Nutrient limitation of primary productivity in the Southeast Pacific

Abstract. Iron is an essential nutrient involved in a variety of biological processes in the ocean, including photosynthe-sis, respiration and dinitrogen fixation. Atmospheric depo-sition of aerosols is recognized as the main source of iron for the surface ocean. In high nutrient, low chlorophyll ar-eas, it is now clearly established that iron limits phytoplank-ton productivity but its biogeochemical role in low nutrient, low chlorophyll environments has been poorly studied. We investigated this question in the unexplored southeast Pa-cific, arguably the most oligotrophic area of the global ocean. Situated far from any continental aerosol source, the atmo-spheric iron flux to this province is amongst the lowest of the world ocean. Here we report that, despite low dissolved iron concentrations (∼0.1 nmol l−1) across the whole gyre (3 stations located in the center and at the western and th