An Unusual Inverted Saline Microbial Mat Community in an Interdune Sabkha in the Rub' al Khali (the Empty Quarter), United Arab Emirates

• Published in: PloS one 2016-03, Vol.11 (3), p.e0150342-e0150342
• Main Authors: McKay, Christopher P, Rask, Jon C, Detweiler, Angela M, Bebout, Brad M, Everroad, R Craig, Lee, Jackson Z, Chanton, Jeffrey P, Mayer, Marisa H, Caraballo, Adrian A L, Kapili, Bennett, Al-Awar, Meshgan, Al-Farraj, Asma
• Format: Article
• Language: English
• Subjects: Analogs; Analysis; Aquatic ecosystems; Aquifers; Archaea - classification; Archaea - isolation & purification; Aridity; Bacteria - classification; Bacteria - isolation & purification; Biology and Life Sciences; Biomarkers; Deoxyribonucleic acid; Desert environments; Deserts; DNA; Earth Sciences; Ecosystem; Ecosystems; Extraterrestrial life; Flats (landforms); Gases; Genomes; Groundwater; Gypsum; Halites; Influence; Life on Mars; Mars; Mars surface; Microbial colonies; Microbiology; Microbiota; Microorganisms; Oxidation; Physical Sciences; Research and Analysis Methods; Salinity; Salinity gradients; Salt deposits; Salt flats; Salts; Sediments; Surface flow; United Arab Emirates; Water Microbiology
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0150342

Salt flats (sabkha) are a recognized habitat for microbial life in desert environments and as analogs of habitats for possible life on Mars. Here we report on the physical setting and microbiology of interdune sabkhas among the large dunes in the Rub' al Khali (the Empty Quarter) in Liwa Oasis, United Arab Emirates. The salt flats, composed of gypsum and halite, are moistened by relatively fresh ground water. The result is a salinity gradient that is inverted compared to most salt flat communities with the hypersaline layer at the top and freshwater layers below. We describe and characterize a rich photosynthetically-based microbial ecosystem that is protected from the arid outside environment by a translucent salt crust. Gases collected from sediments under shallow ponds in the sabkha contain methane in concentrations as high as 3400 ppm. The salt crust could preserve biomarkers and other evidence for life in the salt after it dries out. Chloride-filled depressions have been identified on Mars and although surface flow of water is unlikely on Mars today, ground water is possible. Such a near surface system with modern groundwater flowing under ancient salt deposits could be present on Mars and could be accessed by surface rovers.