Estimating the contribution of Spartina anglica biomass to salt-marsh sediments using compound specific stable carbon isotope measurements

Compound specific δ13C analyses were used to determine the relative input of a C4 temperate grass (Spartina anglica) to primary biomass in a salt-marsh sediment. Lipid distributions revealed a C32 n-alkanol homologue as a characteristically dominant component of Spartina anglica whilst the cohabiting C3 species, Puccinellia maritima, exhibited a C26 maximum. The C32 n-alkanol component was used to create an isotopic mixing model, between organic matter derived from Spartina anglica and Puccinellia maritima, to estimate their relative contribution to the primary biomass input of salt-marsh sediments. The application of sedimentary lipid isotope data to the model gave values of Spartina anglica contributions ranging from 37 to 100%. This investigation represents the first attempt to quantify inputs to sedimentary biomass based on compound specific stable carbon isotope techniques.