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Earths Future. 2016 Apr;4(4):110-121. Epub 2016 Apr 28.

Contributions of organic and inorganic matter to sediment volume and accretion in tidal wetlands at steady state.

Author information

1
Department of Biological Sciences, Belle W. Baruch Institute for Marine & Coastal Sciences University of South Carolina Columbia South Carolina USA.
2
Department of Geology Bryn Mawr College Bryn Mawr Pennsylvania USA.
3
Department of Environmental Science University of San Francisco San Francisco California USA.
4
Keck Environmental Field Laboratory College of William and Mary Williamsburg Virginia USA.
5
Department of Civil & Environmental Engineering and Center for Computation & Technology Louisiana State University Baton Rouge Louisiana USA.
6
Department of Marine Sciences University of Georgia Athens Georgia USA.
7
Department of Geology Bates College Lewiston Maine USA.
8
Smithsonian Environmental Research Center Edgewater Maryland USA.
9
Department of Biology Virginia Commonwealth University Richmond Virginia USA.
10
Department of Biological Sciences, Southeast Environmental Research Center Florida International University Miami Florida USA.
11
Atlantic Ecology Division U.S. EPA, Office of Research and Development, National Health and Environmental Effects Research Laboratory Narragansett Rhode Island USA.

Abstract

A mixing model derived from first principles describes the bulk density (BD) of intertidal wetland sediments as a function of loss on ignition (LOI). The model assumes that the bulk volume of sediment equates to the sum of self-packing volumes of organic and mineral components or BD = 1/[LOI/k1 + (1-LOI)/k2], where k1 and k2 are the self-packing densities of the pure organic and inorganic components, respectively. The model explained 78% of the variability in total BD when fitted to 5075 measurements drawn from 33 wetlands distributed around the conterminous United States. The values of k1 and k2 were estimated to be 0.085 ± 0.0007 g cm-3 and 1.99 ± 0.028 g cm-3, respectively. Based on the fitted organic density (k1) and constrained by primary production, the model suggests that the maximum steady state accretion arising from the sequestration of refractory organic matter is ≤ 0.3 cm yr-1. Thus, tidal peatlands are unlikely to indefinitely survive a higher rate of sea-level rise in the absence of a significant source of mineral sediment. Application of k2 to a mineral sediment load typical of East and eastern Gulf Coast estuaries gives a vertical accretion rate from inorganic sediment of 0.2 cm yr-1. Total steady state accretion is the sum of the parts and therefore should not be greater than 0.5 cm yr-1 under the assumptions of the model. Accretion rates could deviate from this value depending on variation in plant productivity, root:shoot ratio, suspended sediment concentration, sediment-capture efficiency, and episodic events.

KEYWORDS:

LOI; accretion; bulk density; marsh; sediment

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