HR: 0800h
AN: B41C-0205    [Abstracts]
TI: Distribution and Carbon-Isotope Composition of Lipid Biomarkers in Lake Sediments on the Tibetan Plateau, China
AU: * Tuo, J
EM:
AF: Key Laboratory of Gas Geochemistry, Institute of Geology and Geophysics, CAS, Donggang West Road 324, Lanzhou, 730000 China
AU: Li, Q
EM:
AF: College of Resources and Environment, Lanzhou Univ., Donggang West Road 324, Lanzhou, 730000 China
AU: Li, Y
EM:
AF: Savannah River Ecology Laboratory, Univ. Georgia, Bldg 737A Savannah River Site, Aiken, SC 29802 United States
AU: Jiang, H
EM:
AF: Department of Geology, Miami University, 127 Shideler Hall, Oxford, OH 45056 United States
AU: Dong, H
EM:
AF: Department of Geology, Miami University, 127 Shideler Hall, Oxford, OH 45056 United States
AU: Zhang, C L
EM: zhang@srel.edu
AF: Savannah River Ecology Laboratory, Univ. Georgia, Bldg 737A Savannah River Site, Aiken, SC 29802 United States
AB: The goal of this study was to determine the carbon source and microbial community structure in different lake environments on the Tibetan Plateau using carbon isotopes and lipid biomarkers. Microbial mats and sediments were collected from Erhai-, Qinghai-, Gahai-, and Chaka-lakes, which have different pHs (7.4-9.5) and salinities (0.1-21%). Phospholipid fatty acids (PLFA) have different distribution patterns in algal mats, sandy mud, and salt deposits, which may reflect changes in microbial community structure in different environments. For example, terminally branched fatty acids reflect heterotrophic bacteria and varied from less than 1% in a brown algal mat in Lake Gahai to 23% in a salt deposit in Lake Chaka. The cyclopropyl fatty acids may reflect stress conditions under different salinities. These compounds varied from 0% in algal mats living on the bank of the lake, which received freshwater run off, to 12% in grey mud in the saline lake water. On the other hand, long-chain n-alkanes in these samples reflect contributions of a mixture of epicuticular waxes of higher plants and submerged or floating aquatic macrophytes. Carbon isotopes of lipid biomarkers indicate different sources of organic carbon in different lake sediments. For example, carbon isotopes of total organic carbon and lipid biomarkers averaged -23.9 ± 1.5‰ (n = 2) and -26.0 ± 3.1‰ (n = 18), respectively, in Lake Erhai, and averaged -30.0 ± 1.5‰ (n = 4) and -33.5 ± 3.3‰ (n = 92), respectively, in Lake Gahai. These results suggest that a relatively heavy carbon source is going into Lake Erhai compared to carbon sources going into Lake Gahai. This study indicates that the distribution patterns of the lipid biomarkers and theirs carbon-isotope compositions can be used to evaluate the community structure and the source of carbon that supports microbial growth in lake sediments on the Tibetan Plateau.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0429 Climate dynamics (1620)
DE: 0448 Geomicrobiology
DE: 0456 Life in extreme environments
SC: Biogeosciences [B]
MN: Fall Meeting 2005