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Cycling of dissolved and particulate nitrogen and carbon in the Framvaren Fjord, Norway; stable isotopic variations
Journal article   Peer reviewed

Cycling of dissolved and particulate nitrogen and carbon in the Framvaren Fjord, Norway; stable isotopic variations

David J. Velinsky and Marilyn L. Fogel
Marine chemistry, v 67(3-4)
Nov 1999

Abstract

anaerobic environment Atlantic Ocean biochemical sedimentation biogenic processes C-13/C-12 carbon carbon cycle Europe fjords Framvaren Fjord geochemical cycle geochemistry glacial features Hydrochemistry isotope ratios isotopes N-15/N-14 nitrogen North Atlantic Northeast Atlantic Norway Oceanography particulate materials Scandinavia sea water sedimentation shore features solutes Southern Norway stable isotopes Western Europe
The reaction pathways of nitrogen and carbon in the Framvaren Fjord (Norway) were studied through stable isotope analysis (delta (super 15) N and delta (super 13) C) of dissolved inorganic and particulate organic matter (POM). The variations in the isotopic compositions of the various C and N pools within the water column were used to evaluate the historical deposition of material to the sediments. The high delta (super 15) N-NH (sub 4) (super +) at the O (sub 2) /H (sub 2) S interface, as a consequence of microbial uptake between 19 and 25 m, results in extremely depleted delta (super 15) N-particulate nitrogen (PN) of approximately 1 per mil within the particulate maximum at approximately 19 m. The carbon isotopic distribution of dissolved inorganic carbon (DIC) and particulate organic carbon (POC) within the interface suggests that the distinct microbial flora (Chromatium sp. and Chlorobium sp.) fractionate inorganic carbon to different degrees. The extremely light delta (super 13) C-POC within the interface (-31 per mil) appears to be a result of carbon uptake by Chromatium sp. while delta (super 13) C-POC of -12 per mil is more indicative of Chlorobium sp. Nitrogen isotopic mass balance calculations suggested that approximately 75% of the material sinking to the sediments was derived from the dense particulate maximum between 19 and 25 m. The sediment distribution of nitrogen isotopes varied from 2 per mil at the surface to approximately 6 per mil at 30 cm. The nitrogen isotopic variations with depth may be an indicator of the depth or position of the O (sub 2) /H (sub 2) S interface in the fjord. Low sediment delta (super 15) N indicated that the interface was within the photic zone of the water column, while more enriched values suggested that the interface was lower in the water column potentially allowing for less fractionation during biological incorporation of dissolved inorganic nitrogen. Results indicate that the dense layers of photo-autotrophic bacteria in the upper water column impart unique carbon and nitrogen isotopic signals that help follow processes within the water column and deposition to the sediments. Abstract Copyright (1999) Elsevier, B.V.

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Collaboration types
Domestic collaboration
Web of Science research areas
Chemistry, Multidisciplinary
Oceanography
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