Electrical conductivity as a driver of biological and geological spatial heterogeneity in the Puquios, Salar de Llamara, Atacama Desert, Chile

Abstract

Reputed to be the driest desert in the world, the Atacama Desert in the Central Andes of Northern Chile is an extreme environment with high UV radiation, wide temperature variation, and minimum precipitation. Scarce lagoons associated with salt flats (salars) in this desert are the surface expression of shallow groundwater; these ponds serve as refugia for life and often host microbial communities associated with evaporitic mineral deposition. Results based on multidisciplinary field campaigns and associated laboratory examination of samples collected from the Puquios of the Salar de Llamara in the Atacama Desert during austral summer provide unprecedented detail regarding the spatial heterogeneity of physical, chemical, and biological characteristics of these salar environments. Four main lagoons (‘Puquios’) and more than 400 smaller ponds occur within an area less than 5 km2, and are characterized by high variability in electrical conductivity, benthic and planktonic biota, microbiota, lagoon bottom type, and style of mineral deposition. Results suggest that electrical conductivity is a driving force of system heterogeneity. Such spatial heterogeneity within the Puquios is likely to be expanded with temporal observations incorporating expected seasonal changes in electrical conductivity. The complexity of these Andean ecosystems may be key to their ability to persist in extreme environments at the edge of habitability.

Detection of biosignatures in terrestrial Mars analogs: Strategical and technical assessments

“…El Tatio in the high-altitude Atacama is another representative Mars analog that demonstrates the presence of opaline silica deposits discovered on Mars, and silicified filaments of microorganisms are observed in many silica sinters of the El Tatio geothermal system (Ruff and Farmer, 2016). Moreover, A myriad of evaporitic salars (e.g., Salar de Atacama, Salar Grande, and Salar de Llamara) in the Atacama Desert are similar to evaporite-rich sedimentary deposits on Mars (Fernández-Remolar et al, 2013;Cubillos et al, 2018;Reid et al, 2021).…”

Environmental and Biological Controls on Sedimentary Bottom Types in the Puquios of the Salar de Llamara, Northern Chile

“…Most of the smaller ponds are located between Puquio 1 and Puquio 2, in a region termed the "Transition Zone" (Figure 1). A strong gradient in water chemistry and diverse bottom types are exhibited between Puquios 1 and 2 [3][4][5]. This sub-system, consisting of two main lakes and the smaller ponds characteristic of the Transition Zone are designated as the P1/P2 subsystem, and it is the focus of the present study.…”

“…Small lakes, often with high salinity, are common throughout the Atacama Desert, and many of these ponds host microbial ecosystems with associated mineral precipitation [2]. A recent study of one of these Andean Microbial Ecosystems, the Puquios in the Salar de Llamara, documented the spatial heterogeneity of water chemistry, freeliving biota, microbial communities, and bottom types, as well as identified electrical conductivity as the overall driver of biologic and geologic heterogeneity from data collected in the summer of 2017/2018 [3]. In the present paper, we extend the analysis of bottom types in the Puquios system with field data and samples collected in March 2019 and examine the effects of additional environmental parameters on mineral deposition to identify specific linkages between environmental factors and bottom types.…”

“…This sub-system, consisting of two main lakes and the smaller ponds characteristic of the Transition Zone are designated as the P1/P2 subsystem, and it is the focus of the present study. The ponds in the P1/P2 subsystem are all hydrologically connected, with ground water flow from southwest to northeast, and increasing EC from P1 to P2 [3][4][5]. Evaporation and subsurface water-rock interactions significantly influence brine composition across this gradien [4][5][6][7].…”

“…Evaporation and subsurface water-rock interactions significantly influence brine composition across this gradien [4][5][6][7]. Across this gradient, Reid et al [3] and Oehlert et al [5] observed a variety of microbial and crystalline bottom types that could be correlated with the EC. Ponds with relatively low EC values typically had flocculent microbial mat substrates with microbially influenced gypsum, carbonate and clay minerals.…”