Precise indices based on n-alkane distribution for quantifying sources of sedimentary organic matter in coastal systems |
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| Institution: | 1. Univ. Bordeaux, Laboratoire d’Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), UMR CNRS 5805, Allée Geoffroy Saint-Hilaire, 33615 Pessac Cedex, France;2. CNRS, Laboratoire d’Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), UMR CNRS 5805, Allée Geoffroy Saint-Hilaire, 33615 Pessac Cedex, France;1. State Key Laboratory of Loess and Quaternary Geology, IEE, CAS, Xi’an 710075, China;2. School of Human Settlement and Civil Engineering, Xi’an Jiaotong University, Xi’an 710049, China;3. Laboratory for Terrestrial Environments, College of Arts and Sciences, Bryant University, Smithfield, RI 02917, USA;4. University of Chinese Academy of Sciences, Beijing 100049, China;1. State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography & Limnology, Chinese Academy of Sciences, Nanjing 210008, China;2. Department of Ecology and Hydrobiology, Jinan University, Guangzhou 510632, China;1. School of Geography Science, Nanjing Normal University, 1 Wenyuan Road, Qixia, Nanjing 210023, China;2. College of Economics and Management, Nanjing University of Aeronautics & Astronautics, Nanjing, Jiangsu 210016, China;1. MARUM – Center for Marine Environmental Sciences, University of Bremen, Leobener Straße, 28359 Bremen, Germany;2. Alfred-Wegener-Institut Helmholtz – Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany;3. Alfred-Wegener-Institut Helmholtz – Zentrum für Polar- und Meeresforschung, Telegrafenberg A43, 14473 Potsdam, Germany;4. Department of Earth Science, University of Bergen and Bjerknes Centre for Climate Research, Allégaten 41, 5007 Bergen, Norway;5. Geomorphology and Polar Research (GEOPOLAR), Institute of Geography, University of Bremen, Celsiusstr. FVG-M, D-28359 Bremen, Germany;6. Institute of Geography, Friedrich-Alexander-Universität Erlangen-Nürnberg, Wetterkreuz 15, D-91058 Erlangen, Germany;7. Paleontology & Geobiology and GeoBio-Center, Ludwig-Maximilians-Universität München, Richard-Wagner-Str. 10, D-80333 München, Germany;8. Institute of Bio- and Geosciences, IBG-3: Agrosphere, Research Center Jülich, D-52428 Jülich, Germany;1. Institute of Geography, University of Jena, Löbdergraben 32, D-07743 Jena, Germany;2. Institute of Geography and Oeschger Centre for Climate Change Research, University of Bern, Hallerstrasse 12, CH-3012 Bern, Switzerland;3. Research Area Geography, Department of Geosciences, Eberhard Karls Universität Tübingen, Rümelinstraße 19-23, D-72070 Tübingen, Germany;4. Institute of Geography, University of Leipzig, Johannisallee 19a, D-04103 Leipzig, Germany |
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| Abstract: | Precise indices based on n-alkane signatures were developed in order to determine the sources and composition of sedimentary organic matter (SOM) in coastal systems. The Arcachon Bay (France), a well-studied temperate lagoon, was used as an example of a complex coastal system sheltering a wide diversity of OM sources. Three main groups of sources were well discriminated from their n-alkane signatures: seagrass (Zostera sp.) produced mainly n-C17, n-C19, n-C21, n-C23 and n-C25 alkanes, algae (Rhodophyta, Chlorophyta) produced n-C15 and n-C17 and the terrigenous input Quercus sp., Spartina sp. and river suspended particulate OM (SPOM)] was characterized by n-C25, n-C27, n-C29, n-C31 and n-C33. From the above and literature n-alkane fingerprints, we developed a set of indices (n-alkane ratios) to quantify the contribution of these three major sources of the SOM. At the Arcachon Bay scale, they indicated that SOM was composed mainly of seagrass (ca. 53 ± 19%) and terrestrial (ca. 41 ± 17%) material, followed by algae (ca. 6 ± 9%). Moreover, the new n-alkane indices exhibited more relevant spatial patterns than classical ones – the TAR (C27 + C29 + C31/C15 + C17 + C19; terrestrial to aquatic ratio) and the Paq (C23 + C25/C23 + C25 + C29 + C31; aquatic plant %) – with a greater contribution from marine sources in the central part of the lagoon where a high density of Zostera seagrass was observed. Therefore, the development of precise indices adapted to the local diversity of OM sources is needed when using n-alkanes for quantifying the source composition of SOM in complex coastal systems. |
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| Keywords: | Sedimentary organic matter Coastal system Arcachon Bay |
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