Seagrass ecosystems as a globally significant carbon stock

Journal name:
Nature Geoscience
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Published online


The protection of organic carbon stored in forests is considered as an important method for mitigating climate change. Like terrestrial ecosystems, coastal ecosystems store large amounts of carbon, and there are initiatives to protect these ‘blue carbon’ stores. Organic carbon stocks in tidal salt marshes and mangroves have been estimated, but uncertainties in the stores of seagrass meadows—some of the most productive ecosystems on Earth—hinder the application of marine carbon conservation schemes. Here, we compile published and unpublished measurements of the organic carbon content of living seagrass biomass and underlying soils in 946 distinct seagrass meadows across the globe. Using only data from sites for which full inventories exist, we estimate that, globally, seagrass ecosystems could store as much as 19.9Pg organic carbon; according to a more conservative approach, in which we incorporate more data from surface soils and depth-dependent declines in soil carbon stocks, we estimate that the seagrass carbon pool lies between 4.2 and 8.4Pg carbon. We estimate that present rates of seagrass loss could result in the release of up to 299Tg carbon per year, assuming that all of the organic carbon in seagrass biomass and the top metre of soils is remineralized.

At a glance


  1. Mediterranean seagrass meadows of P. oceanica have the largest documented Corg stores, which can form /`mattes/' of high Corg content not reported for other seagrass species.
    Figure 1: Mediterranean seagrass meadows of P. oceanica have the largest documented Corg stores, which can form ‘mattes’ of high Corg content not reported for other seagrass species.

    An erosional escarpment in a P. oceanica meadow in Es Pujols Cove, Formentera, Balearic Islands, Spain, in the Mediterranean Sea illustrating the organic-rich soils.The water depth at the top of the formation is 3m, the exposed face of the matte has a thickness of 2.7m. The age of the base of the exposure is 1,200yearsBP. Photo credit: Miguel Angel Mateo.

  2. Locations of data on the Corg content of seagrass meadows, showing seagrass bioregions.
    Figure 2: Locations of data on the Corg content of seagrass meadows, showing seagrass bioregions.
  3. Frequency distribution of reported and calculated observations of soil Corg from seagrass meadows.
    Figure 3: Frequency distribution of reported and calculated observations of soil Corg from seagrass meadows.

    Mean values are given ±95% confidence interval. LOI, loss on ignition (see Methods).

  4. Frequency histogram of estimates of soil Corg stored in the world/'s seagrass meadows.
    Figure 4: Frequency histogram of estimates of soil Corg stored in the world’s seagrass meadows.

    Light grey shading indicates estimates made from surficial sediments, as well as general patterns in increases in DBD (see Methods) and decreases in Corg with depth, and should be considered as preliminary until more detailed, site-specific studies of Corg in deeper soils are done at these sites.

  5. A comparison of seagrass soil Corg storage in the top metre of the soil with total ecosystem Corg storage for major forest types.
    Figure 5: A comparison of seagrass soil Corg storage in the top metre of the soil with total ecosystem Corg storage for major forest types.

    Terrestrial forest C storage data from ref. 3; mangrove storage data from ref. 7. Note that individual forests can have Corg storage above or below these mean values. The individual points represent the individual values for seagrass meadows in the database. Living seagrass biomass C storage is minor when compared with that found in forests and when compared with the soil Corg storage in seagrass meadows, so it has been omitted for clarity.


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Author information


  1. Department of Biological Sciences and Southeast Environmental Research Center, Marine Science Program, Florida International University, 3000 NE 151 St, North Miami, Florida 33181, USA

    • James W. Fourqurean
  2. Department of Global Change Research. IMEDEA (CSIC-UIB) Institut Mediterrani d’Estudis Avançats, C/ Miguel Marqués 21, 07190 Esporles (Mallorca), Spain

    • Carlos M. Duarte &
    • Núria Marbà
  3. The UWA Oceans Institute, University of Western Australia, 35 Stirling Highway, Crawley 6009, Australia

    • Carlos M. Duarte &
    • Gary A. Kendrick
  4. School of Ocean Sciences, College of Natural Sciences, Bangor University, Askew Street, Menai Bridge, LL59 5AB, UK

    • Hilary Kennedy
  5. Institute of Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark

    • Marianne Holmer
  6. Centre for Advanced Studies of Blanes, (CEAB-CSIC), Acceso Cala S. Francesc 14, 17300 Blanes, Spain

    • Miguel Angel Mateo &
    • Oscar Serrano
  7. Institute of Oceanography, Hellenic Centre for Marine Research, PO Box 2214, 71003, Heraklion—Crete, Greece

    • Eugenia T. Apostolaki
  8. School of Plant Biology, University of Western Australia, Crawley, Western Australia 6009, Australia

    • Gary A. Kendrick
  9. Department of Bioscience, Aarhus University, Vejlsøvej 25, DK-8600 Silkeborg, Denmark

    • Dorte Krause-Jensen
  10. Department of Environmental Sciences, University of Virginia, PO Box 400123, Clark Hall, Charlottesville, Virginia 22904, USA

    • Karen J. McGlathery


All authors contributed extensively to the work presented in this paper.

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