title: Assessment of nitrogen and oxygen isotopic fractionation during nitrification and its expression in the marine environment.
abstract: Nitrification is a microbially-catalyzed process whereby ammonia (NH(3)) is oxidized to nitrite (NO(2)(-)) and subsequently to nitrate (NO(3)(-)). It is also responsible for production of nitrous oxide (N(2)O), a climatically important greenhouse gas. Because the microbes responsible for nitrification are primarily autotrophic, nitrification provides a unique link between the carbon and nitrogen cycles. Nitrogen and oxygen stable isotope ratios have provided insights into where nitrification contributes to the availability of NO(2)(-) and NO(3)(-), and where it constitutes a significant source of N(2)O. This chapter describes methods for determining kinetic isotope effects involved with ammonia oxidation and nitrite oxidation, the two independent steps in the nitrification process, and their expression in the marine environment. It also outlines some remaining questions and issues related to isotopic fractionation during nitrification.
authors.affiliation: Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Casciotti
authors.forename: Carolyn
authors.initials: C
authors.lastname: Buchwald
authors.forename: Alyson E
authors.initials: AE
authors.lastname: Santoro
authors.forename: Caitlin
authors.initials: C
authors.lastname: Frame
mesh_terms: D000641:Ammonia / Q000378:metabolism; D001105:Archaea / Q000378:metabolism; D052818:Autotrophic Processes / Q000502:physiology; D057486:Carbon Cycle; D005591:Chemical Fractionation; D004777:Environment; D007553:Isotope Labeling; D009566:Nitrates / Q000378:metabolism; D058465:Nitrification; D009573:Nitrites / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D058458:Nitrogen Cycle; D009587:Nitrogen Isotopes / Q000737:chemistry*; D009606:Nitrosomonas / Q000378:metabolism; D009609:Nitrous Oxide / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010103:Oxygen Isotopes / Q000737:chemistry*; D012623:Seawater / Q000737:chemistry* / Q000382:microbiology; D014871:Water Microbiology
chemical_list: D009566:Nitrates; D009573:Nitrites; D009587:Nitrogen Isotopes; D010103:Oxygen Isotopes; D000641:Ammonia; D009609:Nitrous Oxide; D009584:Nitrogen; D010100:Oxygen