Benthic habitats in shallow oxbow lakes may serve as permanent nitrogen (N) sinks by facilitating denitrification. Oxbow sediments may also accumulate nutrients through uptake, deposition and heterotrophic N₂ fixation, and ultimately provide a significant internal source of N and phosphorus (P) through sediment release to the water column. To better understand nutrient source-sink dynamics in oxbow lakes, we explored seasonal and habitat specific patterns in sediment dissolved dinitrogen gas (N₂-N) and nutrient flux within an oxbow in the Mississippi Alluvial Plain. Time series models indicate a higher probability of positive N₂-N fluxes in fall through spring, significant negative summer fluxes, and clear differences among habitats with net annual N₂-N fluxes, ranging from − 2.34 g m⁻² Y⁻¹ in open water habitat to 0.26 g m⁻² Y⁻¹ in shoreline areas. Integrated lake-wide N₂-N sediment flux estimates were negative indicating the significant role of net N₂ fixation. More complex models explained similar amounts of variation (Adj. R² = 0.57 vs. 0.45) and indicated that benthic N₂-N fluxes were associated with changes in temperature, dissolved inorganic N, sediment oxygen demand, and sediment carbon:N ratios. Ammonium and P flux from sediments were substantial across all habitats and internal N regeneration far outpaced removal from the system by sediment N₂-N flux. Results indicate that nutrient release from sediments generate internal nutrient loads proportional to external loading from the watershed. Our results highlight the significant potential for internal nutrient loading and benthic N₂ fixation within sediments to regulate biogeochemical processes within understudied oxbow lake ecosystems.

浅水牛轭湖中的底栖栖息地可以通过促进反硝化作用作为永久性氮 (N) 汇。Oxbow 沉积物还可能通过吸收、沉积和异养 N ₂固定来积累养分，并最终通过沉积物释放到水柱中提供重要的 N 和磷 (P) 内部来源。为了更好地了解牛轭湖中的营养源-汇动态，我们探索了密西西比冲积平原牛轭内沉积物溶解的氮气 (N _{2 -N) 和营养通量的季节性和栖息地特定模式。时间序列模型表明，秋季到春季 N 2} -N正通量的概率较高，夏季负通量显着，以及具有年净 N 的栖息地之间的明显差异₂ -N 通量，范围从开阔水域栖息地的 - 2.34 g m ^-2 Y ^{-1到海岸线地区的 0.26 g m -2} Y ^-1。综合湖泊范围内的 N ₂ -N 沉积物通量估计为负值，表明净 N ₂固定的重要作用。更复杂的模型解释了相似的变化量（Adj. R ²  = 0.57 vs. 0.45）并表明底栖 N ₂-N 通量与温度、溶解的无机 N、沉积物需氧量和沉积物碳：N 比率的变化有关。来自沉积物的铵和磷通量在所有生境中都很大，内部 N 再生远远超过了沉积物 N ₂ -N 通量从系统中去除的速度。结果表明，沉积物中的养分释放产生的内部养分负荷与流域的外部负荷成正比。_{我们的研究结果强调了沉积物中内部养分负载和底栖 N 2}固定在调节未充分研究的牛轭湖生态系统中的生物地球化学过程方面的巨大潜力。