Rocky Mountain Section - 64th Annual Meeting (9–11 May 2012)

Paper No. 3
Presentation Time: 9:00 AM


KOOSER, Ara1, CROSSEY, Laura J.1, HUGHES, Kaitlyn J.2, NORTHUP, Diana E.2, SPILDE, Michael N.3, MELIM, Leslie A.4 and BOSTON, Penelope J.5, (1)Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 87131, (2)Biology, University of New Mexico, MSC03-2020, 1 University of New Mexico, Albuquerque, NM 87131, (3)Institute of Meteoritics, University of New Mexico, MSC03-2050, Albuquerque, NM 87131, (4)Geology Department, Western Illinois Univ, 1 University Circle, Macomb, IL 61455, (5)Dept. of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, NM 87801,

Caves provide a unique window to study infiltrating meteoric water and underground microbial communities in an aquifer system. The caves of Carlsbad Caverns National Park in southeastern New Mexico contain numerous cave pools that trap infiltrating meteoric water as it passes through various faults and fractures in the bedrock. This study of the chemistry of waters in cave pools was conducted to determine the variation in cave pool water geochemistry, explain hydrogeologic variations in a geologic context, identify the processes that control variations in geochemistry and determine geochemical controls on modern bacteria communities.

Water samples were collected from 19 new cave pools; the results were integrated with published geochemistry from 192 cave pools, aquifer samples, and surface sites. The waters were analyzed for major and minor ions, modeled to explain flow paths, correlated with trends in structural data, and examined for thermodynamic potential to support metabolic reactions.

Infiltrating dolomitic waters dominate the character of the cave pools in the park. Variations in geochemistry of the cave pools can be explained by several geochemical processes: 1) meteoric water-rock interactions 2) outgassing of CO2 3) precipitation of minerals 4) evaporation and 5) mixing with deeply sourced CO2 charged waters. The geochemical data can then be coupled to microbial 16s sequences to produce an energetic profile of the bacteria cave pool community. The thermodynamic model of available energy for use by microbial communities predicted the potential for nitrate, nitrite, oxygen, and sulfate to be used as terminal electron acceptors.

A small number of geochemical processes that govern the variation in pool geochemistry give rise to a complex, unique geochemical history for each pool, thus each pool also has a unique microbial community.