Harmful Algae最新文献

{"title":"What initiates cyanobacterial blooms in the Baltic Sea?","authors":"Mati Kahru ,&nbsp;Bronwyn Cahill ,&nbsp;Ragnar Elmgren ,&nbsp;Gregor Rehder","doi":"10.1016/j.hal.2025.102924","DOIUrl":"10.1016/j.hal.2025.102924","url":null,"abstract":"<div><div>Massive summer blooms of cyanobacteria are a regular feature of the Baltic Sea, with impacts on primary production, nitrogen cycling, food chain structure and bottom layer oxygen deficiency. While many attempts have been made to associate the initiation of those blooms with certain forcing factors, the resulting models have had very limited predictive power. Here we analyse the statistical relationships between the timing of cyanobacteria blooms in the Baltic Sea and various forcing factors. Our analysis is based on a 25-year time series (2000–2024) of satellite-derived frequency of cyanobacteria accumulations (FCA) in 36 characteristic areas. We find that sea surface temperature (SST) does not control the initiation of a bloom but, on the contrary, SST during bloom initiation is a function of the bloom timing. Bloom initiation is associated with increasing SST caused by surface irradiance, coupled with low wind speed that results in reduced vertical mixing. However, while this combination of factors is required, it is not always sufficient to start a bloom, suggesting that additional factors or interactions are required.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102924"},"PeriodicalIF":5.5,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144580791","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}

{"title":"Paralytic shellfish toxins and seabirds: evaluating sublethal effects, behavioral responses, and ecological implications of saxitoxin ingestion by common murres (Uria aalge)","authors":"Matthew M. Smith ,&nbsp;Robert J. Dusek ,&nbsp;Tuula Hollmen ,&nbsp;Sarah K. Schoen ,&nbsp;Caroline Van Hemert ,&nbsp;Kristen Steinmetzer ,&nbsp;Aidan Lee ,&nbsp;Jenna Schlener ,&nbsp;Vijay Patil ,&nbsp;D. Ransom Hardison ,&nbsp;David Kulis ,&nbsp;Donald M. Anderson ,&nbsp;Clark D. Ridge ,&nbsp;Sherwood Hall","doi":"10.1016/j.hal.2025.102919","DOIUrl":"10.1016/j.hal.2025.102919","url":null,"abstract":"<div><div>Paralytic shellfish toxins (PSTs), including saxitoxin (STX) and its congeners, are neurotoxins that can be produced during harmful algal blooms and cause illness or death in humans, fish, seabirds, and marine mammals. Since 2014, multiple large-scale seabird mortality events have occurred in Alaska waters, with STXs detected in some carcasses. To investigate the sublethal behavioral and ecological effects of STX on seabirds, we conducted captive dosing trials with common murres (<em>Uria aalge</em>). We gavaged purified STX (dehydrated STX dihydrocholoride, STX-diHCl) or an <em>Alexandrium catenella</em> culture extract into murres, monitored behavioral responses and recovery times, and assessed tissue concentrations in individuals that died or were euthanized. Using a modified up-and-down dose-finding scheme, we estimated a median effective dose (ED₅₀) of 89 µg STX-equivalents (eq) kg^-1 for STX-diHCl and 366 µg STX-eq kg^-1 for the <em>A. catenella</em> extract based on ecologically relevant behavior. Differences between the ED₅₀ estimates could reflect uncertainties in toxin equivalency factors for PST congeners, which are based on studies using purified toxins in mice and may vary across taxa or toxin matrices. Post-dosing concentrations of STX varied by tissue type across individuals, with quantifiable levels ranging from 3 to 379 µg STX-eq 100g^-1. Evidence of biotransformation of STX in <em>A. catenella</em> extract-dosed birds was observed. We also measured the chronic effects of dosing with sublethal levels of STX-diHCl over seven-days, which resulted in lower fish intake among treatment birds compared to controls (-187 g day^-1). This investigation improves our understanding of the ecological effects of PSTs on seabird health.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102919"},"PeriodicalIF":5.5,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144572209","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}

{"title":"Predator-induced defense reduces growth rate and carrying capacity in a toxic diatom, Pseudo-nitzschia seriata","authors":"Junjie Jia ,&nbsp;Thomas Kiørboe ,&nbsp;Erik Selander ,&nbsp;Fredrik Ryderheim","doi":"10.1016/j.hal.2025.102920","DOIUrl":"10.1016/j.hal.2025.102920","url":null,"abstract":"<div><div>Phytoplankton employ a wide variety of defenses to reduce mortality from zooplankton grazing. Many such defenses are inducible, that is, they are upregulated in the event of increased predation. Thus, theory predicts that they should come at a cost to the organism. When exposed to predatory cues from a copepod predator, the diatom <em>Pseudo-nitzschia seriata</em> upregulates the production of the neurotoxin domoic acid (DA). DA has recently been found to have grazer deterrent effects, but whether its production comes with trade-offs is still unclear. Here, we expose a strain of <em>P. seriata</em> to cues from copepods to induce increased DA production through the population growth phases. We find that not only do the induced cells grow slower, but because they take up more nitrogen per cell from the media, they produce less cells overall. &lt;1 % of cellular nitrogen went into DA production, suggesting that the lower growth rate does not reflect a direct allocation cost, but rather that cells manipulate growth rate to reach higher toxin content per cell, or other costs associated with a higher toxin load. Such a mechanistic understanding of phytoplankton trade-offs is essential to accurately describe and model ocean plankton dynamics.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102920"},"PeriodicalIF":5.5,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144581035","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}

{"title":"Physiological responses of Arctic and Baltic Sea populations of toxigenic Alexandrium ostenfeldii (Dinophyceae) to different climate change stressors","authors":"Simon Tulatz ,&nbsp;Urban Tillmann ,&nbsp;Bernd Krock ,&nbsp;Jan Tebben ,&nbsp;Cédric Leo Meunier","doi":"10.1016/j.hal.2025.102918","DOIUrl":"10.1016/j.hal.2025.102918","url":null,"abstract":"<div><div>The harmful algal bloom species <em>Alexandrium ostenfeldii</em> has a worldwide distribution from polar to tropical habitats and from oceanic to brackish waters. Among other species of the genus <em>Alexandrium</em>, it is one of the causative organisms of paralytic shellfish toxins, but additionally, <em>A. ostenfeldii</em> has also been shown to produce another class of toxins, cyclic imines. The wide distribution of <em>A. ostenfeldii</em> suggests population-specific adaptations to a multitude of environmental parameters and therefore, variable responses to global change drivers, such as warming and shifts in sea surface salinity. In this study we quantified growth and toxin cell quota of two strains of <em>A. ostenfeldii</em> isolated from the arctic Kongsfjord and two strains from the northern European Baltic Sea at various temperature conditions, to assess the impact of global warming on locally adapted populations. Overall, growth of the arctic strains was detected at temperatures between 7.5 and 20 °C, with a maximum growth rate at 15 °C for both strains. The two strains from the Baltic Sea revealed intraspecific differences concerning their thermal tolerance. One strain showed no growth at 25 °C, while the other still had a positive growth rate at 27 °C. Furthermore, three of the strains were exposed to salinities between 10 and 40, revealing a tolerance to a broad range of salinities. Neither temperature nor salinity affected the qualitative toxin composition of any strain, but we detected novel cyclic imines in three of the four tested strains. Furthermore, different temperatures and salinities led to dynamic shifts in total toxin cell quota. Additionally, we detected novel spirolides in both arctic strains of <em>A. ostenfeldii</em>. These findings suggest that arctic <em>A. ostenfeldii</em> might significantly benefit from global warming, while populations from the Baltic Sea may not, and that the Baltic Sea might become unfavourable for western Baltic <em>A. ostenfeldii</em> due to climate change driven decreasing salinity in this area.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102918"},"PeriodicalIF":5.5,"publicationDate":"2025-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144563083","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}

{"title":"The toxin-producing diversity of Prorocentrum lima (Dinophyceae) populations of coastal China","authors":"Caihong Chen ,&nbsp;Jixing Peng ,&nbsp;Haoyu Zhang ,&nbsp;Guanchao Zheng ,&nbsp;Zhijun Tan ,&nbsp;Haiyan Wu","doi":"10.1016/j.hal.2025.102915","DOIUrl":"10.1016/j.hal.2025.102915","url":null,"abstract":"<div><div><em>Prorocentrum lima</em> (<em>P. lima)</em> is distributed in the four major seas of China. The diversity distribution of <em>P. lima</em> is confirmed by existing studies. The impact of this diversity feature on the difference of diarrhetic shellfish toxins (DSTs) components requires immediate investigation. Ten strains of <em>P. lima</em> were isolated from four major seas of China to explore the geographical differences in growth, toxicity production, and esterified composition. After 21 days of cultivation, strains isolated from the Bohai and Yellow China Sea (SHG and QD) exhibited slow growth and a maximum cell density of 3.3 × 10⁴ cells·mL^–1, whereas strains from the South China Sea (WZD and 3XS) demonstrated the highest growth rate and maximum algal density of 9.4 × 10⁴ cells·mL^–1. The total toxin content in single cells varied from 4.8 to 10.1 pg·cell^–1, with SHG and QD displaying the highest total toxin content at 10.1 pg·cell^–1. A total of 24 kinds of esterified components were identified across all ten strains of <em>P. lima</em>, comprising 43.9 %–92.2 % of total toxins, with the highest levels found in SHG and QD strains. Growth, toxicity production, and esterification of <em>P. lima</em>, taken from the four major sea areas of China, were significantly different. The contrasts in growth and toxicity potential revealed the existence of adaptive mechanisms of <em>P. lima</em> in different geographic environments, and the role of toxins in the adaptation mechanism requires further exploration.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102915"},"PeriodicalIF":5.5,"publicationDate":"2025-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144581039","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}

{"title":"Physiological changes and gene expression in the mixotrophic haptophyte, Prymnesium parvum, respond to mixed nitrogen sources","authors":"Fengmiao Li ,&nbsp;Hailong Huang ,&nbsp;Qinfei Zhang ,&nbsp;Yun Shen ,&nbsp;Ningjian Luo ,&nbsp;Xinwei Wang ,&nbsp;Weizhong Chen ,&nbsp;Kaho Pak ,&nbsp;Jie Han ,&nbsp;Zhibing Jiang ,&nbsp;Chengxu Zhou ,&nbsp;Haibo Jiang","doi":"10.1016/j.hal.2025.102916","DOIUrl":"10.1016/j.hal.2025.102916","url":null,"abstract":"<div><div><em>Prymnesium parvum</em> is a toxin-producing haptophyte that adapts to various conditions in aquaculture wastewater, using strategies like allelopathy, toxicity, and predation to survive. However, knowledge about physiological and genetic responses of <em>P. parvum</em> to mixed nitrogen sources in aquaculture wastewater is still limited. Here, we cultured <em>P. parvum</em> in simulated aquaculture wastewater nitrogen composition, and revealed physiological and gene expression responses of <em>P. parvum</em> to mixed nitrogen sources. Under high concentrations mixed nitrogen sources (8.83 × 10³ μmol/L), <em>P. parvum</em> shows strong adaptability and competitiveness, predisposing it to harmful algal blooms (HABs) outbreaks. At low concentrations 8.83 × 10¹ μmol/L), it compensates by consuming other algae and producing toxins for defense. Transcriptomic data indicate that <em>P. parvum</em> upregulates nitrogen-related genes when transitioning from nitrate to mixed nitrogen, and downregulates them with increasing concentrations, significantly impacting glutamate metabolism and potentially enhancing direct ammonia conversion to <span>l</span>-glutamate, bypassing <span>l</span>-glutamine. Metabolic reprogramming in <em>P. parvum</em> may drive cell proliferation and HABs formation, with ecological consequences for aquaculture nitrogen dynamics.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102916"},"PeriodicalIF":5.5,"publicationDate":"2025-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144548669","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}

{"title":"Utilization of two types of dissolved organic phosphate by axenic and nonaxenic harmful Amphidinium carterae: Response of photosynthetic and hemolytic activity","authors":"Lianhong Tu ,&nbsp;Lingling Zhan ,&nbsp;Yu Gu ,&nbsp;Kehan Yi ,&nbsp;Mengmeng Tong","doi":"10.1016/j.hal.2025.102913","DOIUrl":"10.1016/j.hal.2025.102913","url":null,"abstract":"<div><div>Phosphorus (P) is a major limiting nutrient of phytoplankton in the current coastal ocean due to the overload of nitrogen; however, the dominance of the harmful dinoflagellate <em>Amphidinium carterae</em> has increased in the coastal ocean, leading to the hypothesis that <em>A. carterae</em> potentially utilizes dissolved organic phosphate (DOP)<em>.</em> Therefore, a series of experiments were conducted on axenic and nonaxenic <em>A. carterae</em> to investigate how dissolved inorganic phosphate (DIP) and two types of DOP (β-glycerol phosphate disodium salt hydrate (BGP) and 2-aminoethylphosphonic acid (2-AEP)) interact with the photosynthetic and hemolytic activities of <em>A. carterae</em>. The results showed that <em>A. carterae</em> could directly utilize BGP (C-O-P bonds of DOP) but had a limited ability to use 2-AEP (C-P bonds of DOP). A low amount of DIP (&lt;0.36 µM) reduced the growth, biomass, and photosynthetic activity of <em>A. carterae</em>; in contrast, it induced the hemolytic activity of <em>A. carterae</em>. However, the reduction in the hemolytic activity of <em>A. carterae</em> mostly relied on cell division rather than the utilization of DIP or DOP, as indicated by the significant negative relationship between the growth rate and hemolytic activity of <em>A. carterae</em>. The healthier the cells (high value of photosynthetic efficiency), the lower the hemolytic activity of <em>A. carterae</em>. Taken together, the ability to utilize the BGP makes it possible for <em>A. carterae</em> to become dominant in a BGP-sufficient environment, whereas the stress of cells, i.e., in P-limited conditions, may drive toxic events during blooms of <em>A. carterae</em>.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102913"},"PeriodicalIF":5.5,"publicationDate":"2025-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144501598","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}

{"title":"Three-dimensional micro-mapping of microorganisms in the plastisphere using laser scanning confocal fluorescence microscopy","authors":"Aya Yamamoto Hoshihara ,&nbsp;Tetsuichi Fujiki ,&nbsp;Tetsuro Ikuta ,&nbsp;Shinji Shimode ,&nbsp;Youta Sugai ,&nbsp;Victor S. Kuwahara","doi":"10.1016/j.hal.2025.102914","DOIUrl":"10.1016/j.hal.2025.102914","url":null,"abstract":"<div><div>We investigated the attachment patterns of microorganisms within plastispheres on plastic surfaces through three-dimensional (3D) micro-mapping of the plastisphere using multichannel laser scanning confocal fluorescence microscopy (DNA staining, chlorophyll autofluorescence, exopolysaccharides staining, and reflection). This approach allowed us to focus on information derived from the 3D structures of the plastisphere. Four-channel observations of four types of plastics—polyethylene terephthalate (PET), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), and polycarbonate (PC)—and glass plates immersed in coastal Sagami Bay for 10 days revealed the layered 3D structure of plastispheres composed mainly of diatoms and bacteria. Some dinoflagellates were also observed in the plastispheres. Morphological characteristics and chlorophyll content indicated that the observed dinoflagellates were in a vegetative form and included potentially toxic and/or red-tide-causing harmful dinoflagellates. This reaffirms previous concerns about environmental changes caused by toxic dinoflagellates captured on plastics and drifting in the ocean as hitchhikers, thereby spreading over a wider area than their original dispersion. Quantitative analysis of the 3D micro-mapped plastispheres suggested that a biofilm layer a few micrometers thick was required for dinoflagellates to attach to the plastic surface. Since extracellular polymeric substances (EPS) may be associated with the stickiness of the plastisphere, we performed five-channel observations, including exopolysaccharide staining to label EPS. These results suggested that the viscosity of EPS was responsible for these dinoflagellates’ attaching to plastic surfaces. These results provided a new perspective on the potential for the formation of plastispheres containing dinoflagellates.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102914"},"PeriodicalIF":5.5,"publicationDate":"2025-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144510738","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}

{"title":"Deciphering nonlinear effects of climate and eutrophication synergies on Microcystis blooms using a causal inference framework","authors":"Jingkai Wang ,&nbsp;Mengqi He ,&nbsp;Min Pan ,&nbsp;Lirong Song ,&nbsp;Qichao Zhou ,&nbsp;Kun Shan","doi":"10.1016/j.hal.2025.102911","DOIUrl":"10.1016/j.hal.2025.102911","url":null,"abstract":"<div><div>Harmful cyanobacterial blooms (CyanoHABs) pose a significant threat to global water quality. Although eutrophication and climate change are recognized as key drivers of CyanoHABs proliferation, their synergistic effects remain elusive, hindering effective mitigation strategies. Here, we present a causal inference framework that leverages state-space reconstruction and empirical dynamic modeling to unravel the complex, nonlinear interactions governing CyanoHABs dynamics. Focusing on <em>Microcystis</em> blooms dynamics in Dianchi Lake (China), our approach uniquely integrates causal inference with time-series embedding, reconstructing the ecosystem’s hidden dynamics in a higher-dimensional geometric space. This foundation enables us to rigorously quantify causal drivers—such as nutrient loading and temperature—while overcoming the limitations of traditional correlation-based analyses. Our causal network analysis reveals distinct nonlinear responses of chlorophyll-<em>a</em> (Chl-<em>a</em>) concentration and <em>Microcystis</em> density to different nutrient drivers. Specifically, we found that in-lake total phosphorus (TP) exerts a stronger causal influence on overall algal dynamics than total nitrogen (TN). In contrast, external nutrient loading shows greater influence over <em>Microcystis</em> density compared to in-lake nutrients. Through scenario simulations, we further demonstrate that rising air temperatures amplify Chl-<em>a</em> concentration and <em>Microcystis</em> biomass through increased water temperatures, whereas precipitation-induced nutrient changes preferentially stimulate Chl-<em>a</em> production over <em>Microcystis</em> growth. Notably, we identified contrasting seasonal response patterns, with Chl-<em>a</em> exhibiting greater sensitivity to dry-season conditions while <em>Microcystis</em> density responded more strongly to wet-season drivers. By bridging mechanistic understanding and predictive modeling, our work offers a transformative tool for forecasting and managing CyanoHABs in changing climates.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102911"},"PeriodicalIF":5.5,"publicationDate":"2025-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144501597","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}

{"title":"Determinism of anatoxin-a production in Phormidium-dominated biofilms of a regulated river (Ain, France)","authors":"Charlotte Robichon ,&nbsp;Delphine Latour ,&nbsp;Fanny Perrière ,&nbsp;Sylvain Dolédec ,&nbsp;Joël Robin","doi":"10.1016/j.hal.2025.102912","DOIUrl":"10.1016/j.hal.2025.102912","url":null,"abstract":"<div><div>Benthic cyanobacteria have been increasingly held responsible for bird and mammal deaths along riverbanks in the last decades. However, little is known about the environmental conditions that favor their development, spatiotemporal dynamics and associated toxins. In the summer of 2020, we monitored physical, chemical and biological variables, quantified benthic cyanobacteria and measured anatoxin-a concentration in the biofilms of four reaches of the dam-regulated Ain River, France. The main potential anatoxin producer was <em>Phormidium</em>, often associated with <em>Oscillatoria</em> mats in the same field campaigns. Anatoxin-a detectable concentrations ranged from 0.5 to 197µg/g of dry weight showing a high spatial heterogeneity. According to structural equation modelling, anatoxin-a concentrations increased with water depth in a range of 20 to 80 cm. In contrast, the chlorophyta biovolume and the flow velocity were the main factors negatively correlated with anatoxin-a concentrations. Although flow velocity did not limit the biovolume of potential anatoxin producers, it could induce stress to the cyanobacterial mats within the river, causing a limitation of anatoxin-a concentrations. Finally, the effects of these drivers on anatoxin-a production demonstrated a high variability over the summer. This high temporal variability of both benthic cyanobacteria biomass and anatoxin-a concentration makes risk assessment relatively challenging.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102912"},"PeriodicalIF":5.5,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144517090","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}