In:
Biogeosciences, Copernicus GmbH, Vol. 15, No. 14 ( 2018-07-18), p. 4333-4352
Abstract:
Abstract. 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.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-15-4333-2018
DOI:
10.5194/bg-15-4333-2018-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2018
detail.hit.zdb_id:
2158181-2
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