To cope with increasing nitrogen loading to estuarine systems, the demand for removal via denitrification is rising. Understanding how the connections between biogeochemistry and ecology regulate denitrification rates along gradients of nutrient and sediment loading is necessary to predict ecosystem function. Previous studies have shown that denitrification rates are typically highest in muddy, nutrient-rich sediments and decrease in sandy, nutrient-poor sites. Denitrification rates were measured at four subtidal sites positioned from the upper to lower estuary. Site 1 was closest to the primary riverine nutrient supply with the highest suspended sediment and benthic mud content that decreased with distance downstream. Contrary to expectations, denitrification rates were lowest at the most upstream site (22.35 ± 13.34 μmol N₂ m⁻² h⁻¹) and higher downstream (57.84 ± 5.72 μmol N₂ m⁻² h⁻¹). While respiration, primary production, and sediment characteristics affected net denitrification rates and efficiency, results indicated that macrofaunal abundance (Site 1, 60.8 ± 7.3 individuals/core; Sites 2–4, 177.7 ± 10.8 individuals/core), primarily tube-dwelling polychaetes (Site 1, 0.5 ± 0.5 individuals/core; sites 2–4, 122.5 ± 8.0 individuals/core), played an important role. Their influence was highest in muddier sediments (median grain size < 85 μm) where an increase in pseudopolydorid abundance (0.5 ± 0.5 to 149.5 ± 13.4 individuals per core) resulted in a ~ 3-fold rise in denitrification rate (22.3 ± 13.3 to 62.24 ± 11.1 μmol N₂ m⁻² h⁻¹). The linkage between macrofauna and denitrification demonstrates their role in maintaining ecosystem function and bolstering resilience in sites affected by sediment and nutrient pollution.

中文翻译：

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沉积物中反硝化作用及其跨河口的大型动物的作用

为了应付河口系统中氮的增加，通过反硝化去除氮的需求正在增加。了解生物地球化学和生态学之间的联系如何沿着养分和沉积物负荷梯度调节反硝化速率对于预测生态系统功能是必要的。先前的研究表明，在泥泞，富含营养的沉积物中反硝化率通常最高，而在含沙，缺乏营养的地点则反硝化率降低。在从上河口到下河口的四个潮下地点测量反硝化率。站点1最接近河流的主要养分供应源，具有最高的悬浮沉积物和底泥含量，随下游距离的增加而减少。与预期相反，最上游位置的反硝化率最低（22.35±13.34μmolN₂  m ^-2  h ^-1）和更高的下游（57.84±5.72μmolN ₂  m ^-2  h ^-1）。尽管呼吸作用，初级生产力和沉积物特征影响净反硝化率和效率，但结果表明，大型动物丰度（站点1、60.8±7.3个人/核心；站点2-4、177.7±10.8个人/核心），主要是管栖多毛cha （站点1、0.5±0.5个人/核心；站点2-4、122.5±8.0个人/核心）发挥了重要作用。它们的影响在泥泞的沉积物中最大（中值粒径<85μm），其中假多虫类的丰度增加（每个岩心0.5±0.5至149.5±13.4个人），反硝化速率增加约3倍（22.3±13.3至62.24） ±11.1μmolN ₂  m ^-2 小时^-1）。大型动物区系和反硝化之间的联系表明它们在维持生态系统功能和增强受沉积物和养分污染影响的地点的复原力中的作用。