Organic matter (OM) loading drives benthic metabolism and controls nitrogen (N), phosphorus (P), and carbon (C) cycling in coastal sediments. To better understand the influence of OM on benthic metabolism, we conducted sediment core incubations in Long Island Sound, NY (USA), an estuary heavily influenced by anthropogenic nutrient loading. Cores were collected during the summer and winter at five stations along a west to east transect representing a gradient of high to low nutrient inputs and subsequent OM deposition. Here we provide a comprehensive analysis of environmental drivers of benthic fluxes as well as the first directly measured rates of sediment denitrification and N-fixation, thus providing a missing piece of the N budget for Long Island Sound. Our findings show greatest sediment oxygen demand (SOD) in the western basin during the summer. Sediments were a source of dissolved inorganic N and P. Compared to historic SOD and ammonium fluxes, our measurements were about 50% lower, potentially reflecting larger scale perturbations (e.g., warming temperatures, decrease wind speed) or reduced N loading through improved management of wastewater treatment facilities. Sediments were a source of nitrous oxide (mean (± standard error): 8.63 ± 3.18 nmol m⁻² h⁻¹) and methane (23.80 ± 18.05 nmol m⁻² h⁻¹). Net sediment denitrification rates were low (10.34 ± 7.61 µmol N₂–N m⁻² h⁻¹) and did not vary significantly across stations or seasons. These sediments have a N removal efficiency of ~ 30% with the potential to remove approximately 9% of the total land-based N load entering Long Island Sound.

有机物（OM）的负载驱动底栖生物的代谢并控制沿海沉积物中氮（N），磷（P）和碳（C）的循环。为了更好地了解OM对底栖生物代谢的影响，我们在美国纽约州长岛湾（Long Island Sound）进行了沉积物核心孵化，这是一个受人为营养物负荷严重影响的河口。在夏季和冬季，沿西至东断面的五个站点采集了岩心，代表了高到低的养分输入和随后的OM沉积的梯度。在这里，我们对底流通量的环境驱动因素以及沉积物的反硝化和固氮率进行了首次直接测量，从而为长岛峡提供了N预算的一部分。我们的研究结果表明，夏季西部盆地的沉积物需氧量（SOD）最大。沉积物是溶解的无机N和P的来源。与以往的SOD和铵通量相比，我们的测量值降低了约50％，这可能反映出较大的尺度扰动（例如，温度升高，风速降低）或通过改善对N2P的管理而减少了N负荷。废水处理设施。沉积物是一氧化二氮的来源（平均值（±标准误差）：8.63±3.18 nmol m^-2  h ^-1）和甲烷（23.80±18.05 nmol m ^-2  h ^-1）。净沉积物反硝化率较低（10.34±7.61 µmol N ₂ -N m ^-2  h ^-1），并且在不同站点或季节之间均无显着变化。这些沉积物的N去除效率约为30％，有可能去除进入长岛海峡的大约9％的陆地氮含量。