Zooplankton diversity of a protected and vulnerable wetland system in southern South America (Llancanelo area, Argentina)

Abstract

In arid regions, climatic conditions exert a great control on the aquatic systems present, but recent changes in climate have produced an enhanced salinization of the aquatic environments located there. Consequently, a major reduction in biodiversity would be expected in those wetlands that were originally fresh water. Salinity is a principal cause of reduced biodiversity particularly in zooplankton because few of those species can adapt to the salt pressure of saline environments. Therefore, the aim of this study was to gain essential information on the diversity of aquatic invertebrates in Llancanelo basin by focussing the analysis on the zooplankton community and exploring seasonal and spatial differences in the zooplankton assemblages of this vulnerable wetland system within an arid region of Argentina. Seasonal samples were taken at nine sites in the basin (a shallow lake, 4 springs, streams, and the Malargüe River). A total of 45 species were identified. The zooplankton abundance in the lake displayed a clear seasonal contrast and was higher than that recorded in the springs and lotic environments. Boeckella poopoensis, Fabrea salina, and Brachionus plicatilis predominated in the lake, indicating their halophilia. The presence of the crustaceans Alona sp., Macrocyclops albidus, and Paracyclops fimbriatus was restricted to the springs; whereas Notholca labis and Notholca squamula were found only in running water. The zooplankton species richness in the Llancanelo area is low because of both the salt content in the lake and the irregularity of freshwater entry in all locations during the annual cycle.

Life-history strategies in zooplankton promote coexistence of competitors in extreme environments with high metal content

“…Salinity was a main abiotic factor differentially affecting the two rotifer species. Salinity is known as a relevant driver of density and composition of zooplankton communities and populations of inland aquatic ecosystems 55 – 57 . In general, higher salinities are stressful 58 , and there is an inverse relationship between salinity and zooplankton richness and density 55 .…”

: Seasonal zooplankton dynamics and its relations with environmental factors in Dalcar Urban Lake (Córdoba, Argentina)

“…Para analizar la relación entre la abundancia de los diferentes taxa y su frecuencia de aparición, se aplicó el test no paramétrico con gráficos de cuadrantes de Olmstead y Tukey (Sokal & Rohlf, 1995), en el que se graficó la abundancia de cada especie sobre las ordenadas versus la frecuencia de ocurrencia de cada una (%) en las abscisas. Esto permite distinguir cuatro categorías: especies frecuentes y abundantes (dominantes, cuadrante I); abundantes e infrecuentes (especies ocasionales, cuadrante II), especies infrecuentes y escasas (especies raras, cuadrante III) y frecuentes pero escasas (comunes, cuadrante IV) (D'Ambrosio et al, 2016).…”

Is the zooplankton of mesosaline lakes in protected areas in the semiarid Pampa of Argentina different from those in lakes with high anthropic influence?

“…The dry Pampas region is located in the center of the arid and semiarid diagonal that crosses Argentina in a north-south direction (Ruggiero & Ezcurra 2003;D'Ambrosio et al 2016). The central Pampa has a precipitation gradient ranging from about 800 mm/yr to the east to about 300 mm/yr to the west (Casagrande et al 2006), which determines marked phytogeographical differences (Cabrera 1976) and therefore differences in the human activities that develop along that gradient.…”