A Deeper Look into the Biodiversity of the Extremely Acidic Copahue volcano-Rio Agrio System in Neuquen, Argentina

The Copahue volcano-Rio Agrio system, on Patagonia Argentina, comprises the naturally acidic river Rio Agrio, that runs from a few meters down the Copahue volcano crater to more than 40 km maintaining low pH waters, and the acidic lagoon that sporadically forms on the crater of the volcano, which is studied for the first time in this work. We used next-generation sequencing of the 16S rRNA gene of the entire prokaryotic community to study the biodiversity of this poorly explored extreme environment. The correlation of the operational taxonomic units (OTUs)s presence with physicochemical variables showed that the system contains three distinct environments: the crater lagoon, the Upper Rio Agrio, and the Salto del Agrio waterfall, a point located approximately 12 km down the origin of the river, after it emerges from the Caviahue lake. The prokaryotic community of the Copahue Volcano-Rio Agrio system is mainly formed by acidic bacteria and archaea, such as Acidithiobacillus, Ferroplasma, and Leptospirillum, which have been isolated from similar environments around the world. These results support the idea of a ubiquitous acidic biodiversity; however, this highly interesting extreme environment also has apparently autochthonous species such as Sulfuriferula, Acidianus copahuensis, and strains of Acidibacillus and Alicyclobacillus.