Zooplankton richness, abundance and biomass of two hypertrophic shallow lakes with different salinity

The zooplankton of lakes is controlled by biological and physico-chemical parameters. Among the former, predation by fish can determine the replacement of large-sized species by small-sized ones and among the latter, salinity exerts negative effects on richness and abundance. Since it has been suggested that saline lakes without fishes have higher zooplankton biomass than low salinity ones, the aim of this study was to determine the richness, abundance and biomass of zooplankton in two lakes with different salinity and test the hypothesis that in the presence of zooplanktivorous fishes and at equal concentrations of nutrients and chlorophyll a, saline lakes have higher biomass than those with low salinity. The study was conducted in two shallow lakes of the Province of La Pampa (central Argentina): a subsaline lake and a hyposaline lake, which shared high concentrations of chlorophyll a and total phosphorus, reduced transparency and presence of planktivorous fish. Zooplankton richness was different and higher in the subsaline lake, whereas abundance and total biomass were similar, even when the taxonomic groups were considered separately. It is suggested that the presence of a halotolerant planktivorous fish controlled the size of zooplankton due to the predation on larger species and prevented the development of higher biomass in the saline lake, which is an important difference from previously recorded situations. This study shows that, regardless of the differences in salinity, the top-down effect in the food chain may have been a factor that equalized the zooplankton biomass by allowing only the development of small species and highlights the possible importance of fish predation in determining chlorophyll a concentrations and water transparency.Fil: Echaniz, Santiago Andrés. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Vignatti, Alicia María. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Cabrera, Gabriela Cecilia. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Jose, Susana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentin

Dynamics of the limnological parameters and zooplankton of La Brava, a shallow lake of the Atuel-Salado-Chadileuvú-Curacó system (La Pampa, Argentina)

La Brava is a shallow lake that is different from others of La Pampa, as it is part of the fluvial system of Desaguadero-Atuel-Salado-Chadileuvú-Curacó rivers. However, dams built upstream disrupt runoff, so water only enters when excessive snowfall in the Andes mountains forces the reservoirs to be opened. Once water enters, it is slowly lost through evaporation, which can lead to drying of the lake. As the ecology of La Brava is unknown, the objective of this study was to determine the limnological parameters, density and taxonomic composition of zooplankton during a period that contained water and salinity increased by evaporation. Samples between January 2009 and November 2010 were taken. The maximum depth (2.1 m) was recorded in October 2009 but declined and in November 2010 was 0.66 m. Na+ and Cl- predominated in ionic composition and the salinity rose from 15.83 to 49.89 g.L-1. The mean transparency was 0.65 m (±0.12) and despite the high concentration of nutrients (TP: 6.02 ±2.87; TKN: 11.17 ±5.92 mg.L-1) the phytoplankton chlorophyll-a concentration was reduced (1.29 ±1.27 mg.m-3). One cladoceran, four copepods and eight rotifers were registered. The greatest diversity was observed during the first month, specially provided by rotifers, when the group reached its greatest density (385.8 ind.L-1), especially given by Brachionus plicatilis Müller, 1786. Increasing salinity affects the diversity, so in June and August 2009 the copepod Boeckella gracilis (Daday, 1902) was recorded, later replaced by the halotolerant Boeckella poopoensis Marsh, 1906. October 2009 was the only occasion when the cladoceran Daphnia menucoensis Paggi, 1996 was registered, in low density (5.7 ind.L-1). Despite their differences with other Pampean environments, in La Brava the typical zooplankton association of the center of the country and northern Patagonia was found, but it differs from another lake of Curacó system where only the halophilic anostracan Artemia persimilis Piccinelli & Prosdocimi, 1968 was registered.Fil: del Ponti, Omar. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Cabrera, Gabriela Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Confluencia; Argentina. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Vignatti, Alicia María. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Confluencia; ArgentinaFil: Echaniz, Santiago Andrés. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Confluencia; Argentin

Associations of ostracods in shallow lakes in the northeast of La Pampa province (Argentina)

Los lagos someros son frecuentes en La Pampa. Aunque muchas características de su biota son conocidas, la información sobre la distribución y ecología de los ostrácodos es escasa, a pesar de su importancia como indicadores biológicos y en actuopaleontología. El objetivo de este estudio es conocer la composición taxonómica, la densidad de ostrácodos y sus relaciones con parámetros ambientales en lagos del noreste de La Pampa. Se estudiaron cinco lagos desde septiembre de 2016 hasta marzo de 2017. Se tomaron muestras de sedimentos superficiales e in situ se midieron: conductividad, temperatura y transparencia y se tomaron muestras para determinar salinidad, pH y composición iónica. Los lagos difirieron en su salinidad, composición iónica y transparencia. Se registraron diez taxa, algunos hallados previamente en la provincia de Buenos Aires (Heterocypris similis, Heterocypris incongruens, Cypridopsis vidua y Chlamydotheca incisa), la cuenca de Llancanelo (H. incongruens y C. vidua) y lagos del norte de Patagonia (C. incisa, C. vidua, Potamocypris unicaudata, H. incongruens y Amphicypris argentiniensis). Se comprobó la influencia de la salinidad ya que algunas especies (A. argentinensis, Limnocythere rionegroensis y Limnocythere titicaca) se encontraron sólo en el lago más salino. La existencia en La Pampa de tres ecorregiones diferentes (Llanura Pampeana, Espinal y Estepa Patagónica) y la presencia en los lagos estudiados de ostrácodos del noroeste argentino (L. titicaca), de la llanura bonaerense (H. similis, H. incongruens) y otras de Patagonia (L. rionegroensis), permitiría afirmar que los lagos de La Pampa están en una zona de transición entre faunas diferentes.Shallow lakes are common in the center of Argentina. Although many characteristics of its biota are known, information on the distribution and ecology of ostracods is scarce despite their importance as biological indicators and in actuopaleontology. The objective of this study was to determine the taxonomic composition, the density of ostracods, and their relationships with environmental parameters in lakes in the northeast of La Pampa. Five aquatic ecosystems were studied from September 2016 to March 2017. Samples of superficial sediments were collected, and conductivity, temperature, and transparency were measured in situ. Water samples were collected to determine salinity, pH, and ionic composition. The lakes differed in salinity, ionic composition, and transparency. Ten taxa were registered, some previously found in the province of Buenos Aires (Heterocypris similis, Heterocypris incongruens, Cypridopsis vidua, and Chlamydotheca incisa), the Llancanelo basin (H. incongruens and C. vidua), and North Patagonia lakes (C. incisa, C. vidua, Potamocypris unicaudata, H. incongruens, and Amphicypris argentiniensis). The influence of salinity was verified because some species (A. argentinensis, Limnocythere rionegroensis, and Limnocythere titicaca) were found only in the most saline lake. The existence in La Pampa of three different ecoregions (Pampean Plains, Espinal, and Patagonian Steppe) and the presence of ostracods in the studied lakes of northwestern Argentina (L. titicaca), the Buenos Aires province plain (H. similis, H. incongruens), and Patagonia (L. rionegroensis) allowed for affirming that the lakes of La Pampa are in a transition zone among different ostracods faunas.Fil: Kihn, Romina Gisela. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Echaniz, Santiago Andrés. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Vignatti, Alicia María. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Cabrera, Gabriela Cecilia. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Stella, Cesar A.. Museo Provincial de Ciencias Naturales; Argentin

Dinámica del zooplancton y de los parámetros limnológicos de un lago mesosalino de un área protegida en la Pampa semiárida de Argentina

Most of the mesosaline lakes in the semiarid central Pampas have a high anthropogenic influence. The aim was to determine the variation in limnological and zooplankton parameters of a mesosaline lake with little human impact, the West Lake of the Parque Luro Reserve during a year. Monthly samples were taken between 2014 and 2015. The mean depth and salinity were 0.66 m and 29.33 g/L, respectively. The transparency was total; the light reached the bottom and favored the growth of the macrophyte Ruppia cirrhosa. Two cladocerans, three copepods, and eight rotifers were registered. Among crustaceans, autochthonous halophilic species were found (Daphnia menucoensis and Boeckella poopoensis). Zooplankton density was 20 to 100 times lower than that of other Pampean lakes, probably due to the presence of the macrophyte, which distinguishes this lake from others in the regionLa mayoría de los lagos mesosalinos en la Pampa central semiárida sufren alta influencia antrópica. El objetivo fue determinar la variación de los parámetros limnológicos y del zooplancton de un lago mesosalino con poco impacto humano, el lago Oeste de la Reserva Parque Luro a lo largo de un año. Se tomaron muestras mensuales (2014 - 2015). La profundidad y salinidad media fueron 0,66 m y 29.33 g/L. La transparencia fue total, la luz llegó al fondo y favoreció el crecimiento de la macrófita Ruppia cirrhosa. Se registraron dos cladóceros, tres copépodos y ocho rotíferos. Entre los crustáceos se hallaron especies halófilas autóctonas (Daphnia menucoensis y Boeckella poopoensis). La densidad del zooplancton fue 20 a 100 veces menor que la de otros lagos pampeanos parecidos, probablemente debido a la presencia de la macrófita, lo que es un rasgo que distingue a este lago de otros de la regió

Comparación de los parámetros limnológicos y el zooplancton de un lago somero salino de La Pampa (Argentina) durante dos ciclos anuales con condiciones ambientales diferentes

In central Argentina the alternation of cycles of rainfall above or below the historic mean is frequent; so, many saline lakes can dry or fill in a short time. As in La Pampa most of the studies on these lakes were limited to annual cycles, the information about variations under different climatic conditions is scarce. The aims of this study were to determine the limnological and zooplankton parameters of a semi-permanent Pampean saline lake during 2013 posterior to its filling after a drought, to compare the information with that obtained in 2007, because the two annual cycles had relatively different environmental characteristics and to test the hypotheses i) in 2013, after filling, scarce tolerant zooplankton species were recorded, replaced by more tolerant ones as salinity increased and ii) species richness in 2013 was greater than that recorded during higher hydrologic stability. Samples were taken between January and December of both years. In 2007 depth was stable and in 2013 it fluctuated markedly. The mean salinity was similar, close to 26 g/L. In 2007 it was stable, but in 2013 rose from 14.3 g/L (January) to 40.4 g/L (December). Transparency was the highest in 2007 (0.76 m ± 0.26) and the lowest in 2013 (0.17 m ± 0.05). The concentration of chlorophyll a in 2007 was lower ( (1.73 mg/ m3 ± 1.25) than in 2013 (38.16 mg/m3 ± 42.33). Species richness showed six species in 2007 and seven species in 2013. In 2007 crustaceans predominated, especially Boeckella poopoensis, but in 2013 rotifers dominated. Among them, Brachionus plicatilis and B. dimidiatus presented a maximum in autumn (1702 and 2062 ind/L, respectively). Daphnia menucoensis was absent during 2013 and the inverse correlation between the density of this cladoceran and chlorophyll a concentration could show its influence on water transparency because of its grazing on phytoplankton. The differences in limnological parameters allow us to know the variability of environmental conditions of a Pampean saline lake and to expand our knowledge about tolerance ranges of some endemic species as B. poopoensis and Moina eugeniae.Facultad de Ciencias Naturales y Muse

Comparación de los parámetros limnológicos y el zooplancton de un lago somero salino de La Pampa (Argentina) durante dos ciclos anuales con condiciones ambientales diferentes

In central Argentina the alternation of cycles of rainfall above or below the historic mean is frequent; so, many saline lakes can dry or fill in a short time. As in La Pampa most of the studies on these lakes were limited to annual cycles, the information about variations under different climatic conditions is scarce. The aims of this study were to determine the limnological and zooplankton parameters of a semi-permanent Pampean saline lake during 2013 posterior to its filling after a drought, to compare the information with that obtained in 2007, because the two annual cycles had relatively different environmental characteristics and to test the hypotheses i) in 2013, after filling, scarce tolerant zooplankton species were recorded, replaced by more tolerant ones as salinity increased and ii) species richness in 2013 was greater than that recorded during higher hydrologic stability. Samples were taken between January and December of both years. In 2007 depth was stable and in 2013 it fluctuated markedly. The mean salinity was similar, close to 26 g/L. In 2007 it was stable, but in 2013 rose from 14.3 g/L (January) to 40.4 g/L (December). Transparency was the highest in 2007 (0.76 m ± 0.26) and the lowest in 2013 (0.17 m ± 0.05). The concentration of chlorophyll a in 2007 was lower ( (1.73 mg/ m3 ± 1.25) than in 2013 (38.16 mg/m3 ± 42.33). Species richness showed six species in 2007 and seven species in 2013. In 2007 crustaceans predominated, especially Boeckella poopoensis, but in 2013 rotifers dominated. Among them, Brachionus plicatilis and B. dimidiatus presented a maximum in autumn (1702 and 2062 ind/L, respectively). Daphnia menucoensis was absent during 2013 and the inverse correlation between the density of this cladoceran and chlorophyll a concentration could show its influence on water transparency because of its grazing on phytoplankton. The differences in limnological parameters allow us to know the variability of environmental conditions of a Pampean saline lake and to expand our knowledge about tolerance ranges of some endemic species as B. poopoensis and Moina eugeniae.In central Argentina the alternation of cycles of rainfall above or below the historic mean is frequent; so, many saline lakes can dry or fill in a short time. As in La Pampa most of the studies on these lakes were limited to annual cycles, the information about variations under different climatic conditions is scarce. The aims of this study were to determine the limnological and zooplankton parameters of a semi-permanent Pampean saline lake during 2013 posterior to its filling after a drought, to compare the information with that obtained in 2007, because the two annual cycles had relatively different environmental characteristics and to test the hypotheses i) in 2013, after filling, scarce tolerant zooplankton species were recorded, replaced by more tolerant ones as salinity increased and ii) species richness in 2013 was greater than that recorded during higher hydrologic stability. Samples were taken between January and December of both years. In 2007 depth was stable and in 2013 it fluctuated markedly. The mean salinity was similar, close to 26 g/L. In 2007 it was stable, but in 2013 rose from 14.3 g/L (January) to 40.4 g/L (December). Transparency was the highest in 2007 (0.76 m ± 0.26) and the lowest in 2013 (0.17 m ± 0.05). The concentration of chlorophyll a in 2007 was lower ( (1.73 mg/ m3 ± 1.25) than in 2013 (38.16 mg/m3 ± 42.33). Species richness showed six species in 2007 and seven species in 2013. In 2007 crustaceans predominated, especially Boeckella poopoensis, but in 2013 rotifers dominated. Among them, Brachionus plicatilis and B. dimidiatus presented a maximum in autumn (1702 and 2062 ind/L, respectively). Daphnia menucoensis was absent during 2013 and the inverse correlation between the density of this cladoceran and chlorophyll a concentration could show its influence on water transparency because of its grazing on phytoplankton. The differences in limnological parameters allow us to know the variability of environmental conditions of a Pampean saline lake and to expand our knowledge about tolerance ranges of some endemic species as B. poopoensis and Moina eugeniae

Diversity of zooplankton in aquatic ecosystems of the northeast of La Pampa (Argentina) with emphasis on new species registered for the province

En la región noreste de la provincia de La Pampa existe una gran cantidad de ecosistemas acuáticos muy heterogéneos, sin embargo los estudios limnológicos sobre ellos son escasos. El objetivo es describir la composición del zooplancton de cinco cuerpos de agua y reportar la presencia de seis especies no registradas en la provincia. Entre 2016 y 2017 se tomaron muestras en dos pequeños lagos (“ojos de agua”) subsalinos, de alta transparencia, con vegetación arraigada y en tres lagunas sub o hiposalinas, sin vegetación y menor transparencia. Se registraron ocho cladóceros, nueve copépodos y 27 rotíferos. En todos los casos los rotíferos dominaron en número de especies y densidad pero las comunidades zooplanctónicas de los ojos de agua fueron diferentes de las de las lagunas. Los ambientes estudiados están en un área geográfica reducida, pero su diversidad fue mayor que la encontrada en áreas más extensas de La Pampa, lo que puede deberse a la heterogeneidad de los ecosistemas acuáticos incluidos en este estudio. Tres copépodos (Argyrodiaptomus bergi, Boeckella bergi y Eucyclops neumani) y tres rotíferos (Euchlanis dilatata, Lecane closterocerca y Plationus patulus) son citados por primera vez para la provincia de La Pampa. Este estudio confirma que la distribución de A. bergi y E. neumani es más amplia que la conocida hasta ahora, restringida a Brasil y la cuenca del Paraná - del Plata, pero el resto son especies extensamente distribuidas en Argentina. En consecuencia, la falta de información en La Pampa se debió a la ausencia de investigaciones previas.The northeastern region of La Pampa province has a large number of heterogenic aquatic ecosystems; however, limnological studies of these ecosystems are scarce. The objective of this study is to describe the composition of the zooplankton of five water bodies and report the presence of six species not previously registered in the province. Between 2016 and 2017, samples were taken in two small, highly transparent subsaline lakes (“water holes”) with rooted vegetation and in three sub- or hyposaline shallow lakes, without vegetation and with less transparency. Eight cladocerans, nine copepods, and 27 rotifers were recorded. In all cases, rotifers dominated in number of species and density, but the zooplankton communities of the water holes differed from those of the shallow lakes. The aquatic ecosystems studied are in a reduced geographic area, but their diversity was greater than that of larger areas of La Pampa, which may be due to the heterogeneity of the water bodies included in this study. Three copepods (Argyrodiaptomus bergi, Boeckella bergi, and Eucyclops neumani) and three rotifers (Euchlanis dilatata, Lecane closterocerca, and Plationus patulus) have been identified for the first time in La Pampa province. This study confirms that the distribution of A. bergi and E. neumani is wider than known so far, which was restricted to Brazil and the Paraná - del Plata basin, but the remaining zooplankton are species widely distributed in Argentina. Thus, the lack of information in La Pampa was due to the absence of previous investigations.Fil: Echaniz, Santiago Andrés. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Vignatti, Alicia María. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Cabrera, Gabriela Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Kihn, Romina Gisela. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Stella, Cesar A.. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentin

Comparación de los parámetros limnológicos y el zooplancton de un lago somero salino de La Pampa (Argentina) durante dos ciclos anuales de condiciones diferentes

In central Argentina the alternation of cycles of rainfall above or below thehistoric mean is frequent; so, many saline lakes can dry or fill in a short time. As in La Pampamost of the studies on these lakes were limited to annual cycles, the information aboutvariations under different climatic conditions is scarce. The aims of this study were to determinethe limnological and zooplankton parameters of a semi-permanent Pampean saline lake during2013 posterior to its filling after a drought, to compare the information with that obtained in2007, because the two annual cycles had relatively different environmental characteristics andto test the hypotheses i) in 2013, after filling, scarce tolerant zooplankton species were recorded,replaced by more tolerant ones as salinity increased and ii) species richness in 2013 was greaterthan that recorded during higher hydrologic stability. Samples were taken between Januaryand December of both years. In 2007 depth was stable and in 2013 it fluctuated markedly. Themean salinity was similar, close to 26 g/L. In 2007 it was stable, but in 2013 rose from 14.3 g/L(January) to 40.4 g/L (December). Transparency was the highest in 2007 (0.76 m ± 0.26) and thelowest in 2013 (0.17 m ± 0.05). The concentration of chlorophyll a in 2007 was lower ( (1.73 mg/m3 ± 1.25) than in 2013 (38.16 mg/m3 ± 42.33). Species richness showed six species in 2007 andseven species in 2013. In 2007 crustaceans predominated, especially Boeckella poopoensis, but in2013 rotifers dominated. Among them, Brachionus plicatilis and B. dimidiatus presented amaximum in autumn (1702 and 2062 ind/L, respectively). Daphnia menucoensis was absentduring 2013 and the inverse correlation between the density of this cladoceran and chlorophylla concentration could show its influence on water transparency because of its grazing onphytoplankton. The differences in limnological parameters allow us to know the variability ofenvironmental conditions of a Pampean saline lake and to expand our knowledge about toleranceranges of some endemic species as B. poopoensis and Moina eugeniaeFil: Echaniz, Santiago Andrés. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Vignatti, Alicia María. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Cabrera, Gabriela Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Capecce, Candela. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Treffinger Cienfuegos, Maria Soledad. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

La limnología y el plancton de dos lagunas salinas de la reserva Parque Luro, provincia de La Pampa (Argentina)

In La Pampa province, limnological studies have been carried out in saline lakes, generally located in basins with agricultural exploitations. In Parque Luro Provincial Reserve there are two scarcely studied saline lakes: East and West Lakes. The objective was to analyze physical-chemical parameters and those of the plankton of these protected environments and compare them with other Pampean lakes under different anthropic influence. Monthly samples were collected between October 2014 and September 2015. In both lakes, Cl- and Na+ predominated, but salinity differed (East: 276.53 ±42.00 g/L, West 29.33 ±10.25 g/L). West Lake was covered by the macrophyte Ruppia cirrhosa and water was transparent. Accumulated phytoplankton richness was 30 taxa, and was negatively influenced by salinity, since the highest richness (22 taxa) was that of West Lake. In both lakes the most frequent species were Dunaliella salina and D. viridis. Fourteen taxa were found in zooplankton of both lakes, and richness was also influenced by salinity. In East Lake only Artemia persimilis was recorded and in West Lake the typical association of mesosaline Central Argentine lakes was recorded, in low density due to the dense coverage of the macrophyte.En la provincia de La Pampa se han realizado estudios limnológicos en cuerpos de agua de elevada salinidad, generalmente ubicados en cuencas con explotaciones agropecuarias. En la Reserva Parque Luro existen dos lagunas salinas escasamente estudiadas: Este y Oeste. El objetivo fue analizar parámetros físico-químicos y del fito y zooplancton de estos ambientes y compararlos con los de otras lagunas pampeanas bajo diferente influencia antrópica. Se colectaron muestras mensuales entre octubre de 2014 y septiembre de 2015. En ambas lagunas predominaron el Cl- y el Na+ pero la salinidad difirió (Este: 276,53 ±42,00 g/L; Oeste 29,33 ±10,25 g/L). La laguna Oeste se cubrió por la macrófita Ruppia cirrhosa y el agua fue transparente. La riqueza fitoplanctónica acumulada entre ambas lagunas fue 30 taxa y fue influida negativamente por la salinidad, ya que la mayor riqueza (22 taxa) se observó en Oeste. En ambas lagunas las especies más frecuentes fueron Dunaliella salina y D. viridis. En el zooplancton de ambas lagunas se registraron 14 taxa y la riqueza también fue influida por la salinidad. En Este sólo se registró Artemia persimilis y en Oeste se registró la asociación típica de lagos mesosalinos, en baja densidad, debido a la densa cobertura de la macrófita

Calidad de agua y zooplancton del embalse San Roque (Córdoba, Argentina)

Los embalses son lagos artificiales que se construyen con múltiples propósitos. Sólo en la provincia de Córdoba estos ambientes abarcan una superficie superior a las 15.000 ha, entre los cuales San Roque es uno de los más importantes por la multiplicidad de usos que tiene. La calidad del agua es fundamental para mantener la integridad biológica de estos ecosistemas. Por su parte, el zooplancton posee gran importancia ya que además de su influencia sobre la transparencia del agua, transfiere la energía del fitoplancton hacia niveles tróficos superiores. Se evaluaron diferentes variables de calidad del agua y se determinaron riqueza, abundancia y biomasa del zooplancton del embalse San Roque (31º 22? S, 64º 27? W, 2478 ha), comunidad que ha sido poco estudiada actualmente en este reservorio. Se realizaron muestreos estacionales durante un ciclo anual (período 2007-2008). La temperatura, concentración de oxígeno disuelto, pH y transparencia del agua mostraron diferencias significativas entre épocas del año (Kruskal-Wallis, P < 0,01), pero los valores se encuadraron dentro de limites guías. El promedio anual de sólidos disueltos fue 157,3 (± 40,9 mg.l-1), mientras que la concentración de clorofila a máxima fue 66 μg.l-1. En la comunidad zooplanctónica, los cladóceros mostraron diferencias significativas entre épocas del año (P < 0,05), con mayor abundancia y biomasa en primavera (99,1 ind.l-1 y 81,09 μg.l-1 respectivamente), se identificaron 7 especies entre las que Bosmina longirostris fue la más frecuente. Los copépodos, en cambio, no presentaron diferencias estacionales (P = 0,07), con una mayor frecuencia de ciclopoideos.Fil: Mancini, Miguel. Universidad Nacional de Río Cuarto; ArgentinaFil: Bethular, Ana. Universidad Nacional de Río Cuarto; ArgentinaFil: Vignatti, Alicia María. Universidad Nacional de La Pampa; ArgentinaFil: Echaniz, Santiago Andrés. Universidad Nacional de La Pampa; ArgentinaFil: Bonansea, Matias. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; ArgentinaFil: Salinas, Victor Hugo. Universidad Nacional de Río Cuarto; ArgentinaFil: Rodriguez, Maria Claudia. Universidad Nacional de Río Cuarto; Argentin