Paper No. 17
Presentation Time: 1:00 PM


SCOTT, Tabetha Juliann, Geosciences, University of Rhode Island, P.O. Box44, West Kingston, RI 02892, HOEHLER, Tori M., Exobiology Branch, NASA Ames Research Center, Moffett Field, CA 94035, MCCOLLOM, Tom M., Laboratory for Atmospheric and Space Physics, University of Colorado, 1234 Innovation Drive, Boulder, CO 80309, SCHRENK, Matthew O., Biology, East Carolina University, MS 551, Greenville, NC 27858 and CARDACE, Dawn, Department of Geosciences, University of Rhode Island, 9 East Alumni Avenue, Woodward Hall, Kingston, RI 02881,

The deep biosphere in cold, dark sub-seafloor ultramafic rocks (i.e., those rocks rich in Fe and Mg) is stressed by exceedingly high pH, transient, if any, inorganic carbon availability, and little known organic carbon inventories. As a test of heterotrophic carbon use, serpentinite-associated waters (from groundwater sampling wells and associated surface seepages in tectonically uplifted mantle units in ophiolites) were tested for differences with respect to aqueous geochemistry and performance in EcoPlates™ - Biolog Inc. This work focuses on the Coast Range Ophiolite, CA field locations for water sampling.

Characteristics of each sampling site are presented (pH, mineral substrate, Ca2+/Mg2+ ratio, aqueous metal loads, etc.). Complementary EcoPlate™ results [prefabricated 96-well plates, seeded with triplicate experiments for determining microbiological community response to difference organic carbon sources; a triplicate control experiment with just water is built in to the plate also] are also presented. We found that waters from selected California groundwater wells (7 discrete wells) and related surface seeps (5 hydrologically connected sites) sourced in serpentinites were analyzed. EcoPlate™ average well-color development (AWCD), which reflects microbial activities averaged per plate (as in Garland and Mills, 1991), differs across sites. Correlations of AWCD with environmental data (such as pH, oxidation-reduction potential or ORP, Ca2+/Mg2+ ratio, and Fe contents) are evaluated.

Clarifying the geochemical-biological relationships that bear out in these analyses informs discourse on the energetic limits of life in serpentinizing systems, with relevance to ultramafic-hosted life on continents and in the seabed