Microbial biodiversity in saline shallow lakes of the Monegros Desert, Spain

The Monegros Desert contains one of the largest sets of inland saline lakes in Europe constituting a threatened landscape of great scientific and ecological value with large number of reported endemisms. We analyzed bacteria, archaea, and microbial eukaryotes from 11 saline lakes in winter and spring by rRNA gene fingerprinting and sequencing covering large salinity (2.7-22.1%) and temperature ranges (1.5-35.3 degrees C). The highest ecological diversity (Shannon-Weaver index) was found in protists and the lowest in Archaea. Eukaryotes showed higher ecological diversity at intermediate salinities, whereas Bacteria and Archaea did not. The genetic diversity was broad and with remarkable novelty. The highest novelty was found in Archaea at the lowest saline concentrations, whereas for bacteria and protists, no differences were observed along the gradient. Euryarchaeota of the enigmatic group DHVEG-6 and phylotypes distantly related to well-known haloarchaea were present in several sites. Recurrent presence of bacterial phylotypes distantly related to Psychroflexus and Cryomorphaceae initially isolated from polar marine habitats was observed. Saline lakes contained chlorophyta, among other new groups, substantially different from green algae previously reported in marine or freshwater. The great scientific and ecological value found for macroorganisms can be extended to the idiosyncratic microorganisms inhabiting such unique habitat in Europe.