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Provedor de dados:  ArchiMer
País:  France
Título:  In-depth characterization of diazotroph activity across the western tropical South Pacific hotspot of N2 fixation (OUTPACE cruise)
Autores:  Bonnet, Sophie
Caffin, Mathieu
Berthelot, Hugo
Grosso, Olivier
Benavides, Mar
Helias-nunige, Sandra
Guieu, Cecile
Stenegren, Marcus
Foster, Rachel Ann
Data:  2018-07
Ano:  2018
Resumo:  Here we report N2 fixation rates from a  ∼ 4000km transect in the western and central tropical South Pacific, a particularly undersampled region in the world ocean. Water samples were collected in the euphotic layer along a west to east transect from 160°E to 160°W that covered contrasting trophic regimes, from oligotrophy in the Melanesian archipelago (MA) waters to ultra-oligotrophy in the South Pacific Gyre (GY) waters. N2 fixation was detected at all 17 sampled stations with an average depth-integrated rate of 631±286µmol N m−2 d−1 (range 196–1153µmol N m−2 d−1) in MA waters and of 85±79µmol N m−2 d−1 (range 18–172µmol N m−2 d−1) in GY waters. Two cyanobacteria, the larger colonial filamentous Trichodesmium and the smaller UCYN-B, dominated the enumerated diazotroph community ( > 80%) and gene expression of the nifH gene (cDNA > 105 nifH copies L−1) in MA waters. Single-cell isotopic analyses performed by nanoscale secondary ion mass spectrometry (nanoSIMS) at selected stations revealed that Trichodesmium was always the major contributor to N2 fixation in MA waters, accounting for 47.1–83.8% of bulk N2 fixation. The most plausible environmental factors explaining such exceptionally high rates of N2 fixation in MA waters are discussed in detail, emphasizing the role of macro- and micro-nutrient (e.g., iron) availability, seawater temperature and currents.
Tipo:  Text
Idioma:  Inglês

Editor:  Copernicus Gesellschaft Mbh
Relação:  info:eu-repo/grantAgreement/EC/FP7/625185/EU//DIADOM
Formato:  application/pdf
Fonte:  Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2018-07 , Vol. 15 , N. 13 , P. 4215-4232
Direitos:  Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License.


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