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

Authors

James T. Morris, University of South Carolina
Donald C. Barber, Bryn Mawr College
John C. Callaway, University of San Francisco
Randy Chambers, College of William and Mary
Scott C. Hagen, Louisiana State University
Charles S. Hopkins, University of Georgia
Beverly J. Johnson, Bates College
Patrick Megonigal, Smithsonian Environmental Research CenterFollow
Scott C. Neubauer, Virginia Commonwealth University
Tiffany Troxler-Gann, Southeast Environmental Research Center and Department of Biological Sciences, Florida International UniversityFollow
Cathleen Wigand, US Environmental Protection Agency

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.

Comments

© 2016 The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

DOI: 10.1002/2015EF000334.

This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DEB-1237517, #DBI-0620409, and #DEB-9910514. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation

Recommended Citation

Morris, J. T. et al. (2016), Contributions of organic and inorganic matter to sediment volume and accretion in tidal wetlands at steady state, Earth’s Future, 4, 110–121, doi:10.1002/2015EF000334.