Knapp A. N., McCabe K. M., Grosso O., Leblond N., Moutin T., Bonnet Sophie. (2018). Distribution and rates of nitrogen fixation in the western tropical South Pacific Ocean constrained by nitrogen isotope budgets. Biogeosciences, 15 (9), p. 2619-2628. ISSN 1726-4170.
Titre du document
Distribution and rates of nitrogen fixation in the western tropical South Pacific Ocean constrained by nitrogen isotope budgets
Knapp A. N., McCabe K. M., Grosso O., Leblond N., Moutin T., Bonnet Sophie
Source
Biogeosciences, 2018,
15 (9), p. 2619-2628 ISSN 1726-4170
Constraining the rates and spatial distribution of dinitrogen (N-2) fixation fluxes to the ocean informs our understanding of the environmental sensitivities of N-2 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 N-2 fixation as well as its contribution to export production along a zonal transect in the western tropical South Pacific (WTSP) Ocean using N isotope ("delta N-15") budgets. Comparing measurements of water column nitrate + nitrite delta N-15 with the delta N-15 of sinking particulate N at a western, central, and eastern station, these delta N-15 budgets indicate high, modest, and low rates of N-2 fixation at the respective stations. The results also imply that N-2 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 N-2 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 N-2 fixation, which may compensate for N removal in the oxygen-deficient zones of the eastern tropical Pacific.
