Aix Marseille Université, CNRS, Université de Toulon, IRD, OSU Pythéas, Mediterranean Institute of Oceanography (MIO), UM 110, 13288, Marseille, France.
Turing Centre for Living Systems, Aix-Marseille University, 13009, Marseille, France.
Commun Biol. 2024 Aug 2;7(1):929. doi: 10.1038/s42003-024-06576-w.
Mesoscale eddies influence the distribution of diazotrophic (nitrogen-fixing) cyanobacteria, impacting marine productivity and carbon export. Non-cyanobacterial diazotrophs (NCDs) are emerging as potential contributors to marine nitrogen fixation, relying on organic matter particles for resources, impacting nitrogen and carbon cycling. However, their diversity and biogeochemical importance remain poorly understood. In the subtropical North Atlantic along a single transect, this study explored the horizontal and vertical spatial variability of NCDs associated with suspended, slow-sinking, and fast-sinking particles collected with a marine snow catcher. The investigation combined amplicon sequencing with hydrographic and biogeochemical data. Cyanobacterial diazotrophs and NCDs were equally abundant, and their diversity was explained by the structure of the eddy. The unicellular symbiotic cyanobacterium UCYN-A was widespread across the eddy, whereas Trichodesmium and Crocosphaera accumulated at outer fronts. The diversity of particle-associated NCDs varied more horizontally than vertically. NCDs constituted most reads in the fast-sinking fractions, mainly comprising Alphaproteobacteria, whose abundance significantly differed from the suspended and slow-sinking fractions. Horizontally, Gammaproteobacteria and Betaproteobacteria exhibited inverse distributions, influenced by physicochemical characteristics of water intrusions at the eddy periphery. Niche differentiations across the anticyclonic eddy underscored NCD-particle associations and mesoscale dynamics, deepening our understanding of their ecological role and impact on ocean biogeochemistry.
中尺度涡旋影响固氮（氮固定）蓝细菌的分布，从而影响海洋生产力和碳输出。非蓝细菌固氮生物（NCD）作为海洋氮固定的潜在贡献者正在出现，它们依赖有机物质颗粒作为资源，影响氮和碳循环。然而，它们的多样性和生物地球化学重要性仍然知之甚少。在单一横截线上的亚热带北大西洋，本研究通过使用海洋雪收集器收集的悬浮、缓慢下沉和快速下沉颗粒，探索了与悬浮、缓慢下沉和快速下沉颗粒相关的 NCD 的水平和垂直空间变异性。该研究将扩增子测序与水文学和生物地球化学数据相结合。蓝细菌固氮生物和 NCD 的丰度相当，它们的多样性由涡旋的结构解释。单细胞共生蓝细菌 UCYN-A 广泛分布于整个涡旋，而 Trichodesmium 和 Crocosphaera 则在外部前缘积累。与颗粒相关的 NCD 的多样性在水平方向上的变化大于在垂直方向上的变化。NCD 构成了快速下沉部分的大部分读数，主要由α变形菌组成，其丰度与悬浮和缓慢下沉部分显著不同。在水平方向上，γ变形菌和β变形菌呈相反的分布，受涡旋外围水入侵的物理化学特性影响。反气旋涡旋的生态位分化突出了 NCD-颗粒的关联和中尺度动力，加深了我们对它们生态作用及其对海洋生物地球化学影响的理解。
