Organic matter is known to influence community composition and metabolism of marine prokaryotes. However, few studies have addressed this linkage in the deep ocean. We studied the relationship between fluorescent dissolved organic matter and prokaryotic community composition in meso- and bathypelagic water masses along a surface productivity gradient crossing the subtropical and tropical Atlantic Ocean. Four fluorescence components were identified, three humic-like and one protein-like. The distributions of the humic-like components were significantly explained by water mass mixing, apparent oxygen utilisation (AOU) and epipelagic productivity proxies in varying degrees, while the protein-like component was explained only by water mass mixing and epipelagic productivity. The diversity and taxonomic composition of the prokaryotic community differed between water masses: the Nitrosopumilales order dominated in water masses with high AOU and humic-like fluorescence (notably, the SubPolar Mode Water), and tended to co-occur with Marine Group II archaea, the SAR324 clade and Thiomicrospirales, while bathypelagic water masses displayed greater abundances of members of Marinimicrobia, SAR202 and SAR324. Water mass mixing regression models suggested that the distribution of some taxa (e.g., Marinimicrobia, SAR202) was dominated by mixing and selection within the water masses during ageing, while others (chiefly, Alteromonadales) were mostly influenced by local processes. Our results suggest a link between the composition of the prokaryotic community, oxygen utilisation and the signal of fluorescent dissolved organic matter, and has implications for our understanding of the processes that shape carbon cycling and prokaryotic communities in the deep ocean.

已知有机物会影响海洋原核生物的群落组成和新陈代谢。然而，很少有研究解决深海中的这种联系。我们研究了横跨亚热带和热带大西洋的地表生产力梯度中中和深海水团中荧光溶解有机物与原核生物群落组成之间的关系。鉴定了四种荧光成分，三种类腐殖质和一种类蛋白质。类腐殖质成分的分布在不同程度上可以通过水团混合、表观氧利用（AOU）和远洋生产力代理来解释，而类蛋白质组分仅通过水团混合和远洋生产力来解释。原核生物群落的多样性和分类组成因水团而异：Nitrosopumilales 目在具有高 AOU 和类腐殖质荧光的水团中占主导地位（特别是亚极模式水），并倾向于与海洋 II 组古菌共存， SAR324 进化枝和硫微螺旋藻目，而深海水团显示出更多丰富的 Marinimicrobia、SAR202 和 SAR324 成员。水团混合回归模型表明，一些类群（例如，Marinimicrobia，SAR202）的分布主要受老化过程中水团内的混合和选择的影响，而其他类群（主要是交替单胞菌）主要受局部过程的影响。我们的结果表明原核生物群落的组成之间存在联系，