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Blue carbon sequestration dominated by dissolved organic carbon pathways for kelp forests and eelgrass meadows in Nova Scotia, Canada

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Abstract

Existing estimates of carbon sequestration by coastal vegetated ecosystems (e.g., kelp forests, seagrass meadows) remain highly uncertain because they utilize few measurements with high uncertainty or focus on individual stocks or fluxes. Here, we combine empirical data with modeling to generate detailed carbon budgets for kelp forests and eelgrass meadows in Nova Scotia, Canada. Our budgeting showed that the release and export of dissolved organic carbon accounts for substantially more carbon sequestered by these habitats than has been estimated globally (98.5 ± 64.6% for kelp and 84 ± 36.0% for eelgrass), suggesting this carbon pathway has been undervalued. Further, kelp forests are estimated to sequester more carbon than eelgrass by ~1.3 orders of magnitude (27 ± 19% and 12.1 ± 6.3% of annual net primary production for kelp and eelgrass) mainly due to their large habitat area, highlighting their significant but largely overlooked role in ocean carbon sequestration relative to other blue carbon ecosystems.

Data availability

All data are available as supplementary material and at: https://github.com/kirakrumhansl/Carbon-Budget-Code.

Code availability

All code and associated raw data are available at: https://github.com/kirakrumhansl/Carbon-Budget-Code.

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Acknowledgements

We acknowledge Katie Thistle, Shawn Roach, Thomas Baker, Cody Brooks, Danielle Davenport, Claudio DiBacco, Katherine Lee, Jordan Thomson, Benedikte Vercaemer, Chris Corriveau, and Nick Jeffery for their support in the field. We also thank Wendy Gentleman for early input and feedback on the work. KK discloses support for this work from a Fisheries and Oceans Canada Competitive Science Research Fund grant to KK and KA-S.

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Authors and Affiliations

  1. Bedford Institute of Oceanography, Fisheries and Oceans Canada, Dartmouth, NS, Canada

    Kira A. Krumhansl, Melisa C. Wong, Manon M. M. Picard, Meredith Fraser, Carrie-Ellen Gabriel, Yongsheng Wu & Kumiko Azetsu-Scott

Authors

  1. Kira A. Krumhansl
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  2. Melisa C. Wong
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  3. Manon M. M. Picard
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Contributions

K.K. was involved in conceptualization, data curation, formal analysis, funding acquisition, investigation, methodology, project administration, resources, software, supervision, visualization, writing—original draft, writing—reviewing & editing. M.W. was involved in conceptualization, data curation, formal analysis, funding acquisition, investigation, methodology, project administration, resources, software, supervision, writing—original draft, writing—reviewing & editing. M.P. was involved in data curation, formal analysis, investigation, methodology, software, writing—original draft, writing—reviewing & editing. M.F. was involved in data curation, formal analysis, investigation, software, writing—original draft, writing—reviewing & editing. C.–E.G. Gabriel was involved in investigation, methodology, writing—reviewing & editing. Y.W. was involved in Methodology and writing—reviewing & editing. K.A.-S. was involved in conceptualization, methodology, project administration, resources, supervision, writing—reviewing & editing.

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Correspondence to
Kira A. Krumhansl.

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Communications Earth and Environment thanks Richard Zimmerman and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editors: Nezha Mejjad and Alice Drinkwater. A peer review file is available.

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Krumhansl, K.A., Wong, M.C., Picard, M.M.M. et al. Blue carbon sequestration dominated by dissolved organic carbon pathways for kelp forests and eelgrass meadows in Nova Scotia, Canada.
Commun Earth Environ (2026). https://doi.org/10.1038/s43247-025-03122-2

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