The significance of nitrification for oceanic new production

Yool, A; Martin, AP; Fernandez, C.; Clark, DR


The flux of organic material sinking to depth is a major control on the inventory of carbon in the ocean. To first order, the oceanic system is at equilibrium such that what goes down must come up. Because the export flux is difficult to measure directly, it is routinely estimated indirectly by quantifying the amount of phytoplankton growth, or primary production, fuelled by the upward flux of nitrate. To do so it is necessary to take into account other sources of biologically available nitrogen. However, the generation of nitrate by nitrification in surface waters has only recently received attention. Here we perform the first synthesis of open-ocean measurements of the specific rate of surface nitrification and use these to configure a global biogeochemical model to quantify the global role of nitrification. We show that for much of the world ocean a substantial fraction of the nitrate taken up is generated through recent nitrification near the surface. At the global scale, nitrification accounts for about half of the nitrate consumed by growing phytoplankton. A consequence is that many previous attempts to quantify marine carbon export, particularly those based on inappropriate use of the f-ratio (a measure of the efficiency of the 'biological pump'), are significant overestimates. ©2007 Nature Publishing Group.

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Título según WOS: The significance of nitrification for oceanic new production
Título según SCOPUS: The significance of nitrification for oceanic new production
Título de la Revista: NATURE
Volumen: 447
Número: 7147
Editorial: Nature Publishing Group
Fecha de publicación: 2007
Página de inicio: 999
Página final: 1002
Idioma: English