En la investigación en ciencias sociales, la utilización del relato de vida ha mostrado importantes desarrollos, permitiendo articular signifi cados subjetivos de experiencias y prácticas sociales. Son variados los trabajos que muestran resultados de investigaciones, así como variados aquéllos que discuten esta particular forma de concebir y articular conceptualmente las dimensiones subjetiva y social. La literatura sin embargo, ha soslayado aspectos del proceso de diseño e implementación de una investigación con relatos de vida. Este artículo intenta visibilizar estos aspectos, a la luz de las premisas que sustentan la investigación desde un enfoque biográfi co. Se presenta un dispositivo de trabajo implementado en investigaciones realizadas, discutiendo a partir de él las opciones metodológicas tomadas, sugiriendo modos de abordar investigaciones con relatos de vida. Palabras clave: relatos de vida; enfoque biográfi co; investigación cualitativa; opciones metodológicas. In social sciences research, the use of life stories has developed greatly allowing for the articulation of subjective meanings of social practices and experiences. There are several studies that show their fi ndings as there is a variety of such pieces of research that discuss this particular way of conceptually conceiving and articulating subjective and social dimensions. The literature has, however, avoided analyzing aspects of the process of design and implementation of research based on life stories. In this paper there is an attempt to bring these aspects to the forefront, in light of the premises that underlie research from a biographical approach. A working device applied in previous research is presented, with discussion on methodological decisions and suggestions on how to approach research on life stories.

One of the shallowest, most intense oxygen minimum zones (OMZs) is found in the eastern tropical South Pacific, off northern Chile and southern Peru. It has a strong oxygen gradient (upper oxycline) and high N 2 O accumulation. N 2 O cycling by heterotrophic denitrification along the upper oxycline was studied by measuring N 2 O production and consumption rates using an improved acetylene blockage method.

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Abstract. The high availability of electron donors occurring in coastal upwelling ecosystems with marked oxyclines favours chemoautotrophy, in turn leading to high N 2 O and CH 4 cycling associated with aerobic NH + 4 (AAO) and CH 4 oxidation (AMO). This is the case of the highly productive coastal upwelling area off central Chile (36 • S), where we evaluated the importance of total chemolithoautotrophic vs. photoautotrophic production, the specific contributions of AAO and AMO to chemosynthesis and their role in gas cycling. Chemolithoautotrophy was studied at a time-series station during monthly (2007)(2008)(2009)) and seasonal cruises (January 2008, September 2008, January 2009) and was assessed in terms of the natural C isotopic ratio of particulate organic carbon (δ 13 POC), total and specific (associated with AAO and AMO) dark carbon assimilation (CA), and N 2 O and CH 4 cycling experiments. At the oxycline, δ 13 POC averaged −22.2‰; this was significantly lighter compared to the surface (−19.7‰) and bottom layers (−20.7‰). Total integrated dark CA in the whole water column fluctuated between 19.4 and 2.924 mg C m −2 d −1 , was higher during active upwelling, and contributed 0.7 to 49.7% of the total integrated autotrophic CA (photo plus chemoautotrophy), which ranged from 135 to 7.626 mg C m −2 d −1 , and averaged 20.3% for the whole sampling period. Dark CA was reduced by 27 to 48% after adding a specific AAO inhibitor (ATU) and by 24 to 76% with GC7, a specific archaea inhibitor. This indicates that AAO and AMO microbes (most of them archaea) were performing dark CA through the oxidation of NH

Despite the importance of nitrous oxide (N2O) in the global radiative balance and atmospheric ozone chemistry, its sources and sinks within the Earth’s system are still poorly understood. In the ocean, N2O is produced by microbiological processes such as nitrification and partial denitrification, which account for about a third of global emissions. Conversely, complete denitrification (the dissimilative reduction of N2O to N2) under suboxic/anoxic conditions is the only known pathway accountable for N2O consumption in the ocean. In this work, it is demonstrated that the biological assimilation of N2O could be a significant pathway capable of directly transforming this gas into particulate organic nitrogen (PON). N2O is shown to be biologically fixed within the subtropical and tropical waters of the eastern South Pacific Ocean, under a wide range of oceanographic conditions and at rates ranging from 2 pmol N L−1 d− to 14.8 nmol N L−1 d−1 (mean ± SE of 0.522±1.06 nmol N L−1 d−1, n = 93). Additional assays revealed that cultured cyanobacterial strains of Trichodesmium (H-9 and IMS 101), and Crocosphaera (W-8501) have the capacity to directly fix N2O under laboratory conditions; suggesting that marine photoautotrophic diazotrophs could be using N2O as a substrate. This metabolic capacity however was absent in Synechococcus (RCC 1029). The findings presented here indicate that assimilative N2O fixation takes place under extreme environmental conditions (i.e., light, nutrient, oxygen) where both autotrophic (including cyanobacteria) and heterotrophic microbes appear to be involved. This process could provide a globally significant sink for atmospheric N2O which in turn affects the oceanic N2O inventory and may also represent a yet unexplored global oceanic source of fixed N.