N2 FIXATION IN THE SUBTROPICAL NORTHEAST ATLANTIC
The subtropical northeast Atlantic has been identified as a marine environment with an apparent imbalance between low NO3 supply to the surface and high concurrent N export production. We investigated the contribution of N2 fixation to new production in this region using the dual (N and O) isotopic composition of NO3 , as well as that of dissolved organic N in surface waters and sinking particulate N in deep sediment traps. We showed that N2 fixation was a significant source of fixed N that sustains primary productivity, accounting for up to 40% of the estimated export production in this region.
Bourbonnais, A., M. F. Lehmann, J. J. Waniek and D. E. Schultz-Bull (2009), Nitrate isotope anomalies as indicator of N2 fixation in the Azores Front region (subtropical N-E Atlantic), Journal of Geophysical Research, 114, C03003, doi:1029/2007JC004617.