title: An inventory of13C abundances in coastal wetlands of Louisiana, USA: vegetation and sediments.
abstract: Organic carbon-rich sediments from the surface of fresh, intermediate, brackish and salt marshes of coastal Louisiana were sampled and analyzed for their13C content. The average ∂13C from all sites within each wetland type was-27.8‰,-22.1‰,-16.9‰, and-16.2‰, for fresh, intermediate, brackish and salt marshes, respectively. Means from the fresh, intermediate and brackish marshes were significantly different at the 0.01 level. A mixing model using measurements of standing crop and ∂13C of plant carbon was applied to estimate the contribution of each species to the sedimentary carbon at four of the marsh sites. Sedimentary ∂13C values generally reflected that of the dominant species present at each site. Brackish and salt marsh samples, however, showed a negative shift of ∂13C with respect to whole plant carbon. We interpret these depeleted ∂13C values to be the result of more extensive organic matter decomposition and selective preservation of13C-depleted refractory components in sediments from saline sites. The results of this study suggest that ∂13C composition of sedimentary carbon may offer a valuable tool for distinguishing subtle changes in paleohydrology of wetlands resulting from relative sea level changes.
authors.affiliation: Laboratory for Wetland Soils and Sediments and Dept. Marine Science, Center for Wetland Resources, Louisiana State University, 70803, Baton Rouge, LA, USA.
authors.forename: G L
authors.initials: GL
authors.lastname: Chmura
authors.affiliation: Dept. Geology and Geophysics, Louisiana State University, 70803, Baton Rouge, LA, USA.
authors.forename: P
authors.initials: P
authors.lastname: Aharon
authors.affiliation: Dept. Geology and Geophysics, Louisiana State University, 70803, Baton Rouge, LA, USA.
authors.forename: R A
authors.initials: RA
authors.lastname: Socki
authors.affiliation: Coastal Ecology Institute, Center for Wetland Resources, Louisiana State University, 70803, Baton Rouge, LA, USA.
authors.forename: R
authors.initials: R
authors.lastname: Abernethy
keywords: Mississippi delta plain; Organic sediment; Salinity gradient; Stable carbon isotopes; Wetlands