MICROBIAL DIVERSITY AND GEOCHEMICAL CYCLING OF UNIQUE CARBONATE SPINGS IN NOTHERN NEW MEXICO:THE GEOMICROBIOLOGY OF TIERRA AMARILLA ANTICLINE

This interdisciplinary research explores the geochemistry and microbial heterogeneity within a unique set of desert springs in northern-central New Mexico. These travertine-depositing CO₂-rich springs are located along the boundary zone between the Colorado Plateau and Rio Grande rift, on the southern extension of the Nacimiento fault at the Tierra Amarilla anticline (TA). Carbon isotope values range from -4.6 to -8.1 per mil, suggesting that some of the CO₂ is also deeply derived (endogenic). Based on an average of 8 samples, water chemistry modeling indicates CO₂ is 5.49±8 % from dissolved carbonate in the aquifer (Ccarb), 4.77 ± 9.16 % from organic derivation (Corg), and 89.74 ± 11.22 % from deep sources (Cendo). Stable isotopes of the water fall to the right of the meteoric water line suggesting that these warm springs have a component perhaps related to distal effects of the Valles Caldera hydrothermal system with fluid transport up and along extensional faults networks near the boundary of the Rio Grande rift. Microbiological studies involved DGGE and 454-sequencing analyses. Microbiological species identified include Zetaproteobacteria, Vibrio diaztrophicus, and Algoriphagus sp. LYX05, and Candidatus ‘Nitrotoga.’ The Zetaproteobacteria are also found in submarine seamount communities. 454-sequence data deteremined Archaeal species that are within the phylotype Methanosarcinales, a phylotype dominant in Lost City hydrothermal field. We calculated the chemical affinity for metabolically favorable reactions. Results show that oxidation of hydrogen, manganese, and hydrogen sulfide which are all metabolic reactions similar to those utilized by the Lost City Hydrothermal field communities are thermodynamically favorable in the spring at TA. The presence of similar terrestrial communities in TA warm springs is interpreted to reflect endemic ecosystems that have evolved in ambient-temperature terrestrial springs because metabolic processes are similar to chemolithotrophs found in deep-sea vents. Results of this study have important implications for understanding water quality of unique microbial ecosystems in northern New Mexico.