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Ajit Subramaniam (Marine Microbiology Initiative Gordon and Betty Moore Foundation) 
The prevalent paradigm holds that nitrogen fixation (diazotrophy) does not occur in surface waters of upwelling regions because they are thought to be nutrient rich and this inhibits diazotrophy. Diazotrophs are thought to preferentially assimilate nitrate and ammonia instead of expending energy to fix dinitrogen. We found average nitrogen fixation rates to be 2 to 7 times higher in the surface waters of the upwelling region of the Eastern Equatorial Atlantic than typically measured here during non-upwelling periods. We posit that in this region, low nitrate:phosphate ratio waters are upwelled and an initial bloom of non-diazotrophic phytoplankton removes recently upwelled nitrate and thereby diazotrophy is fuelled by residual phosphate and a combination of aeolian and upwelled sources of iron. Annually, we estimate that about 47 Gmol of new nitrogen is introduced by diazotrophy in upwelled waters alone and 195 Gmol N is fixed in the Equatorial Atlantic region. Our findings challenge the paradigm that the highest nitrogen fixation rates occur in oligotrophic gyres and instead provide evidence of its importance in upwelling regimes where phosphate- and iron-rich waters rich are upwelled. A better understanding of the interplay between physical oceanographic and atmospheric processes and consequences to introduction of additional new nitrogen need be taken into account in regional and global carbon and nitrogen budgets.
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