Biogeosciences Discuss., https://doi.org/10.5194/bg-2018-279-AC2, 2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Interactive comment on “Reviews and syntheses: Processes and functional genes involved in nitrogen cycling in marine environments” by Ramiro Ramos and Silvia Pajares Ramiro Ramos and Silvia Pajares spajares@cmarl.unam.mx Received and published: 31 August 2018 We would like to thank the Reviewer for the detailed suggestions. We have taken these comments into consideration and we are sure they will strongly help to improve our manuscript. We address each of the Reviewer’s points raised below: 1. “In their manuscript "Processes and functional genes involved in nitrogen cycling in marine environments," the authors have tried to assemble a comprehensive review of nitrogen cycling in the ocean. However, multiple recent and excellent reviews ex- ist on this topic, foremost Kuypers et al. 2018, which is also frequently cited in this manuscript. Without wanting to offend the authors, it becomes quite clear when reading C1 this manuscript that they cannot (yet) match the knowledge of the authors of some of these recent reviews. This makes me call the purpose of this manuscript into question. The apparent aim here is to present another review of all reactions and microorganisms involved in N cycling in marine systems, for which I must unfortunately say there is no need right now, and the authors lack the necessary expertise in many areas. This be- comes apparent as many (recent) studies on different aspects of N cycling in the ocean are missing (e.g., Delmont et al. 2018, showing the abundance of non-cyanobacterial heterotrophic diazotrophs in marine metagenomes), and many pathways and proteins involved are incomplete and partly wrong (like for instance assimilatory nitrate and ni- trite reduction).” We thank the Reviewer for the comments. As we mentioned to Reviewer #1, we under- stand that writing a review paper on this topic is very risky given the great contributions made by other authors in recent years. However, none of these review papers have covered the main aspects we try to cover with our manuscript. For instance, the re- cent review of Kuypers et al. (2018) summarizes the current understanding of the microbial nitrogen-cycling network but does not focus on the microbially mediated N processes in marine ecosystems. Additionally, other recent papers reviewing N cycling processes in marine environments are too specific (e.g. Devol et al. in 2015 review- ing marine sediments or Lam and Kuypers in 2011 reviewing OMZs) or focus on other aspects of marine N cycling (e.g. Voss et al. in 2013 focusing on the anthropogenic effects or Zehr and Kudela in 2011 analysing the current understanding and identifying knowledge gaps). Again, while most of these papers cover biochemical, genetic or anthropogenic aspects of N cycling, in our manuscript we try to summarize the cur- rent knowledge on the nitrogen processes studied so far in the ocean, as well as the distribution of microorganisms involved in N cycling in marine environments and the factors affecting it, which are aspects that have not been covered in such an integral way so far. We are aware that there has been a great advance in the study of the marine nitrogen cycle in recent years and for that reason we believe it is appropriate to conduct a review in the field including the latest discoveries that have not been covered C2