Harmful Algae最新文献

{"title":"Intraspecific differences in the effects of salinity and light on growth and prymnesin cell quota in Prymnesium parvum","authors":"Fredrik Ryderheim ,&nbsp;Elizabeth M. Mudge ,&nbsp;Andrea Budiša ,&nbsp;Kevin J. Flynn ,&nbsp;Jack Gillies ,&nbsp;Thomas Ostenfeld Larsen ,&nbsp;Per Juel Hansen","doi":"10.1016/j.hal.2025.102926","DOIUrl":"10.1016/j.hal.2025.102926","url":null,"abstract":"<div><div>The haptophyte <em>Prymnesium parvum</em> produces large polyether compounds (prymnesins) with lytic properties that accumulate in the cell or may be released into the surrounding environment. At high cell abundances the prymnesins cause devastating damage to ecosystems. Blooms of <em>P. parvum</em> are frequently reported in inland water bodies and brackish coastal areas, and thus salinity has been suggested as a main regulatory factor in bloom control. However, toxicity has mainly been assessed through bioassay and the effect of abiotic factors on prymnesin production is lacking. Here, we explore the effect of salinity and light on prymnesin production in three strains of <em>P. parvum</em>. We find that <em>P. parvum</em> can grow over a wide range of salinities, but that net production of cellular prymnesin is, contrary to previous suggestions, inhibited at low salinities, presumably due to resources being diverted to deal with hypoosmotic stress. In two of the strains, increased cellular prymnesin quotas during salinity-induced stress were instead due to accumulation of toxins in the cells because of low cell division rates. We further observed intraspecific differences in cell physiology in response to light. We found general negative relationships between growth rate and cellular prymnesin quotas, both within and among strains. Overall, we find large intraspecific variation in cell physiology in response to salinity and light but demonstrate several general patterns. Such broad intraspecific variation may partly explain the success of various strains of <em>P. parvum</em> in a wide range of environments.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102926"},"PeriodicalIF":5.5,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144633289","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":"Algal blooms in Lake Taihu: Earlier onset and extended duration","authors":"Jiangzhaoxia Chen ,&nbsp;Xiaojie Gao ,&nbsp;Xiaoke Xu ,&nbsp;Chongjing Zhu ,&nbsp;Xiaojun She ,&nbsp;Debing Kong ,&nbsp;Kun Xue ,&nbsp;Yao Li","doi":"10.1016/j.hal.2025.102917","DOIUrl":"10.1016/j.hal.2025.102917","url":null,"abstract":"<div><div>Monitoring algal bloom phenology is crucial for managing water quality in eutrophic lakes, particularly under changing climate and environmental conditions. However, the lack of reliable long-term data has limited our understanding of bloom dynamics in inland lakes. Here, we analyzed the spatiotemporal characteristics of algal bloom phenology in Lake Taihu using daily MODIS data from 2000 to 2023. The floating algae index (FAI) and Bayesian land surface phenology (BLSP) model were applied to quantify bloom patterns and explore their climatic and environmental drivers. Over the past 24 years, algal bloom coverage in Lake Taihu averaged 19.88 %, with severe events occurring in 2007 and 2017, reaching frequencies of 9.54 % and 10.60 % and coverages of 42.92 % and 41.10 %, respectively. Bloom durations ranged from 60 to 90 days, typically starting between March and June and ending between July and December. Notably, since 2015, blooms have shown a tendency to start earlier, persist longer, and end later. Bloom phenology was primarily driven by water quality, with wind speed and cumulative evaporation also playing significant roles. These findings provide new insights into the driving mechanisms behind algal bloom phenology and serve as a scientific basis for developing effective lake ecological management strategies and water quality improvement initiatives.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102917"},"PeriodicalIF":5.5,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144679438","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":"Growth inhibition of harmful cyanobacterium Microcystis by picocyanobacterium Cyanobium: transcriptome-based interaction analysis","authors":"Min-Seong Kim ,&nbsp;So-Ra Ko ,&nbsp;Mingyeong Kang ,&nbsp;Seonah Jeong ,&nbsp;Hayoung Lee ,&nbsp;Yuna Shin ,&nbsp;Kyunghyun Kim ,&nbsp;Chi-Yong Ahn","doi":"10.1016/j.hal.2025.102923","DOIUrl":"10.1016/j.hal.2025.102923","url":null,"abstract":"<div><div>The occurrence and collapse of cyanobacterial blooms, particularly those caused by <em>Microcystis</em>, are influenced by interactions with a variety of microorganisms. Recent studies have revealed that <em>Microcystis</em> is affected not only by heterotrophic bacteria but also by interactions with picocyanobacteria. This study investigated how and under what conditions the picocyanobacterium <em>Cyanobium</em> impacts <em>Microcystis</em> growth, suggesting potential mechanisms of these interactions based on transcriptome analysis. <em>Cyanobium gracile</em> A950 exhibited a stronger inhibitory effect on the growth of <em>Microcystis aeruginosa</em> KW at higher temperature. In a co-culture experiment, <em>M. aeruginosa</em> KW downregulated photosynthesis-related genes, including <em>psaC</em> and <em>psaE</em>, which impaired energy production and light harvesting. Reduced expression of phosphate uptake genes, such as <em>phoU</em> and <em>pstA</em>, suggests that <em>M. aeruginosa</em> KW was disadvantaged in nutrient uptake compared to <em>C. gracile</em> A950. In contrast, <em>C. gracile</em> A950 rapidly upregulated photosynthesis-related and ATP synthase genes within 2 h of co-culture, allowing it to gain an early competitive advantage over <em>M. aeruginosa</em> KW. These findings indicate that the inhibitory effect of <em>C. gracile</em> A950 on <em>M. aeruginosa</em> KW was mainly due to the unbalanced expression changes in photosynthesis-related genes between the two species.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102923"},"PeriodicalIF":5.5,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144580792","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":"Transcriptional responses to oxygen gradients in cyanobacterial aggregates","authors":"Dezhuang Gao ,&nbsp;Zhijie Chen ,&nbsp;Yuan Ma ,&nbsp;Ruiyu Wang ,&nbsp;Jie Deng","doi":"10.1016/j.hal.2025.102922","DOIUrl":"10.1016/j.hal.2025.102922","url":null,"abstract":"<div><div>Cyanobacterial aggregates (CAs) are the main cause of harmful cyanobacterial blooms in freshwater lakes, posing serious risks to water quality and ecosystem health. The ecological success of CAs is closely linked to their abilities to adapt to fluctuating dissolved oxygen (DO) levels. In this study, we investigated the transcriptional responses of CA-associated microbial communities across a gradient of DO concentrations (0–6 mg/L) using incubation experiments combined with 16S rRNA transcript and metatranscriptomic sequencing. Distinct transcriptional patterns of clusters of genes were revealed for both cyanobacterial and phycospheric communities. Notably, <em>Microcystis</em>, the dominating cyanobacteria in the CAs, demonstrated markedly elevated transcriptional activities under oxygen-deficient conditions. Under low DO, cyanobacteria actively cope with reactive oxygen species (ROS) stress, and utilized fermentation and O₂-independent alternative electron sink to maintain anaerobic metabolism. Upregulation of gas vesicle protein genes also suggests a role in buoyancy regulation to escape low-oxygen zones. These transcriptomic findings were further supported by physiological assays of <em>Microcystis</em>, which exhibited increased ROS level, extracellular polysaccharides (EPS) content and alcohol production under oxygen-deficient conditions. Moreover, intensified competition for nutrients between cyanobacteria and phycospheic bacteria under low DO were revealed, although the latter may also support cyanobacterial growth through cobalamin (vitamin B₁₂) provisioning. Collectively, our findings uncover key adaptive responses of <em>Microcystis</em> under oxygen-deficient conditions and underscore the importance of redox regulation in shaping the metabolic dynamics of CA-associated microbial communities.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102922"},"PeriodicalIF":5.5,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144596431","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":"Cyanobacterial connectivity from freshwater to estuaries: insights into genotypes and cyanotoxins flow","authors":"Claudia Fournier ,&nbsp;Samuel Cirés ,&nbsp;Albano Diez-Chiappe ,&nbsp;Adrián Pereira ,&nbsp;Rufino Vieira-Lanero ,&nbsp;Sandra Barca-Bravo ,&nbsp;Fernando Cobo ,&nbsp;Antonio Quesada","doi":"10.1016/j.hal.2025.102925","DOIUrl":"10.1016/j.hal.2025.102925","url":null,"abstract":"<div><div>Cyanobacterial blooms are detrimental events that affect the quality of water and the normal functioning of ecosystems, especially when dominated by toxin-producing species. Although cyanobacteria and cyanotoxins have been reported in the land-sea interface since the late 80s, genetic evidence on how inland freshwaters influence the cyanobacterial communities in these systems is very scarce to date. This study aims to investigate the relationship between the cyanobacterial communities of an inland freshwater reservoir and an estuary located in an aquaculture-rich coastal area of NW Spain. During 2022 and 2023, a total of six sampling campaigns were carried out surrounding the blooming seasons. Cyanobacterial communities and their potential toxicity were analyzed through metabarcoding of the 16S rRNA gene and PCR-based screening of genes involved in the biosynthesis of cyanotoxins. Results demonstrate that the reservoir likely contributed significantly to the presence of potentially toxic cyanobacteria in the estuary, with more than 80 % of reservoir shared cyanobacterial ASVs (Amplicon Sequence Variants) belonging to potentially toxic genera. Genes related to microcystins and anatoxins were detected in both systems, accompanied by low toxin concentrations. Most key cyanobacterial genera were consistently dominated by specific ASVs, suggesting the presence of a few genotypes resistant to environmental gradients during transport. These findings highlight the influence of freshwater systems on estuarine cyanobacterial communities and demonstrate the potential of genetic tools for their high-resolution monitoring, useful in water management of ecological and economic risks. Further research is recommended to understand the global impacts of cyanobacterial bloom dispersion towards land-sea interface systems, particularly in economically relevant areas.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102925"},"PeriodicalIF":5.5,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144587682","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":"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 Alexandrium tamarense species complex in Kuwait’s waters (Arabian/Persian Gulf, northern Indian Ocean) with the description of Alexandrium arabiense sp. nov","authors":"Manal Al-Kandari ,&nbsp;Maria Saburova ,&nbsp;Jacob Larsen ,&nbsp;Nina Lundholm ,&nbsp;Igor Polikarpov ,&nbsp;Sumaiah Hussain ,&nbsp;Hadeel Al-Mansouri ,&nbsp;Sabeena F.K. Habeebullah ,&nbsp;Bernd Krock","doi":"10.1016/j.hal.2025.102897","DOIUrl":"10.1016/j.hal.2025.102897","url":null,"abstract":"<div><div>Morphological observations of the <em>Alexandrium tamarense</em> (Dinophyceae) species complex in Kuwait’s waters (Arabian/Persian Gulf, northern Indian Ocean) discerned four morphotypes, of which three corresponded to <em>A. catenella, A. pacificum</em>, and <em>A. tamarense</em>. One <em>Alexandrium</em> morphotype differed in morphology from all previously reported species belonging to the <em>A. tamarense</em> complex and was genetically distinct. Morphologically, it was characterized by a 1ʹ plate without a ventral pore, a lack of anterior and posterior attachment pores in apical pore plate and posterior sulcal plate, and a lack of long chain formation. The thecal surface was perforated by pores of two size classes. Phylogenetic analyses inferred from 18S, ITS/5.8S, and partial 28S nuclear rDNA gene sequences revealed strains of the new morphotype from Kuwait’s waters to appear as sisters to <em>A. pacificum</em> with high support. Based on a unique combination of morphological and molecular features, a new member of the <em>A. tamarense</em> complex, <em>Alexandrium arabiense</em> sp. nov., is described. The holotype strain of <em>A. arabiense</em> was tested for paralytic shellfish poisoning activity and found to be positive by ELISA assay, but negative by ion pair chromatography coupled to post-column derivatization and fluorescence detection. The strain was also tested for other toxins known to be produced by the genus <em>Alexandrium</em>, such as gymnodimines, spirolides, and goniodomins, but none of them were detected. The observed morphological diversity within the <em>A. tamarense</em> complex in Kuwait’s waters thus requires a further close examination of this potentially PSP-causing species group, primarily molecular and toxicological analyses.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102897"},"PeriodicalIF":4.5,"publicationDate":"2025-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144860284","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}