Sources and distribution of organic matter in northern Patagonia fjords,Chile (～44–47°S): A multi-tracer approach for carbon cycling assessment |
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| Authors: | Julio Sepúlveda Silvio Pantoja Konrad A Hughen |
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| Institution: | 1. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, E25-623, Cambridge, MA 02139, USA;2. Department of Oceanography and Center for Oceanographic Research in the eastern South Pacific, and COPAS Sur-Austral, University of Concepción, Casilla 160-C, Concepción, Chile;3. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, MS#25, Woods Hole, MA 02543, USA;1. Departamento de Oceanografía, Universidad de Concepción, Campus Concepción, Víctor Lamas 1290, Casilla 160-C, código postal 4070043, Concepción, Chile;2. Instituto de Ciencias Marinas y Limnológicas, Facultad de Ciencias, Universidad Austral de Chile, Avenida Rector Eduardo Morales, Edificio Emilio Pugín, código postal 5090000, Chile;3. Programa COPAS Sur-Austral, Universidad de Concepción, Campus Concepción, Víctor Lamas 1290, Casilla 160-C, código postal 4070043, Concepción, Chile;4. Department of Civil and Coastal Engineering, University of Florida, Gainesville, FL 32611, USA;1. Programa de Doctorado en Oceanografía, Departamento de Oceanografía, Universidad de Concepción, Chile;2. Departamento de Oceanografía, Universidad de Concepción, Chile;3. Programa COPAS Sur-Austral, Universidad de Concepción, Chile;1. Centro de Investigación en Ecosistemas de la Patagonia, Universidad Austral de Chile, Francisco Bilbao 323, oficina 216, Coyhaique, Chile;2. Pontificia Universidad Católica de Valparaíso, Av. Altamirano 1480, Valparaíso, Chile;3. Centro de Estudios del Cuaternario – Fuego Patagonia, 21 de Mayo 1690, Punta Arenas, Chile;1. Departamento de Biología Marina, Universidad Católica del Norte, Larrondo 1281, Coquimbo, Chile;2. Centro de Estudios Avanzados en Zonas Áridas (CEAZA), Raúl Bitrán S/N, La Serena, Chile;3. Institut für Geographie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany;4. GeoBio-Center and Department für Geo- und Umweltwissenschaften, Ludwig-Maximilians Universität München, Germany |
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| Abstract: | We investigated the provenance of organic matter in the inner fjord area of northern Patagonia, Chile (～44–47°S), by studying the elemental (organic carbon, total nitrogen), isotopic (δ13C, δ15N), and biomarker (n-alkanoic acids from vascular plant waxes) composition of surface sediments as well as local marine and terrestrial organic matter. Average end-member values of N/C, δ13C, and δ15N from organic matter were 0.127±0.010, ?19.8±0.3‰, and 9.9±0.5‰ for autochthonous (marine) sources and 0.040±0.018, ?29.3±2.1‰, and 0.2±3.0‰ for allochthonous (terrestrial) sources. Using a mixing equation based on these two end-members, we calculated the relative contribution of marine and terrestrial organic carbon from the open ocean to the heads of fjords close to river outlets. The input of marine-derived organic carbon varied widely and accounted for 13–96% (average 61%) of the organic carbon pool of surface sediments. Integrated regional calculations for the inner fjord system of northern Patagonia covered in this study, which encompasses an area of ～4280 km2, suggest that carbon accumulation may account for between 2.3 and 7.8×104 ton C yr?1. This represents a storage capacity of marine-derived carbon between 1.8 and 6.2×104 ton yr?1, which corresponds to an assimilation rate of CO2 by marine photosynthesis between 0.06 and 0.23×106 ton yr?1. This rate suggests that the entire fjord system of Patagonia, which covers an area of ～240,000 km2, may represent a potentially important region for the global burial of marine organic matter and the sequestration of atmospheric CO2. |
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