Abstract
Seagrass meadows are natural carbon sinks, yet the effect of ocean acidification on their carbon burial capacity remains poorly understood. Here we investigated natural carbon dioxide vents in Ischia, Italy to assess how seawater pH influences carbon burial in an area dominated by the seagrass Posidonia oceanica. Organic carbon burial rates (mean ± standard error) between 1954 – 2021 were low under ambient conditions (1.5 ± 0.5 g m-2 yr-1) but increased sharply under acidified conditions (7 ± 1 g m-2 yr-1), reaching sevenfold higher values under extreme acidification (10 ± 3 g m-2 yr-1). Stable isotopes suggest that these patterns reflect changes in the relative contribution of seagrass, macroalgae, and epiphytes to buried carbon. These findings reveal that ocean acidification can substantially alter coastal carbon cycling, potentially through shifts in community composition, with important implications for understanding past and future feedbacks between seagrass ecosystems and the marine carbon cycle.
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Data availability
Data are publicly available in the Zenodo repository86 and the R script used to analyze data and produce figures is available at GitHub (https://github.com/dillkotte/Ischia-pH-C).
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Acknowledgements
This study was part of the C-BLUES project (EU Horizon Europe, grant no: HORIZON-CL5-2023-D1-02), and of the French National Research Agency Investments for the Future “4Oceans-Make Our Planet Great Again” grant, (grant no: ANR-17-MOPGA-0001). We thank Gloria Salgado Gispert for assistance with sampling and laboratory analyses, ANS Diving for assistance in the field, and The Marine Protected Area “Regno di Nettuno” for permit collections. We also thank Sarah Bury, Josette Delgado, Ollie Kerr-Hislop, Andrew Marriner and Graeme Moss from the New Zealand Institute for Earth Sciences Ltd. (formerly NIWA) for their assistance with preparations, analysis and data processing of macroalgal stable isotope samples. The IAEA is grateful to the Government of the Principality of Monaco for the support provided to its Marine Environment Laboratories.
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T.K., N.T., S.C., J.-P.G., and P.M. conceived the study; N.T., A.M., and S.C. collected samples; B.G., S.A., I.K., D.B., C.C., and P.M. analyzed samples. T.K. and P.M. analyzed data. T.K. wrote the manuscript with input from all co-authors.
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Kindeberg, T., Teixidó, N., Comeau, S. et al. Enhanced carbon burial in seagrass meadows under ocean acidification revealed by carbon dioxide vents. Commun Earth Environ (2026). https://doi.org/10.1038/s43247-026-03349-7
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DOI: https://doi.org/10.1038/s43247-026-03349-7
