Nitrogen Isotopes in the Ocean

Daniel Mikhail Sigman, K. L. Karsh, K. L. Casciotti

Research output: Chapter in Book/Report/Conference proceedingChapter

159 Scopus citations


This article outlines the isotope systematics of the major processes in the ocean nitrogen (N) cycle, their impact on the isotopic compositions of the major N reservoirs in the ocean, and how the N isotopes in the modern ocean and sedimentary record may record current N fluxes and past changes. The dominant dynamic is of kinetic isotope discrimination, in which the light isotope of N (14N) is preferentially converted from substrate to product, leaving the substrate relatively enriched in 15N. The description of models and of observed N fluxes and pools in the ocean is dominated by two general parameters: (1) the amplitude of the isotope discrimination in a given N conversion, and (2) the degree to which that conversion consumes its substrate. © 2009

Original languageEnglish (US)
Title of host publicationEncyclopedia of Ocean Sciences
PublisherElsevier Ltd
Number of pages15
ISBN (Print)9780123744739
StatePublished - Jan 1 2009

All Science Journal Classification (ASJC) codes

  • General Agricultural and Biological Sciences


  • Ammonium
  • Assimilation
  • Denitrification
  • Dissolved organic nitrogen
  • Fixed nitrogen
  • Isotope fractionation
  • Nitrate
  • Nitrification
  • Nitrogen budget
  • Nitrogen fixation
  • Nutrient
  • Particulate nitrogen
  • Phytoplankton
  • Sediment
  • Sediment trap


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