Harmful Algae最新文献

{"title":"Efficient inhibition of Microcystis aeruginosa using expanded perlite sustained-release pyrogallic acid: performance studies, mechanistic insights and ecological security assessment","authors":"Yuewen Zhang ,&nbsp;Mingjun Ma ,&nbsp;Yujia Gao ,&nbsp;Yu Hong ,&nbsp;Xing Xie","doi":"10.1016/j.hal.2026.103093","DOIUrl":"10.1016/j.hal.2026.103093","url":null,"abstract":"<div><div>Allelochemicals are effective and safe for controlling cyanobacterial blooms, but their direct application suffers from rapid degradation and poor persistence. To address this limitation, we engineered a buoyant, surface-targeting delivery system to inhibit non-toxic and toxic <em>Microcystis aeruginosa</em> by preparing PA/Expanded perlite composites using expanded perlite as a matrix. The results showed that PA was successfully loaded onto expanded perlite, and PA/Expanded perlite could achieve long-term release of phenolic release (PA-dominant). PA/Expanded perlite was effective in removing both non-toxic and toxic <em>M. aeruginosa</em>, with the maximum inhibition rate of 97.60 %, and the EC₅₀ (7d) values were 15.60 and 6.90 mg/L, respectively. The PA/Expanded perlite composite achieved a 97.62 % inhibition rate against <em>M. aeruginosa</em> in natural landscape water. Additionally, treatment with PA/Expanded perlite significantly reduced chlorophyll a and phycobiliprotein content in both algal strains, and the photosynthetic rates of toxic and non-toxic <em>M. aeruginosa</em> decreased to 0.03 and 0.0043 [μmol/(mg·h)], respectively. Meanwhile, the activities of superoxide dismutase (SOD) and catalase (CAT) and the content of malondialdehyde (MDA) were significantly increased. Under current exposure levels, PA/Expanded perlite did not pose harm to <em>Daphnia magna</em> and <em>Pteris vittata,</em> while significantly reducing intracellular microcystin-LR (MC-LR) contents, which has promising application for the control of water blooms.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"155 ","pages":"Article 103093"},"PeriodicalIF":4.5,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147388146","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":"Blooms like it hot, but mussels do not: Influence of invasive quagga mussels on cyanobacteria during summer","authors":"Jonas Mauch ,&nbsp;Maider Erize Gardoki ,&nbsp;Raphael Neiling ,&nbsp;Jan Köhler ,&nbsp;Jordan Facey ,&nbsp;Sabine Hilt","doi":"10.1016/j.hal.2026.103094","DOIUrl":"10.1016/j.hal.2026.103094","url":null,"abstract":"<div><div>Quagga mussels (<em>Dreissena rostriformis bugensis</em>) are among the most impactful invaders in freshwaters of the Northern Hemisphere. As filter-feeders, they can reduce harmful algal blooms (HABs), but their effects are expected to be dependent on cyanobacteria species and water temperature. However, conclusive studies on these traits and their combination are lacking. Here, we combined laboratory experiments with an analysis of long-term data from a temperate shallow lake 10 years before and after quagga mussel invasion, respectively. We tested the hypotheses that quagga mussel filtration rates in the laboratory would 1) vary among common cyanobacteria species and 2) decrease above a critical temperature. Regarding the field data, we expected that 3) quagga mussels can reduce the summer biovolume of palatable cyanobacteria, but that 4) this effect disappears above a critical temperature. Our results support all four hypotheses. In laboratory experiments, <em>Dolichospermum flos-aquae</em> was classified as palatable to quagga mussels, while <em>Aphanizomenon flos-aquae, Anabaenopsis elenkinii</em> and <em>Microcystis aeruginosa</em> were less-palatable cyanobacteria. Filtration rates decreased above 28.9°C (CI: 27.6–30.2°C) with mussels dying at 32°C. Our long-term lake data show that cyanobacteria biovolumes were lower after quagga mussel invasion, but only below 27.7°C (CI: 26.9–28.4°C), confirming a critical thermal window for quagga mussel filtration. Global warming will therefore facilitate HABs by increasing the growth rates of cyanobacteria and reducing the filtration rates of quagga mussels above critical summer water temperatures, which are increasingly being reached in invaded lakes. This critical thermal window must be considered when making HAB predictions.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"155 ","pages":"Article 103094"},"PeriodicalIF":4.5,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147388068","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":"Urea as a rising driver of harmful algal blooms: Integrating global patterns, metabolic pathways, and ecological consequences","authors":"Huaizhi Qin ,&nbsp;Muhamad Syaifudin ,&nbsp;Tangcheng Li ,&nbsp;Wenkang Fan ,&nbsp;Hong Du ,&nbsp;Senjie Lin","doi":"10.1016/j.hal.2026.103087","DOIUrl":"10.1016/j.hal.2026.103087","url":null,"abstract":"<div><div>Urea inputs to aquatic ecosystems have increased rapidly due to intensified fertilizer use, wastewater discharge, and aquaculture expansion, altering nitrogen composition and accelerating eutrophication. However, the physiological, ecological, and evolutionary mechanisms linking urea enrichment to harmful algal blooms (HABs) remain incompletely synthesized. Here, we integrate a bibliometric survey of 818 papers from 2003 to 2024 with a quantitative analysis of 32 physiological studies and a comparative genomic assessment of urea metabolic pathways. Urea concentrations range from the nanomolar scale in open oceans to &gt;20 μM in eutrophic rivers and estuaries—levels sufficient to stimulate urea-preferring taxa. Many HAB-forming dinoflagellates and cyanobacteria exhibit enhanced growth, photosynthetic efficiency, and in some cases, increased toxin production when supplied with urea. Comparative pathway analysis shows that bloom-forming taxa predominantly utilize the energy-efficient urease pathway, whereas non-blooming taxa more commonly rely on the ATP-consuming urea amidolyase (UAL) pathway. Several bloom-forming species are capable of using both pathways, suggesting metabolic flexibility under fluctuating nitrogen regimes. These findings support the hypothesis that anthropogenic urea enrichment acts as a selective pressure favoring taxa capable of rapid and energetically economical nitrogen assimilation. We identify key research gaps—including evolutionary origins of UAL, regulatory divergence between pathways, and interactions with warming and stratification—and provide recommendations for monitoring and management. This synthesis highlights urea as a critical yet underappreciated component of global nitrogen pollution and HAB dynamics.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"155 ","pages":"Article 103087"},"PeriodicalIF":4.5,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147388069","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 suppression of harmful algal blooms in spring 2025 off the Zhe-Min coast, China: A consequence of extreme atmospheric and oceanic forcing","authors":"Weibo Wang ,&nbsp;Haifeng Gu","doi":"10.1016/j.hal.2026.103076","DOIUrl":"10.1016/j.hal.2026.103076","url":null,"abstract":"<div><div>The Zhe-Min coastal region of China, a principal fisheries area, frequently experiences harmful algal blooms (HABs) driven by the nutrient-rich southward current of the Zhe-Min Coastal Current (ZMCC). In spring 2025, however, routine monitoring (since 2001) recorded an unprecedented absence of large-scale HABs. This study investigates the dynamical mechanisms underpinning this suppression. Our analysis indicates that a persistent, record-breaking anomalous northeastward sea surface current inhibited southward nutrient transport to the Fuzhou–Wenzhou coast. Dynamical decomposition shows that this anomalous current resulted from distinct regional processes: off Fuzhou it manifested as a barotropic response to an anomalous cross-shelf sea-level gradient associated with an extremely weak northeasterly monsoon, while off Wenzhou it was predominantly baroclinic, driven by cross-shelf temperature gradients linked to frequent marine heatwaves. The observed thermal extremes are largely attributable to the record-breaking northward shift of the subtropical high-pressure system during the spring of 2025. Moreover, the interaction between a coastal marine cold spell and offshore heatwaves in March promoted cross-shelf transport that exported coastal nutrients offshore. These findings indicate that climate–related shifts—notably weakened monsoonal forcing and increased frequency of extreme thermal events—can act synergistically to form a compound hazard chain that substantially alters coastal physical–biological coupling, however, in this instance, suppressed large-scale HABs outbreak. Future research should pay more attention to the impacts generated by the coupling processes among such extreme events.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"154 ","pages":"Article 103076"},"PeriodicalIF":4.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189068","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":"Zooplankton feeding behaviour and survival to toxic and non-toxic cyanobacteria during the seasonal bloom progression of a eutrophic lake","authors":"Pinelopi Ntetsika ,&nbsp;Salomé Stauffer ,&nbsp;Stefanie Eyring ,&nbsp;Marta Reyes ,&nbsp;Xuejian Wang ,&nbsp;Elisabeth M.-L. Janssen ,&nbsp;Francesco Pomati","doi":"10.1016/j.hal.2025.103045","DOIUrl":"10.1016/j.hal.2025.103045","url":null,"abstract":"<div><div>Harmful cyanobacterial blooms pose increasing threats to aquatic ecosystems and human health; yet, the role of zooplankton grazing in regulating blooms remains understudied. We investigated the seasonal feeding behaviour and fitness consequences of feeding preferences in natural zooplankton communities for toxic (microcystin-producing) versus non-toxic cyanobacteria across temperature gradients in eutrophic Lake Greifen, Switzerland. We conducted monthly experiments from April to October 2023 to test the grazing behaviour of four zooplankton groups (daphnids, calanoid copepods, cyclopoid copepods, and microzooplankton) exposed to mixed diets of green algae and either toxic or non-toxic <em>Microcystis</em> strains at 15 °C and 25 °C.</div><div>Contrary to expectations of cyanobacteria avoidance, zooplankton exhibited predominantly non-selective grazing throughout the seasonal succession, consuming both toxic and non-toxic cyanobacteria at similar rates, regardless of temperature. Notably, during the peaks of phytoplankton abundance (April and September), mesozooplankton demonstrated a selective preference for cyanobacteria over green algae, particularly non-toxic strains. Temperature effects were subtle but revealed metabolic constraints: elevated temperatures occasionally triggered selective consumption of cyanobacteria in copepods, while fitness costs (survival) from exposure to toxic species were mostly restricted to transitional bloom periods and high-temperature conditions.</div><div>These findings suggest that toxic cyanobacteria may not always evade grazing pressure through secondary metabolite deterrent effects. Our results suggest that zooplankton communities can adapt and graze on cyanobacteria regardless of toxicity under the tested conditions, even during bloom conditions. These observations highlight the potential for zooplankton to interact with cyanobacterial populations, which may have implications for bloom prediction and management strategies, particularly under climate warming scenarios.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"154 ","pages":"Article 103045"},"PeriodicalIF":4.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145802022","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":"Evaluation of a field method for qPCR analysis of toxigenic cyanobacteria","authors":"Ian Struewing ,&nbsp;Aimèe Henderson ,&nbsp;Nathan Sienkiewicz ,&nbsp;William Hobbs ,&nbsp;Stacey Cochran ,&nbsp;Jingrang Lu","doi":"10.1016/j.hal.2026.103069","DOIUrl":"10.1016/j.hal.2026.103069","url":null,"abstract":"<div><div>Quantitative Polymerase Chain Reaction (qPCR) is a well-established method for molecular detection and quantification of microorganisms. Molecular detection of toxigenic cyanobacteria using qPCR has also been employed as a useful tool for predicting cyanotoxin production and formation of harmful cyanobacterial blooms (cHABs). Recently, portable thermocyclers and extraction procedures and reagents have been developed for onsite application of qPCR analysis. However, use of portable qPCR analysis for the detection and quantification of toxigenic cyanobacteria has not been evaluated. Here, we provide an evaluation of a field method for DNA extraction and qPCR analysis using the Biomeme Franklin thermocycler for detection of toxigenic cyanobacteria. The results obtained from the portable device provide identification and quantification of toxigenic <em>Microcystis</em> and are comparable with lab-based extraction and analysis. This field method for extraction and qPCR analysis will provide alternative research tools to evaluate source and recreational water for toxic cyanobacteria. This field method allows users to obtain immediate on-site results for identification and quantification of toxigenic <em>Microcystis.</em></div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"154 ","pages":"Article 103069"},"PeriodicalIF":4.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189069","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":"Diversity and toxicity of Coolia from the Ryukyu Islands, with a description of Coolia kabiraensis sp. nov","authors":"Shaun Cunningham ,&nbsp;Siratee Riewluang ,&nbsp;Aika Yamaguchi ,&nbsp;Anne Rolton ,&nbsp;Kevin C. Wakeman","doi":"10.1016/j.hal.2026.103075","DOIUrl":"10.1016/j.hal.2026.103075","url":null,"abstract":"<div><div><em>Coolia</em> is a widely distributed genus of marine benthic dinoflagellates, with some species known to produce bioactive compounds toxic to marine life. In this study, we investigated the diversity and toxicity of <em>Coolia</em> from the Ryukyu Islands (subtropical Japan), integrating morphological characterization, molecular phylogenetics, and <em>Artemia</em> toxicity assays. Five species were identified: four previously described, including the first record of <em>C. palmyrensis</em> in Japan, and one undescribed species, <em>Coolia kabiraensis</em> sp. nov. <em>Coolia kabiraensis</em> closely resembles members of the <em>Coolia monotis</em> species complex, which are difficult to distinguish morphologically. Phylogenetic analysis using ITS1–5.8S–ITS2 and 28S rDNA (D1–D3) genetic markers placed this taxon in a distinct, well-supported clade, supporting its recognition as a new species. A systematic review of global <em>Coolia</em> records, incorporating peer-reviewed studies, GenBank sequences, grey literature, and culture collections, was used to contextualize regional diversity. Species richness in the Ryukyu Islands was relatively high but comparable to that of other subtropical and tropical regions. Toxicity screening assays showed that extracts from <em>C. kabiraensis, C. palmyrensis, C. canariensis</em>, and <em>C. tropicalis</em> caused no statistically significant mortality of <em>Artemia</em> after 48 h. In contrast, <em>C. malayensis</em> extracts caused 40–85% mortality, indicating potential risk to marine life. These findings highlight the cryptic diversity, variable toxicity, and broad geographic distribution of <em>Coolia</em> species. Understanding species composition and toxicity patterns is essential for monitoring harmful algal blooms and anticipating future changes under climate-driven shifts in benthic microalgal assemblages.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"154 ","pages":"Article 103075"},"PeriodicalIF":4.5,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146189070","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 impact of Ulva prolifera green tide on the diatom-dinoflagellate taxa in the Southern Yellow Sea, China","authors":"Xinyu Li ,&nbsp;Yingzhe Wang ,&nbsp;Liqiang Fan ,&nbsp;Jing Zhao ,&nbsp;Xiulin Wang ,&nbsp;Keqiang Li","doi":"10.1016/j.hal.2026.103062","DOIUrl":"10.1016/j.hal.2026.103062","url":null,"abstract":"<div><div>Microalgal taxa distribution trends of diatom dominance, dinoflagellate dominance, and dinoflagellate-to-diatom succession have been observed in the southern, middle, and northern green tide areas, respectively, during <em>Ulva prolifera</em> outbreaks in the Southern Yellow Sea. However, little is known about the interactions between macroalgal and microalgal taxa associated with biogeochemical processes. Focusing on the impact of the <em>Ulva spp.</em> on microalgal communities, we constructed a Nutrient-Ulva-Microalgae-Detritus (NUMAD) model using ship-based mesocosm culture experiments. Culture experiments and the NUMAD model revealed higher dynamic rates of nutrient uptake and growth of <em>U. prolifera</em> than microalgae under oligotrophic conditions, consistent with the <em>R</em> strategy for diatoms with sufficient ambient nutrition. There is an ecological niche overlap between <em>U. prolifera</em> and diatom taxa, which makes the succession from diatom taxa to dinoflagellate taxa in the macro-microalgae co-cultural systems. We demonstrated that diatoms exceeding dinoflagellates with <em>R</em> strategy and ecological niche overlap compete against <em>U. prolifera</em> in the initial stage of the green tide, while dinoflagellates exceeding diatoms with <em>K</em> strategy and ecological niche differences compete against <em>U. prolifera</em> in the expanded stages of the green tide. This study provides new insights into the succession of macro-microalgae and a scientific basis for the mitigation of <em>Ulva spp.</em> green tides in the Yellow Sea.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"153 ","pages":"Article 103062"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146034876","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":"Tropical coastal seas are overlooked hotspots of Pseudo-nitzschia diversity","authors":"Biaobiao Niu ,&nbsp;Cuiwen Liang ,&nbsp;Fang Yue ,&nbsp;Shiyu Wu ,&nbsp;Yang Li ,&nbsp;Songhui Lu","doi":"10.1016/j.hal.2026.103063","DOIUrl":"10.1016/j.hal.2026.103063","url":null,"abstract":"<div><div><em>Pseudo-nitzschia</em> is a globally distributed diatom genus with multiple domoic-acid (DA)–producing species that pose ecological and economic risks. Although tropical waters have recently been hypothesized to host rich <em>Pseudo-nitzschia</em> diversity, their actual diversity, cryptic lineages and toxin-environment relationships remain unclear. Here, we conducted a large-scale summer survey across 65 stations along the Chinese coast of the South China Sea using ITS1 metabarcoding, haplotype network analysis and LC-MS/MS toxin quantification. We identified 50 taxa, including four novel phylotypes and 26 newly recorded in this region, representing the highest richness level documented worldwide. Substantial intraspecific divergence occurred in dominant species, especially <em>P. galaxiae</em>, suggesting a cryptic species complex and ongoing diversification. Dissolved DA (dDA) occurred at 75.4% of stations, with a content of 7.7–351.4 ng L^–1. The higher toxin levels coincided with the co-occurrence of several toxigenic species despite their low relative abundance (&lt;0.4% of total <em>Pseudo-nitzschia</em> reads), indicating a collective contribution to toxin accumulation. Temperature was the strongest environmental predictor of community turnover and toxin variation. Both total and toxigenic <em>Pseudo-nitzschia</em> richness decreased with rising temperature; in particular, a temperature range of 25–29°C corresponded to higher diversity and elevated dDA levels. Contrastly when temperature was above 29°C, <em>Pseudo-nitzschia</em> assemblages were dominated by warm-adapted and largely non-toxic taxa such as <em>P. calliantha</em>, corresponding to low dDA levels. Our findings provide comprehensive molecular evidence that tropical coasts are <em>Pseudo-nitzschia</em> diversity hotspots. Temperature-mediated restructuring of communities links <em>Pseudo-nitzschia</em> diversity to toxin dynamics, highlighting potential climate-driven shifts in HAB risk in low-latitude seas.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"153 ","pages":"Article 103063"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035229","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":"Comparative evaluation of 18S rDNA V4 and 28S rDNA D1–2 regions for resolving Alexandrium species diversity to improve its use for metabarcoding","authors":"Xiangxiang Ding ,&nbsp;Xianliang Huang ,&nbsp;Nansheng Chen","doi":"10.1016/j.hal.2026.103073","DOIUrl":"10.1016/j.hal.2026.103073","url":null,"abstract":"<div><div>Many <em>Alexandrium</em> species can develop harmful algal blooms (HABs) associated with paralytic shellfish poisoning (PSP), making their accurate identification critical. Morphological similarity among <em>Alexandrium</em> species limits their identification, whereas molecular marker-based methods are effective, resulting in the accumulation of vast molecular data. However, the existence of these massive molecular sequences makes it confusing to select reference sequences for taxonomical and diversity studies. To address this, we mined and curated molecular marker sequences of 18S rDNA V4 and 28S rDNA D1–2 for <em>Alexandrium</em> species from NCBI NT database. We built the first reference 28S rDNA D1–2 database for 27 <em>Alexandrium</em> species, and for the 18S rDNA V4 region, our results expanded PR² database by adding sequences for two additional <em>Alexandrium</em> species and proposed to eliminate two contaminated sequences. Furthermore, we characterized intra-genomic variations (IGVs) for both 18S rDNA V4 and 28S rDNA D1–2, and experimentally confirmed the existence of 18S rDNA V4 IGVs in <em>Alexandrium</em> species. Both single-cell sequencing and database analysis results showed that an <em>Alexandrium</em> cell typically harbors IGVs with the co-existence of usually one dominant and multiple non-dominant sequences, with non-dominant sequences potentially matching another species’ dominant sequence. Therefore, only dominant sequences of each <em>Alexandrium</em> species were proposed to be included in reference databases for clarity. We also confirmed that 28S rDNA D1–2 has higher resolution for identifying <em>Alexandrium</em> species. Through clarifying the characteristics of these molecular markers and providing curated datasets, this work enhances metabarcoding accuracy for early detection of toxic <em>Alexandrium</em> populations.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"153 ","pages":"Article 103073"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146188752","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}