Harmful Algae最新文献

{"title":"Shifts in bacterioplankton during cyanobacterial blooms reflect bloom toxicity and lake trophic state","authors":"Lara Jansen ,&nbsp;Nicolas Tromas ,&nbsp;Angela Strecker ,&nbsp;Jesse Shapiro","doi":"10.1016/j.hal.2025.102937","DOIUrl":"10.1016/j.hal.2025.102937","url":null,"abstract":"<div><div>Harmful cyanobacterial blooms (cyanoHABs) typically occur in human-impacted eutrophic lakes suffering from nutrient pollution, but they also occur in pristine lakes spanning the trophic gradient. The drivers and dynamics of blooms in these oligotrophic lakes remain understudied. CyanoHABs alter the composition of bacterioplankton with increases in specific cyanobacteria strains, as well as shifts in heterotrophic taxa. Bacterioplankton community shifts during cyanoHABs can be somewhat predictable but have been only studied in a limited number of lakes, mostly eutrophic and impacted by development. The Cascade Mountains (USA) offer a novel setting to examine microcystin variation and shifts in bacterioplankton communities across trophic in relatively undeveloped lakes with documented cyanoHABs. Using physicochemical measurements, time-integrated toxin monitoring, and 16S rRNA gene sequencing, we explored associations of bacterioplankton communities with cyanoHABs and toxins within a season, as well as across lakes and years. In Cascade Mountain lakes, bacterioplankton communities and cyanoHABs varied spatially, reflecting differences in trophic state, among other factors. The cyanotoxin microcystin exceeded the drinking water chronic exposure level (1 ppb) in two lakes, during which cyanobacteria exceeded 20 % of the bacterioplankton community<em>.</em> Bacterioplankton composition changed notably during the cyanoHAB events, varying with bloom toxicity and lake trophic state. These compositional differences were not only driven by increases in cyanobacteria, specifically from the order Nostocales, but also heterotrophic bacteria such as from the orders Burkholderiales and Cytophagales. Therefore, bacterioplankton composition can potentially be consistent indicators of cyanoHABs and toxicity, more so than climatic factors across lakes that span substantial trophic gradients.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102937"},"PeriodicalIF":4.5,"publicationDate":"2025-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144764123","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":"Cyanotoxin and domoic acid occurrence, relation with salinity, and potential recreational health risks in U.S. coasts in the 2015 US EPA National Coastal Condition Assessment","authors":"Ariel R. Donovan ,&nbsp;Zachary R. Laughrey ,&nbsp;Robin A. Femmer ,&nbsp;Sarena L. Senegal ,&nbsp;Keith A. Loftin","doi":"10.1016/j.hal.2025.102935","DOIUrl":"10.1016/j.hal.2025.102935","url":null,"abstract":"<div><div>In the first nationwide study of cyanotoxins in U.S. estuaries, algal toxins, cyanotoxins, chlorophyll, and salinity were measured in samples collected during the National Coastal Condition Assessment 2015. Anatoxin-a (ANAA), cylindrospermopsin (CYLS), domoic acid (DMAC), and microcystins (MCs) were detected by LC/MS/MS in 0.6, 0.9, 8.3, and 2.0 % of samples with mean concentrations of detections of 0.13, 0.13, 0.53, and 0.49 µg/L, respectively. MCs by ELISA were also evaluated, and 4.0 % of samples had measurable MCs with a mean of 0.78 µg/L. While ANAA and CYLS were detected south of 40° latitude, MCs by ELISA and DMAC occurred nationwide. Results were compared to freshwater recreational health thresholds from the World Health Organization and US Environmental Protection Agency to evaluate potential recreational exposure to MCs and CYLS since marine thresholds do not currently exist. Cyanotoxins were categorized using the 2021 World Health Organization Alert Level Framework for recreational exposure with 99.4, 99.1, 94.7, 98.0, and 44.7 % of samples being at the Vigilance Level for ANAA, CYLS, MCs (ELISA and LC/MS/MS), and chlorophyll, respectively with the remaining samples at Alert Level 1. Chlorophyll had 19.9 and 9.9 % of samples at Alert Level 1 and Alert Level 2, respectively. All cyanotoxins were below US EPA health advisory thresholds. ANAA, CYLS, DMAC, and MCs by ELISA were detected in samples with a wide range of salinities, while MCs by LC/MS/MS only occurred in samples with salinity &lt;5 part per thousand (PPT). The source of cyanotoxins is likely a combination of inland transport and in situ estuarine production.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102935"},"PeriodicalIF":4.5,"publicationDate":"2025-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144764122","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":"Microbial community dynamics and first quantification of the toxin domoic acid in a eutrophic bay in the United Arab Emirates","authors":"Carly M. Moreno ,&nbsp;Iulia Bibire ,&nbsp;Amira Mustafina ,&nbsp;Salah Abdelrazig ,&nbsp;Sreejith Kottuparambil ,&nbsp;Milan Bogosavljevic ,&nbsp;Shady A. Amin","doi":"10.1016/j.hal.2025.102921","DOIUrl":"10.1016/j.hal.2025.102921","url":null,"abstract":"<div><div>The marine planktonic community (eukaryotic, bacterial and archaeal) has been little investigated in the Persian/Arabian Gulf (PAG), despite its crucial role in sustaining biogeochemical cycles and the ecological health of this subtropical ecosystem, which during summer is the hottest marine body of water on Earth. This study explored the temporal changes in the planktonic community in a densely populated, semi-enclosed bay in the United Arab Emirates (UAE), in which seasonal succession of persistent phytoplankton blooms resulted in beach closures. We surveyed the microbial community by analyzing eukaryotic 18S ribosomal RNA (rRNA) and bacterial and archaeal 16S rRNA amplicon gene sequences, alongside measuring environmental parameters over the course of a year. Seasonal differences between cooler winter conditions and extreme high temperatures of summer were evident over the year. Mirroring these environmental changes, phytoplankton and bacterial diversity and community composition were significantly different in both winter and summer. Dinoflagellates dominated the phytoplankton community based on the relative abundance of 18S rRNA, though microscopy revealed a higher biomass contribution from diatoms. We observed several toxin producing dinoflagellates and diatoms in the community composition and seasonal co-occurrence networks. Notably, during a <em>Pseudo-nitzschia</em> bloom, we detected a concentration of 1.12 µg/L of the neurotoxin domoic acid for the first time in UAE coastal waters, highlighting the need for understanding environmental and molecular drivers of toxin production in the region. This study provides a baseline for understanding how environmental and anthropogenic factors influence HABs and microbial dynamics in the Persian/Arabian Gulf.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102921"},"PeriodicalIF":4.5,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144879430","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":"Systems to monitor and forecast pelagic Sargassum inundation of coastal areas across the North Atlantic: present tools and future needs","authors":"Nathan F. Putman ,&nbsp;R. Taylor Beyea ,&nbsp;Emilie G. Ackerman ,&nbsp;Joaquin Trinanes ,&nbsp;Matthieu Le Hénaff ,&nbsp;Chuanmin Hu ,&nbsp;Rick Lumpkin","doi":"10.1016/j.hal.2025.102933","DOIUrl":"10.1016/j.hal.2025.102933","url":null,"abstract":"<div><div>Massive blooms of pelagic Sargassum, a brown macroalgae, have become a seasonally recurrent phenomenon in the Tropical Atlantic since 2011. These blooms have resulted in inundations along coastlines in western Africa and throughout the Intra-American Seas. The widespread nature of this phenomenon and complexities surrounding the growth and transport of these blooms in the open ocean have presented significant challenges to effectively monitoring and forecasting coastal inundations. Here we review 25 existing monitoring and forecasting systems, noting the unique aspects and common features among them and identifying the current gaps. Based on this review we present a conceptual model for the key elements necessary for operational monitoring and forecasting systems; recommending approaches that account for <em>Sargassum</em> distribution, amount, transport, and growth rates in predictions. We then provide specific recommendations for integrating improved monitoring and forecasting elements to the NOAA Atlantic Oceanographic and Meteorological Laboratory’s Sargassum Inundation Risk and Ocean Viewer interactive maps.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102933"},"PeriodicalIF":4.5,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144764124","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":"Phylogenetic analysis of the toxigenic genus Amphidinium (Amphidiniales, Dinophyceae) revealed an unexpectedly high diversity in the Asia–Pacific region","authors":"Haifeng Gu ,&nbsp;Shuning Huang ,&nbsp;Bernd Krock ,&nbsp;Chui Pin Leaw ,&nbsp;Po Teen Lim ,&nbsp;Nur Shazwani Kassim ,&nbsp;Hyeon Ho Shin ,&nbsp;Kakaskasen Andreas Roeroe ,&nbsp;Hao Yuan ,&nbsp;Shimaa Hosny ,&nbsp;Rimi Sasai ,&nbsp;Kazuya Takahashi ,&nbsp;Hikmah Thoha ,&nbsp;Faisal Hamzah ,&nbsp;Dao Viet Ha ,&nbsp;Nantapak Potisarn ,&nbsp;Thaithaworn Lirdwitayaprasit ,&nbsp;Mitsunori Iwataki","doi":"10.1016/j.hal.2025.102934","DOIUrl":"10.1016/j.hal.2025.102934","url":null,"abstract":"<div><div>The dinoflagellate genus <em>Amphidinium</em> encompasses several toxic species known to cause harmful algal blooms. Despite their ecological significance, the diversity within this genus may be underestimated due to the morphological similarities among species. In this study, we established 82 strains of <em>Amphidinium</em> by isolating single cells from the Asia–Pacific region. We examined their morphology using light and transmission electron microscopy. Additionally, we obtained partial sequences of the large subunit ribosomal (LSU) DNA and/or internal transcribed spacer regions for all strains. Furthermore, DNA metabarcoding targeting the LSU D1-D2 region was employed to detect species in the Bohai Sea, Yellow Sea, Mediterranean Sea, and Red Sea, where strain data is limited. The 82 strains were classified into 13 <em>Amphidinium</em> species. Among these were four undescribed species, provisionally named <em>Amphidinium</em> sp. 1 to <em>Amphidinium</em> sp. 4, as well as <em>A. cupulatisquama, A. fijiensis, A. gibbosum, A. massartii, A. operculatum, A. pseudomassartii, A. thermaeum, A. tomasii</em>, and <em>A. trulla</em>, based on both morphological and molecular analyses. DNA metabarcoding detected nine <em>Amphidinium</em> species. While <em>Amphidinium gibbosum</em> and <em>A. tomasii</em> are confined to tropical and warm subtropical waters, the other species exhibit a broader distribution. Molecular phylogenetic analysis revealed two distinct clades within the genus <em>Amphidinium</em>. Species in clade A, including <em>A. uduigamense, A. stirisquamtum, A. operculatum, Amphidinium</em> sp. 1, and <em>Amphidinium</em> sp. 2, share a characteristic sulcus that originates in the posterior one-third of the hypocone. In contrast, species in clade B are characterized by a sulcus that originates in the anterior or middle part of the cell. Additionally, amphidinol analysis was conducted on ten strains of five <em>Amphidinium</em> species using liquid chromatography-tandem mass spectrometry (LC-MS/MS), but amphidinols were below the detection limit. However, one strain of <em>A. massartii</em> produces a new amphidinol variant with a molecular mass of 1402.7 Da (34.47 fg cell⁻¹) and hemolysis assays suggest the potential presence of novel amphidinols or related compounds in <em>A. operculatum</em>. Our findings underscore the significant diversity and potential risk posed by <em>Amphidinium</em> species in the Asia–Pacific region and beyond.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102934"},"PeriodicalIF":4.5,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144725085","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":"Effects of nutrient depletion duration on growth, photosynthesis and toxins (OA and DTX) in the dinoflagellate Prorocentrum lima","authors":"Jeong Hwa Hwang ,&nbsp;Ji-Sook Park ,&nbsp;Young-Seok Han ,&nbsp;Youn-Jung Kim ,&nbsp;Mungi Kim ,&nbsp;Seongjin Hong ,&nbsp;Jang K. Kim","doi":"10.1016/j.hal.2025.102932","DOIUrl":"10.1016/j.hal.2025.102932","url":null,"abstract":"<div><div><em>Prorocentrum lima</em> is a marine benthic dinoflagellate known for producing toxins such as okadaic acid (OA) and dinophysistoxin (DTX), which cause diarrheal shellfish poisoning (DSP). <em>P. lima</em> is known to increase toxin production under low nutrient concentrations, but there have been few studies examining the effect of prolonged nutrient depletion. This study investigates changes in growth, photosynthetic efficiency, pigments (Chl <em>a</em> and carotenoids) and toxin levels (OA and DTX) during the period of nutrient depletion. Nutrient addition was stopped when the cell concentration reached the stationary phase at approximately 200,000 cells ml⁻¹. After stopping nutrient addition, sampling was conducted at 10-day intervals for 30 days. During the exponential growth phase, <em>P. lima</em> took up more than 90 % of nitrate and nitrite from the medium within 3 hours. Even after the nutrient supply was stopped, cell density continued to increase, reaching about 340,000 cells ml⁻¹. Chl <em>a</em> and carotenoids did not show significant differences, but photosynthetic parameters, such as relative electron transport rate (rETR), ETRmax and Ik decreased. The levels of OA and DTX-1 were also significantly higher on day 30 compared to day 0. These results suggest that, while the cell density can be maintained during nutrient depletion, the toxin content per cell increases significantly, and photosynthetic efficiency decreases.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102932"},"PeriodicalIF":5.5,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704395","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":"Morphological, molecular, toxicological, and ecological characterization of Lingulaulax djiboutiensis sp. nov. from the Gulf of Aden (Djibouti) and the Gulf of California (Mexico)","authors":"Mahamoud Ali Chirdon ,&nbsp;Kenneth Neil Mertens ,&nbsp;Lourdes Morquecho ,&nbsp;Gwenaël Bilien ,&nbsp;Veronique Savar ,&nbsp;Moussa Mahdi Ahmed ,&nbsp;Philipp Hess ,&nbsp;Nasri Hassan Ibrahim ,&nbsp;Mohamed Osman Awaleh","doi":"10.1016/j.hal.2025.102931","DOIUrl":"10.1016/j.hal.2025.102931","url":null,"abstract":"<div><div>As part of an exploration program aimed at studying the diversity of potentially toxic dinoflagellates in the coastal waters of Djibouti, located in the Gulf of Tadjoura (GT) at the junction between the Red Sea and the Arabian Sea, a new species of the genus <em>Lingulaulax</em> (formerly known as <em>Lingulodinium</em>) was identified. This new species, designated <em>Lingulaulax djiboutiensis</em> sp. nov., is supported by morphological and molecular data. The plate formula, APC (Po, X, cp), 3ʹ, 3a*, 6ʹʹ, 6c, 6 s, 6ʹʹʹʹ, 2ʹʹʹʹʹʹ, is characteristic of the genus <em>Lingulaulax. L. djiboutiensis</em> sp. nov. can be distinguished morphologically from <em>L. polyedra</em>: (i) individuals of <em>L. djiboutiensis</em> sp. nov. (L: 34.8 ± 1.9 μm, W: 34.7 ± 1.9 μm, L:W ratio of 1.06 ± 0.9) are slightly smaller and more compressed than those of <em>L. polyedra</em>; (ii) in <em>L. djiboutiensis</em> sp. nov., plate 1a contacts the apical pore complex (APC); (iii) the cingulum of <em>L. djiboutiensis</em> sp. nov. (ranging from 2.4 to 3.9 µm) is wider than that of <em>L. polyedra</em> (ranging from 1.8 to 2.8 µm); and (iv) the diameter of the trichocyst pores of <em>L. djiboutiensis</em> sp. nov. (ranging from 0.55 to 1.05 µm) is smaller than that observed in <em>L. polyedra</em> (ranging from 0.94 to 1.33 µm). Phylogenetic analyses based on LSU and ITS ribosomal DNA sequences revealed that L. djiboutiensis sp. nov., belongs to a distinct clade, sister to and separate from <em>L. polyedra</em>, supported by high bootstrap values and Bayesian inferences (BI = 1.00 and ML = 100). The intra-species evolutionary divergence between the two strains of L. djiboutiensis from the Gulf of California (Mexico) and the Gulf of Aden (GA) is remarkably low, with a rate of 0 % in the LSU region and 0.03 % in the ITS region. In contrast, the evolutionary divergence between L. <em>djiboutiensis</em> and <em>L. polyedra</em> is more pronounced, reaching 0.05 % for the LSU region and 0.15 % for the ITS region, thereby highlighting a significant phylogenetic separation between these two species. LC-MS/MS analysis revealed that <em>L. djiboutiensis</em> is non-toxic. Additionally, spatiotemporal studies in the GT have shown that this species is present throughout the year, peaking in abundance at the end of summer.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102931"},"PeriodicalIF":5.5,"publicationDate":"2025-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144687559","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":"Multi-trophic paralytic shellfish toxin risk and management across seafood sectors in Tasmania","authors":"Alison Turnbull ,&nbsp;Steven Rust ,&nbsp;Deborah Bermudes ,&nbsp;Andreas Seger","doi":"10.1016/j.hal.2025.102929","DOIUrl":"10.1016/j.hal.2025.102929","url":null,"abstract":"<div><div>Multi-trophic biotoxin risk management is critically important to regions that suffer from extensive blooms of paralytic shellfish toxin (PST) producing algae. In Australia, Tasmania’s east and south-east coasts are hotspots for PST activity due to recurrent blooms of <em>Alexandrium catenella</em> and <em>Gymnodinium catenatum</em> occurring in differing geographic regions and seasonal patterns. Toxins have been measured above bivalve regulatory levels in filter feeders, predatory crustaceans and herbivorous grazers at maximum levels of 340, 13.6 and 3.0 mg STX.2HCl equiv. kg^-1 respectively, affecting commercial and recreational fisheries with a combined annual value of USD 103M. Toxin accumulation and depuration rates are highest in bivalve shellfish, followed by lobster and then abalone. Managing PST risk across these multiple seafood species in an area of recurrent bloom activity is challenging. Currently a siloed approach is taken, with diverse strategies for each species that reflect the harmful algal bloom dynamics and varied fishing activities. This review of Tasmanian data and the following stakeholder consultation identified benefits to adopting an integrated approach to risk management across all seafood species. Benefits included cost efficiencies (USD 54,100 per annum), improved data sharing for real-time awareness, streamlined communication and improved cross-sector collaboration.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102929"},"PeriodicalIF":5.5,"publicationDate":"2025-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144702563","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":"Effects of increasing light intensities on the cell growth and the RNA m6A upstream regulatory factors in a strain of Alexandrium pacificum","authors":"Zhimei Zhu,&nbsp;Qingyue Zhang,&nbsp;Zhenghong Sui","doi":"10.1016/j.hal.2025.102928","DOIUrl":"10.1016/j.hal.2025.102928","url":null,"abstract":"<div><div><em>Alexandrium pacificum</em> (<em>Alexandrium</em> sp. qd1) is representative of dinoflagellates that cause harmful red tides, and light intensity is an important factor affecting photosynthetic growth of <em>A. pacificum</em> in red tide outbreaks. N⁶ methyladenosine (m⁶A) RNA modification, as an important post-transcriptional molecular regulatory mechanism, may play an important role in the regulation of photosynthetic growth of dinoflagellates, which are known to exhibit minimal transcriptional regulation. In this study, the growth, photosynthesis, and cell sizes of <em>A. pacificum</em> under increasing light-intensity conditions (30, 100, 200, 300, 400 μmol photons m⁻²s^−l) were examined. It was shown that 30 to 300 μmol m⁻²s^−l light intensity gradually promoted the growth of algal cells in the logarithmic growth phase, whereas 400 μmol m⁻²s^−l induced growth photoinhibition. The growth, photosynthetic indicators, and cell size of <em>A. pacificum</em> were significantly affected by light intensity. Meanwhile, the m⁶A modification level within the light-promoted growth range was detected and its correlation with growth indicators was analyzed. It was found that the m⁶A modification level decreased with the increase in light intensity and it has correlation with μ_max, Fv/Fm, NPQ, and cell size. Then, the members of the upstream regulatory factors of m⁶A modification were identified and characterized. Most m⁶A important writers (MT-A70, WTAP), eraser (ALKBH1/3/5/6/8), and readers (YTH, eIF3C/D/G, hnRNPA2B1/C) were present in <em>A. pacificum</em>. The gene and protein expression of multiple members were detected, and multiple m⁶A modification regulators were found to respond to changes in light intensity. The results showed that m⁶A modification may play an important regulatory role in the growth of <em>A. pacificum</em> under different light-intensity conditions. This study provided some basis and insights for studying the growth regulation of red tide <em>A. pacificum</em> from the aspect of epi‑transcriptome (post transcriptional modifications on RNA).</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102928"},"PeriodicalIF":5.5,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144702564","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":"Morphology vs. toxicity: How temperature reshapes Microcystis’ adaptive strategies in a warming world?","authors":"Yan Xiao ,&nbsp;Xiaohan Yu ,&nbsp;Dianchang Wang ,&nbsp;Xinghua Wu ,&nbsp;Lunhui Lu ,&nbsp;Zhe Li","doi":"10.1016/j.hal.2025.102927","DOIUrl":"10.1016/j.hal.2025.102927","url":null,"abstract":"<div><div>Global warming and eutrophication have synergistically intensified cyanobacterial blooms, with <em>Microcystis</em> posing significant ecological and health risks due to microcystin (MC) production. This study investigated how temperature gradients (10 °C, 25 °C, 35 °C, 40 °C) modulate physiological, morphological, and molecular adaptive strategies in <em>M. aeruginosa</em>, focusing on metabolic trade-offs between morphological plasticity and toxin production. Our results demonstrated that robust growth at 35 °C but photosynthetic inhibition at extremes (10 °C/40 °C). High-temperature stress (40 °C) triggered a 101 % increase in MC hypersecretion concurrent with 68 % cell diameter enlargement and 44 % colony fragmentation, comparable to the 25 °C control. In contrast, low-temperature stress (10 °C) promoted intracellular MC retention and a 135 % increase in external layer proportion. Multi-omics analyses demonstrated suppressed carbon fixation, nitrogen metabolism and glycolysis under stress, with compensatory activation of the tricarboxylic acid cycle, the pentose phosphate pathway (NADPH production) and glutathione metabolism for oxidative stress mitigation. Strikingly, MC transporter gene <em>mcyH</em> was pronounced upregulated at 40 °C, and the accompanying polysaccharide synthesis/output (PSO) gene expression strongly correlating with extracellular MC levels, suggesting MC-mediated polysaccharide secretion for environmental adaptation. However, cold-induced external layer formation occurred independently of MC regulatory pathways. Integrative analysis revealed a metabolic trade-off with distinct thermal strategies: high-temperature stress favored MC export, colony downsizing and cellular enlargement, whereas low temperature prioritized intracellular MC storage coupled with antioxidant system activation. These findings elucidate <em>Microcystis</em>’ metabolic trade-offs under thermal stress, highlighting climate-driven bloom persistence mechanisms through synergistic morphological and toxicological adjustments. This study provides critical insights into cyanobacterial dominance mechanisms in warming aquatic ecosystems.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"148 ","pages":"Article 102927"},"PeriodicalIF":5.5,"publicationDate":"2025-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144632677","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}