Comparative Microbiological and Biogeochemical Characterization of Devils Hole and the Ash Meadows Fish Conservation Facility, a Manmade Analog

Devils Hole (DH) is the sole natural habitat of the critically endangered Devils Hole Pupfish (DHP, Cyprinodon diabolis). To establish a backup population, the Ash Meadows Fish Conservation Facility (AMFCF), a manmade full-scale replica of the subaqueous portion of DH, was constructed. Despite efforts to mimic the DH environment, the microbiology and biogeochemical function of the AMFCF remains largely unaddressed. Using next-generation DNA sequencing, we evaluated planktonic and benthic aquatic microbial community composition within the context of biogeochemical controls on nutrient and energy fluxes in both DH and AMFCF. DH and the AMFCF are microbiologically diverse, with over 40 phyla represented at each site, nearly half from candidate divisions. Predicted primary producers (Cyanobacteria) were markedly different between DH and the AMFCF: the genera, Spirulina and Oscillatoria dominated in DH (26.8% and 7.8% mean abundance); yet proved virtually undetectable in the AMFCF. Conversely, the AMFCF was dominated by the Verrucomicrobiaceae family and Planctomyces species (33.3% and 11.9%, respectively); which were comparatively rare (2.2%) and undetected, respectively, in DH. Major ion concentrations and physical parameters were consistent among the two systems; however, bioavailable nitrogen (primarily nitrate) was 5x lower in the AMFCF. DH vs. AMFCF nitrogen:phosphorus molar ratios were 107:1 and 22:1, indicative of different nutrient control mechanisms. We propose that the paucity of nitrate in the AMFCF is reflected in the microbial assemblage disparity, influences biogeochemical cycling of other dissolved constituents, and ultimately impacts survivorship and recruitment of refugium populations of the DHP.