Phytoplankton primary production in Chascomus pond (Provincia de Buenos Aires, Argentina)

In situ phytoplankton primary production in Chascomús pond (eutrophic Pampasic “laguna”) was studied by the oxygen method (light and dark bottle) between.January 1984-January 1985. Valúes obtained ranged from37,9 to 981,6 mg C • m-1 • d-1. Factors influencing it, as suspended particulate matter and hydrological changes, are discussed. Parallel determinations of the artificial light photosynthesis response proved to be useful,almostqualitatively under the experimental conditions applied, to follow the behaviour obtained by incubations in natural environment.In situ phytoplankton primary production in Chascomús pond (eutrophic Pampasic “laguna”) was studied by the oxygen method (light and dark bottle) between.January 1984-January 1985. Valúes obtained ranged from37,9 to 981,6 mg C • m-1 • d-1. Factors influencing it, as suspended particulate matter and hydrological changes, are discussed. Parallel determinations of the artificial light photosynthesis response proved to be useful,almostqualitatively under the experimental conditions applied, to follow the behaviour obtained by incubations in natural environment

Dissolved organic carbon in water fluxes of <i>Eucalyptus grandis</i> plantations in northeastern Entre Ríos Province, Argentina

Water fluxes in tree plantations and other ecosystems carry dissolved organic carbon (DOC) provided by atmospheric inputs, autotrophic and heterotrophic metabolisms and from the lysis of dead material. These compounds may be colorless or provide a yellow-to-brown color to water and may also absorb visible light due to the presence of chromophores in the chemical structure. Concentration and composition of DOC and DOC annual flux in water pathways of a Eucalyptus grandis plantation were studied in Entre Ríos, Argentina. Samples of bulk precipitation, throughfall, stemflow, litter lixiviation, surface runoff and water table were analyzed for DOC concentration and color (optical density). Regression analyses for DOC concentration vs water fluxes intensity and for DOC concentration vs color were done. A DOC circulation model was calculated using available information on water budgets fluxes. Results showed that molecular features, values and range of DOC concentrations varied among fluxes, which may be explained by factors and processes influencing water gains and losses and by composition and availability of organic matter that may be dissolved in water in contact with biomass, necromass, soil and subsoil. Regression parameters from DOC concentration vs optical density were useful for DOC chemical composition analyses and interpretation of DOC changes. Annual circulation of DOC (in kg ha-1 year-1) showed that atmospheric contribution is low (ca. 30), aboveground biomass lixiviation is about 3-4 times the atmospheric input (126.7 to 101.4), and inputs to mineral soil (374.4 to 348.0) came mainly (74 to 78 %) from litter lixiviation.Los flujos de agua en los ecosistemas transportan carbono orgánico disuelto (COD) de los aportes atmosféricos, el metabolismo autotrófico y heterotrófico y la lisis de materia muerta. Estos compuestos pueden ser incoloros o coloreados, y absorber luz visible debido a la presencia de cromóforos. Se estudiaron la concentración, composición y flujo anual de COD en las vías hídricas de una plantación de Eucalyptus grandis, Entre Ríos, Argentina. Se determinó la concentración de COD y color (densidad óptica) en muestras de agua de precipitación bruta, trascolación, flujo caulinar, lixiviación del mantillo, escurrimiento superficial y napa freática. Se realizaron regresiones COD vs flujo hídrico y COD vs color. Se modeló la circulación de COD. Las características moleculares y los valores y rangos de concentración de COD variaron entre flujos hídricos que se explicarían por factores y procesos que influencian las ganancias y pérdidas de agua y la composición y disponibilidad de materia orgánica que puede disolverse en aguas en contacto con la biomasa, la necromasa, los horizontes del suelo y el subsuelo. Los parámetros de regresión COD vs color resultaron útiles para analizar la composición del COD e interpretar los cambios en COD en las aguas. La circulación anual de COD muestra que la contribución (kg ha-1 año-1) atmosférica es baja (ca. 30), el lixiviado de la biomasa aérea es alrededor de 3-4 veces el suministrado por la atmósfera (126,7 a 101,4) y el ingreso al suelo (374,4 a 348,0) deriva principalmente (74 a 78 %) de la lixiviación del mantillo

Aplicabilidad de las determinaciones de absorción en el UV-visible para la caracterización de las sustancias húmicas en ambientes acuáticos

The applicability of UV-visible absorption measurements was analyzed as a rapid and easy way for the determination and characterization of humic substances in aquatic environments taking into account their ecological meaning. Samples for these studies were taken from Río Samborombón, Arroyo Vitel and Laguna de Chascomús (Provincia de Buenos Aires, Argentina). In spite of the different absorption of humic and fulvic acids at the wavelengths employed, the method proved to be useful to account for the relative proportion of them, to make comparisons betwcen different ecosystems and to give the possibility of using it to follow the dinamycs of these substances in a given water body. In an attempt to use absorbance determinations as a measure of soluble organic matter content, correlation between Chemical oxygen demand and absorbance at 250 nm and at 365 nm was analyzed. Good results were obtained for Río Samborombón at both wavelengths, while in the other cases correlation was more significative at 365 nm.&nbsp;The applicability of UV-visible absorption measurements was analyzed as a rapid and easy way for the determination and characterization of humic substances in aquatic environments taking into account their ecological meaning. Samples for these studies were taken from Río Samborombón, Arroyo Vitel and Laguna de Chascomús (Provincia de Buenos Aires, Argentina). In spite of the different absorption of humic and fulvic acids at the wavelengths employed, the method proved to be useful to account for the relative proportion of them, to make comparisons betwcen different ecosystems and to give the possibility of using it to follow the dinamycs of these substances in a given water body. In an attempt to use absorbance determinations as a measure of soluble organic matter content, correlation between Chemical oxygen demand and absorbance at 250 nm and at 365 nm was analyzed. Good results were obtained for Río Samborombón at both wavelengths, while in the other cases correlation was more significative at 365 nm.&nbsp

La teoría de Florentino Ameghino y el Plan Maestro Integral Cuenca del Río Salado en el tramo de la desembocadura en la Bahía de Samborombón : Propuesta de construcción de un dique de retención

The Theory of Florentino Ameghino and the Plan Maestro Integral Cuenca del Río Salado at the mouth in the Samborombón Bay. A retention dam building proposal. Florentino Ameghino established that the Buenos Aires Province needs retention structures and not drainage ones in order to prevent drought and flood events. In the lower Salado River drainage basin, Channel Aliviador and Channel 15, that reach the Samborombón Bay, were built with the purpose of control water excess during flooded periods. But Channel 15 was made wider and deeper during 1997, then almost all the water coming from the river goes directly to the Samborombón Bay and this causes a lesser supply of freshwater, that promotes a change in the ecological and socioeconomic conditions in that region. As a consequence, the government taking into account the results of the project Plan Maestro Integral Cuenca del Río Salado (PMI), decided to build threshold bottom dams in the two channels. On the other way, near the mouth of Samborombón Bay, it is located the rock shell littoral chain, which generates an aquifer of a low salinity water. At present, hydrochemical studies indicate that the absence of the river makes the water of the aquifer goes to the bed of the river, which reaches the bay in the moment of low tide and, on the contrary, during high tide a mix with high salinity water coming from the bay takes place. In both cases a loss of freshwater occurs. So in order to minimize this effect, the construction of a retention dam was suggested in a previous work. Since, once the dams of the PMI will be concluded, still a probability of a lack of water may persist in case of drought event as well as for the intensive use of water in the rest of the drainage basin, then the aim of the present work is to maintain the proposal of the construction of the retention dam to assure a source of freshwater in the region and to preserve the rock shell littoral chain aquifer.Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Instituto de Limnología "Dr. Raul A. Ringuelet" (ILPLA

La teoría de Florentino Ameghino y el Plan Maestro Integral Cuenca del Río Salado en el tramo de la desembocadura en la Bahía de Samborombón

The Theory of Florentino Ameghino and the Plan Maestro Integral Cuenca del Río Salado at the mouth in the Samborombón Bay. A retention dam building proposal. Florentino Ameghino established that the Buenos Aires Province needs retention structures and not drainage ones in order to prevent drought and flood events. In the lower Salado River drainage basin, Channel Aliviador and Channel 15, that reach the Samborombón Bay, were built with the purpose of control water excess during flooded periods. But Channel 15 was made wider and deeper during 1997, then almost all the water coming from the river goes directly to the Samborombón Bay and this causes a lesser supply of freshwater, that promotes a change in the ecological and socioeconomic conditions in that region. As a consequence, the government taking into account the results of the project Plan Maestro Integral Cuenca del Río Salado (PMI), decided to build threshold bottom dams in the two channels. On the other way, near the mouth of Samborombón Bay, it is located the rock shell littoral chain, which generates an aquifer of a low salinity water. At present, hydrochemical studies indicate that the absence of the river makes the water of the aquifer goes to the bed of the river, which reaches the bay in the moment of low tide and, on the contrary, during high tide a mix with high salinity water coming from the bay takes place. In both cases a loss of freshwater occurs. So in order to minimize this effect, the construction of a retention dam was suggested in a previous work. Since, once the dams of the PMI will be concluded, still a probability of a lack of water may persist in case of drought event as well as for the intensive use of water in the rest of the drainage basin, then the aim of the present work is to maintain the proposal of the construction of the retention dam to assure a source of freshwater in the region and to preserve the rock shell littoral chain aquifer.Florentino Ameghino established that the Buenos Aires Province needs retention structures and not drainage ones in order to prevent drought and flood events. In the lower Salado River drainage basin, Channel Aliviador and Channel 15, that reach the Samborombón Bay, were built with the purpose of control water excess during flooded periods. But Channel 15 was made wider and deeper during 1997, then almost all the water coming from the river goes directly to the Samborombón Bay and this causes a lesser supply of freshwater, that promotes a change in the ecological and socioeconomic conditions in that region. As a consequence, the government taking into account the results of the project Plan Maestro Integral Cuenca del Río Salado (PMI), decided to build threshold bottom dams in the two channels. On the other way, near the mouth of Samborombón Bay, it is located the rock shell littoral chain, which generates an aquifer of a low salinity water. At present, hydrochemical studies indicate that the absence of the river makes the water of the aquifer goes to the bed of the river, which reaches the bay in the moment of low tide and, on the contrary, during high tide a mix with high salinity water coming from the bay takes place. In both cases a loss of freshwater occurs. So in order to minimize this effect, the construction of a retention dam was suggested in a previous work. Since, once the dams of the PMI will be concluded, still a probability of a lack of water may persist in case of drought event as well as for the intensive use of water in the rest of the drainage basin, then the aim of the present work is to maintain the proposal of the construction of the retention dam to assure a source of freshwater in the region and to preserve the rock shell littoral chain aquifer

Humic Substances from sediments of Lobos Pond (Argentina). Isolation, Characterization and Limnological Implications

Humic substances (HS) were isolated from the sediments of Lobos Pond (Argentina) using mild conditions to preserve their native structure. The HS (humic and fulvic acids) were characterized by means of elemental analysis and FTIR spectroscopy. Also a by-product obtained during fulvic acids (FA) fractionation (an amorphous white solid residue) was analyzed. Results revealed possible interactions between FA and inorganic-organic substances that may have implications referring to bioavailability. Other limnological implications, such as autochtonous origin of HS linked with the hydrology, and change of pH during stormy weather that affects HS interactions, are discussed.Laboratorio de Investigación de Sistemas Ecológicos y Ambientale

Humic Substances from sediments of Lobos Pond (Argentina). Isolation, Characterization and Limnological Implications

Humic substances (HS) were isolated from the sediments of Lobos Pond (Argentina) using mild conditions to preserve their native structure. The HS (humic and fulvic acids) were characterized by means of elemental analysis and FTIR spectroscopy. Also a by-product obtained during fulvic acids (FA) fractionation (an amorphous white solid residue) was analyzed. Results revealed possible interactions between FA and inorganic-organic substances that may have implications referring to bioavailability. Other limnological implications, such as autochtonous origin of HS linked with the hydrology, and change of pH during stormy weather that affects HS interactions, are discussed.Laboratorio de Investigación de Sistemas Ecológicos y Ambientale

La teoría de Florentino Ameghino y el Plan Maestro Integral Cuenca del Río Salado en el tramo de la desembocadura en la Bahía de Samborombón : Propuesta de construcción de un dique de retención

The Theory of Florentino Ameghino and the Plan Maestro Integral Cuenca del Río Salado at the mouth in the Samborombón Bay. A retention dam building proposal. Florentino Ameghino established that the Buenos Aires Province needs retention structures and not drainage ones in order to prevent drought and flood events. In the lower Salado River drainage basin, Channel Aliviador and Channel 15, that reach the Samborombón Bay, were built with the purpose of control water excess during flooded periods. But Channel 15 was made wider and deeper during 1997, then almost all the water coming from the river goes directly to the Samborombón Bay and this causes a lesser supply of freshwater, that promotes a change in the ecological and socioeconomic conditions in that region. As a consequence, the government taking into account the results of the project Plan Maestro Integral Cuenca del Río Salado (PMI), decided to build threshold bottom dams in the two channels. On the other way, near the mouth of Samborombón Bay, it is located the rock shell littoral chain, which generates an aquifer of a low salinity water. At present, hydrochemical studies indicate that the absence of the river makes the water of the aquifer goes to the bed of the river, which reaches the bay in the moment of low tide and, on the contrary, during high tide a mix with high salinity water coming from the bay takes place. In both cases a loss of freshwater occurs. So in order to minimize this effect, the construction of a retention dam was suggested in a previous work. Since, once the dams of the PMI will be concluded, still a probability of a lack of water may persist in case of drought event as well as for the intensive use of water in the rest of the drainage basin, then the aim of the present work is to maintain the proposal of the construction of the retention dam to assure a source of freshwater in the region and to preserve the rock shell littoral chain aquifer.Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Instituto de Limnología "Dr. Raul A. Ringuelet" (ILPLA

La teoría de Florentino Ameghino y el Plan Maestro Integral Cuenca del Río Salado en el tramo de la desembocadura en la Bahía de Samborombón : Propuesta de construcción de un dique de retención

The Theory of Florentino Ameghino and the Plan Maestro Integral Cuenca del Río Salado at the mouth in the Samborombón Bay. A retention dam building proposal. Florentino Ameghino established that the Buenos Aires Province needs retention structures and not drainage ones in order to prevent drought and flood events. In the lower Salado River drainage basin, Channel Aliviador and Channel 15, that reach the Samborombón Bay, were built with the purpose of control water excess during flooded periods. But Channel 15 was made wider and deeper during 1997, then almost all the water coming from the river goes directly to the Samborombón Bay and this causes a lesser supply of freshwater, that promotes a change in the ecological and socioeconomic conditions in that region. As a consequence, the government taking into account the results of the project Plan Maestro Integral Cuenca del Río Salado (PMI), decided to build threshold bottom dams in the two channels. On the other way, near the mouth of Samborombón Bay, it is located the rock shell littoral chain, which generates an aquifer of a low salinity water. At present, hydrochemical studies indicate that the absence of the river makes the water of the aquifer goes to the bed of the river, which reaches the bay in the moment of low tide and, on the contrary, during high tide a mix with high salinity water coming from the bay takes place. In both cases a loss of freshwater occurs. So in order to minimize this effect, the construction of a retention dam was suggested in a previous work. Since, once the dams of the PMI will be concluded, still a probability of a lack of water may persist in case of drought event as well as for the intensive use of water in the rest of the drainage basin, then the aim of the present work is to maintain the proposal of the construction of the retention dam to assure a source of freshwater in the region and to preserve the rock shell littoral chain aquifer.Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) - Instituto de Limnología "Dr. Raul A. Ringuelet" (ILPLA

Nutrientes y clorofila-a durante el período de inundación 2001-2002 en la Laguna Chascomús (Argentina)

Total phosphorus, total nitrogen and chlorophyll-a concentrations were determined weekly in a pelagic zone in Chascomús Pond between April 2001 and September 2002. Two flood periods took part with 8 metres over sea level (IGM) during this time (June- January 2002 and April-June 2002), where in both of them two maximum peaks with about 9 meters were registered. As a consequence a diminution of the salinity to one third of the mean value of 1,57 g.l-1 was observed, because of the dilution promoted by rainwater which was higher in a 40% of the mean 600 mm of the latest five years. Nevertheless, this fact had not occurred with total phosphorus, mean 0,48 mg.l-1, referring to 0,48 mg.l-1 obtained in 1999-2000, while total nitrogen, mean 1,45 mg N.l-1, was nearly in the same order in relation to a previous value of 1,56 mg N.l-1 (1983-1984) and chlorophyll-a, mean 198,2 μg.l-1, showed a significant increment taking into account the concentration of 89,1 μg.l-1 determined during 1999-2002. These results indicate that because of flood events a supply of nutrients reaches the pond coming from wastes of the city (30000 inhabitants), as well as from the effluent of the treatment plant. Normally, the latter go to Girado stream and finally are received by Adela Pond in direction to Salado River, but the inversion of the flux makes these wastes reach Chascomús Pond during flood periods.Facultad de Ciencias Naturales y Muse