Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 12, issue 20
Biogeosciences, 12, 6251–6258, 2015
https://doi.org/10.5194/bg-12-6251-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 12, 6251–6258, 2015
https://doi.org/10.5194/bg-12-6251-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 30 Oct 2015

Research article | 30 Oct 2015

Radiocarbon isotopic evidence for assimilation of atmospheric CO2 by the seagrass Zostera marina

K. Watanabe and T. Kuwae K. Watanabe and T. Kuwae
  • Coastal and Estuarine Environment Research Group, Port and Airport Research Institute, 3-1-1 Nagase, Yokosuka 239-0826, Japan

Abstract. Submerged aquatic vegetation takes up water-column dissolved inorganic carbon (DIC) as a carbon source across its thin cuticle layer. It is expected that marine macrophytes also use atmospheric CO2 when exposed to air during low tide, although assimilation of atmospheric CO2 has never been quantitatively evaluated. Using the radiocarbon isotopic signatures (Δ14C) of the seagrass Zostera marina, DIC and particulate organic carbon (POC), we show quantitatively that Z. marina takes up and assimilates atmospheric modern CO2 in a shallow coastal ecosystem. The Δ14C values of the seagrass (−40 to −10 ‰) were significantly higher than those of aquatic DIC (−46 to −18 ‰), indicating that the seagrass uses a 14C-rich carbon source (atmospheric CO2, +17 ‰). A carbon-source mixing model indicated that the seagrass assimilated 0–40 % (mean, 17 %) of its inorganic carbon as atmospheric CO2. CO2 exchange between the air and the seagrass might be enhanced by the presence of a very thin film of water over the air-exposed leaves during low tide. Our radiocarbon isotope analysis, showing assimilation of atmospheric modern CO2 as an inorganic carbon source, improves our understanding of the role of seagrass meadows in coastal carbon dynamics.

Publications Copernicus
Download
Short summary
Our empirical study demonstrates the quantitative evidence of assimilating atmospheric modern CO2 by the seagrass Zostera marina, by analyzing the radiocarbon isotope concentrations (Δ14C) of both the seagrass and two carbon sources in a brackish lagoon. CO2 exchange between the air and water would occur at the very thin film of water over the air-exposed seagrass leaves. Our finding offers better understanding of the role of seagrass meadows in global coastal carbon dynamics.
Our empirical study demonstrates the quantitative evidence of assimilating atmospheric modern...
Citation