Long-term responses of microbial plankton to ocean warming reveal shifts in air–sea CO₂ exchange in the late 21st century

Long-term responses of microbial plankton to ocean warming reveal shifts in air–sea CO₂ exchange in the late 21st century | 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 Long-term responses of microbial plankton to ocean warming reveal shifts in air–sea CO₂ exchange in the late 21st century Luciana Frazão, Marcos Tonelli, Camila Signori This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7284245/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Ongoing ocean warming threatens to disrupt microbial plankton communities and impair the efficiency of the biological carbon pump (BCP), a central mechanism driving air–sea CO₂ exchange and carbon sequestration. The carbon cycle is primarily driven by the metabolic balance of the ocean, which is regulated by the coupling between autotrophic and heterotrophic microbiota. However, the extent to which rising sea surface temperature (SST) will alter these communities remains uncertain. Here, we combine projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6), machine learning techniques, and a global microbial plankton dataset to assess long-term biomass responses for autotrophic and heterotrophic microbial plankton by the late 21st century. Our projections, performed under four Shared Socioeconomic Pathways (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5), indicate a significant decline in total microbial biomass and the decoupling between autotrophic and heterotrophic metabolism, leading to a near-global prevalence of heterotrophy. These shifts have important implications for the biological carbon pump’s efficiency and, consequently, for the ocean’s role as a CO₂ sink, potentially intensifying atmospheric CO₂ feedbacks. Our predictions highlight the pivotal role of microbial plankton trophic dynamics in climate projections and underscore the importance of incorporating multiple plankton trophic levels into future CMIP models. Earth and environmental sciences/Climate sciences/Ocean sciences/Marine biology Biological sciences/Ecology/Climate-change ecology ocean warming biological carbon pump ocean metabolic balance microbial plankton CMIP6 model machine learning Full Text Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryMaterialTableS1Dataset.xlsx Dataset1 SupplementaryMaterialTableS2projections.xlsx Dataset2 Cite Share Download PDF Status: Posted Version 1 posted 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-7284245","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":495278794,"identity":"caf4dc3e-5dba-4c34-8299-829e91fec633","order_by":0,"name":"Luciana Frazão","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAArUlEQVRIiWNgGAWjYBACPgbGB2AGP4hgbCBCCxsDswGYIdlAshaDA0RrkUhm+/Djj52c8Y30Zw8Yd9wjSgvzzB6eZGOzGznmBoxnionRkn+YgUeCOXHbjRw2Cca2BOJsYfxjUJ+4eUb6M+K1MPMkHE7cIJFgRqQWnsfMzDIHjhtLnHljbpB4hggt/OxAh735Uy3H3w4MsY87iNCCYiMDiRpAWkbBKBgFo2AUYAMAGwgwveqRgs4AAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0003-0310-000X","institution":"Institute of Oceanography - 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