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      Zooplankton richness, abundance and biomass of two hypertrophic shallow lakes with different salinity in central Argentina Translated title: Riqueza, abundancia y biomasa zooplanctónica de dos lagos someros hipertróficos de distinta salinidad de la región central de Argentina

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          Abstract

          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.

          Translated abstract

          El zooplancton lacustre es controlado por parámetros biológicos y fisicoquímicos. Entre los primeros, la depredación por peces puede determinar el reemplazo de especies de talla grande por pequeñas y entre los segundos la salinidad ejerce efectos negativos sobre la riqueza y abundancia. Dado que se ha indicado que los lagos salinos sin peces tienen mayores biomasas zooplanctónicas que los de baja salinidad, el objetivo de este trabajo es conocer la riqueza, abundancia y biomasa del zooplancton de dos lagos de diferente salinidad y probar la hipótesis de que a iguales concentraciones de nutrientes y clorofila "a" los lagos salinos tienen mayor biomasa que los de baja salinidad. El estudio se desarrolló en dos lagos de la provincia de La Pampa, en el centro de Argentina, uno subsalino y otro hiposalino, que compartieron elevadas concentraciones de clorofila a y fósforo total, reducida transparencia y presencia de un pez planctófago. Aunque la riqueza resultó diferente y más elevada en el lago subsalino, no ocurrió lo mismo con la abundancia y biomasa totales, ni al considerar los grupos taxonómicos por separado. La presencia de un pez planctívoro halotolerante controló la talla del zooplancton debido a la depredación sobre las especies de mayor tamaño e impidió el desarrollo de mayor biomasa en el lago salino, lo que constituye una importante diferencia con situaciones registradas anteriormente. Este estudio mostró que a pesar de la diferencia en la salinidad, el efecto en cascada en la cadena trófica (top down) es un factor que iguala la biomasa zooplanctónica al permitir sólo el desarrollo de especies pequeñas y pone en evidencia la importancia de la depredación por peces en la determinación de las concentraciones de clorofila y transparencia del agua.

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          Most cited references 51

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          Biostatistical Analisis

           J.H. Zar,  JH Zar,  J. H. ZAR (1999)
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            The dry weight estimate of biomass in a selection of Cladocera, Copepoda and Rotifera from the plankton, periphyton and benthos of continental waters

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              Ecology of shallow lakes

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                Author and article information

                Contributors
                Role: ND
                Role: ND
                Role: ND
                Role: ND
                Journal
                bn
                Biota Neotropica
                Biota Neotrop.
                Instituto Virtual da Biodiversidade | BIOTA - FAPESP (Campinas )
                1676-0611
                June 2012
                : 12
                : 2
                : 41-48
                Affiliations
                [1 ] Universidad Nacional de La Pampa Argentina
                [2 ] Consejo Nacional de Investigaciones Cientificas y Técnicas
                [3 ] Universidad Nacional del Litoral Argentina
                Article
                S1676-06032012000200005
                10.1590/S1676-06032012000200005
                Product
                Product Information: website
                Categories
                BIODIVERSITY CONSERVATION

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