Re-assessing the nitrogen signal in continental margin sediments: New insights from the high northern latitudes |
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| Institution: | 1. BRIDGE, School of Geographical Sciences, University of Bristol, University Road, Bristol BS8 1SS, United Kingdom;2. Faculty of Geosciences, Utrecht University, Utrecht 3584CD, The Netherlands;3. Department of Bioscience-Center for Geomicrobiology, Aarhus University, Ny Munkegade 114, DK-8000 Aarhus C, Denmark;4. Department of Earth Sciences, University of Southern California, Zumberge Hall of Science, 3651 Trousdale Pkwy, Los Angeles, CA 90089-0740, USA;5. Organic Geochemistry Unit, The Cabot Institute and Bristol Biogeochemistry Research Centre, School of Chemistry, University of Bristol, United Kingdom;6. Dept. of Earth & Environmental Sciences, Université Libre de Bruxelles, Bruxelles 1050, Belgium;1. Department of Environment and Geography, University of Manitoba, Winnipeg, MB R3T 2N2, Canada;2. Geological Survey of Canada, 601 Booth St, Ottawa, ON K1A 0E8, Canada;3. Department of Fisheries and Oceans, P.O. Box 6000, Sidney, BC V8L 4B2, Canada;4. Geological Survey of Canada, 3303-33rd Street N.W., Calgary, AB T2L 2A7, Canada;5. Department of Fisheries and Oceans, 501 University Crescent, Winnipeg, MB R3T 2N6, Canada |
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| Abstract: | Organic and inorganic nitrogen and their isotopic signatures were studied in continental margin sediments off Spitsbergen. We present evidence that land-derived inorganic nitrogen strongly dilutes the particulate organic signal in coastal and fjord settings and accounts for up to 70% of the total nitrogen content. Spatial heterogeneity in inorganic nitrogen along the coast is less likely to be influenced by clay mineral assemblages or various substrates than by the supply of terrestrial organic matter (TOM) within eroded soil material into selected fjords and onto the shelf. The δ15N signal of the inorganic nitrogen (δ15Ninorg) in sediments off Spitsbergen seems to be appropriate to trace TOM supply from various climate- and ecosystem zones and elucidates the dominant transport media of terrigenous sediments to the marine realm. Moreover, we postulate that with the study of sedimentary δ15Ninorg in the Atlantic–Arctic gateway, climatically induced changes in catchment's vegetations in high northern latitudes may be reconstructed. The δ15Norg signal is primarily controlled by the availability of nitrate in the dominating ocean current systems and the corresponding degree of utilization of the nitrate pool in the euphotic zone. Not only does this new approach allow for a detailed view into the nitrogen cycle for settings with purely primary-produced organic matter supply, it also provides new insights into both the deposition of marine and terrestrial nitrogen and its ecosystem response to (paleo-) climate changes. |
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