Biological Control of Harmful Algal Blooms Using Padina sp. and Sargassum sp. from the coastal waters of the Persian Gulf and Gulf of Oman

Biological Control of Harmful Algal Blooms Using Padina sp. and Sargassum sp. from the coastal waters of the Persian Gulf and Gulf of Oman | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Biological Control of Harmful Algal Blooms Using Padina sp. and Sargassum sp. from the coastal waters of the Persian Gulf and Gulf of Oman Saeid Tamadoni Jahromi, Mohsen Gozari, Sajjad Pourmozaffar, Noora Barzkar This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8185876/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract Harmful algal blooms (HABs) are increasingly recognized as serious threats to coastal ecosystems, public health, and local economies. This study investigates the potential of two native macroalgal genera, Padina sp. and Sargassum sp., collected from the coastal waters of the Persian Gulf (Bandar Abbas) and the Gulf of Oman (Chabahar), as biological control agents against the harmful species Cochlodinium polykrikoides . We identified the species using a combination of morphological observations and DNA barcoding (rbcL and psbA), which was necessary because some specimens displayed overlapping or variable traits that made morphology alone insufficient. After confirming the identities, we prepared methanolic extracts and tested their effects on harmful microalgae. Both species showed inhibitory activity, although the strength of the effect differed. Extracts from Padina sp. A were the most potent, with an LC₅₀ of 122.2 µg/mL, while Sargassum sp. B showed moderate but still significant inhibition (LC₅₀ = 182.6 µg/mL).Importantly, the extracts had minimal impact on non-target microalgae. Growth of Chlorella vulgaris and Isochrysis galbana remained largely unaffected, even at the highest concentrations tested. Toxicity assays further indicated no adverse effects on shrimp larvae ( Litopenaeus vannamei ) or human endothelial cells (HUVEC), suggesting a high degree of selectivity. These results suggest a notable degree of selectivity, which is critical for any candidate compound intended for use in aquaculture or environmental applications. Chemical profiling through TLC and HPLC provided further insight into the nature of the active constituents. Several fractions showed strong chromatographic signals characteristic of terpenoids, phenolic compounds, flavonoids, and various carbohydrate-associated metabolites. Although the specific structures require further elucidation, the chemical signatures align with secondary metabolite profiles commonly reported for Padina and Sargassum species. Taken together, the findings indicate that these macroalgae possess bioactive metabolites capable of suppressing harmful microalgal species while leaving beneficial microalgae and non-target organisms largely unharmed. This combination of efficacy and selectivity underscores their potential as environmentally compatible tools for mitigating harmful algal blooms in marine and aquaculture systems. Chemical analysis using TLC and HPLC revealed several active fractions, with signals characteristic of terpenoids, phenolic compounds, flavonoids, and carbohydrate-associated metabolites. While the exact structures remain to be determined, these chemical signatures are consistent with secondary metabolites commonly found in Padina and Sargassum . Overall, our findings indicate that these macroalgae produce bioactive compounds capable of suppressing harmful microalgae while leaving beneficial species and non-target organisms largely unharmed, highlighting their potential as environmentally compatible agents for managing harmful algal blooms in marine and aquaculture settings. Biological sciences/Biochemistry Biological sciences/Biotechnology Biological sciences/Ecology Earth and environmental sciences/Ecology Earth and environmental sciences/Environmental sciences Biological sciences/Plant sciences Harmful algal blooms biological control allelopathic macroalgae anti-microalgal metabolites Padina sp. Sargassum sp. Cochlodinium polykrikoides sustainable aquaculture Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 24 Dec, 2025 Reviews received at journal 23 Dec, 2025 Reviews received at journal 22 Dec, 2025 Reviewers agreed at journal 03 Dec, 2025 Reviewers agreed at journal 03 Dec, 2025 Reviewers agreed at journal 03 Dec, 2025 Reviewers invited by journal 03 Dec, 2025 Editor assigned by journal 03 Dec, 2025 Editor invited by journal 02 Dec, 2025 Submission checks completed at journal 02 Dec, 2025 First submitted to journal 02 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8185876","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":554694759,"identity":"4ab52abb-3534-4a33-b97b-d3122f7a70ef","order_by":0,"name":"Saeid Tamadoni Jahromi","email":"","orcid":"","institution":"Persian Gulf and Oman Sea Ecology Research Center, Iranian Fisheries Sciences Research Institute, Agricultural Research Education and Extension Organization 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Oman","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Harmful algal blooms, biological control, allelopathic macroalgae, anti-microalgal metabolites, Padina sp., Sargassum sp., Cochlodinium polykrikoides, sustainable aquaculture","lastPublishedDoi":"10.21203/rs.3.rs-8185876/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8185876/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eHarmful algal blooms (HABs) are increasingly recognized as serious threats to coastal ecosystems, public health, and local economies. This study investigates the potential of two native macroalgal genera, \u003cem\u003ePadina\u003c/em\u003e sp. and \u003cem\u003eSargassum\u003c/em\u003e sp., collected from the coastal waters of the Persian Gulf (Bandar Abbas) and the Gulf of Oman (Chabahar), as biological control agents against the harmful species \u003cem\u003eCochlodinium polykrikoides\u003c/em\u003e. We identified the species using a combination of morphological observations and DNA barcoding (rbcL and psbA), which was necessary because some specimens displayed overlapping or variable traits that made morphology alone insufficient. After confirming the identities, we prepared methanolic extracts and tested their effects on harmful microalgae. Both species showed inhibitory activity, although the strength of the effect differed. Extracts from \u003cem\u003ePadina\u003c/em\u003e sp. A were the most potent, with an LC₅₀ of 122.2 \u0026micro;g/mL, while \u003cem\u003eSargassum\u003c/em\u003e sp. B showed moderate but still significant inhibition (LC₅₀ = 182.6 \u0026micro;g/mL).Importantly, the extracts had minimal impact on non-target microalgae. Growth of \u003cem\u003eChlorella vulgaris\u003c/em\u003e and \u003cem\u003eIsochrysis galbana\u003c/em\u003e remained largely unaffected, even at the highest concentrations tested. Toxicity assays further indicated no adverse effects on shrimp larvae (\u003cem\u003eLitopenaeus vannamei\u003c/em\u003e) or human endothelial cells (HUVEC), suggesting a high degree of selectivity. These results suggest a notable degree of selectivity, which is critical for any candidate compound intended for use in aquaculture or environmental applications. Chemical profiling through TLC and HPLC provided further insight into the nature of the active constituents. Several fractions showed strong chromatographic signals characteristic of terpenoids, phenolic compounds, flavonoids, and various carbohydrate-associated metabolites. Although the specific structures require further elucidation, the chemical signatures align with secondary metabolite profiles commonly reported for \u003cem\u003ePadina\u003c/em\u003e and \u003cem\u003eSargassum\u003c/em\u003e species. Taken together, the findings indicate that these macroalgae possess bioactive metabolites capable of suppressing harmful microalgal species while leaving beneficial microalgae and non-target organisms largely unharmed. This combination of efficacy and selectivity underscores their potential as environmentally compatible tools for mitigating harmful algal blooms in marine and aquaculture systems. Chemical analysis using TLC and HPLC revealed several active fractions, with signals characteristic of terpenoids, phenolic compounds, flavonoids, and carbohydrate-associated metabolites. While the exact structures remain to be determined, these chemical signatures are consistent with secondary metabolites commonly found in \u003cem\u003ePadina\u003c/em\u003e and \u003cem\u003eSargassum\u003c/em\u003e. Overall, our findings indicate that these macroalgae produce bioactive compounds capable of suppressing harmful microalgae while leaving beneficial species and non-target organisms largely unharmed, highlighting their potential as environmentally compatible agents for managing harmful algal blooms in marine and aquaculture settings.\u003c/p\u003e","manuscriptTitle":"Biological Control of Harmful Algal Blooms Using Padina sp. and Sargassum sp. from the coastal waters of the Persian Gulf and Gulf of Oman","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-05 13:06:02","doi":"10.21203/rs.3.rs-8185876/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-12-24T11:45:17+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-23T19:27:26+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-22T11:46:31+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"108966679988062201612275137574602327589","date":"2025-12-03T13:02:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"268256897275720506385824368384407483509","date":"2025-12-03T12:58:38+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"242069349418267604547090352146432887160","date":"2025-12-03T07:58:13+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-03T05:55:54+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-03T05:11:44+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-12-02T15:27:51+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-02T05:11:41+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-12-02T05:03:20+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"642e8f11-9a65-4db2-a9a1-2573a8f26e8a","owner":[],"postedDate":"December 5th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":59031326,"name":"Biological sciences/Biochemistry"},{"id":59031327,"name":"Biological sciences/Biotechnology"},{"id":59031328,"name":"Biological sciences/Ecology"},{"id":59031329,"name":"Earth and environmental sciences/Ecology"},{"id":59031330,"name":"Earth and environmental sciences/Environmental sciences"},{"id":59031331,"name":"Biological sciences/Plant sciences"}],"tags":[],"updatedAt":"2026-05-25T13:38:18+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-05 13:06:02","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8185876","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8185876","identity":"rs-8185876","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}