All about nitrite: exploring nitrite sources and sinks in the eastern tropical North Pacific oxygen minimum zone

John C. Tracey, Andrew R. Babbin, Elizabeth Wallace, Xin Sun, Katherine L. Durussel, Claudia Frey, Donald E. Martocello, Tyler Tamasi, Sergey Oleynik, Bess B. Ward

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Oxygen minimum zones (OMZs), due to their large volumes of perennially deoxygenated waters, are critical regions for understanding how the interplay between anaerobic and aerobic nitrogen (N) cycling microbial pathways affects the marine N budget. Here, we present a suite of measurements of the most significant OMZ N cycling rates, which all involve nitrite (NO2-) as a product, reactant, or intermediate, in the eastern tropical North Pacific (ETNP) OMZ. These measurements and comparisons to data from previously published OMZ cruises present additional evidence that NO3- reduction is the predominant OMZ N flux, followed by NO2- oxidation back to NO3-. The combined rates of both of these N recycling processes were observed to be much greater (up to nearly 200 times) than the combined rates of the N loss processes of anammox and denitrification, especially in waters near the anoxic-oxic interface. We also show that NO2- oxidation can occur when O2 is maintained near 1 nM by a continuous-purge system, NO2- oxidation and O2 measurements that further strengthen the case for truly anaerobic NO2- oxidation. We also evaluate the possibility that NO2- dismutation provides the oxidative power for anaerobic NO2- oxidation. The partitioning of N loss between anammox and denitrification differed widely from stoichiometric predictions of at most 29 % anammox; in fact, N loss rates at many depths were entirely due to anammox. Our new NO3- reduction, NO2- oxidation, dismutation, and N loss data shed light on many open questions in OMZ N cycling research, especially the possibility of truly anaerobic NO2- oxidation.

Original languageEnglish (US)
Pages (from-to)2499-2523
Number of pages25
Issue number12
StatePublished - Jun 30 2023

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes


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