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| Titel |
Data-based assessment of environmental controls on global marine nitrogen fixation |
| VerfasserIn |
Y.-W. Luo, I. D. Lima, D. M. Karl, C. A. Deutsch, S. C. Doney |
| 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 ; 11, no. 3 ; Nr. 11, no. 3 (2014-02-06), S.691-708 |
| Datensatznummer |
250117191
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| Publikation (Nr.) |
 copernicus.org/bg-11-691-2014.pdf |
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| Zusammenfassung |
| There are a number of hypotheses concerning the environmental controls on marine
nitrogen fixation (NF). Most of these hypotheses have not been assessed
against direct measurements on the global scale. In this study, we use
~ 500 depth-integrated field measurements of NF covering the Pacific
and Atlantic oceans to test whether the spatial variance of these
measurements can be explained by the commonly hypothesized environmental
controls, including measurement-based surface solar radiation, mixed layer
depth, average solar radiation in the mixed layer, sea surface temperature,
wind speed, surface nitrate and phosphate concentrations, surface excess
phosphate (P*) concentration and subsurface minimum dissolved oxygen
(in upper 500 m), as well as model-based P* convergence and
atmospheric dust deposition. By conducting simple linear regression and
stepwise multiple linear regression (MLR) analyses, surface solar radiation
(or sea surface temperature) and subsurface minimum dissolved oxygen are
identified as the predictors that explain the most spatial variance in the
observed NF data, although it is unclear why the observed NF decreases when
the level of subsurface minimum dissolved oxygen is higher than
~ 150 μM. Dust deposition and wind speed do not appear to
influence the spatial patterns of NF on global scale. The weak correlation
between the observed NF and the P* convergence and concentrations
suggests that the available data currently remain insufficient to fully
support the hypothesis that spatial variability in denitrification is the
principal control on spatial variability in marine NF. By applying the
MLR-derived equation, we estimate the global-integrated NF at 74 (error range
51–110) Tg N yr−1 in the open ocean, acknowledging that it could be
substantially higher as the 15N2-assimilation method used by most
of the field samples underestimates NF. More field NF samples in the Pacific
and Indian oceans, particularly in the oxygen minimum zones, are needed to
reduce uncertainties in our conclusion. |
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