More Like this

1. Estimating fixed nitrogen loss and associated isotope effects using concentration and isotope measurements of NO3–, NO2–, and N2 from the Eastern Tropical South Pacific oxygen deficient zone

   https://doi.org/10.1016/j.dsr2.2018.02.011  

   Peters, Brian ; Horak, Rachel ; Devol, Alan ; Fuchsman, Clara ; Forbes, Matthew ; Mordy, Calvin W. ; Casciotti, Karen L. ( October 2018 , Deep Sea Research Part II: Topical Studies in Oceanography)
2. Distribution of iron in the Western Indian Ocean and the Eastern tropical South pacific: An inter-basin comparison

   https://doi.org/10.1016/j.chemgeo.2019.119334  

   Moffett, James W. ; German, Christopher R. ( January 2020 , Chemical Geology)

   null (Ed.)
3. Pathways of Nitrous Oxide Production in the Eastern Tropical South Pacific Oxygen Minimum Zone

   https://doi.org/10.1029/2022GB007670  

   McCoy, Daniel ; Damien, Pierre ; Clements, Daniel ; Yang, Simon ; Bianchi, Daniele ( June 2023 , Global Biogeochemical Cycles)

   Oceanic emissions of nitrous oxide (N₂O) account for roughly one‐third of all natural sources to the atmosphere. Hot‐spots of N₂O outgassing occur over oxygen minimum zones (OMZs), where the presence of steep oxygen gradients surrounding anoxic waters leads to enhanced N₂O production from both nitrification and denitrification. However, the relative contributions from these pathways to N₂O production and outgassing in these regions remains poorly constrained, in part due to shared intermediary nitrogen tracers, and the tight coupling of denitrification sources and sinks. To shed light on this problem, we embed a new, mechanistic model of the OMZ nitrogen cycle within a three‐dimensional eddy‐resolving physical‐biogeochemical model of the Eastern Tropical South Pacific (ETSP), tracking contributions from remote advection, atmospheric exchange, and local nitrification and denitrification. The model indicates that net N₂O production from denitrification is approximately one order of magnitude greater than nitrification within the ETSP OMZ. However, only ∼32% of denitrification‐derived N₂O production ultimately outgasses to the atmosphere in this region (contributing ∼36% of the air‐sea N₂O flux on an annual basis), while the remaining is exported out of the domain. Instead, remotely produced N₂O advected into the OMZ region accounts for roughly half (∼57%) of the total N₂O outgassing, with smaller contributions from nitrification (∼7%). Our results suggests that, together with enhanced production by denitrification, upwelling of remotely derived N₂O contributes the most to N₂O outgassing over the ETSP OMZ.

    

   more » « less
4. Dissolved Organic Nitrogen Production and Consumption in Eastern Tropical South Pacific Surface Waters

   https://doi.org/10.1029/2017GB005875  

   Knapp, A. N. ; Casciotti, K. L. ; Prokopenko, M. G. ( May 2018 , Global Biogeochemical Cycles)
5. Low rates of dinitrogen fixation in the eastern tropical South Pacific

   https://doi.org/10.1002/lno.11159  

   Chang, Bonnie X. ; Jayakumar, Amal ; Widner, Brittany ; Bernhardt, Peter ; Mordy, Calvin W. ; Mulholland, Margaret R. ; Ward, Bess B. ( March 2019 , Limnology and Oceanography)

   Recent work has suggested that the oxygen deficient zone (ODZ) and overlying surface waters of the eastern tropical South Pacific (ETSP) is a potential niche for dinitrogen (N₂) fixation. Rates of dinitrogen fixation were measured in the ETSP above and within the ODZ in July 2013 using a modified¹⁵N₂bubble addition method, wherein a bubble was added, mixed, and then removed, and the isotopic enrichment of the dissolved N₂was measured directly for each incubation. N₂fixation rates in the euphotic zone ranged from below detection to 3.9 nmol L⁻¹d⁻¹and were below detection at all depths surveyed within the ODZ. Depth‐integrated rates ranged from below detection to 289.7μmol m⁻²d⁻¹. DNA and RNA of diversenifHgenes were detected at both surface waters and in the ODZ. However, the results of this study suggest that N₂fixation rates were low and contribute little to N cycling in the ETSP.

    

   more » « less