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| Titel |
Spatial distribution of benthic foraminiferal stable isotopes and dinocyst assemblages in surface sediments of the Trondheimsfjord, central Norway |
| VerfasserIn |
G. Milzer, J. Giraudeau, J. Faust, J. Knies, F. Eynaud, C. Rühlemann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 7 ; Nr. 10, no. 7 (2013-07-01), S.4433-4448 |
| Datensatznummer |
250018322
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| Publikation (Nr.) |
 copernicus.org/bg-10-4433-2013.pdf |
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| Zusammenfassung |
| Instrumental records from the Norwegian Sea and the Trondheimsfjord show
evidence that changes of bottom water temperature and salinity in the fjord
are linked to the salinity and temperature variability of the North Atlantic
Current (NAC). Changes in primary productivity and salinity in the surface
and intermediate water masses in the Trondheimsfjord as well as the fjord
sedimentary budget are mainly driven by changes in riverine input. In this
study we use 59 surface sediment samples that are evenly distributed in the
fjord to examine whether dinocyst assemblages and stable isotope ratios of
benthic foraminifera reflect the present-day hydrology and can be used as
palaeoceanographic proxies. In general, modern benthic δ18O and
δ13C values decrease from the fjord entrance towards the fjord head
with lowest values close to river inlets. This is essentially explained by
gradients in the amounts of fresh water and terrigenous organic matter
delivered from the hinterland. The distribution of benthic δ13C
ratios across the fjord is controlled by the origin (terrigenous vs. marine)
of organic matter, local topography-induced variability in organic matter
flux at the water–sediment interface, and organic matter degradation. The
dinocyst assemblages display the variations in hydrography with respect to
the prevailing currents, the topography, and the freshwater and nutrient
supply from rivers. The strength and depth of the pycnocline in the fjord
strongly vary seasonally and thereby affect water mass characteristics as
well as nutrient availability, temporally creating local conditions that
explain the observed species distribution. Our results prove that dinocyst
assemblages and benthic foraminiferal isotopes reliably mirror the complex
fjord hydrology and can be used as proxies of Holocene climatic variability. |
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