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

• Published in: Nature Communications
• Main Authors: Tang, Weiyi, Wang, Seaver, Fonseca-Batista, Debany, Dehairs, Frank, Gifford, Scott, Gonzalez, Aridane G., Gallinari, Morgane, Planquette, Helene, Sarthou, Geraldine, Cassar, Nicolas
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2019
• Subjects: 251002 Oceanografía química; Atlantic Time-Series; Nitrogen-Fixation; Dinitrogen-Fixation; Gas-Exchange; Carbon-Cycle; Cavity Ring; N2 Fixation; Rates; Coastal; Acetylene; North Atlantic
• Online Access: http://hdl.handle.net/10553/59375; https://doi.org/10.1038/s41467-019-08640-0

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 chlorophylla 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.