Different synthetic chemical dispersants elicit distinct bacterial community responses to crude oil

Different synthetic chemical dispersants elicit distinct bacterial community responses to crude oil | 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 Research Article Different synthetic chemical dispersants elicit distinct bacterial community responses to crude oil Ciara Keating, Laura Duran Suja, Stephen Summers, Ian M. Head, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8280185/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 7 You are reading this latest preprint version Abstract Background: Dispersants are commonly used worldwide as a primary response tool to treat oil spills at sea, yet their use is debated due to their toxicological effects and potential to affect oil biodegradation rates. We examined the effect of three globally stockpiled synthetic chemical dispersants (Superdispersant 25, Slickgone EW, Slickgone NS) on the microbial response to crude oil and its biodegradation in a subarctic marine environment during 2015 and 2017 using 16S rRNA gene amplicon sequencing. Results: Across both years, communities were dominated by known hydrocarbon-degrading bacteria, including Alcanivorax , Alteromonas , and Pseudoalteromonas . Superdispersant 25 enriched for Dokdonia , Thalassospira , and Roseobacter , genera with demonstrated alkane and PAH degradation pathways. Slickgone EW and NS selected Marinomonas , Colwellia , Psychromonas , and Alcanivorax . Samples without dispersant also contained hydrocarbon degraders, however, the community composition was altered. In 2017, we quantified hydrocarbon degradation using GC-FID/MS for aliphatic and aromatic hydrocarbons respectively. Hydrocarbon biomarker ratios showed n-alkane depletion (Pr/C17 and Ph/C18 ratios increased 3–12 fold) in dispersant treatments. Selective weathering was evident in all treatments. 1MP/9MP ratios indicated limited or variable effects on aromatic hydrocarbon biodegradation, particularly in the presence of dispersant. We integrated aromatic hydrocarbon concentrations with microbial community data using DIABLO (Data Integration Analysis for Biomarker discovery using Latent variable approaches for Omics studies). Several taxa were negatively correlated to specific aromatic hydrocarbons – i.e. they increased when the hydrocarbon was reduced suggesting these may have served carbon sources. Taxa included Aquibacter , Hyphomonas , Thalassospira , Alteromonas , Sphingopyxis , and Paraperlucidibaca . Marine oil snow (MOS) formed in all oil-amended treatments and showed high microbial colonisation, whereas marine dispersant snow showed little colonisation. Conclusion: This study provides evidence that different dispersants affect different microbial responses to crude oil contamination, including the enrichment of key oil-degrading bacterial taxa. However, this did not correlate with enhanced aromatic hydrocarbon degradation. MOS formation with high microbial colonisation suggests natural aggregation processes may provide an effective biodegradation pathway. These findings question the functional benefit of synthetic chemical dispersants and highlight that the marine environment naturally harbours hydrocarbon-degrading microbial communities with the potential to respond to oil spills. dispersant oil spill biodegradation marine oil snow (MOS) marine dispersant snow (MDS) Faroe-Shetland Channel Full Text Additional Declarations No competing interests reported. Supplementary Files Supplementarydatafile1.xlsx SupplementaryDataFile2.xlsx SupplementaryDataFile3.xlsx SupplementaryDataFile4.xlsx KeatingSupplementaryInformation.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 26 Mar, 2026 Reviews received at journal 26 Mar, 2026 Reviewers agreed at journal 16 Mar, 2026 Reviewers invited by journal 03 Mar, 2026 Editor assigned by journal 25 Feb, 2026 Submission checks completed at journal 20 Jan, 2026 First submitted to journal 18 Jan, 2026 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-8280185","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":599822436,"identity":"c250c7a6-a444-4079-9273-4d05821cb07b","order_by":0,"name":"Ciara Keating","email":"","orcid":"","institution":"Durham University","correspondingAuthor":false,"prefix":"","firstName":"Ciara","middleName":"","lastName":"Keating","suffix":""},{"id":599822437,"identity":"dafaaa95-62f5-4cc9-9835-84c98124717a","order_by":1,"name":"Laura Duran Suja","email":"","orcid":"","institution":"Heriot-Watt University","correspondingAuthor":false,"prefix":"","firstName":"Laura","middleName":"Duran","lastName":"Suja","suffix":""},{"id":599822438,"identity":"7d9d0a3d-c535-434b-b083-710c0322a91d","order_by":2,"name":"Stephen Summers","email":"","orcid":"","institution":"National University of Singapore","correspondingAuthor":false,"prefix":"","firstName":"Stephen","middleName":"","lastName":"Summers","suffix":""},{"id":599822439,"identity":"9007e8fb-13e5-4bab-b0bb-c18ec4ec4457","order_by":3,"name":"Ian M. 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oil","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":"environmental-microbiome","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"sigs","sideBox":"Learn more about [Environmental Microbiome](https://environmentalmicrobiome.biomedcentral.com)","snPcode":"40793","submissionUrl":"https://submission.nature.com/new-submission/40793/3","title":"Environmental Microbiome","twitterHandle":"@bmc","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"dispersant, oil spill, biodegradation, marine oil snow (MOS), marine dispersant snow (MDS), Faroe-Shetland Channel","lastPublishedDoi":"10.21203/rs.3.rs-8280185/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8280185/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground:\u003c/h2\u003e \u003cp\u003eDispersants are commonly used worldwide as a primary response tool to treat oil spills at sea, yet their use is debated due to their toxicological effects and potential to affect oil biodegradation rates. We examined the effect of three globally stockpiled synthetic chemical dispersants (Superdispersant 25, Slickgone EW, Slickgone NS) on the microbial response to crude oil and its biodegradation in a subarctic marine environment during 2015 and 2017 using 16S rRNA gene amplicon sequencing.\u003c/p\u003e\u003ch2\u003eResults:\u003c/h2\u003e \u003cp\u003eAcross both years, communities were dominated by known hydrocarbon-degrading bacteria, including \u003cem\u003eAlcanivorax\u003c/em\u003e, \u003cem\u003eAlteromonas\u003c/em\u003e, and \u003cem\u003ePseudoalteromonas\u003c/em\u003e. Superdispersant 25 enriched for \u003cem\u003eDokdonia\u003c/em\u003e, \u003cem\u003eThalassospira\u003c/em\u003e, and \u003cem\u003eRoseobacter\u003c/em\u003e, genera with demonstrated alkane and PAH degradation pathways. Slickgone EW and NS selected \u003cem\u003eMarinomonas\u003c/em\u003e, \u003cem\u003eColwellia\u003c/em\u003e, \u003cem\u003ePsychromonas\u003c/em\u003e, and \u003cem\u003eAlcanivorax\u003c/em\u003e. Samples without dispersant also contained hydrocarbon degraders, however, the community composition was altered. In 2017, we quantified hydrocarbon degradation using GC-FID/MS for aliphatic and aromatic hydrocarbons respectively. Hydrocarbon biomarker ratios showed n-alkane depletion (Pr/C17 and Ph/C18 ratios increased 3\u0026ndash;12 fold) in dispersant treatments. Selective weathering was evident in all treatments. 1MP/9MP ratios indicated limited or variable effects on aromatic hydrocarbon biodegradation, particularly in the presence of dispersant. We integrated aromatic hydrocarbon concentrations with microbial community data using DIABLO (Data Integration Analysis for Biomarker discovery using Latent variable approaches for Omics studies). Several taxa were negatively correlated to specific aromatic hydrocarbons \u0026ndash; i.e. they increased when the hydrocarbon was reduced suggesting these may have served carbon sources. Taxa included \u003cem\u003eAquibacter\u003c/em\u003e, \u003cem\u003eHyphomonas\u003c/em\u003e, \u003cem\u003eThalassospira\u003c/em\u003e, \u003cem\u003eAlteromonas\u003c/em\u003e, \u003cem\u003eSphingopyxis\u003c/em\u003e, and \u003cem\u003eParaperlucidibaca\u003c/em\u003e. Marine oil snow (MOS) formed in all oil-amended treatments and showed high microbial colonisation, whereas marine dispersant snow showed little colonisation.\u003c/p\u003e\u003ch2\u003eConclusion:\u003c/h2\u003e \u003cp\u003eThis study provides evidence that different dispersants affect different microbial responses to crude oil contamination, including the enrichment of key oil-degrading bacterial taxa. However, this did not correlate with enhanced aromatic hydrocarbon degradation. MOS formation with high microbial colonisation suggests natural aggregation processes may provide an effective biodegradation pathway. These findings question the functional benefit of synthetic chemical dispersants and highlight that the marine environment naturally harbours hydrocarbon-degrading microbial communities with the potential to respond to oil spills.\u003c/p\u003e","manuscriptTitle":"Different synthetic chemical dispersants elicit distinct bacterial community responses to crude oil","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-05 18:47:21","doi":"10.21203/rs.3.rs-8280185/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"200266024372503531684397255935896925140","date":"2026-03-27T03:25:06+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-26T13:42:52+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"310360013789140402167851411048218632996","date":"2026-03-16T06:40:42+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-03T08:18:33+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-26T04:35:16+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-01-20T08:49:55+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Microbiome","date":"2026-01-18T20:46:48+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-microbiome","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"sigs","sideBox":"Learn more about [Environmental Microbiome](https://environmentalmicrobiome.biomedcentral.com)","snPcode":"40793","submissionUrl":"https://submission.nature.com/new-submission/40793/3","title":"Environmental Microbiome","twitterHandle":"@bmc","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"1e20fc60-40d5-416a-b6f7-a68eb0e55c19","owner":[],"postedDate":"March 5th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-03-05T18:47:21+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-05 18:47:21","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8280185","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8280185","identity":"rs-8280185","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}