Pub Date : 2026-03-01Epub Date: 2026-01-06DOI: 10.1016/j.hal.2026.103059
Nicolas Chomérat , Nikita Rose , Laura Lavenu , Lisbet Díaz-Asencio , Clara Belmont , Stéphanie Hollanda , Francois Oberhansli , Alina Tunin-Ley , Jean Turquet , Marie-Yasmine Dechraoui Bottein
Benthic dinoflagellates associated with human ciguatera poisoning are present in the Indian Ocean and species such as Fukuyoa (formerly Gambierdiscus) yasumotoi, G. toxicus and G. belizeanus have been reported since the mid 90s. Even though, very little information is available concerning the occurrence of Gambierdiscus species and toxicity in the Seychelles waters. This study investigates four Gambierdiscus belizeanus strains isolated from Seychelles, focusing on their morphological and genetic characterization, as well as their potential for neurotoxin production. Water samples were collected in Bay Ternay (West Mahé) and around Saint Anne Island. Culture aliquots were fixed for species identification using microscopy and molecular tools (sequencing of D1-D3 and D8-D10 of LSU rDNA) and toxin production analyzed in a 21-day culture using the N2a bioassay. This revealed detectable low CTX activity in only one of the four strains, estimated to 1.7 fg CTX3C equiv/cell, while the other strains were non-cytotoxic. These findings represent the first molecular and toxicological characterization of G. belizeanus strains from the Seychelles, contributing to the understanding of ciguatera poisoning risks in the Indian Ocean and highlighting the variable toxin production capacity within Gambierdiscus species. Expanding this project to areas with high ciguatera occurrence in the Indian Ocean could help in characterizing the responsible toxins.
{"title":"Taxonomic characterization and toxicity assessment of strains of Gambierdiscus belizeanus from Seychelles, southwestern Indian Ocean","authors":"Nicolas Chomérat , Nikita Rose , Laura Lavenu , Lisbet Díaz-Asencio , Clara Belmont , Stéphanie Hollanda , Francois Oberhansli , Alina Tunin-Ley , Jean Turquet , Marie-Yasmine Dechraoui Bottein","doi":"10.1016/j.hal.2026.103059","DOIUrl":"10.1016/j.hal.2026.103059","url":null,"abstract":"<div><div>Benthic dinoflagellates associated with human ciguatera poisoning are present in the Indian Ocean and species such as <em>Fukuyoa</em> (formerly <em>Gambierdiscus</em>) <em>yasumotoi, G. toxicus</em> and <em>G. belizeanus</em> have been reported since the mid 90s. Even though, very little information is available concerning the occurrence of <em>Gambierdiscus</em> species and toxicity in the Seychelles waters. This study investigates four <em>Gambierdiscus belizeanus</em> strains isolated from Seychelles, focusing on their morphological and genetic characterization, as well as their potential for neurotoxin production. Water samples were collected in Bay Ternay (West Mahé) and around Saint Anne Island. Culture aliquots were fixed for species identification using microscopy and molecular tools (sequencing of D1-D3 and D8-D10 of LSU rDNA) and toxin production analyzed in a 21-day culture using the N2a bioassay. This revealed detectable low CTX activity in only one of the four strains, estimated to 1.7 fg CTX3C equiv/cell, while the other strains were non-cytotoxic. These findings represent the first molecular and toxicological characterization of <em>G. belizeanus</em> strains from the Seychelles, contributing to the understanding of ciguatera poisoning risks in the Indian Ocean and highlighting the variable toxin production capacity within <em>Gambierdiscus</em> species. Expanding this project to areas with high ciguatera occurrence in the Indian Ocean could help in characterizing the responsible toxins.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"153 ","pages":"Article 103059"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035226","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 : 2026-03-01Epub Date: 2025-12-17DOI: 10.1016/j.hal.2025.103043
Chuanmin Hu , Brian E. Lapointe , Rosa E. Rodríguez-Martínez
{"title":"Preface for special issue on “harmful impacts of the Atlantic pelagic Sargassum”","authors":"Chuanmin Hu , Brian E. Lapointe , Rosa E. Rodríguez-Martínez","doi":"10.1016/j.hal.2025.103043","DOIUrl":"10.1016/j.hal.2025.103043","url":null,"abstract":"","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"153 ","pages":"Article 103043"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146222704","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 : 2026-03-01Epub Date: 2025-12-31DOI: 10.1016/j.hal.2025.103048
Ying Ji , Guowang Yan , Guixiang Wang , Yadong Cao , Jiangbing Qiu , Tianshen Li , Xin Luo , Wenlu Lan , Zhaohui Wang , Aifeng Li
Harmful algal blooms (HABs) pose escalating threats to marine ecosystems and seafood safety worldwide, particularly in nearshore waters. The Beibu Gulf, located in the northwestern South China Sea, supports rich biodiversity and serves as a major fishing area. To comprehensively understand the current status of phycotoxin pollution, we conducted a basin-wide cruise survey in August 2021, collecting 60 phytoplankton samples to characterize the spatial distribution, compositional profile, and molecular origins of 12 target marine phycotoxins, along with their key environmental drivers. Domoic acid (DA), pectenotoxin-2 (PTX2), homo-yessotoxin (homoYTX), and gymnodimine A (GYM-A) were the predominant phycotoxins detected, whereas okadaic acid (OA), dinophysistoxin (DTX1), and yessotoxin (YTX) were found sporadically (< 6.7% detection rate). The DA was present in 20% of samples (mean 14,424 pg L−1, max 163,434 pg L−1), PTX2 in 36.7% (mean 508 pg L−1, max 2995 pg L−1), homoYTX in 43.3% (mean 1717 pg L−1, max 42,680 pg L−1), and GYM-A exhibited the highest detection rate at 68.3% (mean 37 pg L−1, max 902 pg L−1). Phycotoxin concentrations were markedly higher in the northern waters than in the southern gulf. Metabarcoding revealed 14 potential toxigenic microalgae, 12 of which belonged to Dinophyceae. Redundancy analysis indicated that concentrations of the four dominant phycotoxins were positively correlated with dissolved oxygen and chlorophyll a, but negatively correlated with salinity (p < 0.05). This suggests that low-salinity (28−31), resulting from terrestrial inputs and marine circulation, create favorable niches for toxigenic species. This study elucidates the phycotoxin profiles and their putative toxigenic microalgae in the Beibu Gulf, while highlighting environmental factors that promote phycotoxin production. These findings provide foundational insights into HAB dynamics in tropical estuarine systems, aiding future monitoring and management efforts in the region.
{"title":"Tracking marine phycotoxins: spatial distribution and source elucidation of domoic acid and lipophilic shellfish toxins in the Beibu Gulf, South China Sea","authors":"Ying Ji , Guowang Yan , Guixiang Wang , Yadong Cao , Jiangbing Qiu , Tianshen Li , Xin Luo , Wenlu Lan , Zhaohui Wang , Aifeng Li","doi":"10.1016/j.hal.2025.103048","DOIUrl":"10.1016/j.hal.2025.103048","url":null,"abstract":"<div><div>Harmful algal blooms (HABs) pose escalating threats to marine ecosystems and seafood safety worldwide, particularly in nearshore waters. The Beibu Gulf, located in the northwestern South China Sea, supports rich biodiversity and serves as a major fishing area. To comprehensively understand the current status of phycotoxin pollution, we conducted a basin-wide cruise survey in August 2021, collecting 60 phytoplankton samples to characterize the spatial distribution, compositional profile, and molecular origins of 12 target marine phycotoxins, along with their key environmental drivers. Domoic acid (DA), pectenotoxin-2 (PTX2), homo-yessotoxin (homoYTX), and gymnodimine A (GYM-A) were the predominant phycotoxins detected, whereas okadaic acid (OA), dinophysistoxin (DTX1), and yessotoxin (YTX) were found sporadically (< 6.7% detection rate). The DA was present in 20% of samples (mean 14,424 pg L<sup>−1</sup>, max 163,434 pg L<sup>−1</sup>), PTX2 in 36.7% (mean 508 pg L<sup>−1</sup>, max 2995 pg L<sup>−1</sup>), homoYTX in 43.3% (mean 1717 pg L<sup>−1</sup>, max 42,680 pg L<sup>−1</sup>), and GYM-A exhibited the highest detection rate at 68.3% (mean 37 pg L<sup>−1</sup>, max 902 pg L<sup>−1</sup>). Phycotoxin concentrations were markedly higher in the northern waters than in the southern gulf. Metabarcoding revealed 14 potential toxigenic microalgae, 12 of which belonged to Dinophyceae. Redundancy analysis indicated that concentrations of the four dominant phycotoxins were positively correlated with dissolved oxygen and chlorophyll <em>a</em>, but negatively correlated with salinity (<em>p</em> < 0.05). This suggests that low-salinity (28−31), resulting from terrestrial inputs and marine circulation, create favorable niches for toxigenic species. This study elucidates the phycotoxin profiles and their putative toxigenic microalgae in the Beibu Gulf, while highlighting environmental factors that promote phycotoxin production. These findings provide foundational insights into HAB dynamics in tropical estuarine systems, aiding future monitoring and management efforts in the region.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"153 ","pages":"Article 103048"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145891180","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 : 2026-03-01Epub Date: 2026-01-29DOI: 10.1016/j.hal.2026.103068
Xiang Ye , Wen-Jing Sun , Wei-Ping Zhang , Yang Zhou , Shuo-Yu Zhang , Can-Jun Cai , Shu-Feng Zhang , Jae-Seong Lee , Minghua Wang , Da-Zhi Wang
Marine dinoflagellates are increasingly exposed to concurrent ocean warming and eutrophication; however, their responses to multiple concurrent stressors remain inadequately understood. Here, we investigated the individual and combined effects of elevated temperature (26 °C vs. 22 °C) and a high nitrogen-to-phosphorus ratio (180:1) on the harmful algal bloom-causing dinoflagellate Karenia mikimotoi during a 30-day exposure experiment. Elevated temperature and high N:P ratio, individually and in combination, significantly increased growth rate by 16–24 % relative to the control, while chlorophyll a (Chl a) content decreased by 22–29 %. Cellular particulate organic nitrogen (PON) content declined by 21–22 % under elevated temperature alone and in combination with a high N:P ratio, whereas particulate organic carbon (POC) content remained unchanged across all treatments. Interaction analyses revealed antagonistic effects of elevated temperature and high N:P ratio on growth rate, Chl a, and PON contents. Transcriptomic analyses showed that elevated temperature primarily upregulated genes associated with energy production and lipid biosynthesis, whereas a high N:P ratio enhanced the expression of genes involved in nitrogen assimilation and urea cycle-related pathways. Under combined stress, gene expression patterns indicated a transcriptionally inferred shift in energy allocation toward soluble sugar and lipid metabolism, accompanied by downregulation of urea cycle-related genes, suggesting a trade-off between energy conservation and nitrogen utilization. These results highlight the importance of antagonistic interactions between warming and nutrient imbalance in shaping the physiological and molecular responses of dinoflagellates, with implications for predicting harmful algal bloom dynamics under future ocean conditions.
海洋鞭毛藻越来越多地暴露于同时发生的海洋变暖和富营养化；然而，他们对多个并发压力源的反应仍然没有得到充分的了解。在这里，我们研究了高温（26°C vs. 22°C）和高氮磷比（180:1）在30天的暴露实验中对有害藻华引起的mikimotoi甲藻Karenia的单独和联合影响。升高温度和高氮磷比单独或组合处理可显著提高植株生长速率，比对照提高16 - 24%，叶绿素a含量降低22 - 29%。细胞颗粒有机氮（PON）含量在单独和高氮磷比处理下下降了21 - 22%，而颗粒有机碳（POC）含量在所有处理中保持不变。互作分析表明，高温和高氮磷比对生长速率、Chl a和PON含量有拮抗作用。转录组学分析表明，高温主要上调与能量产生和脂质生物合成相关的基因，而高氮磷比则增强了参与氮同化和尿素循环相关途径的基因的表达。在联合胁迫下，基因表达模式显示了能量分配向可溶性糖和脂质代谢的转变，并伴有尿素循环相关基因的下调，这表明在能量节约和氮利用之间存在权衡。这些结果强调了变暖和营养失衡之间的拮抗相互作用在形成鞭毛藻的生理和分子反应中的重要性，对预测未来海洋条件下有害藻华的动态具有重要意义。
{"title":"Responses of a harmful algal bloom-causing dinoflagellate Karenia mikimotoi to elevated temperature and high N:P ratio","authors":"Xiang Ye , Wen-Jing Sun , Wei-Ping Zhang , Yang Zhou , Shuo-Yu Zhang , Can-Jun Cai , Shu-Feng Zhang , Jae-Seong Lee , Minghua Wang , Da-Zhi Wang","doi":"10.1016/j.hal.2026.103068","DOIUrl":"10.1016/j.hal.2026.103068","url":null,"abstract":"<div><div>Marine dinoflagellates are increasingly exposed to concurrent ocean warming and eutrophication; however, their responses to multiple concurrent stressors remain inadequately understood. Here, we investigated the individual and combined effects of elevated temperature (26 °C vs. 22 °C) and a high nitrogen-to-phosphorus ratio (180:1) on the harmful algal bloom-causing dinoflagellate <em>Karenia mikimotoi</em> during a 30-day exposure experiment. Elevated temperature and high N:P ratio, individually and in combination, significantly increased growth rate by 16–24 % relative to the control, while chlorophyll a (Chl <em>a</em>) content decreased by 22–29 %. Cellular particulate organic nitrogen (PON) content declined by 21–22 % under elevated temperature alone and in combination with a high N:P ratio, whereas particulate organic carbon (POC) content remained unchanged across all treatments. Interaction analyses revealed antagonistic effects of elevated temperature and high N:P ratio on growth rate, Chl <em>a</em>, and PON contents. Transcriptomic analyses showed that elevated temperature primarily upregulated genes associated with energy production and lipid biosynthesis, whereas a high N:P ratio enhanced the expression of genes involved in nitrogen assimilation and urea cycle-related pathways. Under combined stress, gene expression patterns indicated a transcriptionally inferred shift in energy allocation toward soluble sugar and lipid metabolism, accompanied by downregulation of urea cycle-related genes, suggesting a trade-off between energy conservation and nitrogen utilization. These results highlight the importance of antagonistic interactions between warming and nutrient imbalance in shaping the physiological and molecular responses of dinoflagellates, with implications for predicting harmful algal bloom dynamics under future ocean conditions.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"153 ","pages":"Article 103068"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146188750","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 : 2026-03-01Epub Date: 2026-01-13DOI: 10.1016/j.hal.2026.103061
Chuang Li , Yicheng Wang , Na Jiang , Shuangqing Li , Chenyang Shao , Fengyuan Zhang , Huajun Zhang , Weizhong Chen , Hailong Huang , Haibo Jiang
The coastal waters of the East China Sea (ECS) are facing severe eutrophication, driven primarily by large inputs of nitrogen and phosphorus from land-based sources, which in turn accelerate harmful algal blooms. However, the understanding of the relationship between eutrophic conditions and the mechanisms of algal bloom occurrence remains insufficient. This study investigates a bloom of the toxic dinoflagellate Prorocentrum cordatum (syn. Prorocentrum minimum) in the coastal waters of Xiangshan Bay (XSB), ECS, through in situ nutrient addition experiments and DNA metabarcoding analysis. The addition of dissolved organic phosphorus (DOP) significantly promoted the growth of P. cordatum compared to the -P control (no phosphorus source: f/2-P) (p < 0.05), whereas dissolved inorganic phosphorus (DIP) had no such effect. In contrast, nitrite (NO₂⁻) and urea significantly inhibited the growth of the species relative to the -N control (no nitrogen source: f/2-N) (p < 0.05), while no significant difference was observed between nitrate and ammonium treatments when compared to the -N control. Network analysis indicated that DOP increased the topological complexity but may have reduced the stability of the community network. In contrast, NO₂⁻ and urea appeared to enhance the network stability. These findings emphasize that DOP was a critical phosphorus source for maintaining P. cordatum blooms, while the input of nitrite and urea may inhibit bloom expansion. In summary, this study suggests that DOP may serve as an important phosphorus source facilitating P. cordatum growth under phosphorus-limited conditions, thereby providing a scientific basis for refining phosphorus control and nitrogen source optimization in the context of ECS eutrophication management.
{"title":"Effects of nutrient forms on the bloom dynamics and phytoplankton community associated with Prorocentrum cordatum","authors":"Chuang Li , Yicheng Wang , Na Jiang , Shuangqing Li , Chenyang Shao , Fengyuan Zhang , Huajun Zhang , Weizhong Chen , Hailong Huang , Haibo Jiang","doi":"10.1016/j.hal.2026.103061","DOIUrl":"10.1016/j.hal.2026.103061","url":null,"abstract":"<div><div>The coastal waters of the East China Sea (ECS) are facing severe eutrophication, driven primarily by large inputs of nitrogen and phosphorus from land-based sources, which in turn accelerate harmful algal blooms. However, the understanding of the relationship between eutrophic conditions and the mechanisms of algal bloom occurrence remains insufficient. This study investigates a bloom of the toxic dinoflagellate <em>Prorocentrum cordatum</em> (syn. <em>Prorocentrum minimum</em>) in the coastal waters of Xiangshan Bay (XSB), ECS, through in situ nutrient addition experiments and DNA metabarcoding analysis. The addition of dissolved organic phosphorus (DOP) significantly promoted the growth of <em>P. cordatum</em> compared to the -P control (no phosphorus source: f/2-P) (<em>p</em> < 0.05), whereas dissolved inorganic phosphorus (DIP) had no such effect. In contrast, nitrite (NO₂⁻) and urea significantly inhibited the growth of the species relative to the -N control (no nitrogen source: f/2-N) (<em>p</em> < 0.05), while no significant difference was observed between nitrate and ammonium treatments when compared to the -N control. Network analysis indicated that DOP increased the topological complexity but may have reduced the stability of the community network. In contrast, NO₂⁻ and urea appeared to enhance the network stability. These findings emphasize that DOP was a critical phosphorus source for maintaining <em>P. cordatum</em> blooms, while the input of nitrite and urea may inhibit bloom expansion. In summary, this study suggests that DOP may serve as an important phosphorus source facilitating <em>P. cordatum</em> growth under phosphorus-limited conditions, thereby providing a scientific basis for refining phosphorus control and nitrogen source optimization in the context of ECS eutrophication management.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"153 ","pages":"Article 103061"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146034875","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 : 2026-03-01Epub Date: 2026-01-12DOI: 10.1016/j.hal.2026.103060
Kristof Moeller , Hans H. Jakobsen , Anette Engesmo , Bengt Karlson , Jacob Carstensen
The harmful dinoflagellate Alexandrium pseudogonyaulax has been associated with the mortality of marine organisms, including fish. Recent evidence, although based on limited data, suggests an increasing presence across Northern European waters. To confirm this hypothesis, we analysed comprehensive long-term time series data from monitoring stations in Germany, Sweden, Denmark and Norway to assess whether A. pseudogonyaulax has established a sustained presence in the study region and to identify potential environmental drivers of its distribution. The findings show that this species is now a recurrent part of the microalgal community, primarily in the Kattegat, Skagerrak, and southern Baltic Sea. The seasonality of this species was found to be consistent across stations as it primarily occurs from May to October, peaking in July. Logistic regression further revealed increasing trends in occurrence at several sites. No consistent environmental drivers of this expansion were found, although its presence was associated with elevated DIN:PO4 ratios at some stations, suggesting that other ecological mechanisms, such as top-down processes or species competition, may have facilitated proliferation of A. pseudogonyaulax. The species’ salinity tolerance, potential dispersal of resting cysts and climate change-induced warming likely promoted its regional spread, especially into the Baltic Sea. The increasing presence and limited understanding of its toxic effects on marine organisms and humans highlight the need for continued monitoring and further research into its ecological impacts.
{"title":"Time series analysis of the toxic dinoflagellate Alexandrium pseudogonyaulax across Northern European waters","authors":"Kristof Moeller , Hans H. Jakobsen , Anette Engesmo , Bengt Karlson , Jacob Carstensen","doi":"10.1016/j.hal.2026.103060","DOIUrl":"10.1016/j.hal.2026.103060","url":null,"abstract":"<div><div>The harmful dinoflagellate <em>Alexandrium pseudogonyaulax</em> has been associated with the mortality of marine organisms, including fish. Recent evidence, although based on limited data, suggests an increasing presence across Northern European waters. To confirm this hypothesis, we analysed comprehensive long-term time series data from monitoring stations in Germany, Sweden, Denmark and Norway to assess whether <em>A. pseudogonyaulax</em> has established a sustained presence in the study region and to identify potential environmental drivers of its distribution. The findings show that this species is now a recurrent part of the microalgal community, primarily in the Kattegat, Skagerrak, and southern Baltic Sea. The seasonality of this species was found to be consistent across stations as it primarily occurs from May to October, peaking in July. Logistic regression further revealed increasing trends in occurrence at several sites. No consistent environmental drivers of this expansion were found, although its presence was associated with elevated DIN:PO<sub>4</sub> ratios at some stations, suggesting that other ecological mechanisms, such as top-down processes or species competition, may have facilitated proliferation of <em>A. pseudogonyaulax</em>. The species’ salinity tolerance, potential dispersal of resting cysts and climate change-induced warming likely promoted its regional spread, especially into the Baltic Sea. The increasing presence and limited understanding of its toxic effects on marine organisms and humans highlight the need for continued monitoring and further research into its ecological impacts.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"153 ","pages":"Article 103060"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146035227","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 : 2026-03-01Epub Date: 2026-01-05DOI: 10.1016/j.hal.2026.103056
Minglan Fang , Jun He , Shijie Zhou , Pei Hong , Lixia Ke , Hailong Wu , Yilin Shu
Exposure to microcystins (MCs) can cause severe intestinal damage. This study aimed to assess the efficacy of Pleurotus ostreatus polysaccharide in alleviating intestinal damage induced by microcystin-leucine-arginine (MC-LR) in tadpoles. Over a 30-day period, tadpoles (Pelophylax nigromaculatus) received daily exposures to MC-LR and were provided with diets either supplemented with or devoid of P. ostreatus polysaccharide. Results revealed that feeding P. ostreatus polysaccharide conferred protection against MC-LR-induced intestinal damage by mitigating barrier damage, lowering intestinal permeability, and reducing the tissue burden of MC-LR. The LPS/TLR4 pathway response was attenuated, reducing inflammation, and oxidative stress-mediated apoptosis response was also diminished. Gram-negative bacteria (e.g., Bacteroides) in the intestine show a positive correlation with LPS content and the transcription of key genes in the LPS/TLR4 pathway. Metagenomic and metabolite analysis of intestinal contents revealed increased abundance of the alanine-glyoxylate aminotransferase gene (agxt)—the key enzyme converting glyoxylic acid to glycine—and elevated glycine content in the MC-LR-exposed group fed polysaccharide. Results from the corresponding fecal microbiota transplantation experiment aligned with the trends observed in the exposure experiment. Therefore, polysaccharide alleviates MC-LR-induced intestinal damage by enhancing intestinal microbiota-mediated glycine synthesis, supplying raw materials for intestinal GSH production, reducing oxidative stress levels, and simultaneously dampening the LPS/TLR4 pathway response. Moreover, feeding polysaccharides might also regulate the intestine’s defense against pathogens after MC-LR exposure by enhancing lysozyme activity. There is no evidence of intestinal damage in the P. ostreatus exopolysaccharide group. This study highlights for the first time the role of P. ostreatus polysaccharides in mitigating MC-LR-induced intestinal tissue damage, potentially offering novel insights for their application in aquaculture.
{"title":"Pleurotus ostreatus polysaccharides improve microcystin-LR-induced intestinal damage in tadpoles by regulating the interaction between microbiota and intestine","authors":"Minglan Fang , Jun He , Shijie Zhou , Pei Hong , Lixia Ke , Hailong Wu , Yilin Shu","doi":"10.1016/j.hal.2026.103056","DOIUrl":"10.1016/j.hal.2026.103056","url":null,"abstract":"<div><div>Exposure to microcystins (MCs) can cause severe intestinal damage. This study aimed to assess the efficacy of <em>Pleurotus ostreatus</em> polysaccharide in alleviating intestinal damage induced by microcystin-leucine-arginine (MC-LR) in tadpoles. Over a 30-day period, tadpoles (<em>Pelophylax nigromaculatus</em>) received daily exposures to MC-LR and were provided with diets either supplemented with or devoid of <em>P. ostreatus</em> polysaccharide. Results revealed that feeding <em>P. ostreatus</em> polysaccharide conferred protection against MC-LR-induced intestinal damage by mitigating barrier damage, lowering intestinal permeability, and reducing the tissue burden of MC-LR. The LPS/TLR4 pathway response was attenuated, reducing inflammation, and oxidative stress-mediated apoptosis response was also diminished. Gram-negative bacteria (e.g., <em>Bacteroides</em>) in the intestine show a positive correlation with LPS content and the transcription of key genes in the LPS/TLR4 pathway. Metagenomic and metabolite analysis of intestinal contents revealed increased abundance of the alanine-glyoxylate aminotransferase gene (<em>agxt</em>)—the key enzyme converting glyoxylic acid to glycine—and elevated glycine content in the MC-LR-exposed group fed polysaccharide. Results from the corresponding fecal microbiota transplantation experiment aligned with the trends observed in the exposure experiment. Therefore, polysaccharide alleviates MC-LR-induced intestinal damage by enhancing intestinal microbiota-mediated glycine synthesis, supplying raw materials for intestinal GSH production, reducing oxidative stress levels, and simultaneously dampening the LPS/TLR4 pathway response. Moreover, feeding polysaccharides might also regulate the intestine’s defense against pathogens after MC-LR exposure by enhancing lysozyme activity. There is no evidence of intestinal damage in the <em>P. ostreatus</em> exopolysaccharide group. This study highlights for the first time the role of <em>P. ostreatus</em> polysaccharides in mitigating MC-LR-induced intestinal tissue damage, potentially offering novel insights for their application in aquaculture.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"153 ","pages":"Article 103056"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923046","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}
Recurrent toxic blooms of Alexandrium minutum, Pseudo-nitzschia spp. and Dinophysis acuminata, impact the European shellfish industry. In temperate latitude embayments with spring-summer upwelling, reset phytoplankton mini-successions develop during short-term (a few days) wind-driven events interspersed by relaxation or downwelling. High resolution observations were made at a reference station during cruise “REMEDIOS-TLP”, 2–14 July 2018 to explore assembly dynamics (cluster analysis) and niche structuring (OMI and WitOMI) processes during a relaxation-upwelling event. A well-mixed “Relaxation habitat” (H1) co-occurred with a shallow warmer and fresher “TS stratified surface layer” (H2) (site of Alexandrium cell maximum) from the confined water mass on the shoreward side of the downwelling front. These two habitats preceded a new upwelling pulse of cold nutrient rich waters which raised the Chl-a rich waters and entrained populations of Pseudo-nitzschia through the new “Bottom upwelled water” (H4). Diatoms (central to pennate and back to central) peaked during spin up and spin down phases within the “Upwelling pycnocline” (H3), site of the subsurface chlorophyll maximum (SCML), and a short-lived thin layer (TLP). Leptocylindrus minimus, suspected threat to caged salmon in Canada and Chile, thrived at the “upwelling diatom bloom maximum” phase but spring 2018 anomalies excluded optimal environmental windows for D. acuminata development. Isolated patches of Dinophysis revealed decimetre-scale niche segregation with Alexandrium populations. Detailed biological parameterization presented here will contribute to improve prediction of assemblages and processes which favour harmful algal blooms.
{"title":"Upwelling-driven vertical segregation of co-occurring phytoplankton, including HAB species, revealed by niche analyses","authors":"Esther Velasco-Senovilla , Beatriz Reguera , Marc Sourisseau , Beatriz Mouriño-Carballido , Enrique Nogueira","doi":"10.1016/j.hal.2026.103064","DOIUrl":"10.1016/j.hal.2026.103064","url":null,"abstract":"<div><div>Recurrent toxic blooms of <em>Alexandrium minutum, Pseudo-nitzschia</em> spp. and <em>Dinophysis acuminata,</em> impact the European shellfish industry. In temperate latitude embayments with spring-summer upwelling, reset phytoplankton mini-successions develop during short-term (a few days) wind-driven events interspersed by relaxation or downwelling. High resolution observations were made at a reference station during cruise “REMEDIOS-TLP”, 2–14 July 2018 to explore assembly dynamics (cluster analysis) and niche structuring (OMI and WitOMI) processes during a relaxation-upwelling event. A well-mixed “Relaxation habitat” (H1) co-occurred with a shallow warmer and fresher “TS stratified surface layer” (H2) (site of <em>Alexandrium</em> cell maximum) from the confined water mass on the shoreward side of the downwelling front. These two habitats preceded a new upwelling pulse of cold nutrient rich waters which raised the Chl-<em>a</em> rich waters and entrained populations of <em>Pseudo-nitzschia</em> through the new “Bottom upwelled water” (H4). Diatoms (central to pennate and back to central) peaked during spin up and spin down phases within the “Upwelling pycnocline” (H3), site of the subsurface chlorophyll maximum (SCML), and a short-lived thin layer (TLP). <em>Leptocylindrus minimus</em>, suspected threat to caged salmon in Canada and Chile, thrived at the “upwelling diatom bloom maximum” phase but spring 2018 anomalies excluded optimal environmental windows for <em>D. acuminata</em> development. Isolated patches of <em>Dinophysis</em> revealed decimetre-scale niche segregation with <em>Alexandrium</em> populations. Detailed biological parameterization presented here will contribute to improve prediction of assemblages and processes which favour harmful algal blooms.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"153 ","pages":"Article 103064"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146188667","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 : 2026-03-01Epub Date: 2025-12-27DOI: 10.1016/j.hal.2025.103047
C. Taylor Armstrong , Michael Gonsior , Allen R. Place
Barley straw bales are commonly used to control cyanobacterial growth in lakes, but the method is time-consuming, labor-intensive, and its effectiveness requires deployment of bales prior to bloom formation. This study investigates brewer’s spent grain (BSG), a byproduct of the brewing process, as an alternative source of allelopathic chemicals shown to negatively impact toxic microalgae. Water extracts of BSG, barley straw, and Sargassum natans were tested for their ability to inhibit the growth of toxin-producing (Microcystis aeruginosa and Karenia brevis) as well as non-toxin-producing (Tetradesmus obliquus and Phaeodactylum tricornutum) algal species. BSG extracts at concentrations above 250 mg/L effectively inhibited the growth of both freshwater and marine toxin-producing species (M. aeruginosa and K. brevis), while exhibiting no significant effect on the diatom and chlorophyte species tested (T. obliquus and P. tricornutum). Additional experiments using antibiotics with K. brevis suggest that growth inhibition may be mediated by changes in the bacterial community, though the specific mechanism of M. aeruginosa death remains unresolved. A microcosm experiment further evaluated the impact of BSG extract on a natural bloom of cyanobacteria (Raphidiopsis raciborskii) in lake water. Application of 250 mg/L BSG extract to natural lake water shifted the community composition from cyanobacteria to chlorophyte dominance. These findings highlight the potential use for a brewery’s waste product as a cost-effective tool for managing harmful algal blooms. However, the high concentrations required, excess nutrient content in BSG, and impact on bacterial communities indicate limitations for large-scale application.
{"title":"Impact of brewer’s spent grain on freshwater and marine harmful algal bloom species","authors":"C. Taylor Armstrong , Michael Gonsior , Allen R. Place","doi":"10.1016/j.hal.2025.103047","DOIUrl":"10.1016/j.hal.2025.103047","url":null,"abstract":"<div><div>Barley straw bales are commonly used to control cyanobacterial growth in lakes, but the method is time-consuming, labor-intensive, and its effectiveness requires deployment of bales prior to bloom formation. This study investigates brewer’s spent grain (BSG), a byproduct of the brewing process, as an alternative source of allelopathic chemicals shown to negatively impact toxic microalgae. Water extracts of BSG, barley straw, and <em>Sargassum natans</em> were tested for their ability to inhibit the growth of toxin-producing (<em>Microcystis aeruginosa</em> and <em>Karenia brevis</em>) as well as non-toxin-producing (<em>Tetradesmus obliquus</em> and <em>Phaeodactylum tricornutum</em>) algal species. BSG extracts at concentrations above 250 mg/L effectively inhibited the growth of both freshwater and marine toxin-producing species (<em>M. aeruginosa</em> and <em>K. brevis</em>), while exhibiting no significant effect on the diatom and chlorophyte species tested (<em>T. obliquus</em> and <em>P. tricornutum</em>). Additional experiments using antibiotics with <em>K. brevis</em> suggest that growth inhibition may be mediated by changes in the bacterial community, though the specific mechanism of <em>M. aeruginosa</em> death remains unresolved. A microcosm experiment further evaluated the impact of BSG extract on a natural bloom of cyanobacteria (<em>Raphidiopsis raciborskii</em>) in lake water. Application of 250 mg/L BSG extract to natural lake water shifted the community composition from cyanobacteria to chlorophyte dominance. These findings highlight the potential use for a brewery’s waste product as a cost-effective tool for managing harmful algal blooms. However, the high concentrations required, excess nutrient content in BSG, and impact on bacterial communities indicate limitations for large-scale application.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"153 ","pages":"Article 103047"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923045","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 : 2026-03-01Epub Date: 2026-01-24DOI: 10.1016/j.hal.2026.103066
Peter F. Cook , Colleen Reichmuth , Megan E. Moriarty , Alissa C. Deming , Vanessa Fravel Hoard , Cara Field , Frances Gulland
Domoic acid-producing algal blooms are increasing in size, frequency, and duration along the eastern Pacific coastline resulting in regular and repeated exposure of marine mammals to the toxin. Because of their prolonged gestation, large numbers of marine mammals are now encountering this excitotoxin in utero, with potential long-term developmental effects. Evidence of developmental neurotoxic effects is accumulating in California sea lions particularly, which serve as an accessible sentinel species for studying the effects of domoic acid exposure in mammals. In biomedical settings, rodent models have revealed some developmental aspects of early domoic acid exposure, including a tendency for gross neurobehavioral changes to emerge after puberty. However, rodents are altricial and have a truncated developmental course. In contrast, marine mammals are precocial and mature slowly. Further, neurobehavioral responses to domoic acid have notable differences between those in adult rodents exposed in vivariums and in free-ranging wildlife. Primate models address some of these gaps, but are limited by practical constraints. There is a clear need to establish an ecologically valid model of brain development and clinical progression of developmental domoic acid exposure in long-lived and precocial mammals. Here we present California sea lions born in wildlife rehabilitation facilities to mothers with documented domoic acid toxicosis as a promising and accessible disease model, and we provide a framework for future research. Hundreds of adult sea lions in rehabilitation centers have already taken part in veterinary assessments and experimental assays of brain and behavior, demonstrating the plausibility of careful and scalable science with these animals. We discuss preliminary work with a juvenile sea lion enrolled in a longitudinal study with repeated clinical, behavioral, and neurobiological assessment, and advocate for cohort-based studies of maternally exposed sea lions.
{"title":"Sea lions as a natural model for charting the developmental course following in utero exposure to domoic acid","authors":"Peter F. Cook , Colleen Reichmuth , Megan E. Moriarty , Alissa C. Deming , Vanessa Fravel Hoard , Cara Field , Frances Gulland","doi":"10.1016/j.hal.2026.103066","DOIUrl":"10.1016/j.hal.2026.103066","url":null,"abstract":"<div><div>Domoic acid-producing algal blooms are increasing in size, frequency, and duration along the eastern Pacific coastline resulting in regular and repeated exposure of marine mammals to the toxin. Because of their prolonged gestation, large numbers of marine mammals are now encountering this excitotoxin in utero, with potential long-term developmental effects. Evidence of developmental neurotoxic effects is accumulating in California sea lions particularly, which serve as an accessible sentinel species for studying the effects of domoic acid exposure in mammals. In biomedical settings, rodent models have revealed some developmental aspects of early domoic acid exposure, including a tendency for gross neurobehavioral changes to emerge after puberty. However, rodents are altricial and have a truncated developmental course. In contrast, marine mammals are precocial and mature slowly. Further, neurobehavioral responses to domoic acid have notable differences between those in adult rodents exposed in vivariums and in free-ranging wildlife. Primate models address some of these gaps, but are limited by practical constraints. There is a clear need to establish an ecologically valid model of brain development and clinical progression of developmental domoic acid exposure in long-lived and precocial mammals. Here we present California sea lions born in wildlife rehabilitation facilities to mothers with documented domoic acid toxicosis as a promising and accessible disease model, and we provide a framework for future research. Hundreds of adult sea lions in rehabilitation centers have already taken part in veterinary assessments and experimental assays of brain and behavior, demonstrating the plausibility of careful and scalable science with these animals. We discuss preliminary work with a juvenile sea lion enrolled in a longitudinal study with repeated clinical, behavioral, and neurobiological assessment, and advocate for cohort-based studies of maternally exposed sea lions.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"153 ","pages":"Article 103066"},"PeriodicalIF":4.5,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146188666","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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