Modelling N2 fixation related to Trichodesmium sp.: driving processes and impacts on primary production in the tropical Pacific Ocean
|Author(s)||Dutheil Cyril1, 2, Aumont Olivier2, Gorgues Thomas3, Lorrain Anne4, Bonnet Sophie5, Rodier Martine6, Dupouy Cecile1, 5, Shiozaki Takuhei7, Menkes Christophe1, 2|
|Affiliation(s)||1 : Ctr IRD, Noumea, New Caledonia.
2 : Univ Paris 06, UPMC, Sorbonne Univ, LOCEAN Lab,IPSL,CNRS,IRD,MNHN, Paris, France.
3 : Univ Brest, CNRS, IFREMER, IRD,LOPS, Plouzane, France.
4 : UBO, CNRS, IFREMER, IRD,IUEM,LEMAR,UMR 6539, Plouzane, France.
5 : Univ Toulon & Var, Aix Marseille Univ, CNRS, INSU,IRD,MIO,UM 110, F-13288 Marseille, France.
6 : Univ Polynesie Francaise, IRD, IFREMER, ILM,EIO,UMR 241, Faaa, French Polynesi, Fr Polynesia.
7 : Japan Agcy Marine Earth Sci & Technol, Res & Dev Ctr Global Change, Yokosuka, Kanagawa, Japan.
|Source||Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2018-07 , Vol. 15 , N. 14 , P. 4333-4352|
|WOS© Times Cited||9|
|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|
Dinitrogen fixation is now recognized as one of the major sources of bio-available nitrogen in the ocean. Thus, N2 fixation sustains a significant part of the global primary production by supplying the most common limiting nutrient for phytoplankton growth. The Oligotrophy to UlTra-oligotrophy PACific Experiment (OUTPACE) improved the data coverage of the western tropical South Pacific, an area recently recognized as a hotspot of N2 fixation. This new development leads us to develop and test an explicit N2 fixation formulation based on the Trichodesmium physiology (the most studied nitrogen fixer) within a 3-D coupled dynamical–biogeochemical model (ROMS-PISCES). We performed a climatological numerical simulation that is able to reproduce the main physical (e.g. sea surface temperature) and biogeochemical patterns (nutrient and chlorophyll concentrations, as well as N2 fixation) in the tropical Pacific. This simulation displayed a Trichodesmium regional distribution that extends from 150°E to 120°W in the south tropical Pacific, and from 120°E to 140°W in the north tropical Pacific. The local simulated maximuma were found around islands (Hawaii, Fiji, Samoa, New Caledonia, Vanuatu). We assessed that 15% of the total primary production may be due to Trichodesmium in the low-nutrient low-chlorophyll regions (LNLC) of the tropical Pacific. Comparison between our explicit and the often used (in biogeochemical models) implicit parameterization of N2 fixation showed that the latter leads to an underestimation of N2 fixation rates by about 25% in LNLC regions. Finally, we established that iron fluxes from island sediments control the spatial distribution of Trichodesmium biomasses in the western tropical South Pacific. Note, this last result does not take into account the iron supply from rivers and hydrothermal sources, which may well be of importance in a region known for its strong precipitation rates and volcanic activity.