Contribución al conocimiento limnológico del Río Paraguay en su tramo inferior

The main limnological feactures of the Paraguay river have been studied in two sampling sites: La Herradura and Puerto Bermejo stations. The former is situated above the confluence with the Bermejo river and the latter is located below the confluence. The phytoplankton community has been dominated by Diatomophyceae (mainly Melosira granulala) and Chlorophyceae (mainly Monoraphídium, Schroederia and Scenedesmus). Crytophyceae (Cryptonomas) and Dinophyceae (Perldlnium) have always been present in low percentage. Cyanophyceae have usually been less than 4% of the total population density. In the low water period of the summer 1978-1979, the maximun phytoplankton density was estimated in 4 000 ind./ml and the production in 750 mg C/m2 d. During the flood period of May through October the lowest phytoplankton density (160 ind./ml) and production (60 mg C/m2 d) were measured. Variations in the suspended solid content and salinity of the water are discussed in relation to the hidrologic regime of the river. The huge amount of sedimenta carried by the Bermejo river to the lower Paraguay produces a drastic decrease in the transparency, phytoplankton density and production of the waters. On the other hand, conductivity, suspended solids and nutrients are highly increased.The main limnological feactures of the Paraguay river have been studied in two sampling sites: La Herradura and Puerto Bermejo stations. The former is situated above the confluence with the Bermejo river and the latter is located below the confluence. The phytoplankton community has been dominated by Diatomophyceae (mainly Melosira granulala) and Chlorophyceae (mainly Monoraphídium, Schroederia and Scenedesmus). Crytophyceae (Cryptonomas) and Dinophyceae (Perldlnium) have always been present in low percentage. Cyanophyceae have usually been less than 4% of the total population density. In the low water period of the summer 1978-1979, the maximun phytoplankton density was estimated in 4 000 ind./ml and the production in 750 mg C/m2 d. During the flood period of May through October the lowest phytoplankton density (160 ind./ml) and production (60 mg C/m2 d) were measured. Variations in the suspended solid content and salinity of the water are discussed in relation to the hidrologic regime of the river. The huge amount of sedimenta carried by the Bermejo river to the lower Paraguay produces a drastic decrease in the transparency, phytoplankton density and production of the waters. On the other hand, conductivity, suspended solids and nutrients are highly increased

Factores ecológicos asociados a la fertilización nitrogenada en los arrozales y su influencia en la producción

This paper compares the effect of the time and form of nitrogen application upon rice yield. A discussion about the influence of the physical and Chemical characteristics of the water on denitrification and ammonia volatilization is included. The highest yield was obtained when fertilization was coincident with the tillering and panicle diferentiation, lower when it was coincident with the sown and panicle diferentiation, and lowest in the control without fertilization. Inorganic nitrogen concentrations in the water were high if the fertilization was coincident with the sown and tillering while it was low at the panicle formation, similar to that recorded in unfcrtilized plots. It was concluded that the lower production in the sown fertilization was due to high nitrogen losses favoured by high water temperatures and inorganic nitrogen concentrations.This paper compares the effect of the time and form of nitrogen application upon rice yield. A discussion about the influence of the physical and Chemical characteristics of the water on denitrification and ammonia volatilization is included. The highest yield was obtained when fertilization was coincident with the tillering and panicle diferentiation, lower when it was coincident with the sown and panicle diferentiation, and lowest in the control without fertilization. Inorganic nitrogen concentrations in the water were high if the fertilization was coincident with the sown and tillering while it was low at the panicle formation, similar to that recorded in unfcrtilized plots. It was concluded that the lower production in the sown fertilization was due to high nitrogen losses favoured by high water temperatures and inorganic nitrogen concentrations

Nutrient concentrations and trophic state of small patagonian andean lakes

We analyzed nutrient, chlorophyll, and ionic concentrations in 17 lakes along a strip of land located in the rainy Andes Mountains and the ecotone with the dry Patagonian steppe, from 36 to 44° S latitude. Most of the sampled lakes had the ionic composition of Andean lakes and showed ultraoligotrophic conditions, while a few with the ionic composition of Patagonian Plateau lakes showed higher nutrient concentrations. Chlorophyll was correlated to P and N concentrations, but chlorophyll/TP ratio was lower than reported in previous worldwide surveys. A lithology dominated by igneous rock together with the remoteness and pristine character of the basins contribute to the oligotrophic status of the lakes. Two other factors appear to be important in maintaining the oligotrophic condition. Andisols, allophanic soils developed over volcanic ash deposits in the rainy areas, have large P retention capability and therefore decrease the load of P to the lakes. Natural dense Nothofagus spp. forests, with a geographical distribution coincident with that of the andisols, are efficient mechanisms for nitrogen retention through nitrogen resorption from senescent leaves.Instituto de Limnología "Dr. Raul A. Ringuelet

Nutrient concentrations and trophic state of small patagonian andean lakes

We analyzed nutrient, chlorophyll, and ionic concentrations in 17 lakes along a strip of land located in the rainy Andes Mountains and the ecotone with the dry Patagonian steppe, from 36 to 44° S latitude. Most of the sampled lakes had the ionic composition of Andean lakes and showed ultraoligotrophic conditions, while a few with the ionic composition of Patagonian Plateau lakes showed higher nutrient concentrations. Chlorophyll was correlated to P and N concentrations, but chlorophyll/TP ratio was lower than reported in previous worldwide surveys. A lithology dominated by igneous rock together with the remoteness and pristine character of the basins contribute to the oligotrophic status of the lakes. Two other factors appear to be important in maintaining the oligotrophic condition. Andisols, allophanic soils developed over volcanic ash deposits in the rainy areas, have large P retention capability and therefore decrease the load of P to the lakes. Natural dense Nothofagus spp. forests, with a geographical distribution coincident with that of the andisols, are efficient mechanisms for nitrogen retention through nitrogen resorption from senescent leaves.Instituto de Limnología "Dr. Raul A. Ringuelet

Trace-Metal Concentrations in Coastal Marshes of the Lower Parana River and the Rio-de-La-Plata Estuary

Fil: Villar, Carlos Alberto. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Stripeikis, J.. INQUlMAE. Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires; ArgentinaFil: Tudino, M.. INQUlMAE. Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires; ArgentinaFil: Dhuicque, L.. INQUlMAE. Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires; ArgentinaFil: Troccoli, O.. INQUlMAE. Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires; ArgentinaFil: Bonetto, Carlos Alberto. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin

Effect of agrochemicals on macroinvertebrate assemblages in Pampasic streams, Buenos Aires, Argentina

Agricultural practices have been intensified in recent decades in Argentina. The Pampa plain is the main agricultural region of the country. The effect of increased application of agrochemicals on the invertebrate fauna of the Pampasic streams remains unreported. In the present study, we compared the abundance and composition of invertebrate assemblages in seven Pampasic streams with contrasting soil use in their basins. Two streams run through intensively cropped plots, two drain basins with livestock fields, while the other three are located within a biosphere Reserve. Higher nutrient and insecticide concentrations were measured in the streams draining cropped basins, related with pesticide applications and crop fertilization. The invertebrate assemblage composition of the cropped streams differed significantly from the others and between the two. Present evidence suggests that the impact of agrochemicals results in a change in composition with decreased abundance or absence of sensitive species such as Hyalellidae, Caenidae, Baetidae and Curculionidae and increased abundance of more tolerant taxa: Ostracoda, Glossiphoniidae (Hirudinea), Ancylidae (Gundlanchia), Ampullariidae (Pomacea canaliculata), Sphaeriidae and Dugesiidae. Available information suggests that macrophyte cover and composition also influence the invertebrate assemblages of the Pampasic streams.Facultad de Ciencias Naturales y MuseoInstituto de Limnología "Dr. Raúl A. Ringuelet

Nonequilibrium dynamics of a stochastic model of anomalous heat transport

We study the dynamics of covariances in a chain of harmonic oscillators with conservative noise in contact with two stochastic Langevin heat baths. The noise amounts to random collisions between nearest-neighbour oscillators that exchange their momenta. In a recent paper, [S Lepri et al. J. Phys. A: Math. Theor. 42 (2009) 025001], we have studied the stationary state of this system with fixed boundary conditions, finding analytical exact expressions for the temperature profile and the heat current in the thermodynamic (continuum) limit. In this paper we extend the analysis to the evolution of the covariance matrix and to generic boundary conditions. Our main purpose is to construct a hydrodynamic description of the relaxation to the stationary state, starting from the exact equations governing the evolution of the correlation matrix. We identify and adiabatically eliminate the fast variables, arriving at a continuity equation for the temperature profile T(y,t), complemented by an ordinary equation that accounts for the evolution in the bulk. Altogether, we find that the evolution of T(y,t) is the result of fractional diffusion.Comment: Submitted to Journal of Physics A, Mathematical and Theoretica

Concentración de nitrogeno y fósforo en el agua de lluvia de Corrientes (Argentina)

Inorganic nitrogen, phosphorus, pH and conductivity in rainwater were measured at Corrientes (27°27’S, 58°47’W) during 1984-1985. Mean water pH was 5.97 (4.60 - 7.15) and mean conductivity was 11.5 uS/cm (2.7 - 21 uS/cm) showing good waterquality. Concentration showed positive correlation with the length of time betweensuccessive rains and were inversely correlated with precipitation volume. Both inorganic nitrogen concentrations and fallout, were low (mean conc.: 315 µg Ninorg/1 mean fallout: 190 µg Ninorg/m2 yr) when compared with the reported figures in unpolluted locations. Total phosphorus concentration (36 µg TP/1) and fallout (16.5 µg TP/m2 yr) were relatively high probably because of dust contribution. Fallout rates resulted an order of magnitude lower than those of very polluted areas.lt was shown that nutrient fallout is important in determining trophic status of shallow lakes and ponds profuselly distributed in Corrientes province.Inorganic nitrogen, phosphorus, pH and conductivity in rainwater were measured at Corrientes (27°27’S, 58°47’W) during 1984-1985. Mean water pH was 5.97 (4.60 - 7.15) and mean conductivity was 11.5 uS/cm (2.7 - 21 uS/cm) showing good waterquality. Concentration showed positive correlation with the length of time betweensuccessive rains and were inversely correlated with precipitation volume. Both inorganic nitrogen concentrations and fallout, were low (mean conc.: 315 µg Ninorg/1 mean fallout: 190 µg Ninorg/m2 yr) when compared with the reported figures in unpolluted locations. Total phosphorus concentration (36 µg TP/1) and fallout (16.5 µg TP/m2 yr) were relatively high probably because of dust contribution. Fallout rates resulted an order of magnitude lower than those of very polluted areas.lt was shown that nutrient fallout is important in determining trophic status of shallow lakes and ponds profuselly distributed in Corrientes province

Freshwater fishes of the Río de la Plata: current assemblage structure

Few studies have addressed the composition of fish assemblages of the freshwater Río de la Plata (RdlP) and have only been limited to species lists gathered over the last two centuries. As such inventories have never been reviewed or validated by fish sampling, the richness and structure of RdlP fish assemblage are poorly known. Hence, we conducted an exhaustive literature review and a fieldwork in six coastal points of Argentina to update the species composition and determine the hierarchical structure of the fish assemblage. From the 206 species registered in the literature, 48 were not confirmed, 13 were absent, five were taken as synonymized species, 29 were supported by literature and 107 were confirmed; one was an established exotic species, and three were a non-established exotic species. The findings reported here suggest that the fish assemblage currently comprises 141 species, including four new records. Analysis of fieldwork data in number and weight of fish captured resulted in an assemblage hierarchical structure of five dominant, 22 frequent, and 45 rare species; 16 dominant, 11 frequent, and 45 rare taxa, respectively. These results could be used as baseline to monitor, manage, and preserve neotropical fish species in their southern distribution boundary.El conocimiento de los ensambles de peces del sector dulceacuícola del Río de la Plata (RdlP) es escaso y limitado a listas de especies de compilaciones realizadas en los últimos dos siglos. Como esos inventarios nunca han sido revisados o validados mediante muestreos de peces, el conocimiento respecto de la riqueza y la estructura de los ensambles del RdlP resulta deficiente. Para ordenar y mejorar la información acerca de la riqueza y estructura de los ensambles de peces del área se realizó una revisión bibliográfica y un muestreo de campo para actualizar la composición de especies y determinar la estructura jerárquica del ensamble de peces. De las 206 especies colectadas de acuerdo a la bibliografía 48 se categorizaron como no reconfirmadas, 13 como ausentes, cinco como especies sinonimizadas, 29 como soportadas por la literatura, 107 como confirmadas, una exótica establecida y tres exóticas no establecidas. Los resultados sugieren que el ensamble de peces actualmente está compuesto por 141 especies, incluyendo cuatro nuevos registros. El análisis de los datos en número y en peso de los peces colectados mostró 5 especies dominantes, 22 frecuentes y 45 raras; y 16 dominantes, 11 frecuentes y 45 raras, respectivamente. Los resultados de este trabajo pueden ser usados como línea de base para el monitoreo, manejo y conservación de las especies de peces neotropicales en su límite de distribución sur.Fil: Maiztegui, Tomás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Limnología "Dr. Raúl A. Ringuelet". Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología; ArgentinaFil: Paracampo, Ariel Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Limnología "Dr. Raúl A. Ringuelet". Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología; ArgentinaFil: Liotta, Jorge. Ministerio de Agricultura, Ganadería, Pesca y Alimento; ArgentinaFil: Cabanellas, Eva. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Limnología "Dr. Raúl A. Ringuelet". Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología; ArgentinaFil: Bonetto, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Limnología "Dr. Raúl A. Ringuelet". Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología; ArgentinaFil: Colautti, Dario César. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Limnología "Dr. Raúl A. Ringuelet". Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología; Argentin

Standardless quantification by parameter optimization in electron probe microanalysis

A method for standardless quantification by parameter optimization in electron probe microanalysis is presented. The method consists in minimizing the quadratic differences between an experimental spectrum and an analytical function proposed to describe it, by optimizing the parameters involved in the analytical prediction. This algorithm, implemented in the software POEMA (Parameter Optimization in Electron Probe Microanalysis), allows the determination of the elemental concentrations, along with their uncertainties. The method was tested in a set of 159 elemental constituents corresponding to 36 spectra of standards (mostly minerals) that include trace elements. The results were compared with those obtained with the commercial software GENESIS Spectrum® for standardless quantification. The quantifications performed with the method proposed here are better in the 74% of the cases studied. In addition, the performance of the method proposed is compared with the first principles standardless analysis procedure DTSA for a different data set, which excludes trace elements. The relative deviations with respect to the nominal concentrations are lower than 0.04, 0.08 and 0.35 for the 66% of the cases for POEMA, GENESIS and DTSA, respectively. © 2012 Elsevier B.V. All rights reserved.Fil: Limandri, Silvina Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Bonetto, Rita Dominga. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Ciencias Aplicadas "Dr. Jorge J. Ronco". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Ciencias Aplicadas; ArgentinaFil: Galván Josa, Víctor Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Carreras, Alejo Cristian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Trincavelli, Jorge Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin