Availability of fixed nitrogen is a pivotal driver on primary productivity in the oceans, thus the identification of key processes triggering nitrogen losses from these ecosystems is of major importance as they affect ecosystems function and consequently global biogeochemical cycles. Denitrification and anaerobic ammonium oxidation coupled to nitrite reduction (Anammox) are the only identified marine sinks for fixed nitrogen. The present study provides evidence indicating that anaerobic ammonium oxidation coupled to the reduction of sulfate, the most abundant electron acceptor present in the oceans, prevails in marine sediments. Tracer analysis with ¹⁵N-ammonium revealed that this microbial process, here introduced as Sulfammox, accounts for up to 5 μg ¹⁵N₂ produced g⁻¹ day⁻¹ in sediments collected from the eastern tropical North Pacific coast. Raman and X-ray diffraction spectroscopies revealed that elemental sulfur and sphalerite (ZnFeS) were produced, besides free sulfide, during the course of Sulfammox. Anaerobic ammonium oxidation linked to Fe(III) reduction (Feammox) was also observed in the same marine sediments accounting for up to 2 μg ¹⁵N₂ produced g⁻¹ day⁻¹. Taxonomic characterization, based on 16S rRNA gene sequencing, of marine sediments performing the Sulfammox and Feammox processes revealed the microbial members potentially involved. These novel nitrogen sinks may significantly fuel nitrogen loss in marine environments. These findings suggest that the interconnections among the oceanic biogeochemical cycles of N, S and Fe are much more complex than previously considered.

中文翻译：

---

与硫酸盐和三价铁还原反应相关的厌氧铵氧化助长了海洋沉积物中的氮损失。

固定氮的可用性是海洋初级生产力的关键驱动力，因此，识别触发这些生态系统氮损失的关键过程非常重要，因为它们会影响生态系统功能，进而影响全球生物地球化学循环。脱氮和厌氧铵氧化再加上亚硝酸盐还原（Anammox）是唯一确定的固定氮海洋汇。本研究提供的证据表明，厌氧铵氧化与硫酸盐的还原相结合，硫酸盐是海洋中存在的最丰富的电子受体，在海洋沉积物中普遍存在。与示踪分析¹⁵的N-铵揭示该微生物的方法，在这里引入Sulfammox，占至多5微克¹⁵ Ñ ₂在从东部热带北太平洋海岸收集的沉积物中产生了g ^-1天^-1。拉曼光谱和X射线衍射光谱表明，在磺胺的过程中，除游离硫化物外，还生成了元素硫和闪锌矿（ZnFeS）。厌氧性氨氧化联成Fe（III）还原（Feammox）在相同的海洋沉积物占最多也观察至2μg ¹⁵ Ñ ₂产生克^-1天^-1。基于进行Sulfammox和Feammox过程的海洋沉积物的分类学特征（基于16S rRNA基因测序）揭示了潜在的微生物成员。这些新颖的氮沉可能会大大增加海洋环境中的氮损失。这些发现表明，N，S和Fe的海洋生物地球化学循环之间的相互联系比以前考虑的要复杂得多。