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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 22
Biogeosciences, 15, 6791-6818, 2018
https://doi.org/10.5194/bg-15-6791-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Biogeosciences, 15, 6791-6818, 2018
https://doi.org/10.5194/bg-15-6791-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Reviews and syntheses 15 Nov 2018

Reviews and syntheses | 15 Nov 2018

Reviews and syntheses: 210Pb-derived sediment and carbon accumulation rates in vegetated coastal ecosystems – setting the record straight

Ariane Arias-Ortiz1, Pere Masqué1,2,3,4, Jordi Garcia-Orellana1,2, Oscar Serrano3, Inés Mazarrasa5, Núria Marbà6, Catherine E. Lovelock7, Paul S. Lavery3,8, and Carlos M. Duarte9 Ariane Arias-Ortiz et al.
  • 1Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain
  • 2Departament de Física, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain
  • 3School of Science and Centre for Marine Ecosystems Research, Edith Cowan University, 270 Joondalup Drive, Joondalup WA 6027, Australia
  • 4UWA Oceans Institute & School of Physics, The University of Western Australia, 35 Stirling Highway, Crawley 6009, Australia
  • 5Environmental Hydraulics Institute “IH Cantabria”, Universidad de Cantabria, C/Isabel Torres No. 15, Parque Científico y Tecnológico de Cantabria, 39011, Santander, Spain
  • 6Global Change Research Group, IMEDEA (CSIC-UIB) Institut Mediterrani d'Estudis Avançats, C/Miguel Marqués 21, 07190 Esporles (Mallorca), Spain
  • 7School of Biological Sciences, The University of Queensland, St Lucia QLD 4072, Australia
  • 8Centro de Estudios Avanzados de Blanes, Consejo Superior de Investigaciones Científicas, 17300 Blanes, Spain
  • 9King Abdullah University of Science and Technology (KAUST), Red Sea Research Center (RSRC), Thuwal, 23955-6900, Saudi Arabia

Abstract. Vegetated coastal ecosystems, including tidal marshes, mangroves and seagrass meadows, are being increasingly assessed in terms of their potential for carbon dioxide sequestration worldwide. However, there is a paucity of studies that have effectively estimated the accumulation rates of sediment organic carbon (Corg), also termed blue carbon, beyond the mere quantification of Corg stocks. Here, we discuss the use of the 210Pb dating technique to determine the rate of Corg accumulation in these habitats. We review the most widely used 210Pb dating models to assess their limitations in these ecosystems, often composed of heterogeneous sediments with varying inputs of organic material, that are disturbed by natural and anthropogenic processes resulting in sediment mixing and changes in sedimentation rates or erosion. Through a range of simulations, we consider the most relevant processes that impact the 210Pb records in vegetated coastal ecosystems and evaluate how anomalies in 210Pb specific activity profiles affect sediment and Corg accumulation rates. Our results show that the discrepancy in sediment and derived Corg accumulation rates between anomalous and ideal 210Pb profiles is within 20% if the process causing such anomalies is well understood. While these discrepancies might be acceptable for the determination of mean sediment and Corg accumulation rates over the last century, they may not always provide a reliable geochronology or historical reconstruction. Reliable estimates of Corg accumulation rates might be difficult at sites with slow sedimentation, intense mixing and/or that are affected by multiple sedimentary processes. Additional tracers or geochemical, ecological or historical data need to be used to validate the 210Pb-derived results. The framework provided in this study can be instrumental in reducing the uncertainties associated with estimates of Corg accumulation rates in vegetated coastal sediments.

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Efforts to include tidal marsh, mangrove and seagrass ecosystems in existing carbon mitigation strategies are limited by a lack of estimates of carbon accumulation rates (CARs). We discuss the use of 210Pb dating to determine CARs in these habitats, which are often composed of heterogeneous sediments and affected by sedimentary processes. Results show that obtaining reliable geochronologies in these systems is ambitious, but estimates of mean 100-year CARs are mostly secure within 20 % error.
Efforts to include tidal marsh, mangrove and seagrass ecosystems in existing carbon mitigation...
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