%0 Journal Article
%9 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES
%A Bonnet, Sophie
%A Dekaezemacker, J.
%A Turk-Kubo, K. A.
%A Moutin, T.
%A Hamersley, R.M.
%A Grosso, O.
%A Zehr, J.P.
%A Capone, D.G.
%T Aphotic N-2 fixation in the Eastern Tropical South Pacific Ocean
%D 2013
%L fdi:010061449
%G ENG
%J Plos One
%@ 1932-6203
%K MILIEU MARIN ; EL NINO ; COUCHE EUPHOTIQUE ; FIXATION BIOLOGIQUE DE L'AZOTE ; OXYGENE ; MICROORGANISME ; ANALYSE QUANTITATIVE ; PROFIL VERTICAL ; PROFONDEUR
%K LA NINA ; COUCHE APHOTIQUE ; OMZ.OXYGENE MINIMUM ZONE
%K ZONE TROPICALE
%K PACIFIQUE SUD
%M ISI:000328731800014
%N 12
%P e81265 [14 ]
%R 10.1371/journal.pone.0081265
%U https://www.documentation.ird.fr/hor/fdi:010061449
%> https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers17-10/010061449.pdf
%V 8
%W Horizon (IRD)
%X We examined rates of N-2 fixation from the surface to 2000 m depth in the Eastern Tropical South Pacific (ETSP) during El Niño (2010) and La Niña (2011). Replicated vertical profiles performed under oxygen-free conditions show that N-2 fixation takes place both in euphotic and aphotic waters, with rates reaching 155 to 509 mu mol N m(-2) d(-1) in 2010 and 24 +/- 14 to 118 +/- 87 mu mol N m(-2) d(-1) in 2011. In the aphotic layers, volumetric N-2 fixation rates were relatively low (< 1.00 nmol N L-1 d(-1)), but when integrated over the whole aphotic layer, they accounted for 87-90% of total rates (euphotic+ aphotic) for the two cruises. Phylogenetic studies performed in microcosms experiments confirm the presence of diazotrophs in the deep waters of the Oxygen Minimum Zone (OMZ), which were comprised of non-cyanobacterial diazotrophs affiliated with nifH clusters 1K (predominantly comprised of alpha-proteobacteria), 1G (predominantly comprised of gamma-proteobacteria), and 3 (sulfate reducing genera of the delta-proteobacteria and Clostridium spp., Vibrio spp.). Organic and inorganic nutrient addition bioassays revealed that amino acids significantly stimulated N-2 fixation in the core of the OMZ at all stations tested and as did simple carbohydrates at stations located nearest the coast of Peru/Chile. The episodic supply of these substrates from upper layers are hypothesized to explain the observed variability of N-2 fixation in the ETSP.
%$ 032MILPHY ; 034MIORG