Nitrogen fixation (N_Fix) is an important, yet understudied, microbial process in aquatic ecosystems, especially in the Laurentian Great Lakes (LGL). To date, a dearth of nitrogen fixation rate measurements exists in the LGL, are from temporally isolated studies, and were collected primarily from near-shore and surface water environments. Evidence of nitrogen accumulation across the Laurentian Great Lakes suggest that we do not have a firm grasp on nitrogen cycling in large lakes. Thus, we sought to quantify the spatial variability of N_Fix in the LGL. We found lakes are significantly different in N_Fix rates from one another and that rates are depth dependent. Overall mean surface N_Fix rates of Lakes Superior, Michigan, Huron, Erie and Ontario were 0.024, 0.020, 0.069, 0.145, and 0.078 (nmol N₂/L/hr), respectively. Likewise, we found the Western, Central and Eastern basins of Lake Erie are significantly different in N_Fix rates (0.1540, 0.1032, 0.0738 nmol N₂/L/hr). However, we found no significant difference in N_Fix rates between near and offshore sites in Lake Erie, which may have been biased due to a cyanobacterial bloom containing a nitrogen-fixing Dolichospermum sp. Linear regression models indicate N_Fix is generally positively correlated with chlorophyll-a concentration and negatively correlated with oxidized nitrogen species concentrations. However, Lakes Erie and Huron exhibited a positive linear relationship with oxidized nitrogen, suggesting that N_Fix may persist to meet cellular and community nitrogen demands. Together, our data highlight N_Fix is important despite the presence of abundant nitrogen in all LGL.

固氮 (N _Fix ) 是水生生态系统中一个重要但尚未得到充分研究的微生物过程，尤其是在劳伦大湖 (LGL)。迄今为止，LGL 中缺乏固氮率测量值，这些测量值来自时间隔离的研究，并且主要是从近岸和地表水环境中收集的。Laurentian Great Lakes 中氮积累的证据表明，我们对大型湖泊中的氮循环没有把握。因此，我们试图量化LGL中 N _Fix的空间可变性。我们发现湖泊在 N _Fix率方面有显着差异，而且该率取决于深度。整体平均表面 N _Fix苏必利尔湖、密歇根湖、休伦湖、伊利湖和安大略湖的比率分别为 0.024、0.020、0.069、0.145 和 0.078 (nmol N ₂ /L/hr)。同样，我们发现伊利湖的西部，中部和东部盆地的N显著不同的_修复率（0.1540，0.1032，0.0738纳摩尔ñ ₂ / L /小时）。然而，我们发现在N无显著差异_修复在伊利湖附近，海上风场，这可能已偏向利率之间由于含有固氮蓝藻开花Dolichospermum SP。线性回归模型表明 N _Fix通常与叶绿素a正相关浓度并与氧化氮物质浓度呈负相关。然而，伊利湖和休伦湖与氧化氮呈正线性关系，表明 N _Fix可能会持续满足细胞和社区对氮的需求。总之，我们的数据强调 N _Fix很重要，尽管所有 LGL 中都存在丰富的氮。