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| Titel |
Phosphate availability and the ultimate control of new nitrogen input by nitrogen fixation in the tropical Pacific Ocean |
| VerfasserIn |
T. Moutin, D. M. Karl, S. Duhamel, P. Rimmelin, P. Raimbault, B. A. S. Mooy, H. Claustre |
| 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 ; 5, no. 1 ; Nr. 5, no. 1 (2008-01-29), S.95-109 |
| Datensatznummer |
250002229
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| Publikation (Nr.) |
 copernicus.org/bg-5-95-2008.pdf |
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| Zusammenfassung |
| Due to the low atmospheric input of phosphate into the open ocean, it is one
of the key nutrients that could ultimately control primary production and
carbon export into the deep ocean. The observed trend over the last 20 years
has shown a decrease in the dissolved inorganic phosphate (DIP) pool in the
North Pacific gyre, which has been correlated to the increase in di-nitrogen
(N2) fixation rates. Following a NW-SE transect, in the Southeast
Pacific during the early austral summer (BIOSOPE cruise), we present data on
DIP, dissolved organic phosphate (DOP) and particulate phosphate (PP) pools
along with DIP turnover times (TDIP) and N2 fixation rates. We
observed a decrease in DIP concentration from the edges to the centre of the
gyre. Nevertheless the DIP concentrations remained above 100 nmol L−1
and T DIP was more than 6 months in the centre of the gyre; DIP
availability remained largely above the level required for phosphate
limitation to occur and the absence of Trichodesmium spp and low nitrogen fixation rates
were likely to be controlled by other factors such as temperature or iron
availability. This contrasts with recent observations in the North Pacific
Ocean at the ALOHA station and in the western Pacific Ocean at the same
latitude (DIAPALIS cruises) where lower DIP concentrations (<20 nmol L−1) and T DIP <50 h were measured during the summer season in
the upper layer. The South Pacific gyre can be considered a High Phosphate
Low Chlorophyll (HPLC) oligotrophic area, which could potentially support
high N2 fixation rates and possibly carbon dioxide sequestration, if
the primary ecophysiological controls, temperature and/or iron availability,
were alleviated. |
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