Climate change in extreme microsystems: an example in microbialites Andean lakes

Abstract

Microbialites outcropping in "High Altitude Andean Lakes" (HAAL) at Puna Argentina, display interesting adaptations to extreme conditions like altitudes of 3000 mamsl, high salinity, UV radiation, As content, among others. Thus, these microbialites are considered fragile structures, unable to resist major environmental changes, and strongly depending of the physicochemical conditions of the lakes. But to what extent this is true?The ?Turquesa? lake (26º39´14´´ S, 68º10´42´´ W) (Catamarca), gives us an interesting opportunity to study the adaptation of microbialites to climatic changes. This lake is located a few meters to the north of ?El Peinado? lake, where Valero-Garces et al., (2001) indicates that the coast line is colonized also by a microbialitic level of finely laminated facies, which form small mounds up to 20cm thick.In 2019, through a field survey, and with the support of satellite images, we identified that in the ?Turquesa? lagoon the microbialitic level described by mentioned authors now is totally subaerial, suggesting that this lagoon was connected with the ?El Peinado? lake, but is supposed a fall of around 120cm in the water level which caused its isolation in the last twenty years. However, the most surprising process about this is the colonization of a new microbilitic system at the current coast level.These new microbialites forming a biostrome covering the entire perimeter of the lake, approximately 300cm below the water level. It is composed of tabular and domic structures, and display an internal carbonatic lamination.This microbialitic level show an exceptional growth rate estimated about of 6 to 8,5 mm/year, compared to modern carbonate microbialites in lakes. Its development, is a well documented evidence of the capability of microbiological communities to stablish new microbialites structures, adapting rapidly to changing conditions along the shoreline