Abstract
Hydrothermal vents release substantial amounts of ancient carbon into the ocean, primarily as carbon dioxide, yet the extent to which this carbon is integrated into marine food webs remains poorly constrained. Here, we present a combination of bulk radiocarbon and stable carbon isotope measurements of particulate organic carbon from water column filters with compound-specific hydrogen and radiocarbon isotope analyses of fatty acids from surface sediments to trace carbon assimilation across benthic and pelagic realms in a low pH, shallow-water hydrothermal system off Taiwan. Isotope correlations indicate that vent-derived carbon dioxide constitutes a substantial fraction of the local microbial and faunal biomass through chemoautotrophic pathways (up to ~30%). Farther from the vents, hydrothermal carbon remains detectable and is incorporated into photoautotrophic biomass in the overlying water column. Notably, ancient carbon content in the standing stock of particulate organic carbon was higher at the lower temperature (“White”) vent, even though fluid and sulfide emissions – and thus potential energy availability – were substantially greater at the higher temperature (“Yellow”) vent. These findings show that physicochemical conditions, including pH and temperature, rather than fluid chemistry alone, control carbon assimilation patterns and ultimately limit the retention of vent-derived carbon in this shallow-water system.
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Data availability
Compound-specific δ2H and Δ14C data, as well as bulk δ2Hwater and Δ14CPOC data, are reported within the supplementary material and are available at https://doi.org/10.5281/zenodo.18310623. Compound-specific δ13C data can be found in Ref. 28 and within the PANGAEA database (Maak et al.73).
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All Code necessary to understand the manuscript can be accessed in Code Ocean.
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Acknowledgements
We express our gratitude to the Taiwan Ministry of Environment for granting permission to access the samples. Additionally, we extend our thanks to the scientists, crew members, and scientific divers who participated in the OR2−2024 and OR2−2095 cruises aboard the RV Ocean Researcher II, as well as those involved in the sampling conducted during a fishing boat expedition from May 25–28, 2015. We further thank Rebecca Aepfler (AWI, Bremerhaven) and Prof. Li-Lian Liu (National Sun Yat-sen University) for their help during sampling. This study was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy (EXC − 2077—390741603), a DFG Emmy Noether Grant awarded to S.I.B. (BU 2606/1−1), and the DAAD (Projektbezogener Personenaustausch − 57138084, awarded to S.I.B. and Y.-S.L.). We are grateful to the several anonymous reviewers for their time, careful reading, and constructive comments that helped improve the manuscript. We also acknowledge financial support for open-access publishing from the University of Bremen’s Open Access Publication Fund.
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Joely Marie Maak: Conceptualization, data analysis, visualization, interpretation, writing—original draft, editing. Marcus Elvert: Conceptualization, supervision, review, editing. Hendrik Grotheer: Conceptualization, data analysis, interpretation, review, editing. Yu-Shih Lin: Sample collection, review, editing. Gesine Mollenhauer: Conceptualization, data analysis, review, editing. In-Tian Lin: Sample collection, interpretation, review, editing. Solveig I. Bühring: Conceptualization, supervision, review, editing. Enno Schefuß: Conceptualization, supervision, review, editing.
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Communications Earth and Environment thanks Huei-Ting Lin and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Alice Drinkwater. [A peer review file is available].
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Maak, J.M., Elvert, M., Grotheer, H. et al. Physicochemical controls on ancient carbon assimilation into ecosystem biomass in shallow-water hydrothermal systems. Commun Earth Environ (2026). https://doi.org/10.1038/s43247-026-03254-z
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DOI: https://doi.org/10.1038/s43247-026-03254-z
