It is assumed that to treat excess NO₃⁻ high soil organic matter content (%OM) is required to maintain high denitrification rates in natural or restored wetlands. However, this excess also represents a risk by increasing soil decomposition rates triggering peat collapse and wetland fragmentation. Here, we evaluated the role of %OM and temperature interactions controlling denitrification rates in eroding (Barataria Bay‐BLC) and emerging (Wax Lake Delta‐WLD) deltaic regions in coastal Louisiana using the isotope pairing (IPT) and N₂:Ar techniques. We also assessed differences between total (direct denitrification + coupled nitrification‐denitrification) and net (total denitrification minus nitrogen fixation) denitrification rates in benthic and wetland habitats with contrasting %OM and bulk density (BD). Sediment (benthic) and soil (wetland) cores were collected during summer, spring, and winter (2015–2016) and incubated at close to in‐situ temperatures (30°C, 20°C, and 10°C, respectively). Denitrification rates were linearly correlated with temperature; maximum mean rates ranged from 40.1–124.1 μmol m⁻² h⁻¹ in the summer with lower rates (30 μM) and water temperature is >10°C. In coastal Louisiana, substrates under these regimes are represented by emergent supra‐tidal flats or land created by sediment diversions under oligohaline conditions (<1 ppt).