Coincident Biogenic Nitrite and pH Maxima Arise in the Upper Anoxic Layer in the Eastern Tropical North Pacific
Name
Global Biogeochemical Cycles - 2022 - Cinay - Coincident Biogenic Nitrite and pH Maxima Arise in the Upper Anoxic Layer in.pdf
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Author(s)
Cinay, Timur
Dumit, Diana
Woosley, Ryan J
Boles, Elisabeth L
Kwiecinski, Jarek V
Mullen, Susan
Tamasi, Tyler J
Wolf, Martin J
Kelly, Colette L
Travis, Nicole M
Date Issued
December 7, 2022
Journal
Global Biogeochemical Cycles
Publisher
American Geophysical Union
Citation
Cinay, T., Dumit, D., Woosley, R. J., Boles, E. L., Kwiecinski, J. V., Mullen, S., et al. (2022). Coincident biogenic nitrite and pH maxima arise in the upper anoxic layer in the Eastern Tropical North Pacific. Global Biogeochemical Cycles, 36, e2022GB007470.
Version
Final published version
Abstract
The Eastern Tropical North Pacific (ETNP), like the other marine oxygen deficient zones
(ODZs), is characterized by an anoxic water column, nitrite accumulation at the anoxic core, and fixed nitrogen
loss via nitrite reduction to N2O and N2 gases. Here, we constrain the relative contribution of biogeochemical
processes to observable features such as the secondary nitrite maximum (SNM) and local pH maximum by
simultaneous measurement of inorganic nitrogen and carbon species. High-resolution sampling within the top
1 km of the water column reveals consistent chemical features previously unobserved in the region, including a
tertiary nitrite maximum. Dissolved inorganic carbon measurements show that pH increases with depth at the
top of the ODZ, peaking at the potential density of the SNM at σθ = 26.15 ± 0.06 (1 s.d.). We developed a novel
method to determine the relative contributions of anaerobic ammonium oxidation (anammox), denitrification,
nitrite oxidation, dissimilatory nitrate reduction to nitrite, and calcium carbonate dissolution to the nitrite
cycling in the anoxic ODZ core. The calculated relative contributions of each reaction are slightly sensitive
to the assumed C:N:P ratio and the carbon oxidation state of the organic matter sinking through the ODZ.
Furthermore, we identify the source of the pH increase at the top of ODZ as the net consumption of protons
via nitrite reduction to N2 by the denitrification process. The increase in pH due to denitrification impacts the
buffering effect of calcite and aragonite dissolving in the ETNP.
MIT Department
Massachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences
Massachusetts Institute of Technology. Center for Global Change Science
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Creative Commons Attribution-NonCommercial-NoDerivatives
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DOI of Published Version
10.1029/2022gb007470
