Compositional and biogeochemical variations of sediments across the terrestrial-marine continuum of the Baker-Martínez fjord system (Chile, 48°S)
| Autor: | Eduardo Quiroga, Sebastien Bertrand, Matthias Troch, Lorena Rebolledo, Paola Cárdenas, Fabián J. Tapia, Carina B. Lange, Silvio Pantoja, Nelson R.F.A. Silva |
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| Rok vydání: | 2019 |
| Předmět: |
0106 biological sciences
chemistry.chemical_classification Total organic carbon Biogeochemical cycle geography geography.geographical_feature_category 010504 meteorology & atmospheric sciences biology 010604 marine biology & hydrobiology Sediment Geology Fjord Aquatic Science biology.organism_classification 01 natural sciences Oceanography Diatom chemistry Organic geochemistry Environmental science Organic matter Terrestrial ecosystem 0105 earth and related environmental sciences |
| Zdroj: | Progress in Oceanography. 174:89-104 |
| ISSN: | 0079-6611 |
| Popis: | The Baker-Martinez fjord system (Chile, 48°S) is a transitional environment between the terrestrial ecosystems of Patagonia and the SE Pacific Ocean. This unique setting makes it an ideal system to evaluate land-ocean gradients in sediment composition and in a range of biogeochemical variables. Here, we studied the composition and organic geochemistry of surface sediments deposited in the Baker-Martinez fjord system to assess spatial changes in sediment properties and identify the best tracers of terrestrial input. We determined concentrations in biogenic opal, organic carbon, calcium carbonate, and lithogenic particles, and we measured diatom abundance, bulk elemental and isotopic organic geochemistry, and n-alkanes distribution, on a series of surface sediment samples distributed along two proximal-to-distal transects (one in the Martinez Channel and a second one in the Baker Channel). Results reveal clear proximal-to-distal trends in the proportion of freshwater diatoms and in the fraction of organic carbon of terrestrial origin calculated from the bulk organic δ13C measurements. Diatoms are particularly sensitive to freshwater input in proximal environments, whereas bulk organic geochemistry better reflects terrestrial input over long distances across the fjord system. Other terrestrial proxies frequently used in the literature, such as the N/C ratio and the n-alkane-based terrestrial/aquatic ratio, did not show clear variations with distance from the fjord head. Our results suggest that the isotopic composition of bulk organic matter (δ13Corg) and the relative proportion of diatoms of freshwater origin are the best-suited proxies to estimate past changes in terrestrial input from fjord sediment archives, irrespective of the glacial status of the fjord and its watershed. |
| Databáze: | OpenAIRE |
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