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| Titel |
Nitrogen uptake and regeneration pathways in the equatorial Pacific: a basin scale modeling study |
| VerfasserIn |
X. J. Wang, R. Murtugudde, R. Borgne |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 6, no. 11 ; Nr. 6, no. 11 (2009-11-24), S.2647-2660 |
| Datensatznummer |
250004099
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| Publikation (Nr.) |
 copernicus.org/bg-6-2647-2009.pdf |
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| Zusammenfassung |
| It is well known that most primary production is fueled by regenerated
nitrogen in the open ocean. Therefore, studying the nitrogen cycle by
focusing on uptake and regeneration pathways would advance our understanding
of nitrogen dynamics in the marine ecosystem. Here, we carry out a
basin-scale modeling study, by assessing model simulations of nitrate and
ammonium, and rates of nitrate uptake, ammonium uptake and regeneration in
the equatorial Pacific. Model-data comparisons show that the model is able
to reproduce many observed features of nitrate, ammonium, such as the deep
ammonium maximum (DAM). The model also reproduces the observed de-coupling
of ammonium uptake and regeneration, i.e., regeneration rate greater than
uptake rate in the lower euphotic zone. The de-coupling largely explains the
observed DAM in the equatorial Pacific Ocean. Our study indicates that
zooplankton excretion and remineralization of organic nitrogen play a
different role in nitrogen regeneration. Rates of zooplankton excretion vary
from <0.01 mmol m−3 d−1 to 0.1 mmol m−3 d−1 in the
upper euphotic zone while rates of remineralization fall within a narrow
range (0.015–0.025 mmol m−3 d−1 . Zooplankton excretion
contributes up to 70% of total ammonium regeneration in the euphotic
zone, and is largely responsible for the spatial variability of nitrogen
regeneration. However, remineralization provides a steady supply of ammonium
in the upper ocean, and is a major source of inorganic nitrogen for the
oligotrophic regions. Overall, ammonium generation and removal are
approximately balanced over the top 150 m in the equatorial Pacific. |
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