Harmful Algae最新文献

{"title":"Effects of cyanobacterium Phormidium nigroviride K3 on zebrafish embryos and genomic insights into its toxic potential","authors":"Petar Davidović ,&nbsp;Dajana Blagojević ,&nbsp;Svetlana Fa Nedeljković ,&nbsp;Miloš Tanurdžić ,&nbsp;Kristina Bekvalac ,&nbsp;Ivana Matić ,&nbsp;Mihajla Đan ,&nbsp;Nebojša Andrić ,&nbsp;Jelica Simeunović","doi":"10.1016/j.hal.2025.102861","DOIUrl":"10.1016/j.hal.2025.102861","url":null,"abstract":"<div><div>Cyanobacterial blooms in freshwater systems pose significant environmental and public health risks, largely due to their production of toxic secondary metabolites. This study investigated the effects of <em>Phormidium nigroviride</em> K3 extracts on early zebrafish development, focusing on organismal toxicity and gene expression changes. Acute toxicity was assessed by monitoring developmental deformities and evaluating relative changes in the expression of six genes associated with xenobiotic metabolism, apoptosis, endoplasmic reticulum stress, and endocrine processes. Whole-genome sequencing, <em>in silico</em> genome annotation and mining were conducted to identify biosynthetic gene clusters involved in toxin production. Zebrafish embryos exposed to <em>P. nigroviride</em> K3 extracts developed spinal deformities, pericardial edema, yolk sac edema and reduced eye size, with spinal deformities being the most prevalent malformation (EC50 of 215.6 µg d.w. mL⁻¹). Significant alterations in the expression of genes involved in xenobiotic metabolism were detected, including a dose-dependent 4.6-fold induction of <em>cyp1a1</em> and a 4.47-fold increase in <em>abcb4</em> expression at the highest extract concentration. Genome analysis of <em>P. nigroviride</em> K3 revealed 15 biosynthetic gene clusters for secondary metabolites, including a match with the <em>Cylindrospermopsis raciborskii</em> AWT205 cluster, responsible for the cyanotoxin cylindrospermopsin biosynthesis. The LC-MS/MS analysis confirmed the production of cylindrospermopsin in <em>P. nigroviride</em> K3, providing new insights into cyanotoxin biosynthesis in <em>Phormidium</em> species, a genus that has been underexplored in the context of toxin production. These findings expand cyanobacterial genomic databases, enhancing our understanding of cyanobacterial toxic potential. Such knowledge is crucial for predicting and mitigating the risks associated with cyanotoxins in aquatic ecosystems.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"145 ","pages":"Article 102861"},"PeriodicalIF":5.5,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143860464","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":"Gambierdiscus polynesiensis from New Caledonia (South West Pacific Ocean): Morpho-molecular characterization, toxin profile and response to light intensity","authors":"Manoëlla Sibat ,&nbsp;Tepoerau Mai ,&nbsp;Nicolas Chomérat ,&nbsp;Gwenael Bilien ,&nbsp;Korian Lhaute ,&nbsp;Philipp Hess ,&nbsp;Véronique Séchet ,&nbsp;Thierry Jauffrais","doi":"10.1016/j.hal.2025.102859","DOIUrl":"10.1016/j.hal.2025.102859","url":null,"abstract":"<div><div><em>Gambierdiscus</em> is known to produce neurotoxins associated with ciguatera poisoning (CP). In New Caledonia (NC), South West Pacific Ocean, there is currently a significant knowledge gap regarding CP and the microalgae linked to this foodborne illness. This study describes a new strain of <em>Gambierdiscus polynesiensis</em>, 19PV93, isolated from the west coast of NC. The strain was isolated and cultured for morpho-molecular characterization to determine its phylogenetic position. Toxic activity was assessed using a cell-based assay with neuroblastoma cells (CBA-N2a), and the toxin profile was characterized using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) to evaluate potential risks to human health. Regarding the toxin profile, <em>G. polynesiensis</em> was characterized by the presence of gambierone, 44-methylgambierone (44-MeG), and an atypical ciguatoxin profile consisting solely of ciguatoxin-4A (CTX4A) and -4B (CTX4B). This finding confirms intraspecific variations in toxin profiles between strains from different geographic origins. In culture, <em>G. polynesiensis</em> demonstrated a preference for relatively low irradiances (50 to 100 µmol photons m⁻² s⁻¹) compared to the higher light intensities often encountered in their natural environment. The impact of light on toxin concentrations was found to be inversely related to light intensity, with higher quotas observed at lower light levels. <em>Gambierdiscus</em> employed non-photochemical quenching as a photoprotective strategy to safeguard PSII from excessive light, particularly during both short-term and long-term exposure. However, this dissipation strategy alone appears insufficient, as photoinhibition was consistently observed, and the electron transfer rate and yield along the electron transfer chain rapidly declined with increasing light intensity.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"145 ","pages":"Article 102859"},"PeriodicalIF":5.5,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143839565","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":"Microcystin contamination of shellfish along the freshwater-to-marine continuum within US mid-Atlantic and Northeast estuaries","authors":"Marcella Kretz Wallace ,&nbsp;Raphael M. Kudela ,&nbsp;Christopher J. Gobler","doi":"10.1016/j.hal.2025.102860","DOIUrl":"10.1016/j.hal.2025.102860","url":null,"abstract":"<div><div>Estuaries are dynamic ecosystems that are an important habitat for bivalves. The freshwater bodies that discharge into estuaries can introduce cyanobacteria and cyanotoxins that may accumulate within food webs. Microcystin is a hepatotoxin that causes adverse health effects in humans and can be harmful to terrestrial and aquatic organisms. Microcystin has been detected in marine bivalves and the rate of microcystin accumulation and depuration differs between bivalve species. No study has explored the presence or dynamics of microcystins in bivalves in the Northeast US, where they represent a major fishery. This study quantified levels of microcystins in wild and cultured bivalves as a time series from 2017 to 2021 in three of the largest US East Coast estuaries (Chesapeake Bay, the Hudson River Estuary, and Long Island Sound) that have hosted microcystin-producing cyanobacterial harmful algal blooms (CHABs) within their watersheds. During this study, microcystins were rarely detected in bivalves across Chesapeake Bay but were commonly quantified in multiple bivalve species in the Hudson River estuary and within two harbors of Long Island Sound, Stony Brook Harbor and Conscience Bay. Microcystins were detected in clams (<em>Mercenaria mercenaria</em> and <em>Corbicula fluminea</em>), Eastern oysters (<em>Crassostrea virginica</em>), and mussels (<em>Mytilus edulis</em> and <em>Geukensia demissa</em>). Eastern oysters (<em>C. virginica</em>) had significantly higher levels of microcystin than other bivalve species <em>(p</em> &lt; 0.05) and often contained microcystin even when other bivalves sampled concurrently did not, suggesting oysters may be a vector for hepatotoxic shellfish poisoning in estuaries. Microcystins were detected in oysters even in fall months after water column cyanobacterial biomass and microcystins had decreased to low levels, suggesting toxin depuration slows during colder months. Collectively, this study demonstrates that microcystin accumulation in estuarine bivalves, particularly Eastern oysters (<em>C. virginica</em>), occurs within several of the larger US East Coast estuaries and could represent a public health risk.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"145 ","pages":"Article 102860"},"PeriodicalIF":5.5,"publicationDate":"2025-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143839566","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":"The effect of temperature and salinity on Margalefidinium polykrikoides group III VA, USA strain growth","authors":"Eduardo Pérez-Vega,&nbsp;Margaret R. Mulholland,&nbsp;Katherine E. Crider,&nbsp;Kimberly E. Powell ,&nbsp;P.Dreux Chappell ,&nbsp;Alexander Bochdansky","doi":"10.1016/j.hal.2025.102837","DOIUrl":"10.1016/j.hal.2025.102837","url":null,"abstract":"<div><div><em>Margalefidinium polykrikoides</em> is a cosmopolitan dinoflagellate that blooms in coastal waters. Despite genomic evidence that it belongs to Group III and so closely related to isolates from Puerto Rico, Malaysia, North America, and Central America, <em>M. polykrikoides</em> blooms in the Chesapeake Bay at warmer temperatures and lower salinities than in coastal ecosystems occupied by its closest relatives. In this study, the effect of temperature and salinity on the growth rate and total cell yield of an <em>M. polykrikoides</em> VA culture isolate were examined and compared with environmental observations made during <em>M. polykrikoides</em> blooms in the Chesapeake Bay. <em>M. polykrikoides</em> group III VA strain grew at 18–32 ̊C and 15–30 salinity. <em>M. polykrikoides</em> group III VA strain grew better at warmer temperatures and lower salinities than other <em>M. polykrikoides</em> strains from related groups, but did not grow at 16 or 34 ̊C or at a salinity of 10. Low salinity and excessively warm temperatures interacted to inhibit <em>M. polykrikoides</em> group III VA strain growth at 32 ̊C and 15 salinity. Temperature and salinity likely interact in estuarine waters to inhibit or promote <em>M. polykrikoides</em> bloom initiation and development. The range of water temperatures observed during <em>M. polykrikoides</em> blooms in the Chesapeake Bay was narrower than what was observed for most of the other dinoflagellate species that bloom there, but the range of salinity was the broadest. <em>M. polykrikoides</em> bloomed at warmer temperatures and higher salinities than most of the other bloom-forming dinoflagellate species in the Bay.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"146 ","pages":"Article 102837"},"PeriodicalIF":5.5,"publicationDate":"2025-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144099265","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":"Spatiotemporal distribution, composition, and influencing factors of lipophilic marine algal toxins in the Beibu Gulf, China: Implications for necessity of offshore seawater monitoring","authors":"Wee Vian Low ,&nbsp;Li Zhang ,&nbsp;Pengbin Wang ,&nbsp;Pengfei Zheng ,&nbsp;Xi Yang ,&nbsp;Lu Lu ,&nbsp;Junjie Zheng ,&nbsp;Zuhao Zhu ,&nbsp;Jie Chen ,&nbsp;Mengmeng Tong","doi":"10.1016/j.hal.2025.102845","DOIUrl":"10.1016/j.hal.2025.102845","url":null,"abstract":"<div><div>Lipophilic marine algal toxins (LMATs) are persistent, bioaccumulative metabolites that pose significant threats to marine biodiversity and seafood safety. To comprehensively understand LMATs pollution in offshore natural fishing grounds, we investigated the spatiotemporal distribution and composition of 13 LMATs in surface seawater in Beibu Gulf's offshore area, along with their key influencing factors and latitudinal variations across coastal regions in China. We detected 20-methyl spirolide G (SPX20G) for the first time in coastal waters in China, alongside other frequently detected LMATs, including okadaic acid (OA), dinophysistoxin-1 (DTX1), pectenotoxin-2 (PTX2), azaspiracid-1 (AZA1), azaspiracid-2 (AZA2), gymnodimine (GYM), and 13-desmethyl spirolide C (SPX1). Significant seasonal variations were observed, with summer exhibiting eight LMAT types and higher total LMAT concentrations (ΣLMATs) (16.92 ± 20.45 ng/L) compared to winter's five LMAT types and ΣLMATs concentrations at 5.63 ± 3.30 ng/L. Predominant PTX2 and OA concentrations showed a decreasing trend from northern to southern Beibu Gulf, while other LMATs were distributed in patches, particularly in summer. Notably, cyclic imines (GYM and SPX1) were detected with high frequencies and concentrations, underscoring the need for their monitoring. Spearman correlation and redundancy analyses identified water depth, chlorophyll <em>a</em> (Chl<em>a</em>), temperature, salinity, nutrients (DIN:DIP and SiO₃²⁻), and dissolved oxygen (DO) as key factors influencing LMATs distribution in the Beibu Gulf. Latitudinal analysis of LMAT contents across Chinese waters revealed DTX1 as more prevalent at higher latitudes, and GYM, SPX1, and AZA1 more common at lower latitudes, while ΣLMATs concentrations from this study ranked at moderate to high levels compared to other regions. Therefore, special attention is required for LMATs pollution in offshore fishing areas.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"145 ","pages":"Article 102845"},"PeriodicalIF":5.5,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143767508","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":"Multi-year dynamics of harmful algae in Disko Bay, West Greenland","authors":"Cora Hoerstmann ,&nbsp;Per Juel Hansen ,&nbsp;Nina Lundholm ,&nbsp;Bernd Krock ,&nbsp;Uwe John","doi":"10.1016/j.hal.2025.102857","DOIUrl":"10.1016/j.hal.2025.102857","url":null,"abstract":"<div><div>Harmful algal blooms (HABs) increasingly affect Arctic coastal ecosystems, due to hydrographic and bathymetric conditions that support the accumulation of cells and cysts, and coupled with increasing temperatures, extensive bloom events can be easily triggered. However, various harmful algae species have been reported in the past and it is unclear which are most threatening in Greenlandic waters, a region that vitally depend on its fisheries. Here, we explore the diversity and succession of harmful algae by metabarcoding at a multi-year station in Greenlandic coastal waters, offering a comprehensive analysis of species dynamics over time. Dinoflagellates, diatoms and haptophytes, known for their toxin production and potential negative effects on ecosystems and food webs, were regularly detected across years and throughout all sampled months. Yet, results also indicate significant interannual variability in harmful algal occurrences, with high abundances of <em>Alexandrium</em> and increasing abundances of <em>Aureococcus, Prymnesium</em>, and <em>Pseudo-nitzschia.</em> Through a boosted regression tree analysis of the ecological drivers of HABs in Arctic waters, we identified an important role of climate-induced environmental variables such as temperature, salinity, and the number of ice-free days year^-1. These findings provide critical baseline data for understanding the future risks of HABs in the Arctic and underscore the importance of ongoing, high-resolution monitoring.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"145 ","pages":"Article 102857"},"PeriodicalIF":5.5,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143816445","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":"Seasonal monitoring of dissolved and particulate algal biotoxins in the northern Salish Sea using high performance liquid chromatography and tandem mass spectrometry","authors":"Andrew R.S. Ross ,&nbsp;Béatrice Ip ,&nbsp;Mackenzie Mueller ,&nbsp;Blair Surridge ,&nbsp;Harry Hartmann ,&nbsp;Navinder Hundal ,&nbsp;Nathan Matthews ,&nbsp;Hayleigh Shannon ,&nbsp;Melissa Hennekes ,&nbsp;Akash Sastri ,&nbsp;R. Ian Perry","doi":"10.1016/j.hal.2025.102854","DOIUrl":"10.1016/j.hal.2025.102854","url":null,"abstract":"<div><div>Harmful algae are present in the coastal waters of British Columbia, Canada yet little is known about the spatial and temporal distributions of the biotoxins produced by these organisms. We describe a method for profiling dissolved and particulate algal biotoxins in sea water including those associated with amnesic, paralytic, and diarrhetic shellfish poisoning (ASP, PSP and DSP). Surface sea water was filtered and biotoxins recovered from filters and filtrate using solvent extraction and solid phase extraction, respectively. Extracts were analyzed by high-performance liquid chromatography and tandem mass spectrometry using hydrophilic interaction liquid chromatography for ASP and PSP toxins and reversed-phased liquid chromatography for DSP and other lipophilic toxins. The method was applied to samples collected in the northern Salish Sea in April, June and October 2022. Highest total concentrations of domoic acid and saxitoxin were found above a shallow sill in the eastern Juan de Fuca Strait whereas those of dinophysistoxin 1, pectenotoxin 2, yessotoxin, and PSP toxins C1 and C2 were measured near the southern end of Malaspina Strait. These maximum concentrations were observed in June when surface salinity was lowest, temperature highest, and harmful algae most abundant, as reflected in the relative high proportion of particulate biotoxins. In contrast, the high proportion of dissolved biotoxins observed in April when temperature and algal abundance were relatively low suggests that certain biotoxins may persist in surface waters and that the risk of biotoxin exposure does not necessarily correlate with the abundance of harmful algae.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"145 ","pages":"Article 102854"},"PeriodicalIF":5.5,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143824313","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":"From bloom to tap: Connecting harmful algal bloom indicators in source water to cyanotoxin presence in treated drinking water","authors":"Lena Abu-Ali,&nbsp;Ryan J. Albert,&nbsp;Angela B. Davis,&nbsp;Rachel Gonsenhauser,&nbsp;Katherine Foreman","doi":"10.1016/j.hal.2025.102846","DOIUrl":"10.1016/j.hal.2025.102846","url":null,"abstract":"<div><div>Cyanotoxins produced by harmful algal blooms (HABs) can negatively impact human health through ingestion of drinking water. Under most circumstances, public water systems (PWSs) have demonstrated that they can successfully manage the removal of low-to-moderate levels of cyanotoxins with conventional treatment. Intense or frequent blooms put some PWSs at higher risk for treatment breakthrough, meaning cyanotoxins can pass through the drinking water treatment process, and there are still some instances of reported cyanotoxin levels in drinking water. This study links cyanotoxin drinking water occurrence data from PWSs sampled under the Fourth Unregulated Contaminant Monitoring Rule (UCMR 4) with qualitative source water HAB information to understand the relationship between source water indicators and drinking water occurrence. During the monitoring period (2018 to 2020), 153 of approximately 110,000 total cyanotoxin analytical results from 67 PWSs were observed at or above the minimum reporting level (MRL), resulting in a 0.14 percent rate of occurrence in drinking water. The associated qualitative data indicated that 23.9 percent of systems with a cyanotoxin reported value ≥ MRL in drinking water also reported the presence of a HAB indicator while 1.7 percent of systems with a reported value ≥ MRL in finished water did not report any HAB indicators. Odds ratio testing revealed that a system is more than twice as likely to have a cyanotoxin detection in drinking water if a HAB indicator is observed. This study demonstrates the importance of monitoring source water changes and observed treatment changes for vulnerable systems, as these can facilitate timely adjustments to treatment and mitigate the risks of cyanotoxin breakthrough in finished water.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"145 ","pages":"Article 102846"},"PeriodicalIF":5.5,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143816485","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":"Does Microcystis exposure history facilitate adaptation of Diaphanosoma dubium to expanding filamentous cyanobacterium Raphidiopsis raciborskii?","authors":"Qiuqi Lin,&nbsp;Xiao Xiao,&nbsp;Xuxin Feng,&nbsp;Lamei Lei","doi":"10.1016/j.hal.2025.102847","DOIUrl":"10.1016/j.hal.2025.102847","url":null,"abstract":"<div><div><em>Diaphanosoma</em>, so-called ‘tropical <em>Daphnia</em>’ are widely distributed in warm waterbodies with <em>Microcystis</em> blooms, and are supposed to have high level of tolerance to <em>Microcystis</em>. However, expanding filamentous cyanobacterium, <em>Raphidiopsis raciborskii</em> is increasingly replacing <em>Microcystis</em>, or becoming co-dominant in warm eutrophic waterbodies. Whether previous experience with <em>Microcystis</em> can facilitate adaptation of <em>Diaphanosoma</em> to <em>R. raciborskii</em> or a shift in cyanobacteria assemblage from <em>Microcystis</em> to <em>R. raciborskii</em> will reduce their tolerance to cyanobacteria is debated. We address this question by investigating the performance of fourteen clones from three <em>Diaphanosoma dubium</em> populations differing in cyanobacteria exposure history. They were fed pure diets of cylindrospermopsin-/non-cylindrospermopsin-producing <em>R. raciborskii</em>, microcystin-producing <em>Microcystis aeruginosa</em> and green alga <em>Auxenochlorella pyrenoidosa</em>. The three cyanobacteria all sustained the growth and reproduction of three <em>D. dubium</em> populations, and both somatic and population growth rates increased with dietary PUFA content for each clone, irrespective of manageability and toxicity. Clones with cyanobacteria exposure history have much better performance than those without exposure history on all food types. Moreover, clones with <em>Microcystis</em> exposure history for &gt;40 years, performed better on all food types than clones with <em>R. raciborskii</em> exposure history for &lt;10 years. The results suggest that <em>D. dubium</em> population with much longer bloom exposure history may adapt to being more tolerant of toxic cyanobacteria in the diet. We infer that previous <em>Microcystis</em> exposure experience might facilitate adaptation of <em>D. dubium</em> to <em>R. raciborskii</em> by enhancing their ability to cope with nutritional constraint and toxicity.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"145 ","pages":"Article 102847"},"PeriodicalIF":5.5,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143759674","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":"Extracellular polymeric substances enhanced photosynthesis over respiration in Microcystis aeruginosa","authors":"Kaikai Deng ,&nbsp;Rui Yang ,&nbsp;Shirong Zhang ,&nbsp;Fang Fang ,&nbsp;Yuanchen Huo ,&nbsp;Peng Yan ,&nbsp;Youpeng Chen ,&nbsp;Jinsong Guo","doi":"10.1016/j.hal.2025.102843","DOIUrl":"10.1016/j.hal.2025.102843","url":null,"abstract":"<div><div>Extracellular polymeric substances (EPS) play a critical role in <em>Microcystis</em>-dominated freshwater cyanobacterial blooms. However, the mechanisms through which EPS affects <em>Microcystis</em> photosynthesis, respiration, and further affects its growth are not understood completely. To address this, we investigated the effects of varying EPS concentrations on the physiological processes of <em>Microcystis aeruginosa</em>. The results demonstrated that increasing EPS concentrations significantly enhanced both cell density and energy fixation efficiency, accompanied by a reduction in CO₂ emission flux. Specifically, compared with the control group, the addition of 20 mg·L^-¹ EPS increased respiratory rates by 2.14 μmol·mg·h^-¹ and photosynthetic rates by 2.48 μmol·mg·h^-¹, suggesting that EPS stimulated both respiration and photosynthesis, with a more pronounced effect on photosynthesis, thereby leading to a substantial increase in algal growth. Further analysis indicated that EPS enhanced respiration by retaining hydrolases capable of breaking down macromolecules into bioavailable micromolecular substrates, which elevated acetyl-CoA concentrations and citrate synthase activity, thus improving respiratory efficiency. In terms of photosynthesis, EPS enhanced light utilization, as indicated by an increase in F_V/F_M, and improved the efficiency of inorganic carbon supply by enriching CO₂ and creating extracellular inorganic carbon gradients. Moreover, EPS enhanced the activities of carbonic anhydrase and ribulose bisphosphate carboxylase/oxygenase. These findings emphasize the essential role of EPS in promoting algal growth and its potential impact on CO₂ fixation. Future research should incorporate the role of EPS in reducing carbon limitation into discussions of algal growth mechanisms and develop technologies that use algal blooms to harvest high-value carbon products such as ethanol, astaxanthin, lipids, and other valuable compounds.</div></div>","PeriodicalId":12897,"journal":{"name":"Harmful Algae","volume":"145 ","pages":"Article 102843"},"PeriodicalIF":5.5,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143725852","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}