Role of tidal wetland stability in lateral fluxes of particulate organic matter and carbon

Abstract

Tidal wetland fluxes of particulate organic matter and carbon (POM, POC) are important terms in global budgets but remain poorly constrained. Given the link between sediment fluxes and wetland stability, POM and POC fluxes should also be related to stability. We measured POM and POC fluxes in eight microtidal salt marsh channels, with net POM fluxes ranging between −121 ± 33 (export) and 102 ± 28 (import) g OM·m−2·year−1 and net POC fluxes ranging between −52 ± 14 and 43 ± 12 g C·m−2·year−1. A regression employing two measures of stability, the unvegetated‐vegetated marsh ratio (UVVR) and elevation, explained >95% of the variation in net fluxes. The regression indicates that marshes with lower elevation and UVVR import POM and POC while higher elevation marshes with high UVVR export POM and POC. We applied these relationships to marsh units within Barnegat Bay, New Jersey, USA, finding a net POM import of 2,355 ± 1,570 Mg OM/year (15 ± 10 g OM·m−2·year−1) and a net POC import of 1,263 ± 632 Mg C/year (8 ± 4 g C·m−2·year−1). The magnitude of this import was similar to an estimate of POM and POC export due to edge erosion (−2,535 Mg OM/year and − 1,291 Mg C/year), suggesting that this system may be neutral from a POM and POC perspective. In terms of a net budget, a disintegrating wetland should release organic material, while a stable wetland should trap material. This study quantifies that concept and demonstrates a linkage between POM/POC flux and geomorphic stability.