RESEARCH: Nitrate (NO3-)

Nitrate is the dominant form of bioavailable nitrogen in the ocean, and the primary form of new nitrogen fueling phytoplankton growth and export in the global surface ocean.

Comparing the δ15N of NO3- with the δ15N of the sinking flux allows us to quantify both the relative and absolute importance of NO3- for supporting export production in any one place over a specific time period.
Additionally, measuring how the δ15N of NO3- changes as phytoplankton assimilate NO3- helps us understand modern as well as paleo nitrogen cycling. Unpublished data, A. Knapp, S. Kranz, R. Thomas.

Where?

Isotopic evidence indicates NO3- is the dominant source of nitrogen fueling export in the Sargasso Sea, the Eastern Tropical South Pacific, and the interior portion of the Western Tropical South Pacific gyre. A current project is evalauting the importance of N2 fixation and NO3- in the Gulf of Mexico, especially as they may support the food web of larval bluefin tuna.

Publications

  • Wilson, S. T., Hawco, N. J., Armbrust, E. V., Barone, B., Bjorkman, K. M., Boysen, A. K., Burgos, M., Burrell, T. J., Casey, J. R., DeLong, E. F., Dugenne, M., Dutkiewicz, S., Dyhrman, S. T., Ferron, S., Follows, M. J., Foreman, R. K., Funkey, C. P., Harke, M. J., Henke, B. A., Hill, C. N., Hynes, A. M., Ingalls, A. E., Jahn, O., Kelly, R. L., Knapp, A. N., Letelier, R. M., Ribalet, F., Shimabukuro, E. M., Tabata, R. K. S., Turk-Kubo, K. A., White, A. E., Zehr, J. P., John, S., & Karl, D. M. (2019). Kilauea lava fuels phytoplankton bloom in the North Pacific Ocean. Science, 365, 1040-1044

    • See associated "Perspective" by Ducklow and Plank

  • Knapp, A.N., K.M. McCabe, O. Grosso, N. Leblond, T. Moutin, and S. Bonnet, Distribution and rates of nitrogen fixation in the western tropical South Pacific Ocean constrained by nitrogen isotope budgets, 2018, Biogeosciences, 15, 2619-2628, doi:10.5194/bg-2619-2018

  • Knapp, A.N., S.E. Fawcett, A. Martinez-Garcia, N. Leblond, T. Moutin, and S. Bonnet, Nitrogen isotopic evidence for a shift from nitrate- to diazotroph-fueled export production in the VAHINE mesocosm experiments, 2016, Biogeosciences, 13, 4645-4657, doi:10.5194/bg-13-4645-2016

  • Haskell, W.Z., M.G. Prokopenko, R.H.R. Stanley, and A.N. Knapp, Estimates of vertical turbulent mixing used to determine a vertical gradient in net and gross oxygen production in the oligotrophic South Pacific Gyre, 2016, Geophysical Research Letters, 43, doi:10.1002/2016GL069523

  • Knapp, A.N., K.L. Casciotti, W.M. Berelson, M.G. Prokopenko, and D.G. Capone, Low rates of nitrogen fixation in the eastern tropical South Pacific surface waters, 2016, Proceedings of the National Academy of Sciences, 113, 4398-4403, doi:10.1073/pnas.1515641113

  • Knapp, A.N., S.E. Fawcett, A. Martinez-Garcia, N. Leblond, T. Moutin, and S. Bonnet, 2016, Nitrogen isotopic evidence for a shift from nitrate- to diazotroph-fueled export production in VAHINE mesocosm experiments, Biogeosciences Discussions, 12, 19901-19939, doi:10.5194/bgd-12-19901-2015.

  • Berelson, W.M., W. Haskell, M.G. Prokopenko, A.N. Knapp, D. Hammond, N. Rollins, D.G. Capone, 2015, Biogenic rain and benthic remineralization in the Eastern Tropical South Pacific, Deep-Sea Research I, 99, 23-34, doi:10.1016/j.dsr.2014.12.006.

  • Haskell, W.Z., D. Kadko, D.E. Hammond, A.N. Knapp, M.G. Prokopenko, W.M. Berelson, and D.G. Capone, 2015, Upwelling velocity and eddy diffusivity from 7Be measurements used to compare vertical nutrient flux to export POC flux in the Eastern Tropical South Pacific, Marine Chemistry, 168, 140-150, doi: 10.1016/j.marchem.2014.10.004

  • Collins, L.E., W. Berelson, D.E. Hammond, A. Knapp, R. Schwartz, and D. Capone, 2011, Particle fluxes in San Pedro Basin, California: A four-year record of sedimentation and physical forcing, Deep-Sea Research I, 58, 898-914.

  • Sigman, D.M., P.J. DiFiore, M.P. Hain, C. Deutsch, Y. Wang, D.M. Karl, A.N. Knapp, M.F. Lehmann, and S. Pantoja, 2009, The dual isotopes of deep nitrate as a constraint on the cycle and budget of oceanic fixed nitrogen. Deep-Sea Res. I, 56, 1419-1439, doi:10.1016/j.dsr.2009.04.007

  • Knapp, A.N., P.J. DiFiore, C. Deutsch, D.M. Sigman, and F. Lipschultz, 2008, Nitrate isotopic composition between Bermuda and Puerto Rico Implications for N2 fixation in the Atlantic Ocean, Global Biogeochem. Cycles, 22, GB3014.

  • Knapp, A.N., D.M. Sigman, and F. Lipschultz, 2005, N isotopic composition of dissolved organic nitrogen and nitrate at the Bermuda Atlantic Time-series Study site, Global Biogeochem. Cycles, 19, GB1018, doi:10.1029/2004GB002320

    This personal Web page is not an official Florida State University Web page.