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

Estuarine, Coastal and Shelf Science
By: , and 

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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.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Salt marsh ecosystem restructuring enhances elevation resilience and carbon storage during accelerating relative sea-level rise
Series title Estuarine, Coastal and Shelf Science
DOI 10.1016/j.ecss.2018.11.003
Volume 217
Year Published 2019
Language English
Publisher Elsevier
Contributing office(s) Woods Hole Coastal and Marine Science Center
Description 13 p.
First page 56
Last page 68
Country United States
State Massachusetts