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 eugeniae

Fil: Treffinger Cienfuegos, Maria Soledad. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Fil: Cabrera, Gabriela Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentina

Fil: Echaniz, Santiago Andrés. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentina

Fil: Vignatti, Alicia María. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentina

Fil: Capecce, Candela. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales; Argentina