Pub Date : 2025-12-01Epub Date: 2025-09-17DOI: 10.1016/j.hal.2025.102978
Kaela E. Natwora , Adam J. Heathcote , Mark B. Edlund , Shane E. Bowe , Benjamin J. Kramer , Jake D. Callaghan , Cody S. Sheik
Late summer, recurring cyanobacterial blooms in Lake of the Woods (LOW) are polycyanobacterial and typically dominated by Aphanizomenon flos-aquae. LOW waters are typically nitrogen limited, relative to phosphorus. As such, the dominance of Aphanizomenon flos-aquae, a putative nitrogen-fixing cyanobacterium, suggests that its ability to fix nitrogen may be advantageous and aid in its ability to bloom. This study sought to quantify nitrogen fixation rates and identify cyanotoxin-producing species during the blooms. Throughout the 2021 season, we quantified nutrients, N-fixation rates, microbial community composition, and gene expression to determine who is responsible for cyanotoxin synthesis and nitrogen fixation. We found nitrogen fixation rates increased throughout the season, coincided with the bloom, but likely cannot fully support the bloom’s nitrogen demand. However, the transcription of nitrogenase genes was solely done by less abundant Dolichospermum spp. and not by A. flos-aquae. Genome analysis suggests this population of A. flos-aquae cannot create a functioning nitrogenase, but they do still express the genes to initiate heterocyst differentiation. Microcystin gene transcripts were primarily from Microcystis spp. and Planktothrix spp. and coincided with microcystin concentrations. Interestingly, Planktothrix highly expressed anabaenopeptin genes, suggesting the presence of additional bioactive compounds in LOW. This work suggests that rare cyanobacterial members drive nitrogen fixation, and may be necessary for the seasonal bloom’s function, toxicity, and longevity.
{"title":"Rare cyanobacteria drive nitrogen-fixation and cyanotoxin production in an Aphanizomenon-dominated bloom","authors":"Kaela E. Natwora , Adam J. Heathcote , Mark B. Edlund , Shane E. Bowe , Benjamin J. Kramer , Jake D. Callaghan , Cody S. Sheik","doi":"10.1016/j.hal.2025.102978","DOIUrl":"10.1016/j.hal.2025.102978","url":null,"abstract":"<div><div>Late summer, recurring cyanobacterial blooms in Lake of the Woods (LOW) are polycyanobacterial and typically dominated by <em>Aphanizomenon flos-aquae</em>. LOW waters are typically nitrogen limited, relative to phosphorus. As such, the dominance of <em>Aphanizomenon flos-aquae,</em> a putative nitrogen-fixing cyanobacterium, suggests that its ability to fix nitrogen may be advantageous and aid in its ability to bloom. This study sought to quantify nitrogen fixation rates and identify cyanotoxin-producing species during the blooms. Throughout the 2021 season, we quantified nutrients, N-fixation rates, microbial community composition, and gene expression to determine who is responsible for cyanotoxin synthesis and nitrogen fixation. We found nitrogen fixation rates increased throughout the season, coincided with the bloom, but likely cannot fully support the bloom’s nitrogen demand. However, the transcription of nitrogenase genes was solely done by less abundant <em>Dolichospermum</em> spp. and not by <em>A. flos-aquae.</em> Genome analysis suggests this population of <em>A. flos-aquae</em> cannot create a functioning nitrogenase, but they do still express the genes to initiate heterocyst differentiation. Microcystin gene transcripts were primarily from <em>Microcystis</em> spp. and <em>Planktothrix</em> spp. and coincided with microcystin concentrations. Interestingly, <em>Planktothrix</em> highly expressed anabaenopeptin genes, suggesting the presence of additional bioactive compounds in LOW. This work suggests that rare cyanobacterial members drive nitrogen fixation, and may be necessary for the seasonal bloom’s function, toxicity, and longevity.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"150 ","pages":"Article 102978"},"PeriodicalIF":4.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106562","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}
Pub Date : 2025-12-01Epub Date: 2025-09-27DOI: 10.1016/j.hal.2025.102988
Albert Calbet
Dinoflagellates and ciliates dominate marine microzooplankton, yet widespread toxin production is largely restricted to dinoflagellates. This perspective synthesizes evolutionary, genomic, and ecological drivers of that asymmetry with direct relevance to harmful algal events. From a molecular and biochemical point of view, dinoflagellates possess vast, repeat-rich genomes that support modular PKS/NRPS pathways yielding chemically diverse metabolites, whereas ciliates generally lack complete PKS/NRPS clusters (apart from a few predatory lineages) and instead emphasize behavioral defenses and rapid reproduction. Most confirmed toxic dinoflagellates are photosynthetic or mixotrophic; robust cases in purely heterotrophic taxa are lacking. Despite environment-dependent costs, dinoflagellate metabolites confer grazer deterrence, allelopathy, prey lysis, and potential nutrient acquisition. Socio-economically, paralytic shellfish toxins (saxitoxins) produced by Alexandrium spp., Gymnodinium catenatum, and Pyrodinium bahamense—non-PKS alkaloids associated with sxt genes—are among the most consequential. An integrated approach coupling genomics, metabolomics, targeted bioassays, and in situ observations will clarify when chemical versus behavioral strategies prevail across ocean regimes, thereby improving HAB risk assessment, monitoring, and mitigation.
{"title":"Why do some dinoflagellates produce toxins, whereas ciliates rarely do?","authors":"Albert Calbet","doi":"10.1016/j.hal.2025.102988","DOIUrl":"10.1016/j.hal.2025.102988","url":null,"abstract":"<div><div>Dinoflagellates and ciliates dominate marine microzooplankton, yet widespread toxin production is largely restricted to dinoflagellates. This perspective synthesizes evolutionary, genomic, and ecological drivers of that asymmetry with direct relevance to harmful algal events. From a molecular and biochemical point of view, dinoflagellates possess vast, repeat-rich genomes that support modular PKS/NRPS pathways yielding chemically diverse metabolites, whereas ciliates generally lack complete PKS/NRPS clusters (apart from a few predatory lineages) and instead emphasize behavioral defenses and rapid reproduction. Most confirmed toxic dinoflagellates are photosynthetic or mixotrophic; robust cases in purely heterotrophic taxa are lacking. Despite environment-dependent costs, dinoflagellate metabolites confer grazer deterrence, allelopathy, prey lysis, and potential nutrient acquisition. Socio-economically, paralytic shellfish toxins (saxitoxins) produced by <em>Alexandrium</em> spp., <em>Gymnodinium catenatum</em>, and <em>Pyrodinium bahamense</em>—non-PKS alkaloids associated with sxt genes—are among the most consequential. An integrated approach coupling genomics, metabolomics, targeted bioassays, and in situ observations will clarify when chemical versus behavioral strategies prevail across ocean regimes, thereby improving HAB risk assessment, monitoring, and mitigation.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"150 ","pages":"Article 102988"},"PeriodicalIF":4.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145217440","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}
Pub Date : 2025-12-01Epub Date: 2025-08-29DOI: 10.1016/j.hal.2025.102963
Daniel I. Peters , Lyndsie M. Collis , Morgan D. Shaw , Zak J. Slagle , Henry A. Vanderploeg , James M. Hood
Mesozooplankton (200–2,000 µm) are an important link between primary producers and higher-level consumers and can influence phytoplankton biomass and community structure via grazing. Yet, during cyanobacteria harmful algal blooms (cHABs) we have a poor understanding of which food resources mesozooplankton use and their grazing pressure on phytoplankton. To investigate this, we conducted two gradient-grazer assays to measure mesozooplankton community grazing rates in western Lake Erie during the 2021 cHAB season. We measured mesozooplankton grazing on various food sources, including: total phytoplankton, phytoplankton major taxa (Cyanobacteria, Cryptophyta/Bacillariophyta, Chlorophyta), and autotrophic and heterotrophic picoplankton and nanoplankton. We used these data to estimate mesozooplankton feeding selectivity, the importance of each food source toward mesozooplankton carbon intake, as well as the percent standing stock and growth consumed by mesozooplankton. Mesozooplankton selected for autotrophic and heterotrophic nanoplankton, were neutrally selective for Cryptophyta/Bacillariophyta, and avoided Cyanobacteria and the total phytoplankton community. Mesozooplankton carbon intake was dominated by autotrophic nanoplankton and Cyanobacteria, indicating these food sources may be important in supporting zooplankton production during these cHAB events, although our understanding of the incorporation of Cyanobacteria carbon into mesozooplankton production is limited. While mesozooplankton grazed a small portion of total phytoplankton (1–12 % d-1) and Cyanobacteria (5–13 % d-1) standing stock biomass (<200 µm), they exerted a relatively stronger control on the growth of total phytoplankton (4–38 % d-1) and Cyanobacteria (64–106 % d-1), primarily due to the low measured growth rates of these food items during the study. Our results demonstrate that mesozooplankton graze on Cyanobacteria during cHAB events, and under the right conditions influence cHAB dynamics through direct consumption of Cyanobacteria and indirect effects on Cyanobacteria grazers and competitors.
{"title":"Mesozooplankton grazing patterns and preferences during a cyanobacterial harmful algal bloom (cHAB) in a large eutrophic lake","authors":"Daniel I. Peters , Lyndsie M. Collis , Morgan D. Shaw , Zak J. Slagle , Henry A. Vanderploeg , James M. Hood","doi":"10.1016/j.hal.2025.102963","DOIUrl":"10.1016/j.hal.2025.102963","url":null,"abstract":"<div><div>Mesozooplankton (200–2,000 µm) are an important link between primary producers and higher-level consumers and can influence phytoplankton biomass and community structure via grazing. Yet, during cyanobacteria harmful algal blooms (cHABs) we have a poor understanding of which food resources mesozooplankton use and their grazing pressure on phytoplankton. To investigate this, we conducted two gradient-grazer assays to measure mesozooplankton community grazing rates in western Lake Erie during the 2021 cHAB season. We measured mesozooplankton grazing on various food sources, including: total phytoplankton, phytoplankton major taxa (Cyanobacteria, Cryptophyta/Bacillariophyta, Chlorophyta), and autotrophic and heterotrophic picoplankton and nanoplankton. We used these data to estimate mesozooplankton feeding selectivity, the importance of each food source toward mesozooplankton carbon intake, as well as the percent standing stock and growth consumed by mesozooplankton. Mesozooplankton selected for autotrophic and heterotrophic nanoplankton, were neutrally selective for Cryptophyta/Bacillariophyta, and avoided Cyanobacteria and the total phytoplankton community. Mesozooplankton carbon intake was dominated by autotrophic nanoplankton and Cyanobacteria, indicating these food sources may be important in supporting zooplankton production during these cHAB events, although our understanding of the incorporation of Cyanobacteria carbon into mesozooplankton production is limited. While mesozooplankton grazed a small portion of total phytoplankton (1–12 % d<sup>-1</sup>) and Cyanobacteria (5–13 % d<sup>-1</sup>) standing stock biomass (<200 µm), they exerted a relatively stronger control on the growth of total phytoplankton (4–38 % d<sup>-1</sup>) and Cyanobacteria (64–106 % d<sup>-1</sup>), primarily due to the low measured growth rates of these food items during the study. Our results demonstrate that mesozooplankton graze on Cyanobacteria during cHAB events, and under the right conditions influence cHAB dynamics through direct consumption of Cyanobacteria and indirect effects on Cyanobacteria grazers and competitors.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"150 ","pages":"Article 102963"},"PeriodicalIF":4.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145106956","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}
Pub Date : 2025-11-01Epub Date: 2025-07-23DOI: 10.1016/j.hal.2025.102934
Haifeng Gu , Shuning Huang , Bernd Krock , Chui Pin Leaw , Po Teen Lim , Nur Shazwani Kassim , Hyeon Ho Shin , Kakaskasen Andreas Roeroe , Hao Yuan , Shimaa Hosny , Rimi Sasai , Kazuya Takahashi , Hikmah Thoha , Faisal Hamzah , Dao Viet Ha , Nantapak Potisarn , Thaithaworn Lirdwitayaprasit , Mitsunori Iwataki
The dinoflagellate genus Amphidinium 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 Amphidinium 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 Amphidinium species. Among these were four undescribed species, provisionally named Amphidinium sp. 1 to Amphidinium sp. 4, as well as A. cupulatisquama, A. fijiensis, A. gibbosum, A. massartii, A. operculatum, A. pseudomassartii, A. thermaeum, A. tomasii, and A. trulla, based on both morphological and molecular analyses. DNA metabarcoding detected nine Amphidinium species. While Amphidinium gibbosum and A. tomasii 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 Amphidinium. Species in clade A, including A. uduigamense, A. stirisquamtum, A. operculatum, Amphidinium sp. 1, and Amphidinium 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 Amphidinium species using liquid chromatography-tandem mass spectrometry (LC-MS/MS), but amphidinols were below the detection limit. However, one strain of A. massartii 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 A. operculatum. Our findings underscore the significant diversity and potential risk posed by Amphidinium species in the Asia–Pacific region and beyond.
{"title":"Phylogenetic analysis of the toxigenic genus Amphidinium (Amphidiniales, Dinophyceae) revealed an unexpectedly high diversity in the Asia–Pacific region","authors":"Haifeng Gu , Shuning Huang , Bernd Krock , Chui Pin Leaw , Po Teen Lim , Nur Shazwani Kassim , Hyeon Ho Shin , Kakaskasen Andreas Roeroe , Hao Yuan , Shimaa Hosny , Rimi Sasai , Kazuya Takahashi , Hikmah Thoha , Faisal Hamzah , Dao Viet Ha , Nantapak Potisarn , Thaithaworn Lirdwitayaprasit , 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<sup>−1</sup>) 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":"2025-11-01","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}
Pub Date : 2025-11-01Epub Date: 2025-08-09DOI: 10.1016/j.hal.2025.102938
Ruifang Wang , Wenguang Zhang , Zhongyong Yan , Shiwen Zhou , Ruoyu Guo , Junjie Zheng , Xinfeng Dai , Douding Lu , Qinglin Mu , Jiangning Zeng , Mengmeng Tong , Zhun Li , Pengbin Wang
The epiphytic dinoflagellate genus Fukuyoa, known for producing ciguatoxins, significantly contributes to ciguatera poisoning (CP) in humans and impacts marine food webs. This study reports the first observation and isolation of two Fukuyoa strains, SIO-DF176 and SIO-DF181, from the Xisha Islands in the South China Sea, both identified as Fukuyoa yasumotoi through morphological and molecular techniques. Molecular analysis, including assessments of small subunit (SSU) rDNA, internal transcribed spacer (ITS) rDNA, and large subunit (LSU) rDNA (D1–D3 and D8–D10 regions), revealed close relationships to strains from Japan and Singapore. The analysis of LSU rDNA regions D8–D10 did not differentiate between F. yasumotoi and F. koreensis as distinct morphospecies, underscoring the need for additional physicochemical data from both species for accurate classification. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was employed to examine the profiles of intracellular and extracellular toxins. Strain SIO-DF176 produced 44-methylgambierone at an intracellular concentration of 10.24 pg/cell, while strain SIO-DF181 produced it at 0.59 pg/cell. Additionally, the extracellular toxin of strain SIO-DF181 comprised 44-methylgambierone at 1.34 pg/cell, whereas SIO-DF176 displayed only trace amounts of 44-methylgambierone, which did not reach the limit of quantitation. Strain SIO-DF181 produced gambierone both intracellularly and extracellularly, with concentrations of 56.22 fg/cell and 66.04 fg/cell, respectively, while strain SIO-DF176 did not produce gambierone. Notably, neither strain produced Pacific ciguatoxin (P-CTX-2 or P-CTX-3). This study highlights the presence of F. yasumotoi in the northwestern South China Sea and its potential CP risk.
{"title":"Discovery of Fukuyoa yasumotoi (Dinophyceae) from the Xisha Islands, South China Sea: A comprehensive study on morphology, molecular phylogeny and toxicity","authors":"Ruifang Wang , Wenguang Zhang , Zhongyong Yan , Shiwen Zhou , Ruoyu Guo , Junjie Zheng , Xinfeng Dai , Douding Lu , Qinglin Mu , Jiangning Zeng , Mengmeng Tong , Zhun Li , Pengbin Wang","doi":"10.1016/j.hal.2025.102938","DOIUrl":"10.1016/j.hal.2025.102938","url":null,"abstract":"<div><div>The epiphytic dinoflagellate genus <em>Fukuyoa</em>, known for producing ciguatoxins, significantly contributes to ciguatera poisoning (CP) in humans and impacts marine food webs. This study reports the first observation and isolation of two <em>Fukuyoa</em> strains, SIO-DF176 and SIO-DF181, from the Xisha Islands in the South China Sea, both identified as <em>Fukuyoa yasumotoi</em> through morphological and molecular techniques. Molecular analysis, including assessments of small subunit (SSU) rDNA, internal transcribed spacer (ITS) rDNA, and large subunit (LSU) rDNA (D1–D3 and D8–D10 regions), revealed close relationships to strains from Japan and Singapore. The analysis of LSU rDNA regions D8–D10 did not differentiate between <em>F. yasumotoi</em> and <em>F. koreensis</em> as distinct morphospecies, underscoring the need for additional physicochemical data from both species for accurate classification. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was employed to examine the profiles of intracellular and extracellular toxins. Strain SIO-DF176 produced 44-methylgambierone at an intracellular concentration of 10.24 pg/cell, while strain SIO-DF181 produced it at 0.59 pg/cell. Additionally, the extracellular toxin of strain SIO-DF181 comprised 44-methylgambierone at 1.34 pg/cell, whereas SIO-DF176 displayed only trace amounts of 44-methylgambierone, which did not reach the limit of quantitation. Strain SIO-DF181 produced gambierone both intracellularly and extracellularly, with concentrations of 56.22 fg/cell and 66.04 fg/cell, respectively, while strain SIO-DF176 did not produce gambierone. Notably, neither strain produced Pacific ciguatoxin (P-CTX-2 or P-CTX-3). This study highlights the presence of <em>F. yasumotoi</em> in the northwestern South China Sea and its potential CP risk.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102938"},"PeriodicalIF":4.5,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144886667","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}
Pub Date : 2025-11-01Epub Date: 2025-07-24DOI: 10.1016/j.hal.2025.102921
Carly M. Moreno , Iulia Bibire , Amira Mustafina , Salah Abdelrazig , Sreejith Kottuparambil , Milan Bogosavljevic , Shady A. Amin
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 Pseudo-nitzschia 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.
{"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 , Iulia Bibire , Amira Mustafina , Salah Abdelrazig , Sreejith Kottuparambil , Milan Bogosavljevic , 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":"2025-11-01","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}
Pub Date : 2025-11-01Epub Date: 2025-08-24DOI: 10.1016/j.hal.2025.102958
Wei-Ping Zhang , Yang Zhou , Wen-Jing Sun , Shuo-Yu Zhang , Shu-Feng Zhang , Jae-Seong Lee , Minghua Wang , Da-Zhi Wang
Elevated temperature and nitrogen (N) availability affect dinoflagellates differently; however, their interactive effects remain largely unexplored. This study investigated the physiological and transcriptomic responses of a harmful algal bloom-causing dinoflagellate, Prorocentrum obtusidens, to elevated temperature (22 °C vs. 26 °C) under three N conditions (16 μM nitrate, 8 and 16 μM urea) after 32 days of exposure. Elevated temperature enhanced cell growth across all N conditions, with a more pronounced increase in urea-grown cells, regardless of the insignificant interaction between temperature and N. Physiological responses to elevated temperature varied under N conditions. The nitrate-grown cells had higher particulate organic carbon (POC) content, C:N ratio, and activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO), phosphoenolpyruvate carboxykinase, and urease, but lower particulate organic N (PON) content. The low urea-grown cells showed higher C:N ratio, total carbohydrate content, and activities of carbonic anhydrase (CA), glutamine synthetase (GS), and urease, but lower phosphoenolpyruvate carboxylase activity, total protein, and total antioxidant capacity. The high urea-grown cells exhibited higher maximum photosynthetic efficiency, POC content, C:N ratio, and activities of CA, RubisCO, GS, and urease. Transcriptomic analysis revealed that elevated temperature increased the expression of genes associated with photosynthesis under all N conditions. The nitrate-grown cells produced more energy to mitigate thermal stress, whereas the urea-grown cells decreased energy production. These findings suggest that P. obtusidens is more resilient to future ocean warming when grown with urea, and predictions of dinoflagellate responses to warming oceans should consider N conditions in the environment.
{"title":"Responses of a harmful algal bloom-causing dinoflagellate Prorocentrum obtusidens to elevated temperature and urea","authors":"Wei-Ping Zhang , Yang Zhou , Wen-Jing Sun , Shuo-Yu Zhang , Shu-Feng Zhang , Jae-Seong Lee , Minghua Wang , Da-Zhi Wang","doi":"10.1016/j.hal.2025.102958","DOIUrl":"10.1016/j.hal.2025.102958","url":null,"abstract":"<div><div>Elevated temperature and nitrogen (N) availability affect dinoflagellates differently; however, their interactive effects remain largely unexplored. This study investigated the physiological and transcriptomic responses of a harmful algal bloom-causing dinoflagellate, <em>Prorocentrum obtusidens</em>, to elevated temperature (22 °C vs. 26 °C) under three N conditions (16 μM nitrate, 8 and 16 μM urea) after 32 days of exposure. Elevated temperature enhanced cell growth across all N conditions, with a more pronounced increase in urea-grown cells, regardless of the insignificant interaction between temperature and N. Physiological responses to elevated temperature varied under N conditions. The nitrate-grown cells had higher particulate organic carbon (POC) content, C:N ratio, and activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO), phosphoenolpyruvate carboxykinase, and urease, but lower particulate organic N (PON) content. The low urea-grown cells showed higher C:N ratio, total carbohydrate content, and activities of carbonic anhydrase (CA), glutamine synthetase (GS), and urease, but lower phosphoenolpyruvate carboxylase activity, total protein, and total antioxidant capacity. The high urea-grown cells exhibited higher maximum photosynthetic efficiency, POC content, C:N ratio, and activities of CA, RubisCO, GS, and urease. Transcriptomic analysis revealed that elevated temperature increased the expression of genes associated with photosynthesis under all N conditions. The nitrate-grown cells produced more energy to mitigate thermal stress, whereas the urea-grown cells decreased energy production. These findings suggest that <em>P. obtusidens</em> is more resilient to future ocean warming when grown with urea, and predictions of dinoflagellate responses to warming oceans should consider N conditions in the environment.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102958"},"PeriodicalIF":4.5,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144912873","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}
Pub Date : 2025-11-01Epub Date: 2025-08-25DOI: 10.1016/j.hal.2025.102961
L.Verónica Monroy-Velázquez , Hazel M. Canizales-Flores , Karla A. Camacho-Cruz , Makeda Corbin , Patricia Briones-Fourzán , Brigitta I. van Tussenbroek
Holopelagic Sargassum spp. (Sargassum from hereon) are the founding seaweeds of biodiverse high-sea rafts. The floating rafts provide substrate, shelter, feeding-, and breeding grounds for numerous marine species, making them unique communities in the high seas. Similar to other pelagic systems, the community associated with the rafts is dynamic, inherently variable, and defined by the dynamics of the rafts and interactions between the seaweed and associated fauna. The high biodiversity, including organisms from different trophic levels, results in multiple interactions and complex food webs, which are covered in this review. Additionally, we highlight how floating Sargassum acts as a vector of ecological connectivity, influencing distant ecosystems such as coastal and deep-sea habitats. These cross-ecosystem interactions occur through organism transport, organic matter export and trophic linkages. Understanding these connections is key to recognizing the broader ecological role of Sargassum rafts and the multiple ecosystem services they provide.
{"title":"Faunal associations of holopelagic Sargassum spp. in the subtropical and tropical northern Atlantic: A review","authors":"L.Verónica Monroy-Velázquez , Hazel M. Canizales-Flores , Karla A. Camacho-Cruz , Makeda Corbin , Patricia Briones-Fourzán , Brigitta I. van Tussenbroek","doi":"10.1016/j.hal.2025.102961","DOIUrl":"10.1016/j.hal.2025.102961","url":null,"abstract":"<div><div>Holopelagic <em>Sargassum</em> spp. (<em>Sargassum</em> from hereon) are the founding seaweeds of biodiverse high-sea rafts. The floating rafts provide substrate, shelter, feeding-, and breeding grounds for numerous marine species, making them unique communities in the high seas. Similar to other pelagic systems, the community associated with the rafts is dynamic, inherently variable, and defined by the dynamics of the rafts and interactions between the seaweed and associated fauna. The high biodiversity, including organisms from different trophic levels, results in multiple interactions and complex food webs, which are covered in this review. Additionally, we highlight how floating <em>Sargassum</em> acts as a vector of ecological connectivity, influencing distant ecosystems such as coastal and deep-sea habitats. These cross-ecosystem interactions occur through organism transport, organic matter export and trophic linkages. Understanding these connections is key to recognizing the broader ecological role of <em>Sargassum</em> rafts and the multiple ecosystem services they provide.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102961"},"PeriodicalIF":4.5,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144920281","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}
Pub Date : 2025-11-01Epub Date: 2025-07-24DOI: 10.1016/j.hal.2025.102933
Nathan F. Putman , R. Taylor Beyea , Emilie G. Ackerman , Joaquin Trinanes , Matthieu Le Hénaff , Chuanmin Hu , Rick Lumpkin
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 Sargassum 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.
{"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 , R. Taylor Beyea , Emilie G. Ackerman , Joaquin Trinanes , Matthieu Le Hénaff , Chuanmin Hu , 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":"2025-11-01","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}
Pub Date : 2025-11-01Epub Date: 2025-08-05DOI: 10.1016/j.hal.2025.102939
Danielle C. Hatt , Lowell Andrew R. Iporac , Julianna T. Arita , Natalie K. Bally , Ligia Collado-Vides
The mass accumulation of pelagic species of the genus Sargassum (referred to as sargassum) on coastlines is a pressing socio-environmental issue that spans the tropical Atlantic region. Since the unprecedented increase in biomass in 2011, innovative monitoring approaches have emerged to track sargassum across varying spatial and temporal scales, including satellite imagery, aerial imagery, citizen science, and traditional in situ evaluations of biomass. This study systematically reviewed peer-reviewed literature (2011–2024), gray literature, and open science sources to assess the methodologies used to monitor sargassum. Conversations with select experts involved in established monitoring programs, often tailored to end users such as government agencies or local communities, provided additional insight into the multidimensional nature of monitoring strategies. We found that while satellite imagery is commonly paired with in situ biomass evaluations in the literature, citizen science is emerging as a scalable, accessible tool to fill spatial and temporal gaps, despite limited representation in scientific publications. Aerial imagery is frequently mentioned as a promising supplement to both satellite and citizen science efforts, but its practical use remains limited. Field-based estimations remain the most direct method to quantify biomass but are constrained by spatial scale, funding, personnel, and feasibility for long-term monitoring. This review highlights the need for improved collaboration and data sharing across programs and scales, and creating platforms to return information to users. Strengthening connections among all involved in the design, participation, and use of community-based monitoring products, including a stronger relationship and clear benefits, will be essential to provide continuity and improve management strategies for this evolving environmental phenomenon.
{"title":"Assessing the interconnectivity across complex dimensions of monitoring pelagic species of Sargassum and the role of citizen science","authors":"Danielle C. Hatt , Lowell Andrew R. Iporac , Julianna T. Arita , Natalie K. Bally , Ligia Collado-Vides","doi":"10.1016/j.hal.2025.102939","DOIUrl":"10.1016/j.hal.2025.102939","url":null,"abstract":"<div><div>The mass accumulation of pelagic species of the genus <em>Sargassum</em> (referred to as sargassum) on coastlines is a pressing socio-environmental issue that spans the tropical Atlantic region. Since the unprecedented increase in biomass in 2011, innovative monitoring approaches have emerged to track sargassum across varying spatial and temporal scales, including satellite imagery, aerial imagery, citizen science, and traditional in situ evaluations of biomass. This study systematically reviewed peer-reviewed literature (2011–2024), gray literature, and open science sources to assess the methodologies used to monitor sargassum. Conversations with select experts involved in established monitoring programs, often tailored to end users such as government agencies or local communities, provided additional insight into the multidimensional nature of monitoring strategies. We found that while satellite imagery is commonly paired with in situ biomass evaluations in the literature, citizen science is emerging as a scalable, accessible tool to fill spatial and temporal gaps, despite limited representation in scientific publications. Aerial imagery is frequently mentioned as a promising supplement to both satellite and citizen science efforts, but its practical use remains limited. Field-based estimations remain the most direct method to quantify biomass but are constrained by spatial scale, funding, personnel, and feasibility for long-term monitoring. This review highlights the need for improved collaboration and data sharing across programs and scales, and creating platforms to return information to users. Strengthening connections among all involved in the design, participation, and use of community-based monitoring products, including a stronger relationship and clear benefits, will be essential to provide continuity and improve management strategies for this evolving environmental phenomenon.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102939"},"PeriodicalIF":4.5,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144988629","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}
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