Harmful Algae最新文献

{"title":"First report of PST-producing Microseira wollei from China reveals its novel toxin profile","authors":"Youxin Chen ,&nbsp;Yongguang Jiang ,&nbsp;Zhongshi He ,&nbsp;Jin Gao ,&nbsp;Renhui Li ,&nbsp;Gongliang Yu","doi":"10.1016/j.hal.2024.102655","DOIUrl":"10.1016/j.hal.2024.102655","url":null,"abstract":"<div><p><em>Microseira wollei</em>, a globally distributed freshwater bloom-forming benthic cyanobacterium, is known for its production of cyanotoxins and taste and odor (T&amp;O). While CYN (Cylindrospermopsin)-producing populations of <em>M. wollei</em> are confined to Australia, PST (Paralytic shellfish toxins)-producing populations have been exclusively documented in North America. In this study, four benthic cyanobacterial strains, isolated from West Lake in China, were identified as <em>M. wollei</em> based on morphological and phylogenetic analyses. Detection of <em>sxtA</em> gene and UPLC-MS/MS analysis conclusively confirmed the PST-producing capability of <em>M. wollei</em> CHAB5998. In the phylogenetic tree of 16S rDNA, <em>M. wollei</em> strains formed a monophyletic group with two subclades. Notably, non-PST-producing Chinese strains clustered with Australian strains in Clade II, while all other strains, including PST-producing ones, clustered in Clade I. Additionally, CHAB5998 contains ten PST variants, of which STX, NEO, GTX2, GTX3, GTX5 and C1 were identified for the first time in <em>M. wollei</em>. Sequence analysis of PST biosynthetic gene cluster (<em>sxt</em>) genes indicated potential base variations, gene rearrangements, insertions, and deletions in the strain CHAB5998. Also, <em>sxt</em> gene has a longer evolutionary history in <em>M. wollei</em> than that in cyanobacteria from Nostocales. Multiple recombination breakpoints detected in <em>sxt</em> genes and the inconsistency in the topology of the phylogenetic trees between <em>sxt</em> and 16S rDNA suggested that multiple horizontal gene transfers (HGT) have occurred. Overall, the present study marks the first documented occurrence of PST-producing <em>M. wollei</em> outside of North America and identifies it as the first toxic freshwater benthic cyanobacterium in China. This revelation implies that benthic cyanobacteria may pose a higher environmental risk in China than previously acknowledged.</p></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"137 ","pages":"Article 102655"},"PeriodicalIF":6.6,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141281802","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 recent disappearance of a persistent Planktothrix bloom: Characterization of a regime shift in the phytoplankton of Sandusky Bay (USA)","authors":"Ryan S. Wagner ,&nbsp;Michelle J. Neudeck ,&nbsp;Alexis E. Heath ,&nbsp;Katelyn B. Barker ,&nbsp;Katelyn M. Brown ,&nbsp;Seth Buchholz ,&nbsp;Christopher S. Ward ,&nbsp;George S. Bullerjahn","doi":"10.1016/j.hal.2024.102656","DOIUrl":"10.1016/j.hal.2024.102656","url":null,"abstract":"<div><p>Sandusky Bay is the drowned mouth of the Sandusky River in the southwestern portion of Lake Erie. The bay is a popular recreation location and a regional source for drinking water. Like the western basin of Lake Erie, Sandusky Bay is known for being host to summer cyanobacterial harmful algal blooms (cHABs) year after year, fueled by runoff from the predominantly agricultural watershed and internal loading of legacy nutrients (primarily phosphorus). Since at least 2003, Sandusky Bay has harbored a microcystin-producing bloom of <em>Planktothrix agardhii,</em> a species of filamentous cyanobacteria that thrives in low light conditions. Long-term sampling (2003–2018) of Sandusky Bay revealed regular <em>Planktothrix</em>-dominated blooms during the summer months, but in recent years (2019–2022), 16S rRNA gene community profiling revealed that <em>Planktothrix</em> has largely disappeared. From 2017–2022, microcystin decreased well below the World Health Organization (WHO) guidelines. Spring TN:TP ratios increased in years following dam removal, yet there were no statistically significant shifts in other physicochemical variables, such as water temperature and water clarity. With the exception of the high bloom of <em>Planktothrix</em> in 2018, there was no statistical difference in chlorophyll during all other years. Concurrent with the disappearance of <em>Planktothrix, Cyanobium</em> spp. have become the dominant cyanobacterial group. The appearance of other potential toxigenic genera (i.e., <em>Aphanizomenon, Dolichospermum, Cylindrospermopsis</em>) may motivate monitoring of new toxins of concern in Sandusky Bay. Here, we document the regime shift in the cyanobacterial community and propose evidence supporting the hypothesis that the decline in the <em>Planktothrix</em> bloom was linked to the removal of an upstream dam on the Sandusky River.</p></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"136 ","pages":"Article 102656"},"PeriodicalIF":6.6,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1568988324000908/pdfft?md5=f28b17e30a5bffbb1b40eed31bed9ccf&pid=1-s2.0-S1568988324000908-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141129997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Photoacclimation and photophysiology of four species of toxigenic Dinophysis","authors":"Nour Ayache ,&nbsp;Lisa Campbell ,&nbsp;Christopher J. Gobler ,&nbsp;Juliette L. Smith","doi":"10.1016/j.hal.2024.102624","DOIUrl":"10.1016/j.hal.2024.102624","url":null,"abstract":"<div><p>This study aimed to explore the effects of different light intensities on the ecophysiology of eight new <em>Dinophysis</em> isolates comprising four species (<em>D. acuminata, D. ovum, D. fortii</em>, and <em>D. caudata</em>) collected from different geographical regions in the US. After six months of acclimation, the growth rates, photosynthetic efficiency (<em>F_v/F_m</em> ratio), toxin content, and net toxin production rates of the <em>Dinophysis</em> strains were examined. The growth rates of <em>D. acuminata</em> and <em>D. ovum</em> isolates were comparable across light intensities, with the exception of one <em>D. acuminata</em> strain (DANY1) that was unable to grow at the lowest light intensity. However, <em>D. fortii</em> and <em>D. caudata</em> strains were photoinhibited and grew at a slower rate at the highest light intensity, indicating a lower degree of adaptability and tolerance to such conditions. Photosynthetic efficiency was similar for all <em>Dinophysis</em> isolates and negatively correlated with exposure to high light intensities. Multiple toxin metrics, including cellular toxin content and net production rates of DSTs and PTXs, were variable among species and even among isolates of the same species in response to light intensity. A pattern was detected, however, whereby the net production rates of PTXs were significantly lower across all <em>Dinophysis</em> isolates when exposed to the lowest light intensity. These findings provide a basis for understanding the effects of light intensity on the eco-physiological characteristics of <em>Dinophysis</em> species in the US and could be employed to develop integrated physical-biological models for species and strains of interest to predict their population dynamics and mitigate their negative effects.</p></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"136 ","pages":"Article 102624"},"PeriodicalIF":6.6,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141052120","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":"Detecting Margalefidinium polykrikoides through high-frequency imagery: Example of a bloom formation, environmental conditions, and phytoplankton community composition changes","authors":"Jessica Carney-Almeida ,&nbsp;Virginie Sonnet ,&nbsp;Colleen B. Mouw ,&nbsp;Jan Rines ,&nbsp;Audrey B. Ciochetto ,&nbsp;Gavino Puggioni","doi":"10.1016/j.hal.2024.102619","DOIUrl":"https://doi.org/10.1016/j.hal.2024.102619","url":null,"abstract":"<div><p>In August 2018, the harmful algae species <em>Margalefidinium polykrikoides</em> bloomed to levels previously unobserved in the open waters of Narragansett Bay, Rhode Island, in a transient but intense bloom. Detected by an Imaging FlowCytobot providing hourly data, it is characterized by a time span of less than a week and patchiness with sub-daily oscillations in concentration. The highest concentrations are recorded at lower salinity and higher temperature, suggesting the bloom may have developed in the upper bay and was transported south. The proportion of chains increased during the height of the bloom, and many of the images contained 4-cells per chain. The development of the bloom was favored by optimal temperature and salinity conditions as well as increased nitrogen coincident with greater precipitation and river flow. The period preceding bloom formation also saw a sharp decrease in the dominating large chain-forming diatom <em>Eucampia</em> sp<em>.</em> and highly abundant <em>Skeletonema</em> spp., thus reducing competition over resources for the slow-growing <em>M. polykrikoides</em>. The height of the bloom was reached during the lowest tidal range of the month when the turbulence and water displacement were lower. This time series highlights an out-of-the-ordinary bloom's environmental and biological conditions and the importance of frequent sampling during known favorable conditions.</p></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"136 ","pages":"Article 102619"},"PeriodicalIF":6.6,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141314807","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":"From genes to toxins: Profiling Prymnesium parvum during a riverine harmful algal bloom","authors":"Demetrio Mora ,&nbsp;Michael Schlüsener ,&nbsp;Helmut Fischer ,&nbsp;Julia Kleinteich ,&nbsp;Manoj Schulz ,&nbsp;Thomas Ternes ,&nbsp;Joana Thiel ,&nbsp;Arne Wick ,&nbsp;Sascha Krenek","doi":"10.1016/j.hal.2024.102644","DOIUrl":"10.1016/j.hal.2024.102644","url":null,"abstract":"<div><p>Blooms of <em>Prymnesium parvum</em>, a unicellular alga globally distributed in marine and brackish environments, frequently result in massive fish kills due to the production of toxins called prymnesins by this haptophyte. In August 2022, a harmful algal bloom (HAB) of this species occurred in the lower Oder River (Poland and Germany), which caused mass mortalities of fish and other organisms. This HAB was linked to low discharge of the Oder and mining activities that caused a significant increase in salinity. In this context, we report on the molecular detection and screening of this haptophyte and its toxins in environmental samples and clonal cultures derived thereof. Both conventional PCR and droplet digital PCR assays reliably detected <em>P. parvum</em> in environmental samples. eDNA metabarcoding using the V4 region of the 18S rRNA gene revealed a single <em>Prymnesium</em> sequence variant, but failed to identify it to species level. Four clonal cultures established from environmental samples were unambiguously identified as <em>P. parvum</em> by molecular phylogenetics (near full-length 18S rRNA gene) and light microscopy. Phylogenetic analysis (ITS1–5.8S-ITS2 marker region) placed the cultured phylotype within a clade containing other <em>P. parvum</em> strains known to produce B-type prymnesins. Toxin-screening of the cultures using liquid chromatography-electrospray ionization - time of flight mass spectrometry identified B-type prymnesins, which were also detected in extracts of filter residues from water samples of the Oder collected during the HAB. Overall, our investigation provides a detailed characterization of <em>P. parvum</em>, including their prymnesins, during this HAB in the Oder River, contributing valuable insights into this ecological disaster. In addition, the droplet digital PCR assay established here will be useful for future monitoring of low levels of <em>P. parvum</em> on the Oder River or any other salt-impacted and brackish water bodies.</p></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"136 ","pages":"Article 102644"},"PeriodicalIF":6.6,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1568988324000787/pdfft?md5=2e2b5e4b5b7d9562373272dbcf89653f&pid=1-s2.0-S1568988324000787-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141031043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Can a shift in dominant species of Microcystis alter growth and reproduction of waterfleas?","authors":"Tao Wang ,&nbsp;Daochun Xu ,&nbsp;Xuexiu Chang ,&nbsp;Hugh J. MacIsaac ,&nbsp;Jingjing Li ,&nbsp;Jun Xu ,&nbsp;Jinlong Zhang ,&nbsp;Hongyan Zhang ,&nbsp;Yuan Zhou ,&nbsp;Runbing Xu","doi":"10.1016/j.hal.2024.102657","DOIUrl":"10.1016/j.hal.2024.102657","url":null,"abstract":"<div><p>The bloom-forming species <em>Microcystis wesenbergii</em> and <em>M. aeruginosa</em> occur in many lakes globally, and may exhibit alternating blooms both spatially and temporally. As environmental changes increase, cyanobacteria bloom in more and more lakes and are often dominated by <em>M. wesenbergii</em>. The adverse impact of <em>M. aeruginosa</em> on co-existing organisms including zooplanktonic species has been well-studied, whereas studies of <em>M. wesenbergii</em> are limited. To compare effects of these two species on zooplankton, we explored effects of exudates from different strains of microcystin-producing <em>M. aeruginosa</em> (Ma905 and Ma526) and non-microcystin-producing <em>M. wesenbergii</em> (Mw908 and Mw929), on reproduction by the model zooplankter <em>Daphnia magna</em> in both chronic and acute exposure experiments. Specifically, we tested physiological, biochemical, molecular and transcriptomic characteristics of <em>D. magna</em> exposed to <em>Microcystis</em> exudates. We observed that body length and egg and offspring number of the daphnid increased in all treatments. Among the four strains tested, Ma526 enhanced the size of the first brood, as well as total egg and offspring number. <em>Microcystis</em> exudates stimulated expression of specific genes that induced ecdysone, juvenile hormone, triacylglycerol and vitellogenin biosynthesis, which, in turn, enhanced egg and offspring production of <em>D. magna</em>. Even though all strains of <em>Microcystis</em> affected growth and reproduction, large numbers of downregulated genes involving many essential pathways indicated that the Ma905 strain might contemporaneously induce damage in <em>D. magna</em>. Our study highlights the necessity of including <em>M. wesenbergii</em> into the ecological risk evaluation of cyanobacteria blooms, and emphasizes that consequences to zooplankton may not be clear-cut when assessments are based upon production of microcystins alone.</p></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"136 ","pages":"Article 102657"},"PeriodicalIF":6.6,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141134963","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 effects of the toxic dinoflagellate Alexandrium on feeding, reproduction and mortality of the copepod Acartia: A systematic review employing weighted linear models","authors":"Aldo Barreiro Felpeto ,&nbsp;Máximo Frangopulos Rivera ,&nbsp;Vitor Manuel Vasconcelos","doi":"10.1016/j.hal.2024.102659","DOIUrl":"https://doi.org/10.1016/j.hal.2024.102659","url":null,"abstract":"<div><p>The study of interactions between copepods of the genus <em>Acartia</em> and toxic dinoflagellates of the genus <em>Alexandrium</em> has been an important topic during the last four decades. Feeding behavior and physiological responses of copepods have been studied in laboratory and field experiments, sometimes with contradictory results. More recently, an evolutionary adaptive mechanism leading to enhanced tolerance of <em>Alexandrium</em> toxins in a population of <em>Acartia</em> experiencing chronic exposure to these dinoflagellates has been reported. In the present work, we collected data from the existing studies on the effects of <em>Alexandrium</em> on feeding, reproduction and mortality of <em>Acartia</em>. With these data, we performed a systematic review consisting of a secondary analysis employing general or generalized linear models, weighting data from different studies by the reciprocal of their standard deviation. Our first aim was to overcome shortcomings of individual studies: limited ranges of the variables and overlooked variables (experiment length, population adaptation). These shortcomings could have led to inconsistent conclusions by missing heterogeneous patterns in copepod responses and in the interactions between variables. Our second aim was to test the enhanced physiological performance of chronically exposed relative to naïve copepod populations over a wide geographic range. We found that the feeding rate is enhanced by increased food biomass, irrespective of the food type. Toxins do not have a clear effect on egg production and have a bi-phasic effect on egg hatching success, which was negative above a specific threshold. Toxins also increased mortality. Experiment length had a positive effect on egg production and negative on egg hatching. Naïve copepod populations showed consistently lower ingestion of <em>Alexandrium</em> and egg hatching rates, thereby supporting the spread of the aforementioned mechanism across populations over a wide geographic range.</p></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"137 ","pages":"Article 102659"},"PeriodicalIF":6.6,"publicationDate":"2024-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1568988324000933/pdfft?md5=5dcf434649afe652003644b2ef11315f&pid=1-s2.0-S1568988324000933-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141429237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Five Karenia species along the Chinese coast: With the description of a new species, Karenia hui sp. nov. (Kareniaceae, Dinophyta)","authors":"Jingyi Cen ,&nbsp;Songhui Lu ,&nbsp;Øjvind Moestrup ,&nbsp;Tao Jiang ,&nbsp;Kin Chung Ho ,&nbsp;Si Li ,&nbsp;Mingmin Li ,&nbsp;Qingliu Huan ,&nbsp;Jianyan Wang","doi":"10.1016/j.hal.2024.102645","DOIUrl":"10.1016/j.hal.2024.102645","url":null,"abstract":"<div><p>Dinoflagellates within the genus <em>Karenia</em> are well known for their potential to cause harmful algal blooms and induce detrimental ecological consequences. In this study, five <em>Karenia</em> species, <em>Karenia longicanalis, Karenia papilionacea, Karenia mikimotoi, Karenia selliformis</em>, and a new species, <em>Karenia hui</em> sp. nov., were isolated from Chinese coastal waters. The new species exhibits the typical characteristics of the genus <em>Karenia</em>, including a linear apical groove and butanoyl-oxyfucoxanthin as the major accessory pigment. It is distinguished from the other <em>Karenia</em> species by a wide-open sulcal intrusion onto the epicone, a conical epicone with an apical crest formed by the rim of the apical groove, and a hunchbacked hypocone. It is most closely related to <em>Karenia cristata</em>, with a genetic divergence of 3.16 % (22 bp out of 883 bp of LSU rDNA). Acute toxicity tests indicated that the five <em>Karenia</em> species from China are all toxic to marine medaka <em>Oryzias melastigma. Karenia selliformis</em> and <em>K. hui</em> were very toxic to <em>O. melastigma</em>, resulting in 100 % mortality within 4 h and 24 h, respectively. Further analysis by high-performance liquid chromatography revealed that four species, <em>K. selliformis, K. longicanalis, K. papilionacea</em> and <em>K. mikimotoi</em> were capable of producing Gymnodimine-A (GYM-A). The highest GYM-A content was in <em>K. selliformis</em> (strain HK-43), in which the value was 889 fg/cell. No GYM-A was detected in the new species <em>K. hui</em>, however and its toxin remains unknown<em>.</em> Below we provide a comprehensive report of the morphology, phylogeny, pigment composition, and toxicity profiles of <em>Karenia</em> species along the Chinese coast. These findings contribute new insights for monitoring of <em>Karenia</em> species, with important toxicological and ecological implications.</p></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"137 ","pages":"Article 102645"},"PeriodicalIF":5.5,"publicationDate":"2024-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141030250","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":"Microcystin removal by microbial communities from a coastal lagoon: Influence of abiotic factors, bacterioplankton composition and estimated functions","authors":"Allan A Santos ,&nbsp;Felipe V Garrute ,&nbsp;Valéria F Magalhães ,&nbsp;Ana Beatriz F Pacheco","doi":"10.1016/j.hal.2024.102646","DOIUrl":"https://doi.org/10.1016/j.hal.2024.102646","url":null,"abstract":"<div><p>Toxic cyanobacterial blooms present a substantial risk to public health due to the production of secondary metabolites, notably microcystins (MCs). Microcystin-LR (MC-LR) is the most prevalent and toxic variant in freshwater. MCs resist conventional water treatment methods, persistently impacting water quality. This study focused on an oligohaline shallow lagoon historically affected by MC-producing cyanobacteria, aiming to identify bacteria capable of degrading MC and investigating the influence of environmental factors on this process. While isolated strains did not exhibit MC degradation, microbial assemblages directly sourced from lagoon water removed MC-LR within seven days at 25 ºC and pH 8.0. The associated bacterial community demonstrated an increased abundance of bacterial taxa assigned to <em>Methylophilales</em>, and also <em>Rhodospirillales</em> and <em>Rhodocyclales</em> to a lesser extent. However, elevated atmospheric temperatures (45 ºC) and acidification (pH 5.0 and 3.0) hindered MC-LR removal, indicating that extreme environmental changes could contribute to prolonged MC persistence in the water column. This study highlights the importance of considering environmental conditions in order to develop strategies to mitigate cyanotoxin contamination in aquatic ecosystems.</p></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"135 ","pages":"Article 102646"},"PeriodicalIF":6.6,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141083669","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 cumulative impact of temperature and nitrogen availability on the potential nitrogen fixation and extracellular polymeric substances secretion by Dolichospermum","authors":"Dailan Deng ,&nbsp;Han Meng ,&nbsp;You Ma ,&nbsp;Yongqi Guo ,&nbsp;Zixuan Wang ,&nbsp;Huan He ,&nbsp;Wenming Xie ,&nbsp;Jin-e Liu ,&nbsp;Limin Zhang","doi":"10.1016/j.hal.2024.102633","DOIUrl":"https://doi.org/10.1016/j.hal.2024.102633","url":null,"abstract":"<div><p>Nitrogen-fixing cyanobacteria not only cause severe blooms but also play an important role in the nitrogen input processes of lakes. The production of extracellular polymeric substances (EPS) and the ability to fix nitrogen from the atmosphere provide nitrogen-fixing cyanobacteria with a competitive advantage over other organisms. Temperature and nitrogen availability are key environmental factors in regulating the growth of cyanobacteria. In this study, <em>Dolichospermum</em> (formerly known as <em>Anabaena</em>) was cultivated at three different temperatures (10 °C, 20 °C, and 30 °C) to examine the impact of temperature and nitrogen availability on nitrogen fixation capacity and the release of EPS. Initially, confocal laser scanning microscopy (CLSM) and the quantification of heterocysts at different temperatures revealed that lower temperatures (10 °C) hindered the differentiation of heterocysts under nitrogen-deprived conditions. Additionally, while heterocysts inhibited the photosynthetic activity of <em>Dolichospermum</em>, the secretion of EPS was notably affected by nitrogen limitation, particularly at 30 °C. Finally, real-time quantitative polymerase chain reaction (qPCR) was used to measure the expression of nitrogen-utilizing genes (<em>ntc</em>A and <em>nif</em>H) and EPS synthesis-related genes (<em>wzb</em> and <em>wzc</em>). The results indicated that under nitrogen-deprived conditions, the expression of each gene was upregulated, and there was a significant correlation between the upregulation of nitrogen-utilizing and EPS synthesis genes (<em>P</em> &lt; 0.05). Our findings suggested that <em>Dolichospermum</em> responded to temperature variation by affecting the formation of heterocysts, impacting its potential nitrogen fixation capacity. Furthermore, the quantity of EPS released was more influenced by nitrogen availability than temperature. This research enhances our comprehension of interconnections between nitrogen deprivation and EPS production under the different temperatures.</p></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"135 ","pages":"Article 102633"},"PeriodicalIF":6.6,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140909858","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}