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

• Published in: Nature Communications
• Main Authors: Tang, W., Wang, S., Fonseca-Batista, D., Dehairs, F., Gifford, S., Gonzalez, A.G., Gallinari, M., Planquette, H., Sarthou, G., Cassar, N.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: North Atlantic
• Online Access: https://www.vliz.be/imisdocs/publications/324549.pdf

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 regulating factors, and reveals thriving diazotrophic communities in coastal waters with potential significance to the global nitrogen and carbon cycles.