Organic chemistry insights for the exceptional soil carbon storage of the seagrass Posidonia australis

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dc.contributor.authorSerrano, O.
dc.contributor.authorRozaimi, M.
dc.contributor.authorLavery, P.S.
dc.contributor.authorSmernik, R.J.
dc.date.issued2020
dc.description.abstractThe high organic carbon (OC) stores in seagrass meadows have led to their recognition as significant Blue Carbon sinks, though the diagenetic conditions that enable OC retention in seagrass soils remain poorly understood. In this study, seagrass soils were sampled from a Posidonia australis meadow in Oyster Harbour (Albany; south-western Australia) to investigate the preservation of sedimentary OC. We analysed soil characteristics (colour, grain size and redox potential), radiocarbon age, and characterised the soil organic matter (OM) using solid state CP/MAS 13C NMR spectroscopy to examine the preservation of OM down the soil profile. There was minimal change in organic composition over 1,700 years of accumulation, indicating long-term OM preservation. Primarily, this preservation appears to be driven by the recalcitrance of seagrass detritus buried in anoxic soils. The majority (70–83%) of total sedimentary OM comprised components directly attributable to seagrass origins (lignin, carbohydrate and black carbon-like matter), while the remainder consisted mostly of protein, some of which may have been present in seagrass biomass, along with likely contributions from algae and microbes. Although black carbon originates from organic matter combustion, here we provide evidence that the 13C NMR signal identified as black carbon-like matter in our soils is possibly associated with seagrass-derived organic matter consisting of degraded lignin products or other non-pyrogenic aromatics. The increase in the relative abundance of this black carbon-like matter with aging suggests its selective preservation. The relative abundances of carbohydrates significantly decreased with age down core (i.e. they appeared to be selectively decomposed), while lignin and protein did not show any quantitative changes in relative abundance (non-selective preservation). These findings demonstrate the exceptional preservation of P. australis derived OC, which contributes to our understanding of the higher OC storage capacity of Posidonia compared to other seagrass species.
dc.description.statementofresponsibilityOscar Serrano, Mohammad Rozaimi, Paul S. Lavery, Ronald J. Smernik
dc.identifier.citationEstuarine, Coastal and Shelf Science, 2020; 237:106662-1-106662-11
dc.identifier.doi10.1016/j.ecss.2020.106662
dc.identifier.issn0272-7714
dc.identifier.issn1096-0015
dc.identifier.orcidSmernik, R.J. [0000-0001-6033-5855]
dc.identifier.urihttp://hdl.handle.net/2440/126116
dc.language.isoen
dc.publisherElsevier
dc.relation.granthttp://purl.org/au-research/grants/arc/DE170101524
dc.rights© 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
dc.source.urihttps://doi.org/10.1016/j.ecss.2020.106662
dc.subjectBlue carbon; coastal vegetated ecosystems; climate change; organic chemistry; diagenesis; CP/MAS ¹³C NMR; Australia
dc.titleOrganic chemistry insights for the exceptional soil carbon storage of the seagrass Posidonia australis
dc.typeJournal article
pubs.publication-statusPublished

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