Accumulation rates of salt-marsh blue carbon at Lindisfarne, northern England, and their relationship with sea-level change

<p>Salt marshes sequester carbon at rates&#160;significantly exceeding those found in terrestrial environments. This ability&#160;arises from the in-situ production of plant&#160;biomass and the effective trapping&#160;and storage of both autochthonous and allochthonous organic carbon. The&#160;importance of this blue carbon store for mitigating&#160;increasing atmospheric&#160;carbon dioxide depends on both the rate at which carbon is buried within&#160;sediments and the rapidity with which that carbon is remineralised. It has been hypothesized that carbon burial rates, in turn, depend on the local rate of sea-level rise, with faster sea-level rise providing more accommodation space for carbon storage. This study addresses&#160;these three key aspects in a salt-marsh sediment study from&#160;Lindisfarne, northern England. We quantify rates of carbon accumulation by&#160;combining a Bayesian age-depth model based on&#160;²¹⁰Pb and&#160;¹³⁷Cs&#160;activities with centimetre-resolution organic carbon density measurements. A&#160;Bayesian isotope&#160;mixing model pinpoints terrestrial sources as providing the&#160;majority of stored carbon. We compare two approaches for&#160;assessing the relative proportions of&#160;labile and recalcitrant carbon based on a&#160;two-pool modelling approach and thermogravimetric analysis. Preliminary results indicate that during the 20^th century more carbon was stored at Lindisfarne salt marsh during decades with relatively high rates of sea-level rise.</p>