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| Titel |
Nitrogen isotope dynamics and fractionation during sedimentary denitrification in Boknis Eck, Baltic Sea |
| VerfasserIn |
K. Dähnke, B. Thamdrup |
| 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. 5 ; Nr. 10, no. 5 (2013-05-07), S.3079-3088 |
| Datensatznummer |
250018239
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| Publikation (Nr.) |
 copernicus.org/bg-10-3079-2013.pdf |
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| Zusammenfassung |
The global marine nitrogen cycle is constrained by nitrogen fixation as a
source of reactive nitrogen, and denitrification or anammox on the sink
side. These processes with their respective isotope effects set the marine
nitrate 15N-isotope value (δ15N) to a relatively constant
average of 5‰. This value can be used to better assess
the magnitude of these sources and sink terms, but the underlying assumption
is that sedimentary denitrification and anammox, processes responsible for
approximately one-third of global nitrogen removal, have little to no
isotope effect on nitrate in the water column.
We investigated the isotope fractionation in sediment incubations, measuring
net denitrification and nitrogen and oxygen stable isotope fractionation in
surface sediments from the coastal Baltic Sea (Boknis Eck, northern
Germany), a site with seasonal hypoxia and dynamic nitrogen turnover.
Sediment denitrification was fast, and regardless of current paradigms
assuming little fractionation during sediment denitrification, we measured
fractionation factors of 18.9‰ for nitrogen and
15.8‰ for oxygen in nitrate. While the input of nitrate
to the water column remains speculative, these results challenge the current
view of fractionation during sedimentary denitrification and imply that
nitrogen budget calculations may need to consider this variability, as both
preferential uptake of light nitrate and release of the remaining heavy
fraction can significantly alter water column nitrate isotope values at the
sediment–water interface. |
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