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Title: Nitrogen wet deposition stoichiometry: the role of organic nitrogen, seasonality, and snow
Award ID(s):
1929148
NSF-PAR ID:
10408521
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
Biogeochemistry
Volume:
160
Issue:
3
ISSN:
0168-2563
Page Range / eLocation ID:
301 to 314
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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  1. Moisander, Pia (Ed.)
    Abstract The availability of nitrogen (N) in ocean surface waters affects rates of photosynthesis and marine ecosystem structure. In spite of low dissolved inorganic N concentrations, export production in oligotrophic waters is comparable to more nutrient replete regions. Prior observations raise the possibility that di-nitrogen (N2) fixation supplies a significant fraction of N supporting export production in the Gulf of Mexico. In this study, geochemical tools were used to quantify the relative and absolute importance of both subsurface nitrate and N2 fixation as sources of new N fueling export production in the oligotrophic Gulf of Mexico in May 2017 and May 2018. Comparing the isotopic composition (“δ15N”) of nitrate with the δ15N of sinking particulate N collected during five sediment trap deployments each lasting two to four days indicates that N2 fixation is typically not detected and that the majority (≥80%) of export production is supported by subsurface nitrate. Moreover, no gradients in upper ocean dissolved organic N and suspended particulate N concentration and/or δ15N were found that would indicate significant N2 fixation fluxes accumulated in these pools, consistent with low Trichodesmium spp. abundance. Finally, comparing the δ15N of sinking particulate N captured within vs. below the euphotic zone indicates that during late spring regenerated N is low in δ15N compared to sinking N. 
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