Extreme climates, extreme habitats : a paleoecological study in Lake EL Sello, the volcanic Buenos Aires Plateau, southern Patagonia

PEREZ, ALEJANDRA PATRICIA; MASSAFERRO, JULIETA; CHARQUEÑO, FLORENCIA; JULIO L. LANCELOTTI

San Carlos de Bariloche

Congreso; Lakes as Memories of the Landscape; 2022

Universidad Nacional de la Patagonia --CONICET

The Buenos Aires Plateau (Santa Cruz, Argentina) is a bed of alkaline basalt formed during tectonic episodes in the Miocene-Pliocene periods. It covers an area of 3650 km2 holding more than 150 endorheic shallow lakes, highly exposed to the westerlies winds. During the last years, several lakes have suffered substantial water level reduction, with negative consequences on the aquatic communities. Example of this is the shallow lake El Sello (-46.9234º, -71.3374º, 1466 m asl), the largest lake of this plateau. In the last 38 years, it was observed a reduction of the area lake by 52% (current area c.a. 8.4 km2, associated with the decrease in rainfall). Four annual samplings were carried out between 2015 and 2019. We present preliminary data obtained from analyzing a sediment core of 50 cm, of this lake to infer the recent past environmental conditions in the area . According to the lake level reduction, we observed in present times a concentration process measured in the physicochemical water properties, i.e increase in electrical conductivity (126 to 204.6 uS/cm), TP (0.012 to 0.1 ug/l), Chla 1.53 to 2.79 ug/l and DOC (9.5 to 19 ppm). Phytoplanktonic community was dominated by the chlorophyceae Monoraphidium, while Boeckella was the most abundant copepod, together with the cladoceran Alona, and the ostracoda Cypridopsis. We also registered the presence of the submerged macrophyte Myriophyllum quitense. We detected 5 tephra levels (1, 8, 23-27, 43 cm) along the core. At the moment, the remains bioproxies recovered were ephippias, cladocerans (Chydorus), testate amoebas (Diffulgia oblonga), chironomids (Cricotopus) and oogoniums (Chara). This is a first attempt to develop a palaeoecological study in these basaltic patagonian plateau. We expect to find changes in the biota assemblage related to the extreme climate conditions of the area which let integrate with environment and climatic events in Patagonia.