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Chemical characterization of microbial-dominated soil organic matter in the Garwood Valley, Antarctica |
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| Authors: | Xiaojuan Feng André J Simpson Bo Elberling David W Hopkins Ashley D Sparrow Lawrence G Greenfield |
| Institution: | a Department of Chemistry and Environmental NMR Centre, University of Toronto, Toronto, Ontario, Canada M1C 1A4 b Agriculture and Agri-Food Canada, Central Experimental Farm, Ottawa, Canada K1A 0C6 c UNIS, The University Centre in Svalbard, N-9171 Longyearbyen, Norway d Department of Geography and Geology, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K., Denmark e Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA Scotland, UK f School of Biological and Environmental Sciences, University of Stirling, Stirling, FK9 4LA Scotland, UK g Department of Natural Resources and Environmental Sciences, University of Nevada, 1000 Valley Road, Reno, NV 89512, USA h Manaaki Whenua - Landcare Research, P.O. Box 40, Lincoln 7640, New Zealand i School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch 8020, New Zealand |
| Abstract: | Despite its harsh environmental conditions, terrestrial Antarctica contains a relatively large microbial biomass. Natural abundance carbon and nitrogen stable isotope signatures of organic materials in the dry valleys indicate mixed provenance of the soil organic matter (SOM) with varying proportions of contributions from lichens, mosses, lake-derived algae and cyanobacteria. Here we employed two complementary analytical techniques, biomarker measurements by gas chromatography/mass spectrometry and solution-state 1H nuclear magnetic resonance spectroscopy, to provide further information at a molecular-level about the composition and possible source of SOM in the Garwood Valley, Antarctica. The predominance of branched alkanes and short-chain lipids in the solvent extracts indicates that the primary contribution to the SOM was microbial-derived. Chemical structures in the NaOH extracts from soils were also dominated by amide, peptides, and a CH3-dominating aliphatic region that were characteristic of microbial signatures. Furthermore, the SOM in the Garwood Valley contained compounds that were different from those in the cyanobacteria-dominated mat from a nearby lake (including monoethyl alkanes and enriched side-chain protons). This observation suggests that easily degradable carbon sources from the nearby lake did not dominate the SOM, which is consistent with a fast turnover of the mat-derived organic matter found in the valley. This study highlights the important role of native soil microbes in the carbon transformation and biogeochemistry in terrestrial Antarctica. |
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