MICROBIAL DIVERSITY, GEOCHEMISTRY AND DIEL FLUCTUATIONS IN TRAVERTINE MOUNDS AT TIERRA AMARILLA ANTICLINE, NEW MEXICO

A series of ambient temperature (~24 ^oC) mound springs located along the Tierra Amarilla (TA) anticline are related to a regional occurrence of CO₂-rich travertine depositing springs in north-central New Mexico. Previous work on CO_²-rich springs in the Southwest has shown that terrestrial CO₂-rich springs contain carbon and helium isotope evidence of the presence of endogenic fluids. In these deeply sourced springs the primary producers are Bacteria and Archaea, microorganisms that utilize redox reactions for metabolic pathways.

In order to answer the question of what role the physical environment has on the microbial diversity we examined the mound springs at TA anticline. We report on the geochemical composition, physical parameters, and the microbial communities of four springs. Microbial community analysis reveals that these springs, though not warm enough to be classified as hydrothermal, also have chemolithotrophic communities that are related to Archaea and Bacteria found in deep-sea hydrothermal vents and aerobic subseafloor methane-rich sediments. The fluctuations in temperature, pH, conductivity, water pressure, and dissolved oxygen were recorded over a four day period at ~5 minute intervals with a YSI-multi parameter sonde. Using site-specific geochemical analyses, the chemical affinities for dozens of metabolic reactions were calculated. Metabolic reactions for sulfur and nitrate reduction were found to be energetically favorable. Using several statistical approaches to evaluate how the chemistry affects the distribution and diversity of these microorgansisms, we compared the geochemical parameters with the community diversity. While the endogenic sources contribute only a small portion of the water in these systems, they provide reduced gases and other key nutrients that affect the community diversity in these springs. This interdisciplinary study incorporates geochemical and molecular results that link geochemical processes with the subsequent evolution of unique microbial communities.