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Proceedings Paper

Changes in carbon cycling under lowered sulfate conditions in hypersaline microbial mats as ascertained by stable carbon isotopes
Author(s): Cheryl A. Kelley; Brad M. Bebout; Leslie E. Prufert-Bebout; Jason M. Smith
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Paper Abstract

The salinity and sulfate concentrations of microbial mats collected from hypersaline salterns were mainipulated to examine the effects of low sulfate concentrations and lowered salinity on carbon metabolism. As sulfate was slowly removed from the mats, methane production and flux increased, with highest fluxes and concentration in mats at lowered salinity (35 ppt) and low sulfate concentrations. The δ13C values of bulk particulate organic carbon (POC) ranged from about -10 to -12 &perthou;, similar to what had been observed previously for these cyanobacterial mats. In mats with higher sulfate concentrations, pore water profiles of dissolved inorganic carbon (DIC) δ13C values decreased with depth. However, in the mats with lowered sulfate, the DIC δ13C values increased substantially, from about -1 &perthou; in the overlying water to +12 &perthou; by 20 mm depth. Although the increase in DIC δ13C values is consistent with biogenic methanogenesis, the measured methane concentrations in these mats were not great enough to be the sole cause of the increase. These positive isotopic values, as well as the higher acetate concentrations observed in the low-sulfate mats, are also consistent with the occurrence of acetogenesis.

Paper Details

Date Published: 14 September 2006
PDF: 10 pages
Proc. SPIE 6309, Instruments, Methods, and Missions for Astrobiology IX, 63090N (14 September 2006); doi: 10.1117/12.682000
Show Author Affiliations
Cheryl A. Kelley, Univ. of Missouri, Columbia (United States)
Brad M. Bebout, NASA Ames Research Ctr. (United States)
Leslie E. Prufert-Bebout, NASA Ames Research Ctr. (United States)
Jason M. Smith, Univ. of Florida (United States)

Published in SPIE Proceedings Vol. 6309:
Instruments, Methods, and Missions for Astrobiology IX
Richard B. Hoover; Gilbert V. Levin; Alexei Y. Rozanov, Editor(s)

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