Distribution and rates of nitrogen fixation in the western tropical South Pacific Ocean constrained by nitrogen isotope budgets

Type Article
Date 2018-05
Language English
Author(s) Knapp Angela N.1, McCabe Kelly M.1, Grosso Olivier2, Leblond Nathalie3, Moutin Thierry2, Bonnet Sophie4
Affiliation(s) 1 : Florida State Univ, Earth Ocean & Atmospher Sci Dept, 117 N Woodward AVE, Tallahassee, FL 32306 USA.
2 : Aix Marseille Univ, CNRS, Univ Toulon, IRD,OSU Pytheas,MIO,UM 110, F-13288 Marseille, France.
3 : Observ Oceanol Villefranche, Lab Oceanog Villefranche, UMR 7093, Villefranche Sur Mer, France.
4 : Aix Marseille Univ, Univ Toulon, CNRS, MIO,UM 110,IRD,OSU Pytheas, Noumea 98848, New Caledonia.
Source Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2018-05 , Vol. 15 , N. 9 , P. 2619-2628
DOI 10.5194/bg-15-2619-2018
WOS© Times Cited 14
Note Special issue Interactions between planktonic organisms and biogeochemical cycles across trophic and N2 fixation gradients in the western tropical South Pacific Ocean: a multidisciplinary approach (OUTPACE experiment) Editor(s): T. Moutin, S. Bonnet, K. Richards, D. G. Capone, E. Marañón, and L. Mémery

Constraining the rates and spatial distribution of di-nitrogen (N2) fixation fluxes to the ocean informs our understanding of the environmental sensitivities of N2 fixation as well as the timescale over which the fluxes of nitrogen (N) to and from the ocean may respond to each other. Here we quantify rates of N2 fixation as well as its contribution to export production along a zonal transect in the Western Tropical South Pacific (WTSP) Ocean using N isotope (δ15N) budgets. Comparing measurements of water column nitrate + nitrite δ15N with the δ15N of sinking particulate N at a western, central, and eastern station, these δ15N budgets indicate high, modest, and low rates of N2 fixation at the respective stations. The results also imply that N2 fixation supports exceptionally high, i.e., > 50 %, of export production at the western and central stations, which are also proximal to the largest iron sources. These geochemically-based rates of N2 fixation are equal to or greater than those previously reported in the tropical North Atlantic, indicating that the WTSP Ocean has the capacity to support globally significant rates of N2 fixation, which may compensate for N removal in the oxygen deficient zones of the eastern tropical Pacific.

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Knapp Angela N., McCabe Kelly M., Grosso Olivier, Leblond Nathalie, Moutin Thierry, Bonnet Sophie (2018). Distribution and rates of nitrogen fixation in the western tropical South Pacific Ocean constrained by nitrogen isotope budgets. Biogeosciences, 15(9), 2619-2628. Publisher's official version : https://doi.org/10.5194/bg-15-2619-2018 , Open Access version : https://archimer.ifremer.fr/doc/00420/53117/