Microbial Communities Composition, Activity, and Dynamics at Salar de Huasco: A Polyextreme Environment in the Chilean Altiplano

Abstract

Salar de Huasco is a high-altitude (3800 m a.s.l.) polyextreme aquatic environment located in the Chilean Altiplano. This chapter highlights over 15 years of microbial ecology research conducted in this fascinating system covering microbial diversity, microbial adaptation to extreme conditions, and the role of microbes in biogeochemical cycles, including the recycling of greenhouse gases. Salar de Huasco is representative of other active saline wetlands in the same area harboring a high biodiversity. The important spatial and temporal variability of this ecosystem configure a unique environment for the study of the diversity and function of microbial communities. Salar de Huasco supports very high microbial diversity: studies so far have identified the presence of more than 50% of all bacterial phyla and the three archaeal superphylum described globally. Eukaryotic communities have been less studied, but recent efforts have highlighted their high endemism in Salar de Huasco. Microbial communities have been shown to play an active role in nitrogen, carbon, and sulfur cycles, intensely recycling greenhouse gases and representing a source of CH4, CO2, and a sink of N2O in this ecosystem. It has become apparent that microbial communities in the salar are highly adapted to polyextreme conditions, allowing them to withstand simultaneous environmental stressors, including extremely high solar radiation, salinity, and marked diel shifts in temperature. The production of compatible solutes within the microbial community plays a key role as a protection mechanism against such harmful conditions. Notwithstanding the concerted efforts by both our group and other colleagues to understand the dynamic of the microbiome in Salar de Huasco, many unsolved questions remain, especially regarding biological and ecological interactions within the microbial communities, as well as other temporal and spatial factors. Evaporitic basins in the Andes are currently under marked threat, largely due to extraction of water to support mining, and there is an urgent and pressing need to preserve and conserve this still understudied environment.