New Mexico Geological Society Annual Spring Meeting — Abstracts

Previous research has shown an increase in microbial activity with decreased oxygen availability in the shallow alluvial aquifer associated with the Middle Rio Grande. The change in groundwater flow from being parallel with the river to flowing from channel to riverside drain has increased Darcian flow velocity and the flux of sulfate, dissolved organic carbon, and nutrients to aquifer sediments. Chemoautotrophic microorganisms substitute terminal electron-accepting processes in the absence of oxygen to drive more thermodynamically favorable mineral changes as they oxidize organic matter. Geochemical evidence of associated groundwater in the Middle Rio Grande from Vinson et al. show authigenic mineral formation as a result of microbial competitive relationships in sulfidic aquifers. Filamentous phosphate growth and increased bicarbonate concentrations from river to drain further suggest active microbial respiration. Bimolecular analysis of groundwater in the San Antonio oxbow, Albuquerque, NM, is used in this study to identify the dominant functional groups and overall diversity of microorganisms in this environment.

DNA was extracted from groundwater samples using a sucrose lysis method and amplified the polymerase chain reaction (PCR). Unique PCR products separated by denaturing-gradient gel electrophoresis (DGGE) and will be identified by sequencing. Preliminary result of the DGGE indicate potentially high bacterial diversity and low heterogeneity within the shallow alluvial groundwater adjacent to the Middle Rio Grande.