固氮的供應(yīng)量是世界一半以上海洋中初級(jí)生產(chǎn)的限制因素。最近的報(bào)告表明,，造成海洋中氧供應(yīng)受限區(qū)域固氮全部或大部喪失的是氨厭氧氧化（anammox）,，而非產(chǎn)生雙氮?dú)怏w（N2）的傳統(tǒng)反硝化作用,。
Ward等人發(fā)現(xiàn)，在阿拉伯海中主導(dǎo)固氮喪失的是反硝化作用,，而非氨厭氧氧化,。在這一區(qū)域，反硝化細(xì)菌比氨厭氧氧化細(xì)菌更多,，即使當(dāng)氨厭氧氧化速度很顯著時(shí)也是如此,。這項(xiàng)工作解決了我們對(duì)全球氮循環(huán)和固氮存量的認(rèn)識(shí)中一大不確定性問題，證實(shí)反硝化作用是整個(gè)海洋氮循環(huán)中的一個(gè)主要過程,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 461, 78-81 (3 September 2009) | doi:10.1038/nature08276
Denitrification as the dominant nitrogen loss process in the Arabian Sea
B. B. Ward1, A. H. Devol2, J. J. Rich3, B. X. Chang2, S. E. Bulow1, Hema Naik4, Anil Pratihary4 & A. Jayakumar1
1 Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA
2 Department of Oceanography, University of Washington, Seattle, Washington 98195, USA
3 Center for Environmental Studies, Brown University, Providence, Rhode Island 02912, USA
4 National Institute of Oceanography, Dona Paula, Goa 403004, India
Primary production in over half of the world's oceans is limited by fixed nitrogen availability. The main loss term from the fixed nitrogen inventory is the production of dinitrogen gas (N2) by heterotrophic denitrification or the more recently discovered autotrophic process, anaerobic ammonia oxidation (anammox). Oceanic oxygen minimum zones (OMZ) are responsible for about 35% of oceanic N2 production and up to half of that occurs in the Arabian Sea1. Although denitrification was long thought to be the only loss term, it has recently been argued that anammox alone is responsible for fixed nitrogen loss in the OMZs2, 3, 4. Here we measure denitrification and anammox rates and quantify the abundance of denitrifying and anammox bacteria in the OMZ regions of the Eastern Tropical South Pacific and the Arabian Sea. We find that denitrification rather than anammox dominates the N2 loss term in the Arabian Sea, the largest and most intense OMZ in the world ocean. In seven of eight experiments in the Arabian Sea denitrification is responsible for 87–99% of the total N2 production. The dominance of denitrification is reproducible using two independent isotope incubation methods. In contrast, anammox is dominant in the Eastern Tropical South Pacific OMZ, as detected using one of the isotope incubation methods, as previously reported3, 5. The abundance of denitrifying bacteria always exceeded that of anammox bacteria by up to 7- and 19-fold in the Eastern Tropical South Pacific and Arabian Sea, respectively. Geographic and temporal variability in carbon supply may be responsible for the different contributions of denitrification and anammox in these two OMZs. The large contribution of denitrification to N2 loss in the Arabian Sea indicates the global significance of denitrification to the oceanic nitrogen budget.
