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

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.

Composition and abundance of the mesozooplancton in Sauce Grande shallow lake (Buenos Aires Province, Argentina)

“…La elevada con-centración de Clo-a y los valores obtenidos a través del índice de estado trófico de Carlson, reflejan el carácter eutrófico de la laguna Sauce Grande, lo cual también se evidencia a través del contenido de nutrientes en dicho cuerpo de agua. La riqueza específica resultó baja en la laguna Sauce Grande, similar a lo mencionado para otros lagos hipohalinos de la región (Echaniz et al 2012, Vignatti et al 2012b. De los siete taxa registrados, dos especies de copépodos (B. poopoensis y A. robustus) y una de cladócero (M. micrura) resultaron dominantes y representativas de la comunidad.…”

“…Esta situación coincide con lo ya indicado por Alfonso (2013) en un estudio restringido a los meses del otoño de 2010, en el cual se observa la dominancia de los cladóceros en marzo y como fue cambiando esa dominancia gradualmente por los copépodos hacia el mes de mayo. Las abundancias registradas en la laguna Sauce Grande fueron menores a las mencionadas para otros cuerpos de agua hipohalinos de la región (Echaniz et al 2009, Arora & Mehra 2009, Echaniz et al 2012. Se destaca la presencia de B. poopoensis, especie característica en cuerpos de agua de salinidad elevada, coexistiendo con especies típicas de baja salinidad (e.g.…”

“…Chascomús, Don Tomás) (e.g. Diovisalvi et al 2010, Echaniz et al 2012) y se ha mencionado en estudios previos en la laguna Sauce Grande (Alfonso 2013). Con excepción de D. spinulata, la cual es comúnmente observada al sur de América del Sur y es considerada como típica de aguas hipohalinas frías de la Argentina (Olivier 1962), los cladóceros hallados durante este estudio representan especies típicas de lagos de la región central de Argentina, caracterizados por salinidades intermedias a bajas (Ringuelet et al 1967b.…”

Influence of environmental factors on zooplankton assemblages in Bosten Lake, a large oligosaline lake in arid northwestern China

“…In the present study, most of the detected zooplankton taxa were freshwater species. Nevertheless, many of them have also been detected in saline lakes, for example, 36,37 , which means that many zooplankton taxa in Bosten Lake have a good adaptability to salinization. Furthermore, the negative relationship between microfauna community and salinity levels in lakes may be driven by one particularly diverse or dominant taxonomic group which constitutes a significant proportion of the species in a system 38 .…”

Determination of the Optimal Culture Medium and Salts for Bioassays with Neotropical Halophilic Cladocerans

“…In the absence of fish predation that may exclude it from aquatic ecosystems, it has been determined that its large size and high filtration efficiency endow it with a high grazing rate for phytoplankton. This means that the lakes it inhabits will be clear, with low chlorophyll-a concentrations and high water transparency [11], despite being hypertrophic [8,17]. In the case of the genus Moina, halophilic species are more common, such as M. mongolica whose distribution extends from northern Africa, eastern and central Europe to Mongolia [18], M. salina with a circummediterranean distribution [18,19], M. baylyi in Australia [18] and M. hutchinsoni in North America [20].…”