Distribution And Rates Of Nitrogen Fixation In The Western Tropical South Pacific Ocean Constrained By Nitrogen Isotope Budgets

• Other Authors: Knapp, Angela N. (authoraut), McCabe, Kelly M. (authoraut), Grosso, Olivier (authoraut), Leblond, Nathalie (authoraut), Moutin, Thierry (authoraut), Bonnet, Sophie (authoraut)
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2018
• Subjects: Pacific; North Atlantic
• Online Access: https://diginole.lib.fsu.edu/islandora/object/fsu%3A606078/datastream/TN/view/Distribution%20And%20Rates%20Of%20Nitrogen%20Fixation%20In%20The%20Western%20Tropical%20South%20Pacific%20Ocean%20Constrained%20By%20Nitrogen%20Isotope%20Budgets.jpg

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. Keywords: fresh-water, n-2 fixation, nitrate, north pacific, iron availability, trichodesmium, export production, global distribution, new-caledonia, phosphate availability Publication Note: The publisher’s version of record is available at https://doi.org/10.5194/bg-15-2619-2018