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

Arias-Ortiz, Ariane; Masqué, Pere; Garcia-Orellana, Jordi; Serrano, Oscar; Mazarrasa, Inés; Marbà, Núria; Lovelock, Catherine E.; Lavery, Paul S.; Duarte, Carlos M.

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 (inline-formulaCorg), also termed blue carbon, beyond the mere quantification of inline-formulaCorg stocks. Here, we discuss the use of the inline-formula210Pb dating technique to determine the rate of inline-formulaCorg accumulation in these habitats. We review the most widely used inline-formula210Pb 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 inline-formula210Pb records in vegetated coastal ecosystems and evaluate how anomalies in inline-formula210Pb specific activity profiles affect sediment and inline-formulaCorg accumulation rates. Our results show that the discrepancy in sediment and derived inline-formulaCorg accumulation rates between anomalous and ideal inline-formula210Pb 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 inline-formulaCorg accumulation rates over the last century, they may not always provide a reliable geochronology or historical reconstruction. Reliable estimates of inline-formulaCorg 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 inline-formula210Pb-derived results. The framework provided in this study can be instrumental in reducing the uncertainties associated with estimates of inline-formulaCorg accumulation rates in vegetated coastal sediments.

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Arias-Ortiz, Ariane / Masqué, Pere / Garcia-Orellana, Jordi / et al: Reviews and syntheses: 210Pb-derived sediment and carbon accumulation rates in vegetated coastal ecosystems – setting the record straight. 2018. Copernicus Publications.

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Rechteinhaber: Ariane Arias-Ortiz et al.

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