Harmful Algae最新文献

{"title":"Ca2+ binding to soluble extracellular polymeric substances promotes loosening of Microcystis colonies under high Ca2+conditions","authors":"Ping Zhang ,&nbsp;Caihong Qin ,&nbsp;Chao Xiong ,&nbsp;Xinyue Li ,&nbsp;Bin Yan ,&nbsp;Xuemei Chen ,&nbsp;Han Wang ,&nbsp;Kai Li ,&nbsp;Yan Xiao","doi":"10.1016/j.hal.2025.103044","DOIUrl":"10.1016/j.hal.2025.103044","url":null,"abstract":"<div><div>Colony formation is crucial for the development of <em>Microcystis</em> blooms, which pose a significant ecological challenge on a global scale. Previous studies have demonstrated that bound extracellular polymeric substances (EPS) play a vital role in the colony formation process. However, the influence of the coexisting soluble EPS (S-EPS) on <em>Microcystis</em> colony formation remains unclear. This study investigated the effect of S-EPS on the colony formation of <em>Microcystis</em> induced by high concentrations of Ca²⁺. The results indicated that the combined treatment of S-EPS (100 mg/L) and Ca²⁺ (200 mg/L) resulted in loosely bound <em>Microcystis</em> colonies, in contrast to the dense colonies induced by 200 mg/L Ca²⁺. In contrast, no colonies were formed when the <em>Microcystis</em> cells were treated with S-EPS alone. In addition, the incorporation of 100 mg/L of S-EPS into 200 mg/L Ca²⁺-treated <em>Microcystis</em> cells reduced the cell zeta potential by 2.09 mV and decreased surface hydrophobicity, as indicated by a 1.60° increase in the water contact angle that increased the interaction energy among <em>Microcystis</em> cells. The energy barrier increased from 293.32 KT in the 200 mg/L Ca²⁺ treatment groups to 538.10 KT following the introduction of 100 mg/L S-EPS, indicating a reduced propensity for colony formation after S-EPS addition. Further studies indicated that Ca²⁺ in the inoculum exhibited a strong binding capacity with the <em>O</em><img><em>H</em> groups of polysaccharides (K_M = 0.032 ± 0.004), <em>C<img>C</em> stretching of aromatics (K_M = 0.022 ± 0.003) and tryptophan-like proteins (K_M = 0.013 ± 0.001) from S-EPS. This resulted in extensive networks and lower free Ca²⁺ concentrations that reduced the bound EPS secretion by approximately 0.15 pg/cell compared to that with a Ca²⁺ concentration of 200 mg/L. This study provides new insights into the mechanism of colony formation in <em>Microcystis</em>.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"152 ","pages":"Article 103044"},"PeriodicalIF":4.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145788111","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}

{"title":"Environmentally relevant concentrations of the antibiotic azithromycin enhance the toxicity of the cyanobacterium Microcystis aeruginosa on the water flea Daphnia similis","authors":"Michael Ribas Celano ,&nbsp;Júlia Vianna De Pinho ,&nbsp;Sandra Maria Feliciano de Oliveira e Azevedo ,&nbsp;Mauro Cesar Palmeira Vilar","doi":"10.1016/j.hal.2025.103040","DOIUrl":"10.1016/j.hal.2025.103040","url":null,"abstract":"<div><div>Artificial eutrophication has degraded water bodies worldwide, promoting harmful cyanobacterial blooms (CyanoHABs). In addition to nutrient loading, antibiotics are increasingly being introduced into aquatic environments, exacerbating water pollution, and the impact on biota. Among antibiotics, azithromycin (AZT) has displayed a rise in environmental occurrence following its increased global consumption during the COVID-19 pandemic. Therefore, we assessed the effect of environmentally relevant concentrations of AZT (≤3 μg <span>l</span>^-1) on the interaction between the toxic cyanobacterium <em>Microcystis aeruginosa</em> and the freshwater zooplankton <em>Daphnia similis</em>. The acute toxicity of both the cyanobacterium and antibiotic on <em>Daphnia</em> was determined, followed by an herbivory and a life-table assay to assess behavioral and sublethal effects under single and combined exposures. The 96-hour LC₅₀ and EC₅₀ for AZT were 35.2 and 29.1 mg <span>l</span>^-1, respectively. The risk quotient for <em>D. similis</em> was 0.098, indicating a low ecological risk (RQ &lt; 0.1). Regarding <em>M. aeruginosa</em>, 96-hour LC₅₀ and EC₅₀ values were 713 and 303 μgC <span>l</span>^-1, respectively, with RQ values &gt;700, indicating a high ecological risk. Environmental levels of AZT did not affect <em>Daphnia</em>, while the cyanobacterium inhibited zooplankter feeding and life-table responses. However, combined exposure to AZT and toxic <em>M. aeruginosa</em> resulted in a greater decrease in survival and overall population fitness, besides an increased cyanobacterial ingestion. These findings suggest that environmental concentrations of AZT may intensify the impacts of toxic cyanobacteria on zooplankton. This highlights the need for further research into the mechanisms underlying the enhanced toxicity of cyanobacteria promoted by antibiotics at environmental levels.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"152 ","pages":"Article 103040"},"PeriodicalIF":4.5,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145735220","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}

{"title":"Cyanotoxin production in shallow subtropical lakes is driven by nutrient enrichment and primary producer abundance on the millennial scale","authors":"Savvas Paradeisis-Stathis ,&nbsp;Matthew N. Waters ,&nbsp;Debra A. Willard ,&nbsp;Sophia Foliano ,&nbsp;Richard S. Vachula","doi":"10.1016/j.hal.2025.103004","DOIUrl":"10.1016/j.hal.2025.103004","url":null,"abstract":"<div><div>Increased cyanotoxin concentrations from harmful algal blooms (HABs) in lake systems pose a global challenge to water quality. Although progress has been made in monitoring cyanotoxins in modern environments over recent decades, identifying the triggers of cyanotoxin release by cyanobacteria has yielded mixed results from experimental and analytical studies. Paleolimnological reconstructions can reveal whole-lake long-term changes, but few studies have directly measured cyanotoxins alongside other water quality proxies. Here, we investigated the drivers of sedimentary total microcystin (MC) concentrations on millennial scales in hypereutrophic Lakes Dora and Marian in central Florida, USA. We analyzed dated sediment records using paleolimnological techniques to reconstruct nutrient deposition, cyanobacteria abundance (photosynthetic pigments), and cyanotoxins (total MCs). The objective was to investigate the linkage between MC concentrations in the sediments with both biotic (cyanobacteria and other primary producers) and abiotic factors (nutrients and climate). We found that MC production occurred throughout the ∼7000-year period, progressing from periods of moderate to low, and then to high concentrations in both lakes. Statistical analyses showed that historical MC concentrations were correlated with sedimentary measurements of total phosphorus (TP), cyanobacteria abundance, and other primary producer groups, such as cryptophytes. However, there was only a minimal correspondence with climate proxies, such as charcoal and pollen, suggesting that internal nutrient cycling and human pressures were the dominant drivers of MC deposition. Our study demonstrates that cyanotoxins have occurred for millennia in both lakes with maintained relationships to nutrients and other environmental factors that existed both in historic and modern limnological conditions.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"151 ","pages":"Article 103004"},"PeriodicalIF":4.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145465113","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}

{"title":"Spatial distribution and diversity of mcyA gene-carrying cyanobacteria in planktic and benthic communities of Swiss alpine lakes","authors":"Anna Carratalà ,&nbsp;Lisa Morales ,&nbsp;Bastiaan W Ibelings","doi":"10.1016/j.hal.2025.103007","DOIUrl":"10.1016/j.hal.2025.103007","url":null,"abstract":"<div><div>Cyanobacteria are notorious for producing harmful toxins, including microcystins, which can severely impact animal and human health. In Swiss alpine lakes, past episodes of cattle deaths have been linked to acute hepatotoxicosis caused by microcystins from benthic cyanobacteria but to date not much is known about the diversity of microcystin-producing cyanobacteria in these ecosystems, their spatial distribution or favorable ecological niches. In this study, we examined the presence and distribution of cyanobacteria communities across 31 alpine lakes in Switzerland, conducting a comparative survey of both planktic and benthic environments. The goal of this study was to better understand the composition and distribution of cyanobacterial communities found in the Swiss Alps that may produce microcystins, as well as to explore their association with selected bioclimatic variables. A total of 64 biomass samples were collected from high-altitude lakes in the Alps between June and October 2022. We used digital PCR (dPCR) to quantify the <em>mcyA</em> gene, a marker for cyanobacteria carrying microcystin genes, and performed high throughput 16S rRNA sequencing to characterize the taxonomic diversity of cyanobacterial communities. The obtained results revealed that 80 % of the planktic samples and 91 % of the benthic samples tested positive for the <em>mcyA</em> gene, indicating the widespread presence of <em>mcyA</em> carrying cyanobacteria in these lakes. Benthic environments showed comparable or higher <em>mcyA</em> concentrations per unit biomass to planktic samples, taken from the same locations, with biofilms and rock mats exhibiting the highest levels. Moran’s I statistic revealed significant spatial clustering of <em>mcyA</em>-carrying cyanobacteria, suggesting the presence of higher-risk locations in the Alps. Principal component analysis (PCA) identified lower precipitation levels as the most influential tested environmental factor driving this clustering. 16S rRNA analysis further revealed distinct cyanobacterial community compositions between planktic and benthic environments in remote altitude lakes, with genera <em>Phormidesmis</em> and <em>Leptolyngbya</em> dominant in benthic habitats, while <em>Pseudanabaena</em> and <em>Tychonema</em> were more prevalent in planktic samples. Our findings suggest that water flow may play a significant role in driving the proliferation of <em>mcyA</em> carrying cyanobacteria in high altitdue lakes of the Swiss Alps and highlight the need for integrated monitoring of both benthic and planktic cyanobacteria to correctly assess the risk of microcystin exposure in alpine lakes.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"151 ","pages":"Article 103007"},"PeriodicalIF":4.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145442614","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}

{"title":"Silencing of apoptotic gene caspase-2 enhances the susceptibility of a keystone aquatic grazer to cyanobacterial stress","authors":"Tiantian Zheng,&nbsp;Xinyu Zhou,&nbsp;Linru Hao,&nbsp;Xinyu Zhang,&nbsp;Yiqin Ma,&nbsp;Yuzhou Hou,&nbsp;Kai Lyu,&nbsp;Zhou Yang","doi":"10.1016/j.hal.2025.103031","DOIUrl":"10.1016/j.hal.2025.103031","url":null,"abstract":"<div><div>The increasing frequency of cyanobacterial blooms poses escalating ecological stress on freshwater ecosystems worldwide. These disturbances primarily act through impacts on basal trophic groups—most notably zooplankton. Apoptosis is a vital mechanism for preserving cellular homeostasis and managing stress at the organismal level, yet the role of its conserved regulators, such as caspase-2, remains poorly understood in aquatic grazers. We characterized a pivotal caspase-2 homolog in the freshwater water flea <em>Moina macrocopa</em>, an important model in aquatic ecology, and designated it Mm-cas2. Mm-cas2 possesses the characteristic caspase CASs domain, and phylogenetic analysis confirmed its classification within the caspase-2 family. Exposure to toxic <em>Microcystis aeruginosa</em> induced a dose-dependent increase in Mm-cas2 expression, confirmed at both mRNA (qRT-PCR) and protein (Western blot) levels. Spatial mapping via Whole-mount in situ hybridization (WISH) further indicated heterogeneous Mm-cas2 expression within the <em>M. macrocopa</em> organism. Critically, RNAi-mediated silencing of Mm-cas2 significantly heightened developmental retardation and reproductive obstruction in cyanobacteria-exposed <em>M. macrocopa</em>, confirming its essential role in governing sensitivity to <em>M. aeruginosa</em>. Our findings collectively reveal how the apoptotic regulator caspase-2 governs the sensitivity of <em>M. macrocopa</em> to <em>M. aeruginosa</em>, establishing Mm-cas2 as a candidate biomarker to evaluate ecological risks in freshwater ecosystems prone to cyanobacterial blooms outbreaks.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"151 ","pages":"Article 103031"},"PeriodicalIF":4.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145577595","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}

{"title":"Strengthening regional cooperation: The role of the Cartagena Convention in addressing the sargassum inundations challenge in the wider Caribbean","authors":"Susana Perera-Valderrama ,&nbsp;Geraldine Conruyt ,&nbsp;Lucile Rossin ,&nbsp;Auriane Petit ,&nbsp;Tamoy Singh-Clarke ,&nbsp;Christopher Corbin","doi":"10.1016/j.hal.2025.103028","DOIUrl":"10.1016/j.hal.2025.103028","url":null,"abstract":"<div><div>The ongoing presence of Sargassum inundations has led to various national and regional initiatives in the Wider Caribbean Region. However, these efforts often lack cohesion, resulting in overlap and duplication, missed opportunities for sharing knowledge and best practices and uncoordinated resource mobilization and partnerships. This review article emphasizes the current role and potential of the Cartagena Convention as an important regional mechanism for cooperation, harmonization, and decision-making. Through the work of the Convention and its Protocols, several cooperative solutions have been implemented on various topics relating to the protection, conservation and sustainable use of marine and coastal biodiversity and the control, reduction and prevention of pollution from land and marine-based sources. The Secretariat, supported by Regional Activity Centres and partner agencies are well placed to foster greater collaboration in addressing the Sargassum inundation issue. We provide an overview of the regional response to Sargassum management in the Caribbean including current gaps and challenges. We identify some key areas requiring regional cooperation, including enhanced monitoring of Sargassum impacts, standardized response protocols, policy harmonization, and public awareness initiatives. Finally, we propose some next steps, including further leveraging the legal framework provided by the Cartagena Convention and its Protocols to support the Caribbean countries and the broader Wider Caribbean Region in strengthening cooperation on Sargassum-related issues, facilitating the adoption of common standards for its management, and promoting collaborative research initiatives.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"151 ","pages":"Article 103028"},"PeriodicalIF":4.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145527429","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}

{"title":"Melatonin promotes dinoflagellate cyst germination by crosstalk with abscisic acid and gibberellin","authors":"Caixia Yue ,&nbsp;Yunyan Deng ,&nbsp;Fengting Li ,&nbsp;Zhaoyang Chai ,&nbsp;Zhe Tao ,&nbsp;Lixia Shang ,&nbsp;Ying Zhong Tang","doi":"10.1016/j.hal.2025.103030","DOIUrl":"10.1016/j.hal.2025.103030","url":null,"abstract":"<div><div>Dinoflagellates play pivotal roles in marine ecosystems, particularly as major contributors to marine harmful algal blooms (HABs). Their resting cysts, analogous to higher plant seeds, directly regulate seasonal population dynamics and initiate HABs through germination. The phytohormone Melatonin (MEL) has been widely documented to regulate seed germination in higher plants. This study investigated the effect of exogenously-added MEL on the germination of dinoflagellate resting cyst assemblage isolated from marine sediment and its possible interplay with two other dormancy-related phytohormones (abscisic acid, ABA, and gibberellic acid, GA3) in regulating germination of cysts both from sediment and the representative cyst-producing dinoflagellate <em>Scrippsiella acuminata</em>. Exogenous addition assays revealed that while MEL significantly inhibited cyst germination when concentrations &gt;100 μM, it enhanced cyst germination dose-dependently within 1.0–8.0 μM. MEL antagonized ABA in regulating cyst germination and repressing ABA biosynthesis genes but up-regulating ABA catabolic genes. However, MEL synergized with GA3 in promoting germination by enhancing GA biosynthesis and via induction of GA receptor. All results collectively suggest MEL promotes dinoflagellate cyst germination by crosstalk with ABA and GA3, and these phytohormones in protists play roles similar to that in higher plants. Our study provides novel evidences for the regulating roles and mechanisms of MEL.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"151 ","pages":"Article 103030"},"PeriodicalIF":4.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145577629","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}

{"title":"Temperature dependent response of microcystin-LR in acclimated M. aeruginosa PCC 7806","authors":"Pierre-Louis Lalloué,&nbsp;Clarisse Mallet,&nbsp;Alexandre Bec,&nbsp;Apostolos-Manuel Koussoroplis,&nbsp;Fanny Perrière,&nbsp;Delphine Latour","doi":"10.1016/j.hal.2025.103018","DOIUrl":"10.1016/j.hal.2025.103018","url":null,"abstract":"<div><div>As climate change raises global temperatures and increases the frequency of cyanobacterial blooms, understanding how rising mean temperatures affect cyanotoxin content is crucial. However, no clear consensus exists, and the use of different methodologies, including different units of measurement and experimental conditions could significantly alter the yield of the relationship between temperature and toxins content. In this study, we assessed free microcystin content and cell volume in <em>Microcystis aeruginosa</em> PCC 7806 acclimated to seven temperatures spanning its entire thermal niche. This experimental design firstly highlighted the significant reduction in cell volume with rising temperatures between 17 °C and 29 °C. As a result, when the microcystin concentration was normalized by its cell volume, its temperature response was transformed from a negative correlation to a bell-shaped curve, with higher free MC-LR content measured at an estimated optimum temperature of 25.5 °C, close to the thermal growth optimum of <em>Microcystis aeruginosa</em>. These findings provide new insights into the effects of climate warming on microcystin content.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"151 ","pages":"Article 103018"},"PeriodicalIF":4.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145527430","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}

{"title":"Occurrence of toxic microalgae and associated toxins in the western Black Sea: insights from the PHYCOB cruise in September 2021","authors":"Nina Dzhembekova ,&nbsp;Fuat Dursun ,&nbsp;Urban Tillmann ,&nbsp;Ivelina Zlateva ,&nbsp;Oana Vlas ,&nbsp;Nataliya Slabakova ,&nbsp;Kristof Möller ,&nbsp;Snejana Moncheva ,&nbsp;Florian Koch ,&nbsp;Laura Boicenco ,&nbsp;Ertuğrul Aslan ,&nbsp;Sabri Mutlu ,&nbsp;Ivan Popov ,&nbsp;Satoshi Nagai ,&nbsp;Bernd Krock","doi":"10.1016/j.hal.2025.103025","DOIUrl":"10.1016/j.hal.2025.103025","url":null,"abstract":"<div><div>Harmful Algal Blooms (HABs) represent a significant global challenge to human health, economies, and ecosystems, including those of the Black Sea. Despite previous reports of potentially toxic microalgae and phycotoxins in the basin, the taxonomy and occurrence of toxigenic species and their associated toxins remain poorly resolved. During the PHYCOB cruise in September 2021, the diversity and distribution of toxigenic microalgae and phycotoxins were investigated across 23 stations in the western Black Sea, covering Bulgarian and Romanian waters. Numerous potentially toxic microalgal taxa were identified using complementary morphological (light microscopy and scanning electron microscopy) and molecular (DNA metabarcoding) methods. The genus <em>Pseudo-nitzschia</em> was the only representative of potentially toxic diatoms, but no domoic acid was found. Among toxic dinoflagellates, <em>Dinophysis</em> spp., <em>Protoceratium reticulatum, Lingulaulax polyedra</em>, and <em>Gonyaulax</em> spp<em>.</em> were frequently observed, along with the related pectenotoxins and yessotoxins. Species distribution modelling indicated that the western Black Sea provides favorable conditions for <em>Dinophysis</em> spp., <em>L. polyedra</em>, and <em>P. reticulatum</em>. Additionally, several <em>Alexandrium</em> species were identified, including the first record of <em>A. fragae</em> in the basin, along with the detection of the associated phycotoxins (GTX-2/3 and GDA). This study provides the first integrated assessment combining light and scanning electron microscopy, DNA metabarcoding, and chemical analyses of toxigenic microalgae in field samples from the western Black Sea, contributing to an improved understanding of their region-specific profiles.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"151 ","pages":"Article 103025"},"PeriodicalIF":4.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145688846","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}

{"title":"Urban eutrophication enhances domoic acid production by Pseudo-nitzschia in the Southern California Bight","authors":"Marco Sandoval-Belmar ,&nbsp;Faycal Kessouri ,&nbsp;Jayme Smith ,&nbsp;Allison R. Moreno ,&nbsp;Clarissa Anderson ,&nbsp;Raphael M. Kudela ,&nbsp;Martha Sutula ,&nbsp;Minna Ho ,&nbsp;Pierre Damien ,&nbsp;Claudia Benitez-Nelson ,&nbsp;James C. McWilliams ,&nbsp;Daniele Bianchi","doi":"10.1016/j.hal.2025.103023","DOIUrl":"10.1016/j.hal.2025.103023","url":null,"abstract":"<div><div>The diatom genus <em>Pseudo-nitzschia</em> and its neurotoxin domoic acid (DA) are major contributors to harmful algal blooms (HABs) along the U.S. West Coast, affecting marine ecosystems and human health. Observations implicate anthropogenic nutrient inputs, upwelling, and climate variability, but their relative importance remains unclear. We couple a mechanistic DA-production model, constrained by culture experiments, to a three-dimensional ocean biogeochemical model to simulate the DA cycle in the Southern California Bight, an urbanized region with a population of 23 million. Using 1-km resolution simulations for 2006–2017 we compare two cases: (i) an anthropogenic scenario (ANTH), in which rivers and wastewater outfalls supply freshwater and enhanced nutrient loads, and (ii) a control (CTRL) with freshwater-only fluxes, and nutrient loads set to zero. Skill assessments show that ANTH captures observed seasonal patterns, vertical distributions, and horizontal gradients of particulate DA. Performance is highest in the San Pedro and Santa Barbara Channels, but lower elsewhere, indicating need for refinements to capture local HAB dynamics. Comparison of the two simulations shows that terrestrial nitrogen inputs enhance coastal diatom production and shift nutrient limitation from nitrogen to silica, amplifying DA production. Surface particulate DA along the coast increases on average by <span><math><mo>∼</mo></math></span>25% with anthropogenic inputs, suggesting a substantial enhancement of the region’s natural susceptibility to DA events. This study advances our ability to disentangle natural versus human drivers of <em>Pseudo-nitzschia</em> HABs, quantifying the role of anthropogenic inputs among the drivers of DA production in the Bight.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"151 ","pages":"Article 103023"},"PeriodicalIF":4.5,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145577567","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}