Spatial heterogeneity in lipid biomarker distributions in the catchment and sediments of a crater lake in central India |
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| Institution: | 1. IDL-FCUL, Instituto Dom Luís, Faculdade de Ciências, Universidade de Lisboa, Campo Grande 1749-016, Portugal;2. ISTE, Geopolis, CH-1015 Lausanne, Switzerland;3. Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143 Rome, Italy;4. Institute of Tectonics and Geophysics, Russian Academy of Sciences, Khabarovsk, Russia;5. Hercules, Evora, Portugal;1. School of Geography and Remote Sensing, Nanjing University of Information Science & Technology, Nanjing 210044, China;2. MOE Key Laboratory of Surficial Geochemistry, Department of Earth Sciences, Nanjing University, 163 Xianlindadao, Nanjing 210046, China;3. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, China;4. Department of Earth and Environmental Sciences, The University of Michigan, Ann Arbor, MI 48109-1005, USA |
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| Abstract: | The basin-scale spatial variability in lipid biomarker proxies in lacustrine sediments, which are established tools for studying continental environmental change, has rarely been examined. It is often implicitly assumed that a lake sediment core provides an average integral of catchment sources. Here we evaluated the distribution of lipid biomarkers in a modern ecosystem and compared it with the sedimentary record. We analyzed lipid biomarkers in terrestrial and aquatic organisms and in lake surface sediments from 17 locations within the saline–alkaline Lonar crater lake in central India. Terrestrial vegetation and lake surface sediments were characterized by relatively high average chain length (ACL) index values (29.6–32.8) of leaf wax n-alkanes, consistent with suggestions that plants in drier and warmer climates produce longer chain alkyl lipids than plants in cooler and humid areas. A heterogeneous spatial distribution of ACL values in lake surface sediments was found: at locations away from the shore, the values were highest (31 or more), possibly indicating different sources and/or transport of terrestrial biomarkers. In floating, benthic microbial mats and surface sediment, n-heptadecane, carotenoids, diploptene, phytol and tetrahymanol occurred in large amounts. Interestingly, these biomarkers of a unique bacterial community were found in substantially higher concentrations in nearshore sediment samples. We suggest that human influence and subsequent nutrient supply resulted in increased primary productivity, leading to an unusually high concentration of tetrahymanol in the nearshore sediments.In summary, the data showed that substantial heterogeneity existed within the lake, but leaf wax n-alkanes in a core from the center of the lake represented an integral of catchment conditions. However, lake level fluctuation may potentially affect aquatic lipid biomarker distributions in lacustrine sediments, in addition to source changes. |
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