MICROBIAL DIVERSITY AND COMMUNITY STRUCTURE OF DESERT SPRINGS ACROSS HYDROGEOCHEMICAL GRADIENTS IN THE SOUTHERN HYDROGRAPHIC GREAT BASIN

The southern hydrographic Great Basin, one of the most arid regions in North America, has many naturally occurring springs, which are oases for aquatic biological diversity. Despite the uniqueness of desert springs, little research has been conducted to explore the microbial communities present in this habitat. To address this gap, planktonic and benthic microbial community samples were collected from more than 70 springs and microbial communities were surveyed using Illumina 16S rRNA gene amplicon sequencing (V4 region). This microbial census has revealed a staggering diversity of microorganisms, with 107,789 unique DNA sequences being recovered, representing over 70 bacterial and archaeal phyla. In most springs, planktonic and benthic communities appear to be distinct. On average, the most abundant phyla in planktonic communities are Proteobacteria, Bacteroidetes, Firmicutes, Verrucomicrobia, Omnitrophica, and Woesearchaeota, whereas the most abundant phyla in benthic communities are Proteobacteria, Bacteroidetes, Cyanobacteria, Chloroflexi, Actinobacteria, and Acidobacteria. High-elevation springs, regardless of host rock (carbonate or granite), have significantly (p-value = 0.001) more similar microbial community structure to each other than to low-elevation springs. Physicochemical parameters observed to significantly (p-value = 0.001) correlate with large-scale shifts in microbial community structure between low- and high-elevation springs include temperature, specific conductance, and various cations and anions, including Ca⁺², Na⁺, Cl^-, and SO₄^-2. These results demonstrate that desert springs in the southern hydrographic Great Basin host incredible microbial diversity and that several factors may influence microbial community structure.