Revisiting the distribution of oceanic N 2 fixation and estimating diazotrophic contribution to marine production ...

• Main Authors: Fonseca-Batista, D., Dehairs, F., Wang, S., Sarthou, G., Planquette, H., Tang, W., Gallinari, M., Gifford, S., Gonzalez, A.G., Cassar, N.
• Format: Text
• Language: English
• Published: Nature Publishing Group 2019
• Subjects: North Atlantic
• Online Access: https://dx.doi.org/10.17615/z5r8-xg78; https://cdr.lib.unc.edu/concern/articles/rv0434809

Marine N 2 fixation supports a significant portion of oceanic primary production by making N 2 bioavailable to planktonic communities, in the process influencing atmosphere-ocean carbon fluxes and our global climate. However, the geographical distribution and controlling factors of marine N 2 fixation remain elusive largely due to sparse observations. Here we present unprecedented high-resolution underway N 2 fixation estimates across over 6000 kilometers of the western North Atlantic. Unexpectedly, we find increasing N 2 fixation rates from the oligotrophic Sargasso Sea to North America coastal waters, driven primarily by cyanobacterial diazotrophs. N 2 fixation is best correlated to phosphorus availability and chlorophyll-a concentration. Globally, intense N 2 fixation activity in the coastal oceans is validated by a meta-analysis of published observations and we estimate the annual coastal N 2 fixation flux to be 16.7 Tg N. This study broadens the biogeography of N 2 fixation, highlights the interplay of ...