Mesoscale oceanic eddies contribute to the redistribution of resources needed for plankton to thrive. However, due to their fluid-trapping capacity, they can also isolate plankton communities, subjecting them to rapidly changing environmental conditions. Diazotrophs, which fix dinitrogen (N₂), are key members of the plankton community, providing reactive nitrogen, particularly in large nutrient-depleted regions such as subtropical gyres. However, there is still limited knowledge about how mesoscale structures characterized by specific local environmental conditions can affect the distribution and metabolic response of diazotrophs when compared with the large-scale dynamics of an oceanic region. Here we investigated genetic diazotroph diversity and N₂ fixation rates in a transect across the Gulf Stream and two associated eddies, a region with intense mesoscale activity known for its important role in nutrient transport into the North Atlantic Gyre. We show that eddy edges are hotspots for diazotroph activity with potential community connectivity between eddies. Using a long-term mesoscale eddy database, we quantified N₂ fixation rates as up to 17 times higher within eddies than in ambient waters, overall providing ~21 µmol N m⁻² yr⁻¹ to the region. Our results indicate that mesoscale eddies are hotspots of reactive nitrogen production within the broader marine nitrogen cycle.

中尺度海洋漩涡有助于浮游生物繁衍生息所需的资源的重新分配。然而，由于它们的液体捕获能力，它们也可以隔离浮游生物群落，使它们受到快速变化的环境条件的影响。固定二氮 （N₂） 的重氮生物是浮游生物群落的关键成员，提供活性氮，特别是在亚热带环流等营养枯竭的大面积地区。然而，与海洋区域的大尺度动力学相比，以特定局部环境条件为特征的中尺度结构如何影响重氮营养生物的分布和代谢反应，人们仍然了解有限。在这里，我们研究了跨越墨西哥湾流和两个相关涡流的样带中的遗传质氮营养因子多样性和 N₂ 固定率，该地区具有强烈的中尺度活动，以其在营养物质运输到北大西洋环流中的重要作用而闻名。我们表明，涡流边缘是重氮营养物质活动的热点，涡流之间具有潜在的群落联系。使用长期的中尺度涡流数据库，我们将涡流内的 N₂ 固定率量化为比环境水域高 17 倍，总体上为该区域提供 ~21 μmol N ^{m-2 yr-1}。我们的结果表明，中尺度涡流是更广泛的海洋氮循环中活性氮产生的热点。