Contributions of organic and inorganic matter to sediment volume and accretion in tidal wetlands at steady state.
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 k1and k2are 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 k1and k2were estimated to be 0.085 ± 0.0007 g cm-3and 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 k2to 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-1under 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.
Department of Biological Sciences, Belle W. Baruch Institute for Marine & Coastal Sciences University of South Carolina Columbia South Carolina USA.
James T
JT
Morris
Department of Geology Bryn Mawr College Bryn Mawr Pennsylvania USA.
Donald C
DC
Barber
Department of Environmental Science University of San Francisco San Francisco California USA.
John C
JC
Callaway
Keck Environmental Field Laboratory College of William and Mary Williamsburg Virginia USA.
Randy
R
Chambers
Department of Civil & Environmental Engineering and Center for Computation & Technology Louisiana State University Baton Rouge Louisiana USA.
Scott C
SC
Hagen
Department of Marine Sciences University of Georgia Athens Georgia USA.
Charles S
CS
Hopkinson
Department of Geology Bates College Lewiston Maine USA.
Beverly J
BJ
Johnson
Smithsonian Environmental Research Center Edgewater Maryland USA.
Patrick
P
Megonigal
Department of Biology Virginia Commonwealth University Richmond Virginia USA.
Scott C
SC
Neubauer
Department of Biological Sciences, Southeast Environmental Research Center Florida International University Miami Florida USA.
Tiffany
T
Troxler
Atlantic Ecology Division U.S. EPA, Office of Research and Development, National Health and Environmental Effects Research Laboratory Narragansett Rhode Island USA.
Cathleen
C
Wigand
LOI; accretion; bulk density; marsh; sediment