Nitrous oxide distribution in the continental shelf off Central Chile (2005-2009)

Continental shelves tend to have high standing stocks of organic carbon and high rates of primary production relative to the open ocean and serve as important link between land and the ocean interior and between the sediment and the water column, playing a key role in the N and C balance, and accounting for up to 50% of the total N loss. One of the widest continental shelves in the eastern South Pacific (ESP) is present off central Chile (36°S). This is an important geographic feature in terms of physical and biological interactions owing to the large area available for coupling between the benthic and pelagic systems. In addition, this area is subjected to a strong coastal upwelling during austral spring and summer; when winds shift to a predominantly northward direction, stressing the sea surface layer and producing an intense cross-shelf transport and uplift of Equatorial Subsurface waters (ESSW) over the shelf. The ESSW, characterized by high NO3- and low O2 content, promotes surface fertilization and, subsequently, intense organic matter respiration and remineralization at depth, along with an efflux of subsurface-accumulated N2O (Farías et al. 2009, Cornejo & Farías, 2012). Thus, periods of maximum productivity and intense suboxia, or even anoxia, when diverse electron donors (e.g., organic matter, NH4+, NO2-, H2S) are present, represent a potential hotspot for fixed N removal processes. We present a data set that has been obtained during different FIP cruises (Fondo de Investigaciones Pesqueras) (2005-2009) which consisted of several transects perpendicular to the coast between 35° and 40°S and from the coast to 77.8° W (central Chile). Data collected include classical oceanographic variables including N2O and important greenhouse gas.