Colonization of a Neotropical Reservoir (Córdoba, Argentina) by Ceratium hirundinella (O. F. Müller) Bergh

Blooms of Ceratium hirundinella (O. F. Müller) Bergh. have been detected in different water bodies in the Neotropical Region since 1990. The colonization began in southern lakes, and during the last decade the dinoflagellate arrived and bloomed in subtropical reservoirs. In this context the colonization of C. hirundinella and its population development have been analyzed from its first record in the Río Tercero Reservoir (February 1999 to February 2001). Phytoplankton and physicochemical samples were obtained from three sampling stations at the Reservoir, one in the outlet of the water cooling channel of the nuclear power plant, and one in the nearest tributary (Quillinzo River). Two blooms of C. hirundinella were detected during the warm seasons with temperatures higher than 18°C, and pH ranging between 8.5 and 8.9. Environmental conditions such as certain light intensity range and percentage of dissolved oxygen mentioned as favorable for Ceratium development were always recorded in Río Tercero Reservoir. Cysts were observed in spring and summer months. Another dinoflagellate (Peridinium gatunense Nygaard) bloomed in previous summer in this water body but its population density decreased during the invasive phase of colonization of C. hirundinella. Asplanchna girodi, became the dominant zooplankter after the first bloom of C. hirundinella. We believe that the presence of this dinoflagellate in the Neotropical Region could be a regional phenomenon associated with some dispersal mechanisms and favorable local conditions for its proliferation like those recorded in the Rio Tercero ReservoirFil: Mac Donagh, María Elicia. Universidad Nacional de La Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Casco, Maria Adela. Universidad Nacional de La Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Claps, Maria Cristina. 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

The Acute Effect of Piretanide upon Serum and Urinary Calcium in Normal Subjects

We gave piretanide, a new diuretic, at two dose levels to six normal subjects. Sodium excretion increased six to eightfold in the first two hours, and diuresis was completed within four hours. There was a simultaneous increase in the excretion of calcium which exceeded the amount present In the mobilized extracellular fluid. The resulting deficit of calcium produced a small but significant fall in serum calcium corrected for protein. After diuresis ended, calcium was retained but not sodium, when compared to basal values on the previous day. The fall in urinary calcium and the failure to correct the sodium deficit may both have resulted from increased secretion of parathyroid hormone (PTH), which increases calcium reabsorption and decreases sodium reabsorption. The role of PTH in the long-term effects of diuretics on sodium and calcium excretion requires further study

Plancton conservation and water basins protection. The case of the Rio Salado Lower Basin, Province of Buenos Aires, Argentina

A diferencia de los principios para la conservación de recursos bióticos terrestres o marinos, en la conservación de recursos hídricos no se asigna importancia a los componentes bióticos y ninguna al plancton. Pocas de las miles de especies identificadas en esta comunidad figuran en una lista de especies en peligro o amenazadas de la Unión Internacional para la Conservación de la Naturaleza (UICN). Por ende, a nivel mundial no se les concede ningún tipo de protección. Desde la década del 1990, en ecología y biogeografía diferentes autores, han enfatizado la necesidad de reconocer la biodiversidad en relación al funcionamiento de los ecosistemas. En este sentido cabe plantearse los siguientes cuestionamientos: ¿Los organismos acuáticos, principalmente del plancton, merecen ser considerados objetos de conservación? ¿Mantener la integridad ecológica de los cuerpos de agua es suficiente para su conservación? La Cuenca del Río Salado, localizada en la provincia de Buenos Aires, transporta excesos de agua y nutrientes durante inundaciones hacia la Bahía Samborombón (un Sitio Ramsar). A pesar de períodos de sequía e inundación, los cambios de la salinidad producto de la influencia marina y el aporte de efluentes agropecuarios, los ambientes acuáticos mantienen un aceptable grado de conservación y biodiversidad. La estructura del plancton se mantiene dominada por clorofitas unicelulares, rotíferos Brachionidae y ciliados tintínidos en la cuenca inferior y crustáceos en sectores vinculados a ambientes lénticos. La comunidad planctónica es compleja, resiliente y está integrada por más de 300 especies. Las especies clave permitirían que el río mantenga su rol como ecosistema de servicio. Proponemos para ríos de llanura la visión territorial, multiescala, dentro del concepto de riverine landscape, que incluye tanto la conservación composicional (Biodiversidad) como funcional (Integridad Ecológica).Fil: Gabellone, Nestor Adrian. 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: Solari, Lía Cristina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; ArgentinaFil: Casco, Maria Adela. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Division Ficologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Claps, Maria Cristina. 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

Epipelon dynamics in a shallow lake through a turbid-and a clear- water regime

Fil: Cano, María Gabriela. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Ficología; ArgentinaFil: Casco, María Adela. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Ficología; ArgentinaFil: Claps, María Cristina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología Dr. Raúl A. Ringuelet; Argentin

Effect of environmental variables on epiphyton in a pampean lake with stable turbid- and clear-water states

In the present study, we examined the variation in composition and biomass of epi-phyton growing on the bulrush Schoenoplectus californicus in a pampean lake that passed through a turbid- and a clear-water period within an annual cycle. Monthly sampling was performed year-round at the center and periphery of a bulrush stand. We measured the physicochem-ical parameters in the water column using standardized field and laboratory methods. The epiphy-ton was sampled by sectioning bulrush stems into segments for pigment analysis, abundance measurements, and biovolume quantification. Two different types of communities were observed during the annual cycle. In the turbid-water period, epiphyton biomass and diversity remained low despite sufficient levels of phosphates. An abrupt increase in epiphyton biomass, along with structural changes in the community, occurred after an improvement in water transparency, suggesting that the epiphyton was strongly dependent on underwater light conditions. Differences in epiphyton composition and biomass between the center and the periphery of the bulrush stand were negligible. We conclude that the availability of colonizing surface is not a relevant driver for the colonization and growth of these epiphyton assemblages. The epiphyton in pampean lakes may remain stable and resilient for relatively long periods, even when confronted with environmental perturbations, and changes in these communities will only occur in relation to radical alterations in light and nutrient availability.Facultad de Ciencias Naturales y Muse

Microfitobenton del canal Mercante en dos condiciones hidrológicas

Fil: Dos Santos, Analía. División Ficología. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Casco, María Adela. División Ficología. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Claps, María Cristina. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin

Epipelon dynamics in a shallow lake through a turbid-and a clear-water regime

In Pampean lakes, very little information is available on epipelon structure and dynamics or the effect of environmental variables on those parameters. We anticipate that light may have the greatest influence on this community and that the nutrient concentration and substrate instability may exert secondary effects. Our objective was to analyze variations in descriptive parameters and in the algal species composition of the epipelon in the Pampean Lake Lacombe over space and time to establish the most influential environmental forces (light climate, wave action, nutrients). Sediment was collected from the benthos with a 3.5-cm-diameter corer in a year-round sampling every month at four sites in the lake that differed from each other in depth, distance from the shore, and the presence of emergent and submerged macrophytes. Although Lacombe is a shallow lake, differences occurred in community descriptive variables and in the epipelon composition (especially diatoms) over space and time. In particular, differences between the site nearest to the shore and the rest of the sites were found with respect to environmental variables (sediment-particle size, total phosphorus, organic matter content, light climate), epipelon descriptive parameters (abundance, chlorophyll a and Margalef’s index) and epipelon composition (especially specific biovolume and diatom-size classes). The epipelon also reflected, though slightly, the change from the turbid- to clear-water states in the lake. Sediment erosion or deposition was evidenced by differences in the sediment-particle composition and the predominant particle-size classes at each site. Statistical analyses indicated linear correlations between the epipelon parameters and variables related to the light climate in the water column. Conductivity and sediment total phosphorus and density were also correlated, but to a lesser extent, with epipelon composition. The epipelon variations in Lacombe Lake would exemplify the reference communities developed during clear or turbid regimes in Pampean shallow lakes. We found evidence for the influence of light climate and wave action (through instability of the substrate) on this community, but the effect of nutrients was negligible. We emphasize that the close relationships maintained by the epipelon with other communities such as the phytoplankton and the epiphyton may superimpose the patterns of variation to those communities onto the epipelon dynamics.Facultad de Ciencias Naturales y MuseoInstituto de Limnología "Dr. Raúl A. Ringuelet

Epipelon dynamics in a shallow lake through a turbid-and a clear-water regime

In Pampean lakes, very little information is available on epipelon structure and dynamics or the effect of environmental variables on those parameters. We anticipate that light may have the greatest influence on this community and that the nutrient concentration and substrate instability may exert secondary effects. Our objective was to analyze variations in descriptive parameters and in the algal species composition of the epipelon in the Pampean Lake Lacombe over space and time to establish the most influential environmental forces (light climate, wave action, nutrients). Sediment was collected from the benthos with a 3.5-cm-diameter corer in a year-round sampling every month at four sites in the lake that differed from each other in depth, distance from the shore, and the presence of emergent and submerged macrophytes. Although Lacombe is a shallow lake, differences occurred in community descriptive variables and in the epipelon composition (especially diatoms) over space and time. In particular, differences between the site nearest to the shore and the rest of the sites were found with respect to environmental variables (sediment-particle size, total phosphorus, organic matter content, light climate), epipelon descriptive parameters (abundance, chlorophyll a and Margalef’s index) and epipelon composition (especially specific biovolume and diatom-size classes). The epipelon also reflected, though slightly, the change from the turbid- to clear-water states in the lake. Sediment erosion or deposition was evidenced by differences in the sediment-particle composition and the predominant particle-size classes at each site. Statistical analyses indicated linear correlations between the epipelon parameters and variables related to the light climate in the water column. Conductivity and sediment total phosphorus and density were also correlated, but to a lesser extent, with epipelon composition. The epipelon variations in Lacombe Lake would exemplify the reference communities developed during clear or turbid regimes in Pampean shallow lakes. We found evidence for the influence of light climate and wave action (through instability of the substrate) on this community, but the effect of nutrients was negligible. We emphasize that the close relationships maintained by the epipelon with other communities such as the phytoplankton and the epiphyton may superimpose the patterns of variation to those communities onto the epipelon dynamics.Facultad de Ciencias Naturales y MuseoInstituto de Limnología "Dr. Raúl A. Ringuelet

Microfitobenton del Canal Mercante (Provincia de Buenos Aires) en dos condiciones hidrológicas

In lotic environments, the erosion-sedimentation processes related to the hydrological conditions differ throughout the hydrological cycle, mainly due to rainfall. These processes can produce disturbances in the phytobenthic community. In canals, the current velocity and the water level are the main forcing variables that act on benthic communities, promoting changes in their structure, composition and biomass. Sediment samples were collected in the canal Mercante during two hydrological conditions: 1) at the beginning of spring, during a period of low rainfall (September 2009) and 2) in early autumn after a summer period with heavy rains (March 2010) to determine the content of organic matter, total phosphorus, chlorophyll a, and also the abundance of microphytobenthic individuals and cells. Simultaneously, some variables were measured in the water column. We identified two states of the community that could be associated with the phenomena of erosion / deposition related to the effect of water flow. In September the algal community in sediments showed a vertical architecture, mainly constituted by benthic algae among which several species had an aggregated distribution. In March, a decrease of the proportion and number of benthic algae was observed coinciding with the presence of planktonic species in sediments. Some benthic taxa exhibited similar abundances in the two periods and could be consider as tolerant to changes in flow velocity and as typical members of the canal Mercante. In conclusion, hydrological changes could have a significant role on the structure and dynamic of phytobenthon.Fil: Dos Santos, Analía Beatriz. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Division Ficología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Casco, Maria Adela. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Division Ficología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Claps, Maria Cristina. 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

Colonization of a Neotropical Reservoir (Córdoba, Argentina) by Ceratium hirundinella (O. F. Müller) Bergh

Blooms of Ceratium hirundinella (O. F. Müller) Bergh. have been detected in different water bodies in the Neotropical Region since 1990. The colonization began in southern lakes, and during the last decade the dinoflagellate arrived and bloomed in subtropical reservoirs. In this context the colonization of C. hirundinella and its population development have been analyzed from its first record in the Río Tercero Reservoir (February 1999 to February 2001). Phytoplankton and physicochemical samples were obtained from three sampling stations at the Reservoir, one in the outlet of the water cooling channel of the nuclear power plant, and one in the nearest tributary (Quillinzo River). Two blooms of C. hirundinella were detected during the warm seasons with temperatures higher than 18°C, and pH ranging between 8.5 and 8.9. Environmental conditions such as certain light intensity range and percentage of dissolved oxygen mentioned as favorable for Ceratium development were always recorded in Río Tercero Reservoir. Cysts were observed in spring and summer months. Another dinoflagellate (Peridinium gatunense Nygaard) bloomed in previous summer in this water body but its population density decreased during the invasive phase of colonization of C. hirundinella. Asplanchna girodi, became the dominant zooplankter after the first bloom of C. hirundinella. We believe that the presence of this dinoflagellate in the Neotropical Region could be a regional phenomenon associated with some dispersal mechanisms and favorable local conditions for its proliferation like those recorded in the Rio Tercero Reservoir.Instituto de Limnología "Dr. Raul A. Ringuelet"Museo de La Plat