HR: 1340h
AN: T33A-0525    [Abstracts]
TI: Bacterial Diversity of Young Seafloor Basalts: A Potential Role for Microorganisms in Ocean Crust Weathering
AU: * Santelli, C M
EM: csantelli@whoi.edu
AF: MIT/WHOI Joint Program, Woods Hole Oceanographic Inst. 360 Woods Hole Rd., MS #8, Woods Hole, MA 02543 United States
AU: Edgcomb, V
EM: vedgcomb@whoi.edu
AF: Dept. of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Inst. 360 Woods Hole Rd., MS #8, Woods Hole, MA 02543 United States
AU: Bach, W
EM: wbach@whoi.edu
AF: Dept. of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Inst. 360 Woods Hole Rd., MS #8, Woods Hole, MA 02543 United States
AU: Edwards, K
EM: katrina@whoi.edu
AF: Dept. of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Inst. 360 Woods Hole Rd., MS #8, Woods Hole, MA 02543 United States
AB: A growing number of studies indicate that microbial communities exist within the oceanic crust on mid-ocean ridge flanks. Young ocean crust that is exposed at the seafloor or in the shallow subseafloor interacts directly with low-temperature, oxygenated fluids and undergoes alteration. The free energy associated with oxidation of reduced species in the basalt could potentially be used by microbial communities for growth. Basaltic rock habitats at and below the seafloor, however, remain poorly studied with respect to the physiological and phylogenetic diversity of microbial communities that may be supported by oxidative weathering reactions. In this study, we have investigated the diversity of microorganisms living on or within basaltic crust at the seafloor, and the changes in these microbial communities with increasing oxidative rock alteration. Seafloor lavas representing various flow morphologies, alteration states, and ages (up to 20 kyrs) were collected from the East Pacific Rise between 9°28'N and 9°50'N. Total community DNA was extracted and bacterial 16S rRNA was amplified by PCR. Clone libraries were constructed and sequenced for phylogenetic analyses. To assess the overall extent of basalt alteration and quantify cell abundance in relation to surfacial weathering products, a combination of confocal laser scanning microscopy and scanning electron microscopy was used on natural, unprocessed samples. Phylogenetic and microscopic analyses indicate that diverse, yet distinct populations of bacteria inhabit different lavas, and these microbial communities shift with changes in basalt alteration state. A general trend from metal and sulfur-oxidizing autotrophic communities towards metal- and sulfur-reducing populations correlates with apparent increasing accumulation of weathering products (oxides, clays, etc.). These results provide insight into phylogenetic population trends among bacterial communities harbored in basalt during ocean crust weathering.
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 3015 Heat flow (benthic)
DE: 4832 Hydrothermal systems (0450, 1034, 3017, 3616, 8135, 8424)
DE: 5139 Transport properties
DE: 8125 Evolution of the Earth (0325)
SC: Tectonophysics [T]
MN: Fall Meeting 2005