The geochemistry and microbiology of two ephemeral playa lakes in the Western United States, Surprise Valley Alkali Lake (SVAL) and Eldorado Playa (EP), were examined over one wetting cycle, revealing dramatic temporal changes in suspended mineralogy, aqueous chemistry, and bacterial populations. In SVAL the predominant suspended mineral changed from smectite to vermiculite and clinoptilolite, which led to a depletion of soluble Mg2+. Nitrate became depleted in both playas as a result of biological nitrogen demand imparted by unusually dense microbial communities reaching ∼1 × 108 cultivable heterotrophs per ml of water. One hundred eighty eight bacterial isolates were obtained, representing sixty phylotypes and four phyla: Actinobacteria, Bacteroidetes, Proteobacteria, and Firmicutes. Phylogenetic analyses suggested that the microbial communities reflected different phases of succession, with SVAL changing from a diverse community with abundant Yonghaparkia to a less diverse late summer community with abundant Bacteroidetes and Proteobacteria such as Loktanella, Rhodobaca, Saccharospirillum, Flexibacter, and phylogenetically novel members of the Flexibacteriaceae. In EP, a diverse assemblage of bacteria often associated with soils was replaced very quickly by a much less even community dominated by Yonghaparkia, Sandarakinorhabdus, and relatives of Belliella baltica. Strikingly, the early summer microbial community from SVAL was not significantly different from the EP community that developed within one week of flooding, even though these playas are almost 1000 km apart, whereas sympatric communities in different phases of succession were different. To our knowledge, this is one of the first geomicrobiological studies of a recharge playa, the dominant playa type worldwide.
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Authors Moser and Labahn are also affiliated with the School of Life Sciences, UNLV. We are grateful to Natasha Zolotova and Everett Shock for assistance with aqueous chemistry and Jeremy A. Dodsworth, Michael R. Rosen, and Trista J. Vick for comments on drafts of the manuscript. This work was supported by NSF Grant Numbers EPS-9977809 and MCB-054865 and start-up funds from UNLV to BPH and from DRI to DPM. KC and JH were supported by fellowships through NSF Grants 0447416 and 0724226. This publication was also made possible by support to the Nevada Genomics Center through Grant Number P20 RR016464 from the National Center for Research Resources (NCRR), a component of the National Institutes of Health (NIH).
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