full dose) or combined (each at half dose) in a 56-day field experiment conducted in a hypereutrophic aquaculture pond. The two copper-containing treatments caused rapid declines (-83%) in algal abundance the day after treatment followed by very large (2,617%) increases after another five days. In contrast, zooplankton were reduced by 43% in the copper treatment but minimally affected (+1%) by the combined treatment the day after application. To further show that copper treatment is the mechanism responsible for the negative effects on zooplankton and phytoplankton, half of the mesocosms for all four treatments were treated with a full dose of copper on day 13 and similar effects on phytoplankton were observed as when copper was initially applied. The combined treatment was more effective at controlling phytoplankton than the copper only treatment, in part, because of lesser negative effects on zooplankton. Overall, this experiment further highlights the long-term, negative effects that chemical treatments, like copper, have on non-target taxa, such as beneficial zooplankton, which limits their potential for ecological and sustainable control of harmful algal blooms.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102800"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.hal.2024.102797
Mathias Fon , An Chen , Rosalie Ghesquière , Silvio Uhlig , Bente Edvardsen , Anita Solhaug
Fish-killing harmful algal blooms (HABs) threaten fisheries and aquaculture globally. In May and June 2019, the haptophyte Chrysochromulina leadbeateri formed the most devastating fish-killing algal bloom ever recorded in Northern Norway. Despite the severe impact of HABs on farmed fish, our understanding of their toxic mechanisms is limited. Here, we investigated the ichthyotoxicity of C. leadbeateri by using the gill epithelial cell line ASG-10 from Atlantic salmon. Extracts of C. leadbeateri showed potent hemolytic activity towards Atlantic salmon red blood cells, and toxicity to the ASG-10 cells with an EC50 of 3.41 × 106 algal cells mL−1 measured by the Alamar Blue viability assay. Furthermore, lower extract concentrations increased caspase-3/7 activity, suggesting induction of apoptosis, while higher concentrations of the extract showed compromised cell membrane integrity. No intracellular reactive oxygen species (ROS) induction was observed. Exposure to C. leadbeateri extracts cultured under different irradiances or with putrescine supplementation to the algal medium did not increase the toxicity. Exposure of living C. leadbeateri cells to ASG-10 did not show any cytotoxicity from imaging or barrier integrity impairment, but the activity of leaked dead-cell proteases revealed a concentration-dependent effect on the ASG-10 cells. Furthermore, incubation of C. leadbeateri in culture with putrescine for 72 h resulted in increased dead-cell proteases leaked from the ASG-10 cells compared to cultures without putrescine. Our findings suggest that living C. leadbeateri cells exert sublethal effects on Atlantic salmon gill cells. Additionally, putrescine seems to increase the ichthyotoxicity of living C. leadbeateri towards ASG-10 cells.
{"title":"The cytotoxicity of the haptophyte Chrysochromulina leadbeateri towards the Atlantic salmon gill cell line ASG-10","authors":"Mathias Fon , An Chen , Rosalie Ghesquière , Silvio Uhlig , Bente Edvardsen , Anita Solhaug","doi":"10.1016/j.hal.2024.102797","DOIUrl":"10.1016/j.hal.2024.102797","url":null,"abstract":"<div><div>Fish-killing harmful algal blooms (HABs) threaten fisheries and aquaculture globally. In May and June 2019, the haptophyte <em>Chrysochromulina leadbeateri</em> formed the most devastating fish-killing algal bloom ever recorded in Northern Norway. Despite the severe impact of HABs on farmed fish, our understanding of their toxic mechanisms is limited. Here, we investigated the ichthyotoxicity of <em>C. leadbeateri</em> by using the gill epithelial cell line ASG-10 from Atlantic salmon. Extracts of <em>C. leadbeateri</em> showed potent hemolytic activity towards Atlantic salmon red blood cells, and toxicity to the ASG-10 cells with an EC<sub>50</sub> of 3.41 × 10<sup>6</sup> algal cells mL<sup>−1</sup> measured by the Alamar Blue viability assay. Furthermore, lower extract concentrations increased caspase-3/7 activity, suggesting induction of apoptosis, while higher concentrations of the extract showed compromised cell membrane integrity. No intracellular reactive oxygen species (ROS) induction was observed. Exposure to <em>C. leadbeateri</em> extracts cultured under different irradiances or with putrescine supplementation to the algal medium did not increase the toxicity. Exposure of living <em>C. leadbeateri</em> cells to ASG-10 did not show any cytotoxicity from imaging or barrier integrity impairment, but the activity of leaked dead-cell proteases revealed a concentration-dependent effect on the ASG-10 cells. Furthermore, incubation of <em>C. leadbeateri</em> in culture with putrescine for 72 h resulted in increased dead-cell proteases leaked from the ASG-10 cells compared to cultures without putrescine. Our findings suggest that living <em>C. leadbeateri</em> cells exert sublethal effects on Atlantic salmon gill cells. Additionally, putrescine seems to increase the ichthyotoxicity of living <em>C. leadbeateri</em> towards ASG-10 cells.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102797"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.hal.2025.102802
Youchul Jeon , Ian Struewing , Kale Clauson , Nathan Reetz , Ned Fairchild , Lacey Goeres-Priest , Theo W. Dreher , Rochelle Labiosa , Kurt D. Carpenter , Barry H. Rosen , Eric N. Villegas , Jingrang Lu
The excessive growth of harmful cyanobacteria, including Dolichospermum (formerly known as Anabaena), in freshwater bodies has become a pressing global concern. However, detailed information about the role of Dolichospermum in shaping bloom dynamics and producing cyanotoxins is limited. In this study, a bloom event dominated by Dolichospermum spp. at Detroit Lake (Oregon, USA) was examined from 2019 to 2021. In 2019, early summer cyanobacterial community succession reached up to 8.7 % of total phytoplankton abundance. Dolichospermum was the major microcystin (MC)-producing genus, with peak MC levels of 7.34 μg L−1. The presence of MCs was strongly correlated with the abundance of Dolichospermum (r = 0.84, p < 0.05) and MC synthetase gene, mcyE-Ana (r = 0.63, p < 0.05). Metabolic analyses further showed that the presence of nif/pst genes linked to nitrogen and phosphorus metabolism was dominated by Dolichospermum from the bloom onset until September. In addition, the abundance of Dolichospermum was significantly correlated with the abundance of nitrogen-fixing nif-Ana gene (r = 0.62, p < 0.05). As the lake experienced a longer N and P scarcity period (May to September), the N2-fixing Dolichospermum was able to dominate over other non-fixing cyanobacteria present, including Microcystis and Planktothrix. Overall, our results facilitate a better understanding of the organism and will help working toward managing/predicting future blooms.
{"title":"Dominant Dolichospermum and microcystin production in Detroit Lake (Oregon, USA)","authors":"Youchul Jeon , Ian Struewing , Kale Clauson , Nathan Reetz , Ned Fairchild , Lacey Goeres-Priest , Theo W. Dreher , Rochelle Labiosa , Kurt D. Carpenter , Barry H. Rosen , Eric N. Villegas , Jingrang Lu","doi":"10.1016/j.hal.2025.102802","DOIUrl":"10.1016/j.hal.2025.102802","url":null,"abstract":"<div><div>The excessive growth of harmful cyanobacteria, including <em>Dolichospermum</em> (formerly known as <em>Anabaena</em>), in freshwater bodies has become a pressing global concern. However, detailed information about the role of <em>Dolichospermum</em> in shaping bloom dynamics and producing cyanotoxins is limited. In this study, a bloom event dominated by <em>Dolichospermum</em> spp. at Detroit Lake (Oregon, USA) was examined from 2019 to 2021. In 2019, early summer cyanobacterial community succession reached up to 8.7 % of total phytoplankton abundance. <em>Dolichospermum</em> was the major microcystin (MC)-producing genus, with peak MC levels of 7.34 μg <em>L</em><sup>−1</sup>. The presence of MCs was strongly correlated with the abundance of <em>Dolichospermum</em> (<em>r</em> = 0.84, <em>p</em> < 0.05) and MC synthetase gene, <em>mcyE-Ana</em> (<em>r</em> = 0.63, <em>p</em> < 0.05). Metabolic analyses further showed that the presence of <em>nif</em>/<em>pst</em> genes linked to nitrogen and phosphorus metabolism was dominated by <em>Dolichospermum</em> from the bloom onset until September. In addition, the abundance of <em>Dolichospermum</em> was significantly correlated with the abundance of nitrogen-fixing <em>nif-Ana</em> gene (<em>r</em> = 0.62, <em>p</em> < 0.05). As the lake experienced a longer N and P scarcity period (May to September), the N<sub>2</sub>-fixing <em>Dolichospermum</em> was able to dominate over other non-fixing cyanobacteria present, including <em>Microcystis</em> and <em>Planktothrix</em>. Overall, our results facilitate a better understanding of the organism and will help working toward managing/predicting future blooms.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102802"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144161","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.hal.2024.102794
So-Ra Ko , Ve Van Le , Sang-Ah Lee , Seung Ho Baek , Chi-Yong Ahn
Margalefidinium polykrikoides blooms inflict significant economic losses on the aquaculture industry. Utilizing algicidal bacteria to mitigate harmful algal blooms (HABs) has emerged as an environment-friendly approach. Despite numerous reports on algicidal bacteria, few studies have thoroughly elucidated their mechanisms against M. polykrikoides. In this study, we present the first documentation of the algicidal effect of a Fictibacillus strain on M. polykrikoides. Strain 5A8M exhibited algicidal effects through physical attachment and the secretion of extracellular algicidal metabolites. The algicidal activity of strain 5A8M was dose- and time-dependent. When inoculated at a ratio of 10 % (v/v), strain 5A8M induced lysis in 97.9 % of M. polykrikoides after 24 h of co-culture. The active chlorophyll-a and transcriptional levels of key genes in M. polykrikoides decreased under the algicidal influence of strain 5A8M. Furthermore, exposure to the cell-free filtrate of strain 5A8M for 12 h triggered lipid peroxidation in M. polykrikoides, resulting in elevated malondialdehyde levels. Analysis via 1H nuclear magnetic resonance (NMR), 13C NMR, and electrospray ionization-mass spectra identified l-phenylalanine and anthranilic acid as the extracellular algicidal metabolites produced by strain 5A8M. The algicidal activity of l-phenylalanine and anthranilic acid (10 μg/ml) against M. polykrikoides reached 74.6 and 72.5 %, respectively, within 24 h of exposure. Collectively, our findings underscore the considerable potential of strain 5A8M in controlling M. polykrikoides HABs.
{"title":"Algicidal effects of Fictibacillus sp. 5A8M on Margalefidinium polykrikoides through attachment and secretion of extracellular metabolites","authors":"So-Ra Ko , Ve Van Le , Sang-Ah Lee , Seung Ho Baek , Chi-Yong Ahn","doi":"10.1016/j.hal.2024.102794","DOIUrl":"10.1016/j.hal.2024.102794","url":null,"abstract":"<div><div><em>Margalefidinium polykrikoides</em> blooms inflict significant economic losses on the aquaculture industry. Utilizing algicidal bacteria to mitigate harmful algal blooms (HABs) has emerged as an environment-friendly approach. Despite numerous reports on algicidal bacteria, few studies have thoroughly elucidated their mechanisms against <em>M. polykrikoides</em>. In this study, we present the first documentation of the algicidal effect of a <em>Fictibacillus</em> strain on <em>M. polykrikoides</em>. Strain 5A8M exhibited algicidal effects through physical attachment and the secretion of extracellular algicidal metabolites. The algicidal activity of strain 5A8M was dose- and time-dependent. When inoculated at a ratio of 10 % (v/v), strain 5A8M induced lysis in 97.9 % of <em>M. polykrikoides</em> after 24 h of co-culture. The active chlorophyll-<em>a</em> and transcriptional levels of key genes in <em>M. polykrikoides</em> decreased under the algicidal influence of strain 5A8M. Furthermore, exposure to the cell-free filtrate of strain 5A8M for 12 h triggered lipid peroxidation in <em>M. polykrikoides</em>, resulting in elevated malondialdehyde levels. Analysis via <sup>1</sup>H nuclear magnetic resonance (NMR), <sup>13</sup>C NMR, and electrospray ionization-mass spectra identified <span>l</span>-phenylalanine and anthranilic acid as the extracellular algicidal metabolites produced by strain 5A8M. The algicidal activity of <span>l</span>-phenylalanine and anthranilic acid (10 μg/ml) against <em>M. polykrikoides</em> reached 74.6 and 72.5 %, respectively, within 24 h of exposure. Collectively, our findings underscore the considerable potential of strain 5A8M in controlling <em>M. polykrikoides</em> HABs.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102794"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.hal.2024.102782
Jingming Hu , Henry Camerón , Joaquín I. Rilling , Marco Campos , Tay Ruiz-Gil , Mariela A. Gonzalez , Gonzalo Gajardo , Karen Vergara , Leonardo Guzmán , Oscar Espinoza-González , Gonzalo Fuenzalida , Carlos Riquelme , Shoko Ueki , Satoshi Nagai , Fumito Maruyama , So Fujiyoshi , Kyoko Yarimizu , Ishara Uhanie Perera , Andrés Ávila , Jacquelinne J. Acuña , Milko A. Jorquera
Harmful algal blooms (HABs) are highly relevant for public health, the economy, the ecosystem, and biodiversity stability in southern Chile (40° to 53°S), where they occur regularly and are frequently monitored. However, HAB events and their associated microbes in northern Chile (17° to 30°S) remain unknown and difficult to track due to a lack of monitoring, particularly in urban areas. We investigated changes in microbial communities in coastal seawater before and during an Akashiwo sanguinea bloom (B) at two sampling points in Antofagasta city (23°38′39S, 70°24′39W). Seawater samples (filtered at 1 and 0.2 μm) were collected during distinct bloom phases (control, prebloom, and in-bloom), and 16S and 18S rDNA gene libraries were constructed and analyzed via the DNA metabarcoding technique. Our findings indicate that species diversity within the 16S rDNA-based community was greater during the prebloom phase than during the control and in-bloom phases. Conversely, species diversity within the 18S rDNA-based community was lower during the in-bloom phase than during the control and prebloom phases. Independent of the sampling points and fractions, principal coordinate analysis (PCoA) revealed distinct differences in both the 16S and 18S rDNA-based communities between the analyzed bloom phases. Our analysis further revealed that the 16S rDNA-based community was dominated by the Flavobacteriaceae and Rhodobacteraceae families, whose abundance decreased and increased, respectively, during the bloom. As anticipated, the structure of the 18S rDNA-based community was predominantly governed by the Gymnodiniaceae family, specifically the Akashiwo genus, during the bloom. The differentiation in microbial communities was more pronounced in taxa with low abundances than in the dominant taxa. Additionally, co-occurrence network analysis revealed predominantly positive relationships within the microbial communities, particularly during the bloom event. Our analysis also identified several bacterial genera as keystone taxa within the microbial communities, notably members of Pseudomonadota and Bacteroidota.
{"title":"Differentiation of microbial communities in coastal seawater before and during an Akashiwo sanguinea (Dinophyceae) bloom in the urban area of Antofagasta city (northern Chile)","authors":"Jingming Hu , Henry Camerón , Joaquín I. Rilling , Marco Campos , Tay Ruiz-Gil , Mariela A. Gonzalez , Gonzalo Gajardo , Karen Vergara , Leonardo Guzmán , Oscar Espinoza-González , Gonzalo Fuenzalida , Carlos Riquelme , Shoko Ueki , Satoshi Nagai , Fumito Maruyama , So Fujiyoshi , Kyoko Yarimizu , Ishara Uhanie Perera , Andrés Ávila , Jacquelinne J. Acuña , Milko A. Jorquera","doi":"10.1016/j.hal.2024.102782","DOIUrl":"10.1016/j.hal.2024.102782","url":null,"abstract":"<div><div>Harmful algal blooms (HABs) are highly relevant for public health, the economy, the ecosystem, and biodiversity stability in southern Chile (40° to 53°S), where they occur regularly and are frequently monitored. However, HAB events and their associated microbes in northern Chile (17° to 30°S) remain unknown and difficult to track due to a lack of monitoring, particularly in urban areas. We investigated changes in microbial communities in coastal seawater before and during an <em>Akashiwo sanguinea</em> bloom (B) at two sampling points in Antofagasta city (23°38′39S, 70°24′39W). Seawater samples (filtered at 1 and 0.2 μm) were collected during distinct bloom phases (control, prebloom, and in-bloom), and 16S and 18S rDNA gene libraries were constructed and analyzed via the DNA metabarcoding technique. Our findings indicate that species diversity within the 16S rDNA-based community was greater during the prebloom phase than during the control and in-bloom phases. Conversely, species diversity within the 18S rDNA-based community was lower during the in-bloom phase than during the control and prebloom phases. Independent of the sampling points and fractions, principal coordinate analysis (PCoA) revealed distinct differences in both the 16S and 18S rDNA-based communities between the analyzed bloom phases. Our analysis further revealed that the 16S rDNA-based community was dominated by the Flavobacteriaceae and Rhodobacteraceae families, whose abundance decreased and increased, respectively, during the bloom. As anticipated, the structure of the 18S rDNA-based community was predominantly governed by the Gymnodiniaceae family, specifically the <em>Akashiwo</em> genus, during the bloom. The differentiation in microbial communities was more pronounced in taxa with low abundances than in the dominant taxa. Additionally, co-occurrence network analysis revealed predominantly positive relationships within the microbial communities, particularly during the bloom event. Our analysis also identified several bacterial genera as keystone taxa within the microbial communities, notably members of Pseudomonadota and Bacteroidota.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102782"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144655","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-01DOI: 10.1016/j.hal.2025.102799
Nur Fatihah Mohd Azmi , Kieng Soon Hii , Minlu Liu , Siti Nursyuhada Baharudin , Nur Syazwani Kassim , Li Keat Lee , Monaliza Mohd Din , Nurin I. Mustapa , Roziawati Mohd Razali , Haifeng Gu , Chui Pin Leaw , Po Teen Lim
The dinoflagellate Tripos furca, known for its frequent and massive blooms in coastal waters, has been associated with significant fish mortality in aquaculture areas. In mid-May 2022, a notable bloom event, characterized by intense red discoloration, was observed along the Penang Strait in the northern Malacca Strait. Our field survey identified a high-density bloom of T. furca. To investigate the mechanisms driving the bloom dynamics of this species, monthly sampling was undertaken until the bloom subsided, covering 19 stations across the Penang Strait. Our results showed that the abundances of T. furca changed over time and space, a bloom peak of 8.2 × 105 cells l-1 was observed in late June, triggered by elevated sea surface temperatures and phosphate availability, while nitrogen was consistently abundant. The bloom's persistence was associated with the influence of the 2020–2022 La Niña and Indian Ocean Dipole, which caused warmer sea temperatures. Metabarcoding of the V7-V9 18S rDNA region revealed high intraspecific genetic diversity within the T. furca bloom subpopulations, suggesting both clonal reproduction and possible sexual processes. The bloom termination was linked to a seasonal shift in temperatures and changes in nutrient regimes that caused a transition of phytoplankton compositions to Noctiluca- and diatom-dominated populations contributed to the bloom's decline. Early detection of the bloom has successfully prevented severe losses to the aquaculture farms in the area, emphasizing the importance of early intervention. This study also enhances our understanding of T. furca bloom dynamics and provides insights into managing harmful algal blooms in tropical coastal regions.
{"title":"Temporal bloom dynamics of the marine dinoflagellate Tripos furca in the Penang Strait","authors":"Nur Fatihah Mohd Azmi , Kieng Soon Hii , Minlu Liu , Siti Nursyuhada Baharudin , Nur Syazwani Kassim , Li Keat Lee , Monaliza Mohd Din , Nurin I. Mustapa , Roziawati Mohd Razali , Haifeng Gu , Chui Pin Leaw , Po Teen Lim","doi":"10.1016/j.hal.2025.102799","DOIUrl":"10.1016/j.hal.2025.102799","url":null,"abstract":"<div><div>The dinoflagellate <em>Tripos furca</em>, known for its frequent and massive blooms in coastal waters, has been associated with significant fish mortality in aquaculture areas. In mid-May 2022, a notable bloom event, characterized by intense red discoloration, was observed along the Penang Strait in the northern Malacca Strait. Our field survey identified a high-density bloom of <em>T. furca.</em> To investigate the mechanisms driving the bloom dynamics of this species, monthly sampling was undertaken until the bloom subsided, covering 19 stations across the Penang Strait. Our results showed that the abundances of <em>T. furca</em> changed over time and space, a bloom peak of 8.2 × 10<sup>5</sup> cells <span>l</span><sup>-1</sup> was observed in late June, triggered by elevated sea surface temperatures and phosphate availability, while nitrogen was consistently abundant. The bloom's persistence was associated with the influence of the 2020–2022 La Niña and Indian Ocean Dipole, which caused warmer sea temperatures. Metabarcoding of the V7-V9 18S rDNA region revealed high intraspecific genetic diversity within the <em>T. furca</em> bloom subpopulations, suggesting both clonal reproduction and possible sexual processes. The bloom termination was linked to a seasonal shift in temperatures and changes in nutrient regimes that caused a transition of phytoplankton compositions to <em>Noctiluca</em>- and diatom-dominated populations contributed to the bloom's decline. Early detection of the bloom has successfully prevented severe losses to the aquaculture farms in the area, emphasizing the importance of early intervention. This study also enhances our understanding of <em>T. furca</em> bloom dynamics and provides insights into managing harmful algal blooms in tropical coastal regions.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102799"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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