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}
Pub 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":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144879430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub 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":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144764124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub 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":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144725085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-21DOI: 10.1016/j.hal.2025.102932
Jeong Hwa Hwang , Ji-Sook Park , Young-Seok Han , Youn-Jung Kim , Mungi Kim , Seongjin Hong , Jang K. Kim
Prorocentrum lima is a marine benthic dinoflagellate known for producing toxins such as okadaic acid (OA) and dinophysistoxin (DTX), which cause diarrheal shellfish poisoning (DSP). P. lima is known to increase toxin production under low nutrient concentrations, but there have been few studies examining the effect of prolonged nutrient depletion. This study investigates changes in growth, photosynthetic efficiency, pigments (Chl a and carotenoids) and toxin levels (OA and DTX) during the period of nutrient depletion. Nutrient addition was stopped when the cell concentration reached the stationary phase at approximately 200,000 cells ml−1. After stopping nutrient addition, sampling was conducted at 10-day intervals for 30 days. During the exponential growth phase, P. lima took up more than 90 % of nitrate and nitrite from the medium within 3 hours. Even after the nutrient supply was stopped, cell density continued to increase, reaching about 340,000 cells ml−1. Chl a and carotenoids did not show significant differences, but photosynthetic parameters, such as relative electron transport rate (rETR), ETRmax and Ik decreased. The levels of OA and DTX-1 were also significantly higher on day 30 compared to day 0. These results suggest that, while the cell density can be maintained during nutrient depletion, the toxin content per cell increases significantly, and photosynthetic efficiency decreases.
{"title":"Effects of nutrient depletion duration on growth, photosynthesis and toxins (OA and DTX) in the dinoflagellate Prorocentrum lima","authors":"Jeong Hwa Hwang , Ji-Sook Park , Young-Seok Han , Youn-Jung Kim , Mungi Kim , Seongjin Hong , Jang K. Kim","doi":"10.1016/j.hal.2025.102932","DOIUrl":"10.1016/j.hal.2025.102932","url":null,"abstract":"<div><div><em>Prorocentrum lima</em> is a marine benthic dinoflagellate known for producing toxins such as okadaic acid (OA) and dinophysistoxin (DTX), which cause diarrheal shellfish poisoning (DSP). <em>P. lima</em> is known to increase toxin production under low nutrient concentrations, but there have been few studies examining the effect of prolonged nutrient depletion. This study investigates changes in growth, photosynthetic efficiency, pigments (Chl <em>a</em> and carotenoids) and toxin levels (OA and DTX) during the period of nutrient depletion. Nutrient addition was stopped when the cell concentration reached the stationary phase at approximately 200,000 cells ml<sup>−1</sup>. After stopping nutrient addition, sampling was conducted at 10-day intervals for 30 days. During the exponential growth phase, <em>P. lima</em> took up more than 90 % of nitrate and nitrite from the medium within 3 hours. Even after the nutrient supply was stopped, cell density continued to increase, reaching about 340,000 cells ml<sup>−1</sup>. Chl <em>a</em> and carotenoids did not show significant differences, but photosynthetic parameters, such as relative electron transport rate (rETR), ETRmax and Ik decreased. The levels of OA and DTX-1 were also significantly higher on day 30 compared to day 0. These results suggest that, while the cell density can be maintained during nutrient depletion, the toxin content per cell increases significantly, and photosynthetic efficiency decreases.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102932"},"PeriodicalIF":5.5,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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