A Unique Natural Laboratory to Study Polyextremophile Microorganisms: Diamante Lake as a Window to the Origin of Life

STEPANENKO, TATIANA MARIEL; SORIA, MARIANA NOELIA; SAONA, LUIS ALBERTO; LENCINA, AGUSTINA INÉS; FARÍAS, MARÍA EUGENIA

Microbial Ecosystems in Central Andes Extreme Environments

Springer

Año: 2020; p. 113 - 120

Diamante Lake is located in the caldera of the Galán Volcano at a height of 4589 ma.s.l. (coordinates: 26°00′51.04″S, 67°01′46.42″O; Fig. 8.1a, b). The Galán, locatedin the province of Catamarca in the Puna Argentina, is cataloged as a supervolcanoand multiple eruptions between the upper Miocene to the Pleistocene are recorded(Ruggieri et al. 2011; Soler et al. 2007). The caldera is elliptical in shape, 40 km by24 km in size, with its longest axis extending in a north?south direction. The floorof the caldera is at an altitude of about 4.5 km; the highest points on the caldera wallreach about 6 km and the resurgent centre reaches a similar height. Doming anduplift in this area presumably preceded the eruption of ignimbrites from ring fracturesand subsequent collapse of the caldera floor along the ring fractures. Severalother major volcanic structures are known in the Central Andes; however, the calderaof the Galán Volcano seems to be unique at present in possessing well definedring fractures and a resurgent centre and in its association with rift faulting (Franciset al. 1978).After the Galán Caldera eruption, a lake formed in the caldera on top of ignimbritesdeposits. Talus apron and fluvial fans formed, sloping into the depression asthe caldera walls eroded (Sparks et al. 1985).Diamante Lake is ~7 km long and ~3 km wide at the widest part, with the longestaxis oriented NW?SE. A larger lake probably existed before resurgence took place(Francis et al. 1978).Diamante Lake presents characteristics that make it a place not only of touristinterest but also a key site for scientific research. It is a natural laboratory?stillunexplored?where we can study, among other things, the adaptation, survival andevolution of microbial ecosystems under extreme conditions. The high UV radiation(84 W m−2 of UVA-B at noon), the high salinity (270 g l−1, 217 mS cm−1),alkaline pH (9?11), the low oxygen pressure, the high heavy metal concentrationfrom volcanic action and high day?night thermal fluctuation (from −20 to 20 °C)are some of the conditions found in Diamante Lake. In the midst of these extremenatural conditions, Andean microbial ecosystems (AME) forming a red biofilmhave been found and studied (Rascovan et al. 2016; Ordoñez et al. 2018 ), and theyare associated with gaylussite crystals on the bottom of the calcareous rocks presentin the lake (Fig. 8.1c, d).