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https://doi.org/10.5194/egusphere-2022-1437
https://doi.org/10.5194/egusphere-2022-1437
19 Dec 2022
 | 19 Dec 2022

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 III, Tyler Tamasi, Sergey Oleynik, and Bess B. Ward

Abstract. 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 200x) 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 in functionally anoxic incubations, 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. Although almost all treatments returned little evidence for dismutation (as based on product inhibition, substrate stimulation, and stoichiometric hypotheses), results from one treatment under conditions closest to in situ NO2 values may support the occurrence of NO2 dismutation. 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 consisted entirely of anammox. Through investigating the magnitudes of NO3 reduction and NO2 oxidation, testing for anaerobic NO2 oxidation, examining the possibility of NO2 dismutation, and further documenting the balance of N loss processes, these new data shed light on many open questions in OMZ N cycling research.

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30 Jun 2023
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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 III, Tyler Tamasi, Sergey Oleynik, and Bess B. Ward
Biogeosciences, 20, 2499–2523, https://doi.org/10.5194/bg-20-2499-2023,https://doi.org/10.5194/bg-20-2499-2023, 2023
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Nitrite is a nexus in nitrogen turnover, especially in oxygen minimum zones. This study works...
Short summary
Nitrogen (N) is essential for life. Thus, its availability plays a key role in determining...
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