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 (<26.2 ± 5.3 μmol m⁻² h⁻¹) in the winter seasons. Direct denitrification was higher than coupled denitrification in all seasons. Denitrification rates were higher in WLD despite lower %OM, lower total N concentration, and higher BD in wetland soils. Therefore, in environments with low carbon availability, high denitrification rates can be sustained as long as NO₃⁻ concentrations are high (>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).

中文翻译：

---

河流改道形成的新兴湿地可以维持沿海三角洲的高反硝化率

假设治疗过量NO ₃ ^-高土壤有机质含量（％OM）必须保持在天然或恢复湿地的高反硝化速率。然而，这种过量也代表了一种风险，因为土壤分解率会增加，从而引发泥炭崩塌和湿地破碎。在这里，我们使用同位素配对 (IPT) 和 N ₂评估了 %OM 和温度相互作用在路易斯安那州沿海侵蚀 (Barataria Bay-BLC) 和新兴 (Wax Lake Delta-WLD) 三角洲地区控制反硝化率的作用:Ar 技术。我们还评估了底栖和湿地栖息地的总（直接反硝化 + 耦合硝化 - 反硝化）和净（总反硝化减去固氮）反硝化率之间的差异，对比 %OM 和体积密度 (BD)。在夏季、春季和冬季（2015-2016 年）收集沉积物（底栖）和土壤（湿地）核心，并在接近原位温度（分别为 30°C、20°C 和 10°C）下培养。反硝化率与温度呈线性相关；夏季的最大平均速率范围为 40.1–124.1 μmol m ^-2 h ^-1，较低速率 (<26.2 ± 5.3 μmol m ^-2 h ^-1) 在冬季。直接反硝化在所有季节均高于耦合反硝化。尽管湿地土壤中的％OM较低，总氮浓度较低且BD较高，但WLD中的反硝化率较高。因此，与低碳可用性环境，高反硝化速率可以持续，只要NO ₃ ^-浓度高（> 30μM）和水温度> 10℃。在路易斯安那州沿海地区，这些制度下的底物以在低盐条件下（<1 ppt）的沉积物改道形成的涌出潮间带或土地为代表。