Phosphate availability and the ultimate control of new nitrogen input by nitrogen fixation in the tropical Pacific Ocean

T. Moutin 1 D. M. Karl 2 S. Duhamel 1 P. Rimmelin 1 Patrick Raimbault 1 B. A. S. van Mooy 3 Hervé Claustre 4
1 LOB - Laboratoire d'océanographie et de biogéochimie
2 Department of Oceanography
3 WHOI - Department of Marine Chemistry and Geochemistry
4 LOV - Laboratoire d'océanographie de Villefranche
Abstract : 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.
Document type :
Journal articles
Complete list of metadatas
https://hal.archives-ouvertes.fr/hal-00330336
Contributor : Publication Egu <>
Submitted on : Tuesday, October 14, 2008 - 10:51:25 AM
Last modification on : Monday, December 16, 2019 - 12:34:01 PM
Long-term archiving on: Tuesday, October 9, 2012 - 12:50:23 PM

File

bg-5-95-2008.pdf
Explicit agreement for this submission

Identifiers

  • HAL Id : hal-00330336, version 1

Collections

EGU | INSU | CNRS | OSU-INSTITUT-PYTHEAS | LOPB | UNIV-AMU | LOV | UPMC | SORBONNE-UNIVERSITE | SU-SCIENCES | UMS-829

Citation

T. Moutin, D. M. Karl, S. Duhamel, P. Rimmelin, Patrick Raimbault, et al.. Phosphate availability and the ultimate control of new nitrogen input by nitrogen fixation in the tropical Pacific Ocean. Biogeosciences, European Geosciences Union, 2008, 5 (1), pp.95-109. ⟨hal-00330336⟩

Export

BibTeX TEI DC DCterms EndNote

Share

Metrics

Record views

562

Files downloads

242

Contact

Informations

CCSD