New Mexico Geological Society Annual Spring Meeting & Ft. Stanton Cave Conference — Abstracts

The Valles Caldera is a large volcanic feature in Northern New Mexico that has had geothermal activity since its formation at 1.25 Ma. Volcanic H2S is currently emitted along the western margin of the Caldera through fumaroles and in natural and artificial hot springs. We explored the microbial communities and processes associated with volcanically-influenced surface waters in the Sulfur Springs and Alamo Canyon area of Valles Caldera National Preserve, and in hot springs along the Jemez River to the south. Surface waters impacted by fumarolic gases in the Alamo Canyon and Sulfur Springs areas had pH values between 1.1 to 3.5, with dissolved sulfide concentrations from 10 μM up to 1 mM in areas with the most intense fumarolic activity. In contrast, hot springs at Soda Dam and an artificial spring in the town of Jemez Springs had temperatures between 37-70ºC, circumneutral pH values, and sulfide concentrations between 5-25 μM. Small subunit rRNA gene libraries from Alamo Bog had diverse eukaryotic algae and a wide variety of bacteria related to known chemoautotrophic sulfur oxidizers, including Sulfurimonas spp., Sulfuriferula spp., Halothiobacillus spp., and Thiomonas spp. The more acidic sites in Sulfur Springs are dominated by the bacterial and archaeal genera Acidithiobacillus, Sulfobacillus, Acidiphilium, and Acidiplasma. Green and white streamers from the Soda Dam springs were dominated by Sulfurovum, Thiofaba, Thiothrix, and several cyanobacterial taxa. The most acidic samples were the least diverse, but there was not a strong correlation between microbial diversity and pH. Diversity was also negatively correlated with dissolved sulfide concentration. Future work will continue to explore how geochemical factors influence microbial communities across the strong pH and temperature gradients in the Valles Caldera region.