How widespread and important is N2 fixation in the North Atlantic Ocean?

• Published in: Global Biogeochemical Cycles
• Main Authors: Reynolds, S. E., Mather, R. L., Wolff, G. A., Williams, R. G., Landolfi, Angela, Sanders, R., Woodward, E. M. S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: AGU (American Geophysical Union) 2007
• Subjects: North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/2399/; https://oceanrep.geomar.de/id/eprint/2399/1/Reynolds_et_al-2007-Global_Biogeochemical_Cycles%281%29.pdf; https://doi.org/10.1029/2006GB002886

The spatial extent of N2 fixation in the Atlantic Ocean is examined by determining the isotopic composition of N in suspended particulate organic nitrogen (δ15N PONsusp). The samples were collected from zonal and meridional transects of the Atlantic Ocean during a 3‐year period. There is a consistent depleted δ15N PONsusp signal extending over the center of the northern subtropical gyre, which partly coincides with a region where the tracer N* increases westward following the gyre circulation. This nonconservative behavior of N* implies that N2 fixation is responsible for the depleted δ15N PONsusp. A mixing model suggests that N2 fixation over parts of the northern gyre provides up to 74% of the N utilized by phytoplankton. However, since the PONsusp represents only a small fraction of the total N pool, N2 fixation probably only plays a minor role in supplying new N to the euphotic zone in the surface waters of the northern subtropical gyre.