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.

Sediment Exchange Between the Created Saltmarshes of Living Shorelines and Adjacent Submersed Aquatic Vegetation in the Chesapeake Bay

“…However, how sediment might be exchanged between the two communities has rarely been investigated (Donatelli et al, 2018;Zhu et al, 2021). A sediment budget is a useful tool for examining this exchange, as it accounts for both the losses and gains of sediment and can help assess whether a planned restoration of a tidal marsh has a high probability of success (Ganju et al, 2013(Ganju et al, , 2019.…”

Mud‐associated organic matter and its direct and indirect role in marsh organic matter accumulation and vertical accretion

“…For example, it is widely recognized that a portion of the OM in marsh soils originates from allochthonous deposition and from photosynthetic algae including microphytobenthos on the marsh surface (Goñi and Thomas 2000; Unger et al 2016; Van de Broek et al 2016; Wollenberg et al 2018; Shields et al 2019). Indeed, a relatively high percentage of suspended particulate matter in tidal channels can be organic (generally within 10–50%; Settlemyre and Gardner 1977, Van de Broek et al 2016; Ganju et al 2019), and material that deposits on marsh surfaces likewise can have high organic concentrations (5–88% on sediment plates; Elsey‐Quirk and Adamowicz 2015). Yet, except for a few cases, the effects of different sources of OM other than in situ plant production on marsh accretion have been neglected in both models and interpretation of field data.…”

The role of short-term and long-term water level and wave variability in coastal carbon budgets

“…Carbon is lost from coastal habitats through shoreline erosion when coastal processes, such as storm waves or fluctuating water levels, erode these SOC-containing environments. While studies have examined the erosional loss of coastal soil carbon ( Ganju et al., 2019 ; Sapkota and White, 2019 ) and the global impact of that carbon loss ( Pendleton et al., 2012 ), the pathways and degradation of coastal SOC are complex and not completely quantified ( Spivak et al., 2019 ). Depending on physical and biogeochemical conditions, the carbon may be remineralized and respired as atmospheric CO 2 or redeposited in other carbon pools ( Hayes et al, 2021 , Sapkota and White, 2021 , Tranvik et al., 2009 ) No matter the fate of this eroded carbon, it is no longer stored in the coastal ecosystems where it originated, thus, natural resource managers must critically evaluate whether a site truly is a carbon sink based on the dominant geomorphic processes.…”