Marine environment anammox

Anammox is the anaerobic reduction of ammonium to N2 using nitrite as the terminal electron acceptor. This process can contribute significantly to benthic N2 production in some marine environments, but studies to date have found that the importance of anammox in organic rich coastal sediments is low (Engstrom et al., 2005). Anammox may be of minor importance in organic rich salt marshes as well. 

An alternative bacterial route from NO to N2, where NH oxidation is coupled to NOj reduction in a process called anammox (anaerobic ammonium oxidation), dominates N2 production in many marine environments, but, unlike classical denitrification, it does not lead to the production of N2O. Together, denitrification and anammox close the nitrogen cycle by returning N2 gas back to the atmosphere. 

Dalsgaard, T., B. Thamdrup, and D. E. Canfield. 2005. Anaerobic ammoninm oxidation (anammox) in the marine environment. Res. Microbiol. 156 457-464. 

Jensen, M. M., Thamdrup, B., and Dalsgaard, T. Effects of specific inhibitors on Anammox and denitrification in marine sediment. Appl. Environ. Microb. 73, 3151—3158. 

Additionally, the anammox reaction mentioned earlier results in the reduction of N02 with the production of N2 gas. Recent direct tracer evidence from both marine sediments (Thamdrup and Dalsgaard, 2002) (see Chapter 6, Devol, this volume) and several anoxic water column systems (Hamersley et al., 2007 Kuypers et al., 2005) has shown that the anammox pathway, rather than conventional denitrification, can be a significant and, at times, predominant source of N2 production. Future studies of combined N loss from reefal environments should also consider this pathway. 

Amano, T., Yoshinaga, I., Okada, K., Yamagishi, T., Ueda, S., Obuchi, A., et al. (2007). Detection of anammox activity and diversity of anammox bacteria-related 16S rRNA genes in coastal marine sediment in japan. Microbes Environ. 22, 232—242. 

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