Nitrogen cycling in oxygen deficient zones : insights from δ15N and δ18O of nitrite and nitrate
type: CreativeWork
description: The stable isotopes, δ15N and δ18O, of nitrite and nitrate can be powerful tools used to interpret nitrogen cycling in the ocean. In order to interpret isotope profiles, the isotope systematics of each process involved must be known. This thesis describes numerous experiments using both cultures of nitrifying organisms as well as natural seawater samples to determine the oxygen isotope systematics of nitrification. These experiments show that the accumulation of nitrite has a large effect on the resulting δ18ONO3. Also, the δ18ONO2 was developed as a unique tracer because it undergoes abiotic equilibration with water δ18O at a predictable rate based on pH, temperature and salinity. This rate, its dependencies, and how the δ18ONO2 values can be used as not only biological source indicators but also indicators of age are described. Finally, using the isotope systematics of nitrification as well as the properties of nitrite oxygen isotope exchange described in this thesis, the final chapter interprets multi-isotope nitrate and nitrite profiles in the Costa Rica Upwelling Dome using a simple 1D model. Overall, this thesis describes new nitrogen and oxygen isotopic tracers and uses them to elucidate the complicated nitrogen biogeochemistry in oxygen deficient zones.
abstract: The stable isotopes, δ15N and δ18O, of nitrite and nitrate can be powerful tools used to interpret nitrogen cycling in the ocean. In order to interpret isotope profiles, the isotope systematics of each process involved must be known. This thesis describes numerous experiments using both cultures of nitrifying organisms as well as natural seawater samples to determine the oxygen isotope systematics of nitrification. These experiments show that the accumulation of nitrite has a large effect on the resulting δ18ONO3. Also, the δ18ONO2 was developed as a unique tracer because it undergoes abiotic equilibration with water δ18O at a predictable rate based on pH, temperature and salinity. This rate, its dependencies, and how the δ18ONO2 values can be used as not only biological source indicators but also indicators of age are described. Finally, using the isotope systematics of nitrification as well as the properties of nitrite oxygen isotope exchange described in this thesis, the final chapter interprets multi-isotope nitrate and nitrite profiles in the Costa Rica Upwelling Dome using a simple 1D model. Overall, this thesis describes new nitrogen and oxygen isotopic tracers and uses them to elucidate the complicated nitrogen biogeochemistry in oxygen deficient zones.
author: Buchwald, Carolyn
language: en_US
keywords: Nitrification, Nitrogen fixation, Melville (Ship) Cruise MV1008, Melville (Ship) Cruise MV1104, Roger Revelle (Ship) Cruise
date published: 2013-02
date modified: 2026-07-27T22:05:04Z
provider: Woods Hole Oceanographic Institute
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Massachusetts Institute of Technology and Woods Hole Oceanographic Institution

PropertyValue
property ID: Handle
value: https://hdl.handle.net/1912/5739

PropertyValue
property ID: DOI
value: 10.1575/1912/5739