Harmful Algae最新文献

{"title":"Dominant Dolichospermum and microcystin production in Detroit Lake (Oregon, USA)","authors":"Youchul Jeon ,&nbsp;Ian Struewing ,&nbsp;Kale Clauson ,&nbsp;Nathan Reetz ,&nbsp;Ned Fairchild ,&nbsp;Lacey Goeres-Priest ,&nbsp;Theo W. Dreher ,&nbsp;Rochelle Labiosa ,&nbsp;Kurt D. Carpenter ,&nbsp;Barry H. Rosen ,&nbsp;Eric N. Villegas ,&nbsp;Jingrang Lu","doi":"10.1016/j.hal.2025.102802","DOIUrl":"10.1016/j.hal.2025.102802","url":null,"abstract":"<div><div>The excessive growth of harmful cyanobacteria, including <em>Dolichospermum</em> (formerly known as <em>Anabaena</em>), in freshwater bodies has become a pressing global concern. However, detailed information about the role of <em>Dolichospermum</em> in shaping bloom dynamics and producing cyanotoxins is limited. In this study, a bloom event dominated by <em>Dolichospermum</em> spp. at Detroit Lake (Oregon, USA) was examined from 2019 to 2021. In 2019, early summer cyanobacterial community succession reached up to 8.7 % of total phytoplankton abundance. <em>Dolichospermum</em> was the major microcystin (MC)-producing genus, with peak MC levels of 7.34 μg <em>L</em>⁻¹. The presence of MCs was strongly correlated with the abundance of <em>Dolichospermum</em> (<em>r</em> = 0.84, <em>p</em> &lt; 0.05) and MC synthetase gene, <em>mcyE-Ana</em> (<em>r</em> = 0.63, <em>p</em> &lt; 0.05). Metabolic analyses further showed that the presence of <em>nif</em>/<em>pst</em> genes linked to nitrogen and phosphorus metabolism was dominated by <em>Dolichospermum</em> from the bloom onset until September. In addition, the abundance of <em>Dolichospermum</em> was significantly correlated with the abundance of nitrogen-fixing <em>nif-Ana</em> gene (<em>r</em> = 0.62, <em>p</em> &lt; 0.05). As the lake experienced a longer N and P scarcity period (May to September), the N₂-fixing <em>Dolichospermum</em> was able to dominate over other non-fixing cyanobacteria present, including <em>Microcystis</em> and <em>Planktothrix</em>. Overall, our results facilitate a better understanding of the organism and will help working toward managing/predicting future blooms.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102802"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144161","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":"Algicidal effects of Fictibacillus sp. 5A8M on Margalefidinium polykrikoides through attachment and secretion of extracellular metabolites","authors":"So-Ra Ko ,&nbsp;Ve Van Le ,&nbsp;Sang-Ah Lee ,&nbsp;Seung Ho Baek ,&nbsp;Chi-Yong Ahn","doi":"10.1016/j.hal.2024.102794","DOIUrl":"10.1016/j.hal.2024.102794","url":null,"abstract":"<div><div><em>Margalefidinium polykrikoides</em> blooms inflict significant economic losses on the aquaculture industry. Utilizing algicidal bacteria to mitigate harmful algal blooms (HABs) has emerged as an environment-friendly approach. Despite numerous reports on algicidal bacteria, few studies have thoroughly elucidated their mechanisms against <em>M. polykrikoides</em>. In this study, we present the first documentation of the algicidal effect of a <em>Fictibacillus</em> strain on <em>M. polykrikoides</em>. Strain 5A8M exhibited algicidal effects through physical attachment and the secretion of extracellular algicidal metabolites. The algicidal activity of strain 5A8M was dose- and time-dependent. When inoculated at a ratio of 10 % (v/v), strain 5A8M induced lysis in 97.9 % of <em>M. polykrikoides</em> after 24 h of co-culture. The active chlorophyll-<em>a</em> and transcriptional levels of key genes in <em>M. polykrikoides</em> decreased under the algicidal influence of strain 5A8M. Furthermore, exposure to the cell-free filtrate of strain 5A8M for 12 h triggered lipid peroxidation in <em>M. polykrikoides</em>, resulting in elevated malondialdehyde levels. Analysis via ¹H nuclear magnetic resonance (NMR), ¹³C NMR, and electrospray ionization-mass spectra identified <span>l</span>-phenylalanine and anthranilic acid as the extracellular algicidal metabolites produced by strain 5A8M. The algicidal activity of <span>l</span>-phenylalanine and anthranilic acid (10 μg/ml) against <em>M. polykrikoides</em> reached 74.6 and 72.5 %, respectively, within 24 h of exposure. Collectively, our findings underscore the considerable potential of strain 5A8M in controlling <em>M. polykrikoides</em> HABs.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102794"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143549","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":"Differentiation of microbial communities in coastal seawater before and during an Akashiwo sanguinea (Dinophyceae) bloom in the urban area of Antofagasta city (northern Chile)","authors":"Jingming Hu ,&nbsp;Henry Camerón ,&nbsp;Joaquín I. Rilling ,&nbsp;Marco Campos ,&nbsp;Tay Ruiz-Gil ,&nbsp;Mariela A. Gonzalez ,&nbsp;Gonzalo Gajardo ,&nbsp;Karen Vergara ,&nbsp;Leonardo Guzmán ,&nbsp;Oscar Espinoza-González ,&nbsp;Gonzalo Fuenzalida ,&nbsp;Carlos Riquelme ,&nbsp;Shoko Ueki ,&nbsp;Satoshi Nagai ,&nbsp;Fumito Maruyama ,&nbsp;So Fujiyoshi ,&nbsp;Kyoko Yarimizu ,&nbsp;Ishara Uhanie Perera ,&nbsp;Andrés Ávila ,&nbsp;Jacquelinne J. Acuña ,&nbsp;Milko A. Jorquera","doi":"10.1016/j.hal.2024.102782","DOIUrl":"10.1016/j.hal.2024.102782","url":null,"abstract":"<div><div>Harmful algal blooms (HABs) are highly relevant for public health, the economy, the ecosystem, and biodiversity stability in southern Chile (40° to 53°S), where they occur regularly and are frequently monitored. However, HAB events and their associated microbes in northern Chile (17° to 30°S) remain unknown and difficult to track due to a lack of monitoring, particularly in urban areas. We investigated changes in microbial communities in coastal seawater before and during an <em>Akashiwo sanguinea</em> bloom (B) at two sampling points in Antofagasta city (23°38′39S, 70°24′39W). Seawater samples (filtered at 1 and 0.2 μm) were collected during distinct bloom phases (control, prebloom, and in-bloom), and 16S and 18S rDNA gene libraries were constructed and analyzed via the DNA metabarcoding technique. Our findings indicate that species diversity within the 16S rDNA-based community was greater during the prebloom phase than during the control and in-bloom phases. Conversely, species diversity within the 18S rDNA-based community was lower during the in-bloom phase than during the control and prebloom phases. Independent of the sampling points and fractions, principal coordinate analysis (PCoA) revealed distinct differences in both the 16S and 18S rDNA-based communities between the analyzed bloom phases. Our analysis further revealed that the 16S rDNA-based community was dominated by the Flavobacteriaceae and Rhodobacteraceae families, whose abundance decreased and increased, respectively, during the bloom. As anticipated, the structure of the 18S rDNA-based community was predominantly governed by the Gymnodiniaceae family, specifically the <em>Akashiwo</em> genus, during the bloom. The differentiation in microbial communities was more pronounced in taxa with low abundances than in the dominant taxa. Additionally, co-occurrence network analysis revealed predominantly positive relationships within the microbial communities, particularly during the bloom event. Our analysis also identified several bacterial genera as keystone taxa within the microbial communities, notably members of Pseudomonadota and Bacteroidota.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102782"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144655","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":"Temporal bloom dynamics of the marine dinoflagellate Tripos furca in the Penang Strait","authors":"Nur Fatihah Mohd Azmi ,&nbsp;Kieng Soon Hii ,&nbsp;Minlu Liu ,&nbsp;Siti Nursyuhada Baharudin ,&nbsp;Nur Syazwani Kassim ,&nbsp;Li Keat Lee ,&nbsp;Monaliza Mohd Din ,&nbsp;Nurin I. Mustapa ,&nbsp;Roziawati Mohd Razali ,&nbsp;Haifeng Gu ,&nbsp;Chui Pin Leaw ,&nbsp;Po Teen Lim","doi":"10.1016/j.hal.2025.102799","DOIUrl":"10.1016/j.hal.2025.102799","url":null,"abstract":"<div><div>The dinoflagellate <em>Tripos furca</em>, known for its frequent and massive blooms in coastal waters, has been associated with significant fish mortality in aquaculture areas. In mid-May 2022, a notable bloom event, characterized by intense red discoloration, was observed along the Penang Strait in the northern Malacca Strait. Our field survey identified a high-density bloom of <em>T. furca.</em> To investigate the mechanisms driving the bloom dynamics of this species, monthly sampling was undertaken until the bloom subsided, covering 19 stations across the Penang Strait. Our results showed that the abundances of <em>T. furca</em> changed over time and space, a bloom peak of 8.2 × 10⁵ cells <span>l</span>^-1 was observed in late June, triggered by elevated sea surface temperatures and phosphate availability, while nitrogen was consistently abundant. The bloom's persistence was associated with the influence of the 2020–2022 La Niña and Indian Ocean Dipole, which caused warmer sea temperatures. Metabarcoding of the V7-V9 18S rDNA region revealed high intraspecific genetic diversity within the <em>T. furca</em> bloom subpopulations, suggesting both clonal reproduction and possible sexual processes. The bloom termination was linked to a seasonal shift in temperatures and changes in nutrient regimes that caused a transition of phytoplankton compositions to <em>Noctiluca</em>- and diatom-dominated populations contributed to the bloom's decline. Early detection of the bloom has successfully prevented severe losses to the aquaculture farms in the area, emphasizing the importance of early intervention. This study also enhances our understanding of <em>T. furca</em> bloom dynamics and provides insights into managing harmful algal blooms in tropical coastal regions.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102799"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143513","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":"Germination of phytoplankton resting cells in surface sediments collected from the tributary and littoral zones of Lake Taihu, China","authors":"Aimin Hao ,&nbsp;Yasushi Iseri ,&nbsp;Zhixiong Yan ,&nbsp;Xin Liu ,&nbsp;Min Zhao","doi":"10.1016/j.hal.2024.102780","DOIUrl":"10.1016/j.hal.2024.102780","url":null,"abstract":"<div><div>Phytoplankton responsible for harmful algal blooms (HABs) may originate from the seed bank present in lake and river sediments. In this study, we investigated the germination of phytoplankton in the laboratory from resting cells in sediments collected during spring from four tributary and littoral zones of Lake Taihu (east, south, west, and north), the season before HABs typically occur. We evaluated the potential for germinated phytoplankton to contribute to HABs. We found that 26 species from three phyla including Cyanobacteria, Bacillariophyta, and Chlorophyta germinated from the sediment during the 15-day incubation experiment. The germinated phytoplankton species from the sediments collected in most areas were moderately or very similar, but dominant species exhibited different temporal and spatial distributions. The densities of germinated cells for different phytoplankton species varied at different times during the incubation period. Cyanobacteria <em>Microcystis</em> spp. (1,511 cells g⁻¹ wet weight) and Bacillariophyta <em>Melosira</em> sp. (2,865 cells g⁻¹ wet weight) had the highest cell densities after 10-day incubation, whereas Chlorophyta had the highest cell density (54 cells g⁻¹ wet weight) after 15-day incubation. There was a high number of Cyanobacteria resting cells that could germinate from the seed bank preserved in the sediments, suggesting potential risks of HABs throughout Lake Taihu.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102780"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143710","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":"Genomic diversity in time and space in the toxic diatom Pseudo-nitzschia multistriata","authors":"Svenja Mager ,&nbsp;Francesco Manfellotto ,&nbsp;Antonella Ruggiero ,&nbsp;Viviana Di Tuccio ,&nbsp;Federica Cerino ,&nbsp;Stefano Accoroni ,&nbsp;Tomohiro Nishimura ,&nbsp;Marta Mikhno ,&nbsp;Neri Fattorini ,&nbsp;Timotej Turk Dermastia ,&nbsp;Jasna Arapov ,&nbsp;Sanda Skejic ,&nbsp;Lesley Rhodes ,&nbsp;Kirsty Smith ,&nbsp;Antonio Longo ,&nbsp;Caterina Manzari ,&nbsp;Lisa Campbell ,&nbsp;Graziano Pesole ,&nbsp;Remo Sanges ,&nbsp;Francesca Raffini ,&nbsp;Maria Immacolata Ferrante","doi":"10.1016/j.hal.2024.102791","DOIUrl":"10.1016/j.hal.2024.102791","url":null,"abstract":"<div><div>Understanding the origin and maintenance of genetic diversity is crucial to elucidate population dynamics of unicellular microalgae, their microevolutionary history and their adaptive ability. The planktonic, domoic acid-producing diatom <em>Pseudo-nitzschia multistriata</em> has a ubiquitous distribution in the world oceans and past population genetics studies, based on few genomic loci, have shown a clear temporal structure over different years in the Gulf of Naples (Italy). Despite the ecological and toxicological importance of this organism, detailed information on its diversity across the whole genome and at the population level is still lacking. We collected <em>P. multistriata</em> strains in the Gulf of Naples in five different years, obtained strains from the Adriatic Sea, the Gulf of Mexico and New Zealand coasts, and resequenced the whole genomes of a total of 28 strains at high coverage. While strains from the first three geographical areas were capable of producing the toxin domoic acid, the New Zealand strains had been reported to be non-toxic. A comparison of the domoic acid biosynthetic (dab) genes sequences between toxic and non-toxic strains showed very little variation among the strains, and no disrupting mutation was found in the <em>dab</em> genes in the non-toxic strains. On the other hand, the <em>dab</em> genes showed higher levels of expression in toxic strains than in non-toxic strains, suggesting that, in this species, absence of toxicity is explained by gene regulation rather than <em>dab</em> sequence divergence. Variant analysis showed stronger spatial than temporal genetic structuring and a clear separation was observed between the New Zealand strains and the others, the former having a greater content of genes under selection. Overall, the genomes of the different groups, including strains from a clonal bloom, did not appear to contain major rearrangements. Our findings contribute to enlarging our understanding of diatom diversity, a key factor underlying diatom success, and provide novel data on the longstanding problem of <em>Pseudo-nitzschia</em> toxicity.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102791"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143514","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":"Evidence of global dispersal of the harmful cyanobacterium, Raphidiopsis raciborskii, in lentic freshwaters through migratory waterbirds","authors":"Zhansen Sha ,&nbsp;Huihuang Chen ,&nbsp;Lei Jin ,&nbsp;Qingping Zheng ,&nbsp;Yifan Lu ,&nbsp;Mekiso Y. Sido ,&nbsp;Anusuya Willis ,&nbsp;Cunqi Liu ,&nbsp;Jun Yang","doi":"10.1016/j.hal.2024.102786","DOIUrl":"10.1016/j.hal.2024.102786","url":null,"abstract":"<div><div>The cyanobacterium <em>Raphidiopsis raciborskii</em> has received much attention due to its global distribution and toxin production in freshwater. However, research on understanding the potential factors facilitating its geographical spread, the pattern of increasing range, and long-distance dispersal (LDD) of this species is very limited. In this study, we investigated the role of migratory waterbirds (using domesticated ducks as a proxy) and reservoirs (lentic waterbodies) in global distribution or dispersal of <em>R. raciborskii</em>. First, the global distribution of <em>R. raciborskii</em> under different reservoir scenarios was assessed through meta-analysis. The results showed a significant positive correlation between the global occurrence of <em>R. raciborskii</em> and the global number of reservoirs. Second, testing the capacity of <em>R. raciborskii</em> to spread via endozoochory or ectozoochory with ducks as a proxy of migratory waterbirds. The results indicated that <em>R. raciborskii</em> could be potentially dispersed through ectozoochory but not endozoochory, with a maximum carrying time of ∼96 hours corresponding to a maximum dispersal distance of ∼2300 km. In addition, the duck-carried <em>R. raciborskii</em> survived and could establish populations under suitable conditions. This study provides experimental evidence for the <em>R. raciborskii</em> dispersal through waterbirds. Overall, our results highlight that artificial reservoirs promote the increase of <em>R. raciborskii</em> populations, which could be dispersed across long distance via waterbird ectozoochory, thereby increasing the geographical range of <em>R. raciborskii</em>.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102786"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144651","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":"First description of the fish-killing raphidophyceae Chattonella marina complex in Argentina: From genetics to ichthyotoxicity unveiled","authors":"Delfina Aguiar Juárez ,&nbsp;Jorge I. Mardones ,&nbsp;Ana Flores-Leñero ,&nbsp;Luis Norambuena ,&nbsp;Javier Paredes-Mella ,&nbsp;Eugenia A. Sar ,&nbsp;Inés Sunesen","doi":"10.1016/j.hal.2025.102804","DOIUrl":"10.1016/j.hal.2025.102804","url":null,"abstract":"<div><div>Species of the harmful algal bloom (HAB)-forming genus <em>Chattonella</em> (Raphidophyceae) are responsible for massive fish kills worldwide. Despite this, the genus remains still unexplored in Argentinean waters in the Southwestern Atlantic. Three <em>Chattonella</em> strains (LPCc045, LPCc046, and LPCc047) were isolated and cultured as part of a harmful phytoplankton monitoring program in the marine coastal waters of Buenos Aires Province to determine: 1) taxonomic and genetic identification, 2) pigment compositions, and 3) ichthyotoxic potency and ROS production. Morphological observations (light and transmission electron microscopy) matched classical descriptions of <em>C. marina</em>. Phylogenetic reconstruction using a partial sequence of the ribosomal gene (LSU D1-D2) confirmed the cluster of the three strains within the <em>C. marina</em> complex clade (99 % bootstrap support). Pigment analyses by HPLC showed that the most abundant was chlorophyll-<em>a</em>, followed by fucoxanthin and other carotenoids. Gill cell damage, used as a proxy of cytotoxicity, was assessed using the rainbow trout RTgill-W1 cell-based assay against cell supernatant and intracellular treatments. Cytotoxic potency was positively correlated with cell abundance, with supernatant treatment causing more gill cell damage than intracellular content, reducing gill cell viability down to 60 % of control at 1.9 × 10³ cells mL^-1. Superoxide production was comparable with other globally distributed strains (supernatant 7.63 ± 0.67 pmol O₂^- cell^-1 h^-1; intracellular 8.1 ± 0.56 pmol O₂^- cell^-1 h^-1). This study provides the first morphological, phylogenetic, physiological and toxicological characterization of the fish-killing algae <em>C. marina</em> complex in Argentinean waters.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102804"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143143510","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":"High Ca2+ concentrations enhance Microcystis colony formation through upregulating polysaccharide-, energy metabolism-, and transmembrane transport-related pathways","authors":"Ping Zhang ,&nbsp;Yazhi Zhu ,&nbsp;Chao Xiong ,&nbsp;Yan Xiao ,&nbsp;Kai Li ,&nbsp;Han Wang","doi":"10.1016/j.hal.2025.102806","DOIUrl":"10.1016/j.hal.2025.102806","url":null,"abstract":"<div><div>Colony formation plays a critical role in <em>Microcystis</em> blooms. Previous studies have demonstrated that high Ca²⁺ concentrations can bring about the rapid aggregation of <em>Microcystis aeruginosa</em>, leading to the formation of colonies with morphologies resembling those observed in the wild over extended periods. However, the mechanisms through which high Ca²⁺ levels enhance colony formation remain inadequately understood. This study investigated the impact of Ca²⁺ concentrations on M<em>. aeruginosa</em> colony formation and elucidated the underlying mechanisms. The results indicated that high Ca²⁺ concentrations (≥50 mg/L) significantly enhanced colony formation, with an increase in colony size observed as Ca²⁺ concentrations rose within the range of 1–400 mg/L. In addition, the cell surface hydrophobicity and zeta potential increased with Ca²⁺ concentrations, primarily due to the augmented secretion of extracellular polymeric substances (EPS) and compression of the double electric layer. This decreased interaction energy among <em>Microcystis</em> cells and facilitated colony formation. The energy barrier decreased from 2684.35 KT to 123.64 KT as the Ca²⁺ concentration rose from 10 mg/L to 400 mg/L, indicating a significantly greater propensity for aggregation in the 400 mg/L Ca²⁺ group compared to the control. Additionally, this study found that high Ca²⁺ concentrations upregulated extracellular polysaccharide-, transmembrane transport-, and energy metabolism-related pathways while downregulating photosynthesis-related pathways. This enhanced polysaccharide content in EPS and ultimately promoted colony formation. These findings provide new insights into the role of elevated Ca²⁺ concentrations in <em>Microcystis</em> colony formation, contributing to the advancements in the knowledge of cyanobacterial bloom mechanisms.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102806"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143144159","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":"Phytoplankton assemblage structure, drivers, and thresholds with a focus on harmful algal bloom ecology in the Lake Okeechobee system, Florida, USA","authors":"Viviana Mazzei ,&nbsp;Kristy Lee Sullivan ,&nbsp;Keith Loftin","doi":"10.1016/j.hal.2024.102744","DOIUrl":"10.1016/j.hal.2024.102744","url":null,"abstract":"<div><div>Untangling the complexities of harmful algal bloom (HAB) dynamics is an ongoing effort that requires a fundamental understanding of spatiotemporal phytoplankton patterns and the environmental filters through which assemblages are structured. To this aim, monthly field surveys were conducted from 2019 to 2021 at 21 sites in Lake Okeechobee, Florida – a large, shallow, eutrophic, and heavily managed lake with coastal connectivity that experiences intense and recurrent HABs. Phytoplankton assemblages were strongly spatially structured forming 7 distinct lake zones with significant dissimilarity in composition and total abundance. While successional patterns were not apparent across seasons or wet/dry periods, total phytoplankton abundance was significantly greater towards the end of the wet season. Distance-based linear models using 16 abiotic variables were used to identify significant explanatory variables of spatial and temporal patterns. The spatial model explained 93 % of the variability suggesting deterministic processes largely control spatial patterns. The temporal model explained only 48 % of the temporal variability suggesting stochasticity in lake-wide shifts in assemblages over time. However, the strong spatial structuring of assemblages may preclude lake-wide succession patterns. Total algal abundance metrics were inversely related to nitrate, orthophosphate, and total alkalinity, the strongest explanatory variables of assemblage patterns, suggesting a lag between peak resources and peak abundance as phytoplankton cycle “boom-to-bust” phases. Consistent with this inverse relationship, Threshold Indicator Taxa Analysis returned almost exclusively negative responder indicator taxa for all three explanatory variable gradients. The assemblage-level threshold defined the gradient boundary between boom- and bust-associated indicator taxa. These data contribute novel information about HABs ecology pertinent to management strategies.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"142 ","pages":"Article 102744"},"PeriodicalIF":5.5,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143379148","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}