EXPLORATION OF THE MICROBIAL DIVERSITY AND THE GEOCHEMICAL CHARACTERISTICS OF HOT SPRING WATERS IN THE BLACK CANYON, SOUTH OF HOOVER DAM, LAKE MEAD NATIONAL RECREATION AREA, NEVADA AND ARIZONA

Springs south of Hoover Dam support unique riparian ecosystems. This work will explore the microbial diversity and the geochemical characteristics of three hot springs to better understand their relationships. Water samples for metagenomics, major ions and stable isotope analysis was collected in 2018 & 2019 from Gold Strike Canyon, White Canyon (Arizona Hot Springs) and Boy Scout Canyon springs. Samples were subjected to whole genome sequencing and 16S amplicon sequencing. The microbiomes of these springs were separated into two physical categories: Surface biofilms and subsurface water borne microbes. Surface biofilms are dominated by thermophilic Cyanobacteria and filamentous Chloroflexi. Water borne samples are low in diversity and are dominated by a single species of thermophilic Deltaproteobacteria. Water temperature ranged from 50 to 60°C. Stable isotope concentrations ranged from δ¹⁸O -11.2 to -13.5 and from δ²H -86.5 to -104.8 ‰. These isotopic values fall in the isotopic trend identified by Moran et al (2015). This pattern indicates different contributions from two different recharge sources: Lake Mead and a local or a regional source. Several faults play an important role in the groundwater flow paths before discharging through volcanic rocks. The relationship between the biodiversity and the geochemistry of these springs may provide further insight into these flow paths.

Moran, M.J., Wilson, J.W., and Beard, L.S., 2015, Hydrogeology and sources of water to select springs in Black Canyon, south of Hoover Dam, Lake Mead National Recreation Area, Nevada and Arizona: U.S. Geological Survey Scientific Investigations Report 2015–5130, 61 p., http://dx.doi.org/10.3133/sir20155130.