@article{76,
  author = {X. Zhang and B.B. Ward and D.M. Sigman},
  title = {Global Nitrogen Cycle: Critical Enzymes, Organisms, and Processes for Nitrogen Budgets and Dynamics},
  abstract = {Nitrogen (N) is used in many of life s fundamental biomolecules, and it is also a participant in environmental redox chemistry. Biogeochemical processes control the amount and form of N available to organisms ("fixed"N). These interacting processes result in N acting as the proximate limiting nutrient in most surface environments. Here, we review the global biogeochemical cycle of N and its anthropogenic perturbation. We introduce important reservoirs and processes affecting N in the environment, focusing on the ocean, in which N cycling is more generalizable than in terrestrial systems, which are more heterogeneous. Particular attention is given to processes that create and destroy fixed N because these comprise the fixed N input/output budget, the most universal control on environmental N availability. We discuss preindustrial N budgets for terrestrial and marine systems and their modern-day alteration by N inputs from human activities. We summarize evidence indicating that the simultaneous roles of N as a required biomass constituent and an environmental redox intermediate lead to stabilizing feedbacks that tend to blunt the impact of N cycle perturbations at larger spatiotemporal scales, particularly in marine systems. As a result of these feedbacks, the anthropogenic "N problem"is distinct from the "carbon dioxide problem"in being more local and less global, more immediate and less persistent. {\textcopyright} 2020 American Chemical Society.},
  year = {2020},
  journal = {Chemical Reviews},
  volume = {120},
  number = {12},
  pages = {5308-5351},
  url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086743038\&doi=10.1021\%2facs.chemrev.9b00613\&partnerID=40\&md5=eb34a5c470ecfbc1300abf84ff64723f},
  doi = {10.1021/acs.chemrev.9b00613},
}