Américo Torres

Metales pesados en organismos marinos de la zona costera de la Patagonia argentina continental

Se analizaron los contenidos de Hg, Cd, Pb, Cu y Zn en moluscos, crustaceos (tejido blando - µg/g peso seco), aves y mamiferos marinos (rinon, higado y musculo - µg/g peso humedo), procedentes de la zona costera de Patagonia argentina. Los niveles de Hg fueron no detectables o muy bajos. Se encontraron niveles de Cd mas elevados que los permitidos para consumo humano en algunos moluscos (hasta 6,75 µg/g), aunque su origen seria fundamentalmente natural. Las concentraciones de Pb en crustaceos de la Bahia San Antonio (10,00 ? 13,20 µg/g) fueron relacionadas con una antigua actividad minera. Los contenidos de Cu y Zn estuvieron en la mayoria de los casos, dentro del rango informado en la literatura.

Assessment of recent sediment influence in an urban polluted subantarctic coastal ecosystem. Beagle Channel (Southern Argentina).

In this study, baseline information about the environmental status of Ushuaia (UB) and Golondrina (GB) bays is presented. Surface and bottom seawater and freshwater discharged from land were evaluated. Multivariate analysis identified different water quality zones within the bays, two of them located next to the north and northwest coastlines of UB, where the majority of human activities are developed. Porosity, total organic matter, biochemical components, ammonium, and phytopigments were determined in sediment samples from each quality zone. Benthic fluxes of nutrients and dissolved oxygen were assessed in situ using opaque chambers. In northwest zone of UB, carbon equivalents of proteins and carbohydrates in surficial sediments were the same order as in hypertrophic ecosystems, whereas ammonium and phosphate released from sediment greatly exceeded the allochthonous sources. Management of municipal wastewater is required to remediate this chronic pollution.

Uptake of sewage derived nitrogen by Ulva rigida (Chlorophyceae) in Bahía Nueva (Golfo Nuevo, Patagonia, Argentine)

AbstractUptake kinetics of nitrogen derived from sewage–seawater mixtures (2.5–20% v/v effluent) were determined in the laboratory for Ulva rigida (Chlorophyceae) native from Bahía Nueva (Golfo Nuevo, Patagonia, Argentine). In terms of nitrogen concentration, experimental enrichment levels varied between 53.7 and 362.3 μM of ammonium and between 0.77 and 6.21 μM of nitrate + nitrite. Uptake rates were fitted to the Michaelis–Menten equation, with the following kinetic parameters: ammonium: Vmax = 591.2 μmol g−1 h−1, Ks=262.3 μM, nitrate + nitrite: Vmax=12.9 μmol g−1 h−1, Ks=3.5 μM). Both nutrients were taken up simultaneously, but ammonium incorporation was faster in all cases. The results show a high capability of Ulva rigida to remove sewage-derived nitrogen from culture media. In the field, most of the nitrogen provided by the effluent would be tied up in algal biomass, supporting low nitrogen levels found at a short distance away from the source.Uptake kinetics of nitrogen derived from sewage–seawater mixtures (2.5–20% v/v effluent) were determined in the laboratory for Ulva rigida (Chlorophyceae) native from Bahía Nueva (Golfo Nuevo, Patagonia, Argentine). In terms of nitrogen concentration, experimental enrichment levels varied between 53.7 and 362.3 μM of ammonium and between 0.77 and 6.21 μM of nitrate + nitrite. Uptake rates were fitted to the Michaelis–Menten equation, with the following kinetic parameters: ammonium: Vmax = 591.2 μmol g−1 h−1, K s=262.3 μM, nitrate + nitrite: V max=12.9 μmol g−1 h−1, K s=3.5 μM). Both nutrients were taken up simultaneously, but ammonium incorporation was faster in all cases. The results show a high capability of Ulva rigida to remove sewage-derived nitrogen from culture media. In the field, most of the nitrogen provided by the effluent would be tied up in algal biomass, supporting low nitrogen levels found at a short distance away from the source.

Las comunidades del intermareal rocoso antes y después de la eliminación de un disturbio antropogénico: un caso de estudio en las costas de Puerto Madryn (Patagonia, Argentina)

In spite of the marked growth of the coastal cities in Patagonia, studies on the effects of the urban development upon marine intertidal communities are scarce. We evaluated the rocky-shore intertidal community composition during (June 1998) and after (June 2005) exposure to a sewage discharge which was eliminated in 2001. A perturbed environment and a control site were analyzed. No significant differences were detected in species richness between sites and years. However, the species composition was different between sites in 1998 and similar in 2005. These results suggest the use of combined indicators in diagnostic studies on stressed environments

Nitrate reduction activity determined with a continuous flow-through system in sediments from a subantarctic coastal environment

La sedimentacion y acumulacion de detritos organicos autoctonos y aloctonos en el sedimento marino, favorece la actividad microbiana, consume el oxigeno disuelto y disminuye el potencial de oxido-reduccion. En condiciones anaerobicas otros aceptores de electrones son utilizados en los procesos de oxidacion de la materia organica. La reduccion de nitrato es un proceso importante que esta relacionado con el ciclo del nitrogeno y la oxidacion. El objetivo de este estudio fue estimar la actividad nitrato reductora en sedimentos de la Bahia Encerrada, la cual se encuentra sometida a una fuerte influencia antropogenica desde la ciudad de Ushuaia. Las muestras de sedimento fueron tomadas en septiembre de 2007 con draga Van-Veen y almacenadas en oscuridad. La actividad nitrato reductora fue estimada in vitro mediante un sistema de flujo continuo. La tasa de incorporacion de nitrato se aproximo a una cinetica del tipo Michaelis-Menten donde los valores de Km y Vmax fueron 1028 mM y 2,7 µmol g-1 h-1, respectivamente. Se concluye que el nitrato es utilizado preponderantemente como aceptor final de electrones durante la oxidacion de compuestos organicos en el sedimento de Bahia Encerrada.

Introductory editorial thematic issue: advances in geochemistry of the surface in Argentina

Abstract Geochemistry involves the study of the distribution, proportion, and association of chemical elements of the earth’s crust that are present in different matrices such as water (sweet, saline, residual, rain, underground), soils, minerals, sediments, rocks, and air. Initially, this discipline was only used to study the composition and formation of rocks, but nowadays simultaneously relates geology to chemistry.