Blue carbon additionality: new insights from the radiocarbon content of saltmarsh soils and their respired CO2

Houston, A., Garnett, M. H. and Austin, W. E.N. (2024) Blue carbon additionality: new insights from the radiocarbon content of saltmarsh soils and their respired CO2. Limnology and Oceanography, 69(3), pp. 548-561. (doi: 10.1002/lno.12508)

Abstract

International policy frameworks recognize the net drawdown and storage of atmospheric greenhouse gases through management interventions on blue carbon ecosystems (saltmarshes, mangroves, seagrasses) as potential emissions offset strategies. However, key questions remain around the “additionality” of the carbon sequestered by these ecosystems, and whether some fraction of the organic carbon (OC) that does not derive from in situ production (allochthonous) should be included in carbon budgets. This study compares the radiocarbon (14C) contents of saltmarsh soils and CO2 evolved from aerobic laboratory incubations to show that young OC is preferentially respired over aged OC, and that the latter is also vulnerable to remineralization under oxic conditions. This highlights that management interventions which reduce the exposure of saltmarsh soils to oxic conditions support the inclusion of some portion of allochthonous OC in carbon budgets. Elevated temperature incubations provide preliminary evidence that the predominant source of respired OC will not change under predicted future warmer conditions. Saltmarsh typology also influences the 14C content of both the bulk soil and respired CO2, highlighting the importance of site selection for optimized blue carbon additionality.

• Item Type: Articles
• Additional Information: We thank the NERC SUPER DTP for funding the PhD through which this research was undertaken. We acknowledge support from the National Environmental Isotope Facility in funding the 14C measurements for this study under grant NE/S011587/1 (allocation numbers 2500.0422, 2594.1022).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Garnett, Dr Mark
• Authors: Houston, A., Garnett, M. H., and Austin, W. E.N.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Limnology and Oceanography
• Publisher: Wiley
• ISSN: 0024-3590
• ISSN (Online): 1939-5590
• Published Online: 22 February 2024
• Copyright Holders: Copyright © 2024 The Authors
• First Published: First published in Limnology and Oceanography 69(3):548-561
• Publisher Policy: Reproduced under a Creative Commons licence