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    Salt marsh ecosystem restructuring enhances elevation resilience and carbon storage during accelerating relative sea-level rise


    Eagle Gonneea, Meagan and Maio, Christopher and Kroeger, Kevin D and Hawkes, Andrea D. and Mora, Jordan and Sullivan, Richard and Madsen, Stephanie and Buzard, Richard M and Cahill, Niamh and Donnelly, Jeffrey P. (2019) Salt marsh ecosystem restructuring enhances elevation resilience and carbon storage during accelerating relative sea-level rise. Estuarine, Coastal and Shelf Science, 217. pp. 56-68. ISSN 0272-7714

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    Abstract

    Salt marshes respond to sea-level rise through a series of complex and dynamic bio-physical feedbacks. In this study, we found that sea-level rise triggered salt marsh habitat restructuring, with the associated vegetation changes enhancing salt marsh elevation resilience. A continuous record of marsh elevation relative to sea level that includes reconstruction of high-resolution, sub-decadal, marsh elevation over the past century, coupled with a lower-resolution 1500-year record, revealed that relative sea-level rose 1.5 ± 0.4 m, following local glacial isostatic adjustment (1.2 mm/yr). As sea-level rise has rapidly accelerated, the high marsh zone dropped 11 cm within the tidal frame since 1932, leading to greater inundation and a shift to flood- and salt-tolerant low marsh species. Once the marsh platform fell to the elevation favored by low-marsh Spartina alterniflora, the elevation stabilized relative to sea level. Currently low marsh accretion keeps pace with sea-level rise, while present day high marsh zones that have not transitioned to low marsh have a vertical accretion deficit. Greater biomass productivity, and an expanding subsurface accommodation space favorable for salt marsh organic matter preservation, provide a positive feed-back between sea-level rise and marsh platform elevation. Carbon storage was 46 ± 28 g C/m2/yr from 550 to 1800 CE, increasing to 129 ± 50 g C/m2/yr in the last decade. Enhanced carbon storage is controlled by vertical accretion rates, rather than soil carbon density, and is a direct response to anthropogenic eustatic sea-level rise, ultimately providing a negative feedback on climate warming.

    Item Type: Article
    Keywords: Salt marsh; Sea-level rise; Carbon storage; Elevation; 14-Carbon; Sea level index point; Accretion;
    Academic Unit: Faculty of Science and Engineering > Mathematics and Statistics
    Item ID: 14576
    Identification Number: https://doi.org/10.1016/j.ecss.2018.11.003
    Depositing User: Niamh Cahill
    Date Deposited: 29 Jun 2021 16:07
    Journal or Publication Title: Estuarine, Coastal and Shelf Science
    Publisher: Elsevier
    Refereed: Yes
    URI:

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