N-187. Exploration of the Microbial Communities at Devils Hole

M. C. Ehrsam1,2, S. K. Labahn1,3, T. Fisk4, M. Bower4, K. Acharya1, M. Stone1, D. P. Moser1;
1Desert Res. Inst., Las Vegas, NV, 2Univ. of Nevada Sch. of Med., Las Vegas, NV, 3Univ. of Nevada, Las Vegas, NV, 4Natl. Park Service, Death Valley, CA.

Devils Hole is a tectonically-formed water-filled cavern within a discharge zone of the vast regional aquifer that underlies much of southern Nevada and southeastern California. Located adjacent to Ash Meadows National Wildlife Refuge, Nye County, NV, Devils Hole is a hydrologic island in the desert; best known for its critically endangered Devils Hole Pupfish (Cyprinodon diabolis). As Devils Hole is filled by upwelling water from the deep regional aquifer via faults, we hypothesize that the microbial communities observed will be a combination of subsurface-derived microorganisms and those that grow within the limited photic zone at the surface. Whereas, the base of the Devils Hole food web remains largely unexplored, intermittent availability of solar energy, none during December and only four hours in July, could create temporally divergent microbial communities, which in turn may affect the availability of food resources for C. diabolis. In conjunction with an ongoing physical and chemical monitoring program, here we describe an initial molecular- and cultivation-based characterization of microbial communities at various times and depths within Devils Hole as well as several deeply sourced reference springs and test wells. Intensive sampling, which bracketed a rare (e.g. roughly semi-annual) storm-driven runoff event, was also performed to document microbial community response to sporadic inputs of allochthanoous C and N. Consistent with oligotrophic nutrient chemistry, Devils Hole consistently showed very low numbers of planktonic cells (e.g. about 1 x 103 aerobic heterotrophs and 1 x 101 iron and sulfate reducers). DNA fingerprinting (T-RFLP) analysis, supported by clone library data (16S rRNA gene sequencing), revealed considerable novel diversity, probably beyond the genus level. Major bacterial groups detected included (in order of abundance): Cyanobacteria; Planktomycetes; Beta-, Gamma- and Deltaproteobacteria; Bacteroidetes, Firmicutes, and OP11. Crenarchaeota within the Thermoprotei, were also detected.