Coral reef health depends on an intricate relationship among the coral animal, photosynthetic algae, and a complex microbial community. The holobiont can impact the nutrient balance of their hosts amid an otherwise oligotrophic environment, including by cycling physiologically important nitrogen compounds. Here we use ¹⁵N-tracer experiments to produce the first simultaneous measurements of ammonium oxidation, nitrate reduction, and nitrous oxide (N₂O) production among five iconic species of reef-building corals (Acropora palmata, Diploria labyrinthiformis, Orbicella faveolata, Porites astreoides, and Porites porites) in the highly protected Jardines de la Reina reefs of Cuba. Nitrate reduction is present in most species, but ammonium oxidation is low potentially due to photoinhibition and assimilatory competition. Coral-associated rates of N₂O production indicate a widespread potential for denitrification, especially among D. labyrinthiformis, at rates of ~1 nmol cm⁻² d⁻¹. In contrast, A. palmata displays minimal active nitrogen metabolism. Enhanced rates of nitrate reduction and N₂O production are observed coincident with dark net respiration periods. Genomes of bacterial cultures isolated from multiple coral species confirm that microorganisms with the ability to respire nitrate anaerobically to either dinitrogen gas or ammonium exist within the holobiont. This confirmation of anaerobic nitrogen metabolisms by coral-associated microorganisms sheds new light on coral and reef productivity.

珊瑚礁的健康取决于珊瑚动物、光合藻类和复杂的微生物群落之间错综复杂的关系。全生物可以在其他贫营养环境中影响宿主的营养平衡，包括循环生理上重要的氮化合物。在这里，我们使用^{15 个}N-示踪剂实验首次同时测量了五种造礁珊瑚的标志性物种（Acropora palmata、Diploria labyrinthiformis、Orbicella faveolata、Porites ）中的铵氧化、硝酸盐还原和一氧化二氮 (N _{2 O) 的产生}astreoides和Porites porites) 在古巴受到高度保护的 Jardines de la Reina 珊瑚礁中。大多数物种都存在硝酸盐还原，但由于光抑制和同化竞争，铵氧化可能很低。珊瑚相关的 N ₂ O 产生速率表明反硝化作用具有广泛的潜力，尤其是在D. labyrinthiformis中，速率约为 1 nmol cm ^-2  d ^-1。相比之下，A. palmata显示出最小的活性氮代谢。提高硝酸盐还原率和 N ₂观察到 O 的产生与暗网呼吸期一致。从多种珊瑚物种中分离出的细菌培养物的基因组证实，在全生物体内存在能够将硝酸盐厌氧呼吸为二氮气体或铵的微生物。这种对珊瑚相关微生物厌氧氮代谢的证实为珊瑚和珊瑚礁的生产力提供了新的思路。