Diversity and changes in the horizontal distribution of crustaceans and rotifers in an episodic wetland of the central region of Argentina

Abstract

Although episodic wetlands are very frequent environments in Argentina, the knowledge about their ecology is scarce. Thus, the aim of this study was to describe the diversity and changes in the horizontal distribution of crustaceans and rotifers in the episodic wetland El Guanaco, Province of La Pampa, Argentina, during the hydroperiod that took place between December 2003 and March 2004. After three years during which it was dry, torrential rains made it reach a depth of 0.42 m. After 48 hours, ovigerous females and males of Metacyclops mendocinus (Wierzejeski 1892), juveniles of Moina wierzejskii (Richard 1895), and larvae of Triops longicaudatus (LeConte 1846) were recorded. The conductivity was reduced, the ionic content was dominated by bicarbonates and sodium and the concentrations of nutrients were high. The samplings were carried out in three stations, which at first were in open waters. The stations presented a homogeneous horizontal distribution of microcrustaceans and rotifers, with a predominance of limnetic species. Later, two of the stations were surrounded by Eleocharis macrostachya Britton plants, which allowed us to determine changes in the taxonomic composition and the appearance of species associated with the presence of vegetation. We recorded 35 taxa, being Moina micrura Kurz 1874 constantly present and highest in numbers. Among rotifers, the genus Brachionus was the predominant one. The species richness was higher in the station which was covered by E. macrostachya plants. After a period of high temperatures, we observed that the richness and abundance of microcrustaceans decreased, whereas those of rotifers increased. Resumen: El conocimiento sobre la ecología de los humedales episódicos de Argentina es escaso, a pesar de que son ambientes muy frecuentes. El objetivo de este estudio es describir la diversidad y los cambios en la distribución horizontal de los crustáceos y rotíferos que ocurrieron durante el hidroperíodo que tuvo lugar entre diciembre de 2003 y marzo de 2004 en El Guanaco, un humedal episódico, alimentado por precipitaciones, de la provincia de La Pampa. Luego de tres años en los que permaneció seco, lluvias torrenciales hicieron que alcanzara una profundidad de 0,42 m. A las 48 horas del llenado se registraron hembras ovígeras y machos de Metacyclops mendocinus (Wierzejeski 1892), juveniles de Moina wierzejskii Richard 1895 y larvas de Triops longicaudatus (LeConte 1846). La conductividad fue reducida, el contenido iónico estuvo dominado por bicarbonatos y sodio y las concentraciones de nutrientes fueron elevadas. Los muestreos se hicieron en tres estaciones, que al inicio estaban en agua abierta, y presentaron una distribución horizontal de microcrustáceos y rotíferos homogénea, con predominio de especies limnéticas. Posteriormente, dos estaciones quedaron ubicadas en un juncal de Eleocharis macrostachya Britton, a partir de lo cual se verificaron cambios en la composición taxonómica, con la aparición de especies asociadas a la vegetación. Se registraron 35 taxa...

Zooplankton diversity and its relationship with environmental changes after the filling of a temporary saline lake in the semi-arid region of La Pampa Argentina

“…The type of water input and high evapotranspiration of the region lead the shallow lakes of La Pampa suffer large variations in their level and extension, sometimes abrupt, a feature also verified in El Guanaco lake, which, after being dry for several years, reached a depth of near 0.5 m during a single rain occurred in December 2003 (Echaniz & Vignatti, 2010).…”

“…Despite the abundance of these ecosystems in the province of La Pampa, in the central region of Argentina, there is only one study on zooplankton diversity and changes in some of the physical and chemical parameters that occurred from the filling until the drying of wetlands (Echaniz & Vignatti, 2010), although this was a subsaline environment (Hammer, 1986).…”

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“…Ethnoherpetology is a subdivision of Ethnozoology that examines the relationships between human cultures and herpetofauna [3,14-16]. Very few ethnoherpetological studies have been undertaken in Brazil [4,13,17-22], which restricts our ability to elaborate adequate conservation strategies for many species [3,23]. …”

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