Nitrogen (N) is a vital and often limiting nutrient to marine productivity, yet fundamental questions about the oceanic N budget remain unresolved. The accurate quantification of processes that result in the loss of fixed N from the ocean (denitrification) is critical for understanding the modern marine N budget. In order to better constrain this budget, measurements of N₂:Ar ratios and the isotopes of N₂ were used to examine rates and pathways of denitrification in both Arctic sediments and oxygen deficient water columns, two important environments for marine fixed N loss.

To quantify the contribution of the Arctic to global sedimentary denitrification, a model was constructed to relate the attenuation of export production with increasing water depth to denitrification rates. Based on the results of this study, the Arctic is responsible for the removal of approximately 13 Tg N yr^-1, or about 4–13% of global denitrification.

Most water column denitrification occurs in the three major oxygen deficient zones (ODZs): the Arabian Sea (AS), the eastern tropical North (ETNP) and South Pacific (ETSP). As no other processes produce or consume N₂ in the ODZ, its excess above background values can be used to estimate fixed N removal rates. The findings of this study suggest that, regardless of the exact pathway to N₂, the source of the denitrified N is either deep-sea nitrate and/or organic matter with an N:P close to the Redfield ratio.

Denitrification rates were found to be approximately an order of magnitude larger than anammox rates in both the ETSP and AS ODZs. The addition of organic carbon had a marked effect on the denitrification in the AS. If carbon availability in the ODZ is linked to surface productivity, the degree to which carbon limits denitrification in either the ETSP or AS ODZ would likely be both spatially and temporally heterogeneous, which could at least partially explain the different findings of independent studies as to the relative contributions of denitrification and anammox to N loss in the ODZs.