Pub Date : 2025-11-01Epub 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":"2025-11-01","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 : 2025-11-01Epub 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":"2025-11-01","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 : 2025-11-01Epub 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":"2025-11-01","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 : 2025-11-01Epub Date: 2025-07-15DOI: 10.1016/j.hal.2025.102928
Zhimei Zhu, Qingyue Zhang, Zhenghong Sui
Alexandrium pacificum (Alexandrium sp. qd1) is representative of dinoflagellates that cause harmful red tides, and light intensity is an important factor affecting photosynthetic growth of A. pacificum in red tide outbreaks. N6 methyladenosine (m6A) RNA modification, as an important post-transcriptional molecular regulatory mechanism, may play an important role in the regulation of photosynthetic growth of dinoflagellates, which are known to exhibit minimal transcriptional regulation. In this study, the growth, photosynthesis, and cell sizes of A. pacificum under increasing light-intensity conditions (30, 100, 200, 300, 400 μmol photons m−2s−l) were examined. It was shown that 30 to 300 μmol m−2s−l light intensity gradually promoted the growth of algal cells in the logarithmic growth phase, whereas 400 μmol m−2s−l induced growth photoinhibition. The growth, photosynthetic indicators, and cell size of A. pacificum were significantly affected by light intensity. Meanwhile, the m6A modification level within the light-promoted growth range was detected and its correlation with growth indicators was analyzed. It was found that the m6A modification level decreased with the increase in light intensity and it has correlation with μmax, Fv/Fm, NPQ, and cell size. Then, the members of the upstream regulatory factors of m6A modification were identified and characterized. Most m6A important writers (MT-A70, WTAP), eraser (ALKBH1/3/5/6/8), and readers (YTH, eIF3C/D/G, hnRNPA2B1/C) were present in A. pacificum. The gene and protein expression of multiple members were detected, and multiple m6A modification regulators were found to respond to changes in light intensity. The results showed that m6A modification may play an important regulatory role in the growth of A. pacificum under different light-intensity conditions. This study provided some basis and insights for studying the growth regulation of red tide A. pacificum from the aspect of epi‑transcriptome (post transcriptional modifications on RNA).
{"title":"Effects of increasing light intensities on the cell growth and the RNA m6A upstream regulatory factors in a strain of Alexandrium pacificum","authors":"Zhimei Zhu, Qingyue Zhang, Zhenghong Sui","doi":"10.1016/j.hal.2025.102928","DOIUrl":"10.1016/j.hal.2025.102928","url":null,"abstract":"<div><div><em>Alexandrium pacificum</em> (<em>Alexandrium</em> sp. qd1) is representative of dinoflagellates that cause harmful red tides, and light intensity is an important factor affecting photosynthetic growth of <em>A. pacificum</em> in red tide outbreaks. N<sup>6</sup> methyladenosine (m<sup>6</sup>A) RNA modification, as an important post-transcriptional molecular regulatory mechanism, may play an important role in the regulation of photosynthetic growth of dinoflagellates, which are known to exhibit minimal transcriptional regulation. In this study, the growth, photosynthesis, and cell sizes of <em>A. pacificum</em> under increasing light-intensity conditions (30, 100, 200, 300, 400 μmol photons m<sup>−2</sup>s<sup>−l</sup>) were examined. It was shown that 30 to 300 μmol m<sup>−2</sup>s<sup>−l</sup> light intensity gradually promoted the growth of algal cells in the logarithmic growth phase, whereas 400 μmol m<sup>−2</sup>s<sup>−l</sup> induced growth photoinhibition. The growth, photosynthetic indicators, and cell size of <em>A. pacificum</em> were significantly affected by light intensity. Meanwhile, the m<sup>6</sup>A modification level within the light-promoted growth range was detected and its correlation with growth indicators was analyzed. It was found that the m<sup>6</sup>A modification level decreased with the increase in light intensity and it has correlation with μ<sub>max</sub>, Fv/Fm, NPQ, and cell size. Then, the members of the upstream regulatory factors of m<sup>6</sup>A modification were identified and characterized. Most m<sup>6</sup>A important writers (MT-A70, WTAP), eraser (ALKBH1/3/5/6/8), and readers (YTH, eIF3C/D/G, hnRNPA2B1/C) were present in <em>A. pacificum</em>. The gene and protein expression of multiple members were detected, and multiple m<sup>6</sup>A modification regulators were found to respond to changes in light intensity. The results showed that m<sup>6</sup>A modification may play an important regulatory role in the growth of <em>A. pacificum</em> under different light-intensity conditions. This study provided some basis and insights for studying the growth regulation of red tide <em>A. pacificum</em> from the aspect of epi‑transcriptome (post transcriptional modifications on RNA).</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102928"},"PeriodicalIF":5.5,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144702564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-01Epub Date: 2025-08-11DOI: 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":"2025-11-01","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 : 2025-11-01Epub Date: 2025-08-23DOI: 10.1016/j.hal.2025.102955
João Pedro Mancio de Amorim , Alexandre Melo Casseb do Carmo , José Eduardo Martinelli Filho
Over the recent years, different areas around the tropical Atlantic Ocean experienced an increase in pelagic Sargassum stranding events. Such incidents pose ecological and socioeconomic challenges, since they are difficult to predict and can impact coastal communities. In this study, we investigate the physical mechanisms behind Sargassum stranding events on the Brazilian Amazon Coast, focusing on the northeastern Pará region (northern Brazil), especially during the sporadic massive events registered in May 2014, April 2015, March 2019 and March 2025. We used a combination of observational data, reanalysis, forecast products, and Lagrangian experiments to explore the role of meteorological and oceanographic conditions during the occurrence of the strandings. Our results suggest that the events are related to the rainy season, when the Intertropical Convergence Zone (ITCZ) is positioned at its southernmost extent, bringing intense rainfall and northeasterly winds to the region. These winds can increase the landward transport of floating particles into the Amazon Continental Shelf (ACS). The results from the Lagrangian simulations highlighted the importance of wind drag and local processes (i.e., tidal currents and Stokes drift) in promoting the intrusion of floating particles into the inner shelf, particularly in the northeastern sector of the ACS, which emerges as a preferential pathway for the entrance of offshore Sargassum patches. This pathway was also highlighted by the sighting of Sargassum close to this area prior to the massive event of 2025, reinforcing the role of winds and tidal currents in connecting the northeastern offshore sector of ACS to the coast. While global reanalysis products and forecast systems provided valuable insights, future research should focus on the implementation of regional models to provide more accurate predictions near the coast, improving predictive capabilities to mitigate the impacts of these phenomena.
{"title":"Sargassum transport to the Amazon Coast: Explaining the stranding through meteorological and oceanographic conditions","authors":"João Pedro Mancio de Amorim , Alexandre Melo Casseb do Carmo , José Eduardo Martinelli Filho","doi":"10.1016/j.hal.2025.102955","DOIUrl":"10.1016/j.hal.2025.102955","url":null,"abstract":"<div><div>Over the recent years, different areas around the tropical Atlantic Ocean experienced an increase in pelagic <em>Sargassum</em> stranding events. Such incidents pose ecological and socioeconomic challenges, since they are difficult to predict and can impact coastal communities. In this study, we investigate the physical mechanisms behind <em>Sargassum</em> stranding events on the Brazilian Amazon Coast, focusing on the northeastern Pará region (northern Brazil), especially during the sporadic massive events registered in May 2014, April 2015, March 2019 and March 2025. We used a combination of observational data, reanalysis, forecast products, and Lagrangian experiments to explore the role of meteorological and oceanographic conditions during the occurrence of the strandings. Our results suggest that the events are related to the rainy season, when the Intertropical Convergence Zone (ITCZ) is positioned at its southernmost extent, bringing intense rainfall and northeasterly winds to the region. These winds can increase the landward transport of floating particles into the Amazon Continental Shelf (ACS). The results from the Lagrangian simulations highlighted the importance of wind drag and local processes (<em>i.e.</em>, tidal currents and Stokes drift) in promoting the intrusion of floating particles into the inner shelf, particularly in the northeastern sector of the ACS, which emerges as a preferential pathway for the entrance of offshore <em>Sargassum</em> patches. This pathway was also highlighted by the sighting of <em>Sargassum</em> close to this area prior to the massive event of 2025, reinforcing the role of winds and tidal currents in connecting the northeastern offshore sector of ACS to the coast. While global reanalysis products and forecast systems provided valuable insights, future research should focus on the implementation of regional models to provide more accurate predictions near the coast, improving predictive capabilities to mitigate the impacts of these phenomena.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102955"},"PeriodicalIF":4.5,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144908900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-01Epub Date: 2025-07-21DOI: 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":"2025-11-01","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}
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":"2025-11-01","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 : 2025-11-01Epub Date: 2025-08-21DOI: 10.1016/j.hal.2025.102957
Felipe Morais Zanon , Bruno Henrique Mioto Stabile , Beatriz Melissa Campos , Érica Oliveira de Lima , Matheus Juan Alarcon Sampaio , Yasmin Rodrigues de Souza , Leonardo Rodrigues Tolardo , Mayra Koma Gomes , Luddy Searom Carias de Moraes , Gabriela Sponchiado Hein , Jaqueline Dantas da Silva , Larissa da Silva Pinha , Loiani Oliveira Santana , Mariana Albuquerque , Vinicius da Silva , João Vitor Bredariol , Gabriel Arthur Lopes da Silva , Gabriel Delabio da Silva , Aline Aparecida Aguiar Ferreira , Luíz Fernando Esser , Luzia Cleide Rodrigues
The invasive cyanobacterium species Raphidiopsis raciborskii was first recorded in the Indo-Malaysian region in 1899, and studies currently report its presence in tropical, subtropical, and temperate environments around the world. In addition to its plasticity in colonizing new environments, R. raciborskii deserves attention for its ability to produce saxitoxin and cylindrospermopsin, which can cause the death of aquatic organisms and harm human health. In this work, we assessed the effect of global climate change towards the end of this century on the potential expansion of R. raciborskii using ecological niche models (ENMs). We applied a set of machine learning algorithms within the ensemble prediction approach to estimate the potential distribution of the species in South America under projected climate change, considering different carbon emission scenarios. In the moderate scenario, the northern Amazon basin, the southern Orinoco basin, and part of the North Atlantic basin showed increased environmental suitability for the species. In the pessimistic scenario, the basin with the greatest increase in suitability was the Paraná-Paraguay basin. Several basins remained highly suitable in both current and future scenarios, especially in Brazil. This study highlights the importance of understanding and addressing the impacts of climate change on the distribution of the invasive species R. raciborskii. South American countries must implement monitoring measures to assess the expansion of blooms of this species, as well as government actions to control water quality, given the strong impact of these organisms on biodiversity and ecosystem services.
{"title":"Climate change will boost the invasion of the harmful cyanobacterium Raphidiopsis raciborskii in South America","authors":"Felipe Morais Zanon , Bruno Henrique Mioto Stabile , Beatriz Melissa Campos , Érica Oliveira de Lima , Matheus Juan Alarcon Sampaio , Yasmin Rodrigues de Souza , Leonardo Rodrigues Tolardo , Mayra Koma Gomes , Luddy Searom Carias de Moraes , Gabriela Sponchiado Hein , Jaqueline Dantas da Silva , Larissa da Silva Pinha , Loiani Oliveira Santana , Mariana Albuquerque , Vinicius da Silva , João Vitor Bredariol , Gabriel Arthur Lopes da Silva , Gabriel Delabio da Silva , Aline Aparecida Aguiar Ferreira , Luíz Fernando Esser , Luzia Cleide Rodrigues","doi":"10.1016/j.hal.2025.102957","DOIUrl":"10.1016/j.hal.2025.102957","url":null,"abstract":"<div><div>The invasive cyanobacterium species <em>Raphidiopsis raciborskii</em> was first recorded in the Indo-Malaysian region in 1899, and studies currently report its presence in tropical, subtropical, and temperate environments around the world. In addition to its plasticity in colonizing new environments, <em>R. raciborskii</em> deserves attention for its ability to produce saxitoxin and cylindrospermopsin, which can cause the death of aquatic organisms and harm human health. In this work, we assessed the effect of global climate change towards the end of this century on the potential expansion of <em>R. raciborskii</em> using ecological niche models (ENMs). We applied a set of machine learning algorithms within the ensemble prediction approach to estimate the potential distribution of the species in South America under projected climate change, considering different carbon emission scenarios. In the moderate scenario, the northern Amazon basin, the southern Orinoco basin, and part of the North Atlantic basin showed increased environmental suitability for the species. In the pessimistic scenario, the basin with the greatest increase in suitability was the Paraná-Paraguay basin. Several basins remained highly suitable in both current and future scenarios, especially in Brazil. This study highlights the importance of understanding and addressing the impacts of climate change on the distribution of the invasive species <em>R. raciborskii</em>. South American countries must implement monitoring measures to assess the expansion of blooms of this species, as well as government actions to control water quality, given the strong impact of these organisms on biodiversity and ecosystem services.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102957"},"PeriodicalIF":4.5,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144895575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-01Epub Date: 2025-08-18DOI: 10.1016/j.hal.2025.102954
Min Liu , Liyan Deng , Yan Wang , Xiaodong Wang , Sen Du , Zhicai She , Zhenjun Kang , Qingxia Liu , Peng Wu , Zexing Kuang , Lingxiang Zhu , Jiajun Wu , Lai Leo Chan , Yuanyue Cheng , Li Zhang , Yang Liu
Lipophilic marine phycotoxins (LMTs), primarily produced by toxigenic dinoflagellates, pose significant risks to marine ecosystems and human health due to their toxicity and widespread distribution. This study investigates the spatial and temporal distribution of LMTs in the surface seawater from representative estuarine and bay areas of the South China Sea (SCS) during period from 2022‒2023. Using active solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry (Active-SPE-LC-MS/MS), the study revealed that significantly higher LMTs concentrations in semi-enclosed bays (13.15 ± 8.61 ng L−1) compared to estuarine regions (8.55 ± 8.59 ng L−1), with Daya Bay (DB) and Jian River Estuary (JRE) exhibiting the highest toxin levels. The most prevalent toxins were diarrhetic shellfish toxins (OA, DTX1) and pectenotoxin-2 (PTX2), with PTX2 being dominant in most regions. Seasonal variations were evident, with higher LMTs concentrations observed during the wet season, particularly in spring and summer. Principal component analysis (PCA) revealed distinct toxin profiles, with PTX2, GYM, and OA being prevalent in the Pearl River Estuary (PRE), while AZA2 and DTX1 were more abundant in Qinzhou Bay (QB). The study highlights the influence of local environmental conditions, such as seasonal and region variations on LMTs distribution. These findings provide critical insights into the ecological dynamics of LMTs in eutrophic coastal waters, emphasizing the need for continuous monitoring to mitigate risks to marine ecosystems and human health. This research contributes to a deeper understanding of LMTs distribution patterns in the SCS, supporting future risk assessments and management strategies.
亲脂性海洋藻毒素（lmt）主要由产毒鞭毛藻产生，由于其毒性和广泛分布，对海洋生态系统和人类健康构成重大风险。研究了2022-2023年南海代表性河口湾区表层海水中lmt的时空分布特征。采用活性固相萃取-液相色谱-串联质谱联用技术（active - spe - lc -MS/MS）研究发现，半封闭海湾地区的毒素浓度（13.15±8.61 ng L−1）显著高于河口地区（8.55±8.59 ng L−1），其中大亚湾（DB）和剑江口（JRE）的毒素含量最高。最常见的毒素是腹泻性贝类毒素（OA、DTX1）和果皮毒素-2 (PTX2)，大部分地区以PTX2为主。季节变化明显，在雨季，特别是春季和夏季，观察到的LMTs浓度较高。主成分分析显示，珠江口（PRE）以PTX2、GYM和OA为主，而钦州湾（QB）以AZA2和DTX1为主。该研究强调了当地环境条件（如季节和区域变化）对LMTs分布的影响。这些发现为富营养化沿海水域中浮游生物的生态动态提供了重要见解，强调需要持续监测以减轻对海洋生态系统和人类健康的风险。这项研究有助于更深入地了解南中国海的LMTs分布模式，为未来的风险评估和管理策略提供支持。
{"title":"Seasonal and regional variability of lipophilic marine phycotoxins in eutrophic coastal waters of the South China Sea","authors":"Min Liu , Liyan Deng , Yan Wang , Xiaodong Wang , Sen Du , Zhicai She , Zhenjun Kang , Qingxia Liu , Peng Wu , Zexing Kuang , Lingxiang Zhu , Jiajun Wu , Lai Leo Chan , Yuanyue Cheng , Li Zhang , Yang Liu","doi":"10.1016/j.hal.2025.102954","DOIUrl":"10.1016/j.hal.2025.102954","url":null,"abstract":"<div><div>Lipophilic marine phycotoxins (LMTs), primarily produced by toxigenic dinoflagellates, pose significant risks to marine ecosystems and human health due to their toxicity and widespread distribution. This study investigates the spatial and temporal distribution of LMTs in the surface seawater from representative estuarine and bay areas of the South China Sea (SCS) during period from 2022‒2023. Using active solid-phase extraction coupled with liquid chromatography-tandem mass spectrometry (Active-SPE-LC-MS/MS), the study revealed that significantly higher LMTs concentrations in semi-enclosed bays (13.15 ± 8.61 ng L<sup>−1</sup>) compared to estuarine regions (8.55 ± 8.59 ng L<sup>−1</sup>), with Daya Bay (DB) and Jian River Estuary (JRE) exhibiting the highest toxin levels. The most prevalent toxins were diarrhetic shellfish toxins (OA, DTX1) and pectenotoxin-2 (PTX2), with PTX2 being dominant in most regions. Seasonal variations were evident, with higher LMTs concentrations observed during the wet season, particularly in spring and summer. Principal component analysis (PCA) revealed distinct toxin profiles, with PTX2, GYM, and OA being prevalent in the Pearl River Estuary (PRE), while AZA2 and DTX1 were more abundant in Qinzhou Bay (QB). The study highlights the influence of local environmental conditions, such as seasonal and region variations on LMTs distribution. These findings provide critical insights into the ecological dynamics of LMTs in eutrophic coastal waters, emphasizing the need for continuous monitoring to mitigate risks to marine ecosystems and human health. This research contributes to a deeper understanding of LMTs distribution patterns in the SCS, supporting future risk assessments and management strategies.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"149 ","pages":"Article 102954"},"PeriodicalIF":4.5,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144895536","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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