Pub Date : 2025-08-14DOI: 10.1016/j.hal.2025.102945
Ruoyu Guo , Xu-Dong Lian , Ruifang Wang , Yue Jiang , Sungmo Kang , Chenjie Zhu , Xiao Ma , Shiwen Zhou , Leo Lai Chan , Xinfeng Dai , Pengbin Wang , Zhun Li
Coolia malayensis is a benthic dinoflagellate widely distributed in tropical to subtropical coastal waters, with some strains exhibiting cytotoxicity, indicating potential ecological and toxicological roles. This study investigated the genetic diversity and adaptability of C. malayensis strains across diverse environmental conditions in Chinese coastal waters. Three distinct genotypes, Genotype 1 (strain DF553), Genotype 2 (DF630), and Genotype 3 comprising strains DF307, DF316, and DF364, were confirmed by the large subunit (LSU) ribosomal DNA phylogenetic analysis, with a protein profiling by the matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry providing supporting evidence for the phenotypic differentiations. The results of growth experiments conducted under varying temperature (15°C to 30°C) and salinity (15 to 35) conditions demonstrated genotype-specific environmental preferences: strain DF553 exhibited an optimal growth at 25°C and 30 salinity, strain DF630 at 30°C and 30, while strains DF307, DF316, and DF364 displayed a wider range of adaptive capacities. These results emphasized the ecological flexibility and adaptive potential of C. malayensis, indicating its ability to thrive in diverse marine environments. The study underscores the importance of genotypic variation in predicting species responses to environmental fluctuations, offering valuable insights for marine ecosystem management and mitigation of harmful algal blooms.
{"title":"Genotypic diversity and growth responses to temperature and salinity variations of Coolia malayensis (Gonyaulacales, Dinophyceae) in Chinese coastal waters","authors":"Ruoyu Guo , Xu-Dong Lian , Ruifang Wang , Yue Jiang , Sungmo Kang , Chenjie Zhu , Xiao Ma , Shiwen Zhou , Leo Lai Chan , Xinfeng Dai , Pengbin Wang , Zhun Li","doi":"10.1016/j.hal.2025.102945","DOIUrl":"10.1016/j.hal.2025.102945","url":null,"abstract":"<div><div><em>Coolia malayensis</em> is a benthic dinoflagellate widely distributed in tropical to subtropical coastal waters, with some strains exhibiting cytotoxicity, indicating potential ecological and toxicological roles. This study investigated the genetic diversity and adaptability of <em>C. malayensis</em> strains across diverse environmental conditions in Chinese coastal waters. Three distinct genotypes, Genotype 1 (strain DF553), Genotype 2 (DF630), and Genotype 3 comprising strains DF307, DF316, and DF364, were confirmed by the large subunit (LSU) ribosomal DNA phylogenetic analysis, with a protein profiling by the matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry providing supporting evidence for the phenotypic differentiations. The results of growth experiments conducted under varying temperature (15°C to 30°C) and salinity (15 to 35) conditions demonstrated genotype-specific environmental preferences: strain DF553 exhibited an optimal growth at 25°C and 30 salinity, strain DF630 at 30°C and 30, while strains DF307, DF316, and DF364 displayed a wider range of adaptive capacities. These results emphasized the ecological flexibility and adaptive potential of <em>C. malayensis</em>, indicating its ability to thrive in diverse marine environments. The study underscores the importance of genotypic variation in predicting species responses to environmental fluctuations, offering valuable insights for marine ecosystem management and mitigation of harmful algal blooms.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102945"},"PeriodicalIF":4.5,"publicationDate":"2025-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144865732","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 : 2025-08-13DOI: 10.1016/j.hal.2025.102944
Lianbao Chi , Xiaona Zhang , Yongquan Yuan , Huihui Shen , Zhiming Yu , Xiuxian Song
Karenia brevis blooms have emerged as an increasing global concern due to their capacity to produce brevetoxins (BTXs), which are potent marine neurotoxins. The ecological impact of BTXs is significantly modulated by the natural attenuation process, with photodegradation playing a pivotal role. Nevertheless, the fate of BTXs following photodegradation remains inadequately understood. This study elucidates the photodegradation kinetics of three representative BTXs and identifies their transformation products (TPs). The observed first-order photodegradation rate coefficient, based on the logarithmic transformation of dissolved BTXs concentrations against irradiation time, ranged from 0.84 to 2.49 h-1. Utilizing high-resolution liquid chromatography‒mass spectrometry, three, four, and five TPs were identified for BTX-1, BTX-2, and BTX-3, respectively. All TPs underwent substantial structural modifications with significant mass reductions. Proposed primary photodegradation pathways encompass Ring-opening, alkyl chain cleavage, hydrolysis, dehydroxylation, epoxidation, and β-elimination. Additionally, in silico prediction indicated that the biodegradability of TPs was significantly higher than that of the parent toxins. However, certain TPs exhibited greater toxicities compared to their parent toxins. The coexistence of multiple BTXs and TPs may lead to synergistic toxicity, thereby posing secondary risks to aquatic organisms. Overall, this research will enhance a comprehensive understanding of the environmental behaviors and risks associated with BTXs.
{"title":"Deciphering the photodegradation fate of Brevetoxins: Kinetics, degradation pathways, and toxicity evaluation","authors":"Lianbao Chi , Xiaona Zhang , Yongquan Yuan , Huihui Shen , Zhiming Yu , Xiuxian Song","doi":"10.1016/j.hal.2025.102944","DOIUrl":"10.1016/j.hal.2025.102944","url":null,"abstract":"<div><div><em>Karenia brevis</em> blooms have emerged as an increasing global concern due to their capacity to produce brevetoxins (BTXs), which are potent marine neurotoxins. The ecological impact of BTXs is significantly modulated by the natural attenuation process, with photodegradation playing a pivotal role. Nevertheless, the fate of BTXs following photodegradation remains inadequately understood. This study elucidates the photodegradation kinetics of three representative BTXs and identifies their transformation products (TPs). The observed first-order photodegradation rate coefficient, based on the logarithmic transformation of dissolved BTXs concentrations against irradiation time, ranged from 0.84 to 2.49 h<sup>-1</sup>. Utilizing high-resolution liquid chromatography‒mass spectrometry, three, four, and five TPs were identified for BTX-1, BTX-2, and BTX-3, respectively. All TPs underwent substantial structural modifications with significant mass reductions. Proposed primary photodegradation pathways encompass Ring-opening, alkyl chain cleavage, hydrolysis, dehydroxylation, epoxidation, and β-elimination. Additionally, <em>in silico</em> prediction indicated that the biodegradability of TPs was significantly higher than that of the parent toxins. However, certain TPs exhibited greater toxicities compared to their parent toxins. The coexistence of multiple BTXs and TPs may lead to synergistic toxicity, thereby posing secondary risks to aquatic organisms. Overall, this research will enhance a comprehensive understanding of the environmental behaviors and risks associated with BTXs.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102944"},"PeriodicalIF":4.5,"publicationDate":"2025-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144903026","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 : 2025-08-12DOI: 10.1016/j.hal.2025.102943
Guanbing Feng , Jingfei Liu , Ning Wang , Lihua Xia , Jiahao Fan , Qingqing Mu , Yuqing Sun , Peiming He , Jianheng Zhang
Green tides serve as indicators of coastal ecosystem imbalance, yet their interannual variability and driving mechanisms remain poorly characterized. This study develops the Comprehensive Green Tide Magnitude Index (GTMI) to quantitatively classify South Yellow Sea green tide events (2008–2023) into large- and small-magnitude years. By integrating Seasonal-Trend decomposition (STL) and Random Forest Regression (RFR), we systematically decompose the trend and seasonal components of the time series while preserving its integrity, significantly enhancing the ability to interpret key environmental factors. The results identify silicate, salinity, nitrate, and sea surface temperature as key controlling factors influencing both the magnitude and periodic variability of green tide outbreaks. A partial least squares path model (PLS-PM) reveals a potential mechanism involving nutrient competition, biological interaction, and hydrological regulation. Nutrient overlap between Ulva and phytoplankton triggers resource exclusion, enabling Ulva to dominate through niche preemption and suppress phytoplankton growth, while hydrological forces amplify Ulva expansion and inhibitory effects. The GTMI provides a quantitative assessment tool, and the STL-RF-PLS framework advances mechanistic understanding of multifactorial drivers, offering critical insights for regional green tide mitigation and coastal ecosystem management.
{"title":"Synergistic effects of nutrient competition, biotic interactions, and hydrological regulation drive green tide outbreaks in the South Yellow Sea","authors":"Guanbing Feng , Jingfei Liu , Ning Wang , Lihua Xia , Jiahao Fan , Qingqing Mu , Yuqing Sun , Peiming He , Jianheng Zhang","doi":"10.1016/j.hal.2025.102943","DOIUrl":"10.1016/j.hal.2025.102943","url":null,"abstract":"<div><div>Green tides serve as indicators of coastal ecosystem imbalance, yet their interannual variability and driving mechanisms remain poorly characterized. This study develops the Comprehensive Green Tide Magnitude Index (GTMI) to quantitatively classify South Yellow Sea green tide events (2008–2023) into large- and small-magnitude years. By integrating Seasonal-Trend decomposition (STL) and Random Forest Regression (RFR), we systematically decompose the trend and seasonal components of the time series while preserving its integrity, significantly enhancing the ability to interpret key environmental factors. The results identify silicate, salinity, nitrate, and sea surface temperature as key controlling factors influencing both the magnitude and periodic variability of green tide outbreaks. A partial least squares path model (PLS-PM) reveals a potential mechanism involving nutrient competition, biological interaction, and hydrological regulation. Nutrient overlap between <em>Ulva</em> and phytoplankton triggers resource exclusion, enabling <em>Ulva</em> to dominate through niche preemption and suppress phytoplankton growth, while hydrological forces amplify <em>Ulva</em> expansion and inhibitory effects. The GTMI provides a quantitative assessment tool, and the STL-RF-PLS framework advances mechanistic understanding of multifactorial drivers, offering critical insights for regional green tide mitigation and coastal ecosystem management.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102943"},"PeriodicalIF":4.5,"publicationDate":"2025-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144852956","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 : 2025-08-11DOI: 10.1016/j.hal.2025.102942
Albano Diez-Chiappe, María Ángeles Muñoz-Martín, Samuel Cirés, Antonio Quesada, Elvira Perona
Toxic Microcoleus remains poorly studied in mountain freshwaters, where cyanotoxins threaten public and ecological health, particularly in protected areas that hold high ecological value and attract a high density of visitors. This study investigated the proliferation of cyanobacterial mats and cyanotoxin production in two high-mountain rivers flowing through a National Park. Our results confirmed the widespread and recurrent proliferation of Microcoleus-dominated mats containing the neurotoxins anatoxin-a and homoanatoxin-a. Mat coverage showed potentially hazardous levels, reaching up to 40-50 % of the riverbed. Comprehensive genetic characterization through metabarcoding sequencing (targeting 16S rRNA and cyanotoxin-biosynthesis genes) revealed a significant differential distribution of Microcoleus genotypes between two adjacent high-mountain rivers, as well as the persistence of the anaF gene from Microcoleus. Although saxitoxins and microcystins were not detected, the sxtA gene closely related to Scytonema and mcyE from Nostoc-like species were occasionally found. This is the first report of abundant proliferations of anatoxin-producing Microcoleus in Spain, broadening research into Southern and Mediterranean Europe, where toxic Microcoleus remains underreported. These results reinforce the importance of genetic analyses as valuable tools for understanding Microcoleus population dynamics. Our findings highlight that toxic mats should be considered a potential threat in minimally impacted mountain freshwaters, especially those frequently visited for their high ecological value.
{"title":"Protected high-mountain rivers harbor widespread toxic Microcoleus-dominated mats with distinct genetic profiles","authors":"Albano Diez-Chiappe, María Ángeles Muñoz-Martín, Samuel Cirés, Antonio Quesada, Elvira Perona","doi":"10.1016/j.hal.2025.102942","DOIUrl":"10.1016/j.hal.2025.102942","url":null,"abstract":"<div><div>Toxic <em>Microcoleus</em> remains poorly studied in mountain freshwaters, where cyanotoxins threaten public and ecological health, particularly in protected areas that hold high ecological value and attract a high density of visitors. This study investigated the proliferation of cyanobacterial mats and cyanotoxin production in two high-mountain rivers flowing through a National Park. Our results confirmed the widespread and recurrent proliferation of <em>Microcoleus</em>-dominated mats containing the neurotoxins anatoxin-a and homoanatoxin-a. Mat coverage showed potentially hazardous levels, reaching up to 40-50 % of the riverbed. Comprehensive genetic characterization through metabarcoding sequencing (targeting 16S rRNA and cyanotoxin-biosynthesis genes) revealed a significant differential distribution of <em>Microcoleus</em> genotypes between two adjacent high-mountain rivers, as well as the persistence of the <em>anaF</em> gene from <em>Microcoleus.</em> Although saxitoxins and microcystins were not detected, the <em>sxtA</em> gene closely related to <em>Scytonema</em> and <em>mcyE</em> from <em>Nostoc</em>-like species were occasionally found. This is the first report of abundant proliferations of anatoxin-producing <em>Microcoleus</em> in Spain, broadening research into Southern and Mediterranean Europe, where toxic <em>Microcoleus</em> remains underreported. These results reinforce the importance of genetic analyses as valuable tools for understanding <em>Microcoleus</em> population dynamics. Our findings highlight that toxic mats should be considered a potential threat in minimally impacted mountain freshwaters, especially those frequently visited for their high ecological value.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102942"},"PeriodicalIF":4.5,"publicationDate":"2025-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144841945","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 : 2025-08-10DOI: 10.1016/j.hal.2025.102941
Zhe Tao , Yuyang Liu , Xiaohan Liu , Caixia Yue , Xiaoying Song , Zhangxi Hu , Shuo Shi , Ruoxi Li , Yunyan Deng , Lixia Shang , Zhaoyang Chai , Ying Zhong Tang
<div><div>Over the past several decades, harmful algal blooms (HABs) caused by dinoflagellates frequently occurred along the coastal waters of China, with an increasing number of emerging HAB species. Due to the vital roles played by the resting cyst in the ecology of HABs, the investigation of resting cyst diversity and distribution of dinoflagellates, those causing HABs in particular, in marine sediment is of great significance. However, it has been difficult to unambiguously identify cyst species via obtaining both morphological and molecular evidence due to a variety of technological limitations (e.g. extremely simple morphology and/or small sizes of many cyst species). Although the application of high-throughput metabarcoding analysis has greatly improved the efficiency (high throughput) and accuracy (molecular identification) of cyst identification, lacking morphological evidence makes it less convincing because the sequences obtained with this approach may be doubted to be from fragmental vegetative cells or relics of eDNA. Furthermore, insufficient sequencing depths commonly adopted in studies using this technique together with the extremely large and widely-varying genome sizes of dinoflagellates have also led to the potential oversight of those species having small cell sizes and/or relatively low abundances. In this study, we employed a single-cyst morpho-molecular method (ScPCR sequencing) to identify dinoflagellate cysts from 23 sediments collected from all four seas of China. From 702 individually picked-up, micrographed, and sequenced cysts, we identified 127 species of dinoflagellates, with 63 (49.6%) fully identified to well-described species, and 64 (50.4%) that could not be determined for their species identity due to the unavailability of reference sequences. Notably, among the 63 fully-identified species, 6 had not been reported from China before, 19 are well-documented HABs-causing species (e.g. 8 <em>Alexandrium</em> spp., <em>Gymnodinium catenatum, Karenia mikimotoi</em>), and 22 were identified for the first time from one of the four seas of China. In addition, from 44 sediment samples that were collected from the East China Sea (ECS, a “hotspot” of HABs in China) and pre-processed with the sodium polytungstate protocol to concentrate their cyst assemblages, we fully identified 61 species of dinoflagellate cysts via metabarcoding analysis, including 27 species causing HABs, 10 as new records in Chinese waters, 13 as new records in the ECS, and 10 previously unreported as cyst producers. It is noteworthy that 7 (35%) of the 20 cyst species identified via ScPCR sequencing from the ECS were not detected by the metabarcoding analysis. Contrasting to that 64 species of dinoflagellate cysts had been unequivocally identified from China by 2021, the total number of cyst species identified in this study using ScPCR sequencing demonstrated the robustness of the detection technique. This study also suggests that the species diversit
{"title":"Single-cyst morpho-molecular identification detected an unexpected high species diversity of dinoflagellate resting cysts from the coastal seas of China","authors":"Zhe Tao , Yuyang Liu , Xiaohan Liu , Caixia Yue , Xiaoying Song , Zhangxi Hu , Shuo Shi , Ruoxi Li , Yunyan Deng , Lixia Shang , Zhaoyang Chai , Ying Zhong Tang","doi":"10.1016/j.hal.2025.102941","DOIUrl":"10.1016/j.hal.2025.102941","url":null,"abstract":"<div><div>Over the past several decades, harmful algal blooms (HABs) caused by dinoflagellates frequently occurred along the coastal waters of China, with an increasing number of emerging HAB species. Due to the vital roles played by the resting cyst in the ecology of HABs, the investigation of resting cyst diversity and distribution of dinoflagellates, those causing HABs in particular, in marine sediment is of great significance. However, it has been difficult to unambiguously identify cyst species via obtaining both morphological and molecular evidence due to a variety of technological limitations (e.g. extremely simple morphology and/or small sizes of many cyst species). Although the application of high-throughput metabarcoding analysis has greatly improved the efficiency (high throughput) and accuracy (molecular identification) of cyst identification, lacking morphological evidence makes it less convincing because the sequences obtained with this approach may be doubted to be from fragmental vegetative cells or relics of eDNA. Furthermore, insufficient sequencing depths commonly adopted in studies using this technique together with the extremely large and widely-varying genome sizes of dinoflagellates have also led to the potential oversight of those species having small cell sizes and/or relatively low abundances. In this study, we employed a single-cyst morpho-molecular method (ScPCR sequencing) to identify dinoflagellate cysts from 23 sediments collected from all four seas of China. From 702 individually picked-up, micrographed, and sequenced cysts, we identified 127 species of dinoflagellates, with 63 (49.6%) fully identified to well-described species, and 64 (50.4%) that could not be determined for their species identity due to the unavailability of reference sequences. Notably, among the 63 fully-identified species, 6 had not been reported from China before, 19 are well-documented HABs-causing species (e.g. 8 <em>Alexandrium</em> spp., <em>Gymnodinium catenatum, Karenia mikimotoi</em>), and 22 were identified for the first time from one of the four seas of China. In addition, from 44 sediment samples that were collected from the East China Sea (ECS, a “hotspot” of HABs in China) and pre-processed with the sodium polytungstate protocol to concentrate their cyst assemblages, we fully identified 61 species of dinoflagellate cysts via metabarcoding analysis, including 27 species causing HABs, 10 as new records in Chinese waters, 13 as new records in the ECS, and 10 previously unreported as cyst producers. It is noteworthy that 7 (35%) of the 20 cyst species identified via ScPCR sequencing from the ECS were not detected by the metabarcoding analysis. Contrasting to that 64 species of dinoflagellate cysts had been unequivocally identified from China by 2021, the total number of cyst species identified in this study using ScPCR sequencing demonstrated the robustness of the detection technique. This study also suggests that the species diversit","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102941"},"PeriodicalIF":4.5,"publicationDate":"2025-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144828289","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 : 2025-08-09DOI: 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":"2025-08-09","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 : 2025-08-08DOI: 10.1016/j.hal.2025.102940
Brian E. Lapointe, Deanna F. Webber, Rachel A. Brewton
This review examines the changing distribution of pelagic Sargassum in the North Atlantic over the past four decades and how boundary current circulation enhances nutrient supply, productivity, and growth. Early explorers first described Sargassum in the Sargasso Sea and recognized the physical connectivity of “Gulfweed” to neritic populations in the Gulf of Mexico/America. In the 1980s, studies showed that Sargassum is more productive in neritic waters where it has lower carbon to nitrogen (C:N) and C to phosphorus (C:P) ratios. Sargassum productivity and growth are limited by both N and P, although P is often the primary limiting nutrient. The origin of the Great Atlantic Sargassum Belt (GASB) in 2011 was north the Amazon River mouth, suggesting this riverine nutrient source contributed to its development. This is supported by Sargassum tissue analysis and biomass increases/decreases between extreme flood/drought years in the Amazon basin. Comparison of the nutrient composition of Sargassum tissue (n= 849) from the 1980s with post-2010 and post-2020 showed increased %C (28 %), %N (55 % overall; 95 % in the Sargasso Sea), and N:P (50 %) but decreased %P (6 %) over the past four decades. Measurement of stable N isotopes (δ15N) in Sargassum revealed enriched δ15N correlated with increasing %N, pointing to the importance of terrestrial runoff, wastewater discharges, and coastal upwelling as potential N sources. We additionally report enriched levels of N and P in the western tropical region of the GASB, illustrating the importance of recent nutrient enrichment, especially P, to the excessive Sargassum biomass in the GASB.
{"title":"Productivity, growth, and biogeochemistry of pelagic Sargassum in a changing world","authors":"Brian E. Lapointe, Deanna F. Webber, Rachel A. Brewton","doi":"10.1016/j.hal.2025.102940","DOIUrl":"10.1016/j.hal.2025.102940","url":null,"abstract":"<div><div>This review examines the changing distribution of pelagic <em>Sargassum</em> in the North Atlantic over the past four decades and how boundary current circulation enhances nutrient supply, productivity, and growth. Early explorers first described <em>Sargassum</em> in the Sargasso Sea and recognized the physical connectivity of “Gulfweed” to neritic populations in the Gulf of Mexico/America. In the 1980s, studies showed that <em>Sargassum</em> is more productive in neritic waters where it has lower carbon to nitrogen (C:N) and C to phosphorus (C:P) ratios. <em>Sargassum</em> productivity and growth are limited by both N and P, although P is often the primary limiting nutrient. The origin of the Great Atlantic <em>Sargassum</em> Belt (GASB) in 2011 was north the Amazon River mouth, suggesting this riverine nutrient source contributed to its development. This is supported by <em>Sargassum</em> tissue analysis and biomass increases/decreases between extreme flood/drought years in the Amazon basin. Comparison of the nutrient composition of <em>Sargassum</em> tissue (<em>n</em>= 849) from the 1980s with post-2010 and post-2020 showed increased %C (28 %), %N (55 % overall; 95 % in the Sargasso Sea), and N:P (50 %) but decreased %P (6 %) over the past four decades. Measurement of stable N isotopes (δ<sup>15</sup>N) in <em>Sargassum</em> revealed enriched δ<sup>15</sup>N correlated with increasing %N, pointing to the importance of terrestrial runoff, wastewater discharges, and coastal upwelling as potential N sources. We additionally report enriched levels of N and P in the western tropical region of the GASB, illustrating the importance of recent nutrient enrichment, especially P, to the excessive <em>Sargassum</em> biomass in the GASB.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"150 ","pages":"Article 102940"},"PeriodicalIF":4.5,"publicationDate":"2025-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145047228","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 : 2025-08-05DOI: 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":"2025-08-05","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}
Harmful cyanobacterial blooms (cyanoHABs) typically occur in human-impacted eutrophic lakes suffering from nutrient pollution, but they also occur in pristine lakes spanning the trophic gradient. The drivers and dynamics of blooms in these oligotrophic lakes remain understudied. CyanoHABs alter the composition of bacterioplankton with increases in specific cyanobacteria strains, as well as shifts in heterotrophic taxa. Bacterioplankton community shifts during cyanoHABs can be somewhat predictable but have been only studied in a limited number of lakes, mostly eutrophic and impacted by development. The Cascade Mountains (USA) offer a novel setting to examine microcystin variation and shifts in bacterioplankton communities across trophic in relatively undeveloped lakes with documented cyanoHABs. Using physicochemical measurements, time-integrated toxin monitoring, and 16S rRNA gene sequencing, we explored associations of bacterioplankton communities with cyanoHABs and toxins within a season, as well as across lakes and years. In Cascade Mountain lakes, bacterioplankton communities and cyanoHABs varied spatially, reflecting differences in trophic state, among other factors. The cyanotoxin microcystin exceeded the drinking water chronic exposure level (1 ppb) in two lakes, during which cyanobacteria exceeded 20 % of the bacterioplankton community. Bacterioplankton composition changed notably during the cyanoHAB events, varying with bloom toxicity and lake trophic state. These compositional differences were not only driven by increases in cyanobacteria, specifically from the order Nostocales, but also heterotrophic bacteria such as from the orders Burkholderiales and Cytophagales. Therefore, bacterioplankton composition can potentially be consistent indicators of cyanoHABs and toxicity, more so than climatic factors across lakes that span substantial trophic gradients.
{"title":"Shifts in bacterioplankton during cyanobacterial blooms reflect bloom toxicity and lake trophic state","authors":"Lara Jansen , Nicolas Tromas , Angela Strecker , Jesse Shapiro","doi":"10.1016/j.hal.2025.102937","DOIUrl":"10.1016/j.hal.2025.102937","url":null,"abstract":"<div><div>Harmful cyanobacterial blooms (cyanoHABs) typically occur in human-impacted eutrophic lakes suffering from nutrient pollution, but they also occur in pristine lakes spanning the trophic gradient. The drivers and dynamics of blooms in these oligotrophic lakes remain understudied. CyanoHABs alter the composition of bacterioplankton with increases in specific cyanobacteria strains, as well as shifts in heterotrophic taxa. Bacterioplankton community shifts during cyanoHABs can be somewhat predictable but have been only studied in a limited number of lakes, mostly eutrophic and impacted by development. The Cascade Mountains (USA) offer a novel setting to examine microcystin variation and shifts in bacterioplankton communities across trophic in relatively undeveloped lakes with documented cyanoHABs. Using physicochemical measurements, time-integrated toxin monitoring, and 16S rRNA gene sequencing, we explored associations of bacterioplankton communities with cyanoHABs and toxins within a season, as well as across lakes and years. In Cascade Mountain lakes, bacterioplankton communities and cyanoHABs varied spatially, reflecting differences in trophic state, among other factors. The cyanotoxin microcystin exceeded the drinking water chronic exposure level (1 ppb) in two lakes, during which cyanobacteria exceeded 20 % of the bacterioplankton community<em>.</em> Bacterioplankton composition changed notably during the cyanoHAB events, varying with bloom toxicity and lake trophic state. These compositional differences were not only driven by increases in cyanobacteria, specifically from the order Nostocales, but also heterotrophic bacteria such as from the orders Burkholderiales and Cytophagales. Therefore, bacterioplankton composition can potentially be consistent indicators of cyanoHABs and toxicity, more so than climatic factors across lakes that span substantial trophic gradients.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102937"},"PeriodicalIF":4.5,"publicationDate":"2025-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144764123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-27DOI: 10.1016/j.hal.2025.102935
Ariel R. Donovan , Zachary R. Laughrey , Robin A. Femmer , Sarena L. Senegal , Keith A. Loftin
In the first nationwide study of cyanotoxins in U.S. estuaries, algal toxins, cyanotoxins, chlorophyll, and salinity were measured in samples collected during the National Coastal Condition Assessment 2015. Anatoxin-a (ANAA), cylindrospermopsin (CYLS), domoic acid (DMAC), and microcystins (MCs) were detected by LC/MS/MS in 0.6, 0.9, 8.3, and 2.0 % of samples with mean concentrations of detections of 0.13, 0.13, 0.53, and 0.49 µg/L, respectively. MCs by ELISA were also evaluated, and 4.0 % of samples had measurable MCs with a mean of 0.78 µg/L. While ANAA and CYLS were detected south of 40° latitude, MCs by ELISA and DMAC occurred nationwide. Results were compared to freshwater recreational health thresholds from the World Health Organization and US Environmental Protection Agency to evaluate potential recreational exposure to MCs and CYLS since marine thresholds do not currently exist. Cyanotoxins were categorized using the 2021 World Health Organization Alert Level Framework for recreational exposure with 99.4, 99.1, 94.7, 98.0, and 44.7 % of samples being at the Vigilance Level for ANAA, CYLS, MCs (ELISA and LC/MS/MS), and chlorophyll, respectively with the remaining samples at Alert Level 1. Chlorophyll had 19.9 and 9.9 % of samples at Alert Level 1 and Alert Level 2, respectively. All cyanotoxins were below US EPA health advisory thresholds. ANAA, CYLS, DMAC, and MCs by ELISA were detected in samples with a wide range of salinities, while MCs by LC/MS/MS only occurred in samples with salinity <5 part per thousand (PPT). The source of cyanotoxins is likely a combination of inland transport and in situ estuarine production.
{"title":"Cyanotoxin and domoic acid occurrence, relation with salinity, and potential recreational health risks in U.S. coasts in the 2015 US EPA National Coastal Condition Assessment","authors":"Ariel R. Donovan , Zachary R. Laughrey , Robin A. Femmer , Sarena L. Senegal , Keith A. Loftin","doi":"10.1016/j.hal.2025.102935","DOIUrl":"10.1016/j.hal.2025.102935","url":null,"abstract":"<div><div>In the first nationwide study of cyanotoxins in U.S. estuaries, algal toxins, cyanotoxins, chlorophyll, and salinity were measured in samples collected during the National Coastal Condition Assessment 2015. Anatoxin-a (ANAA), cylindrospermopsin (CYLS), domoic acid (DMAC), and microcystins (MCs) were detected by LC/MS/MS in 0.6, 0.9, 8.3, and 2.0 % of samples with mean concentrations of detections of 0.13, 0.13, 0.53, and 0.49 µg/L, respectively. MCs by ELISA were also evaluated, and 4.0 % of samples had measurable MCs with a mean of 0.78 µg/L. While ANAA and CYLS were detected south of 40° latitude, MCs by ELISA and DMAC occurred nationwide. Results were compared to freshwater recreational health thresholds from the World Health Organization and US Environmental Protection Agency to evaluate potential recreational exposure to MCs and CYLS since marine thresholds do not currently exist. Cyanotoxins were categorized using the 2021 World Health Organization Alert Level Framework for recreational exposure with 99.4, 99.1, 94.7, 98.0, and 44.7 % of samples being at the Vigilance Level for ANAA, CYLS, MCs (ELISA and LC/MS/MS), and chlorophyll, respectively with the remaining samples at Alert Level 1. Chlorophyll had 19.9 and 9.9 % of samples at Alert Level 1 and Alert Level 2, respectively. All cyanotoxins were below US EPA health advisory thresholds. ANAA, CYLS, DMAC, and MCs by ELISA were detected in samples with a wide range of salinities, while MCs by LC/MS/MS only occurred in samples with salinity <5 part per thousand (PPT). The source of cyanotoxins is likely a combination of inland transport and in situ estuarine production.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102935"},"PeriodicalIF":4.5,"publicationDate":"2025-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144764122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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