The subtropical northeast Atlantic has been identified as a marine environment with an apparent imbalance between low NO 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 NO, 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. 

Relevant publication:

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.



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