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| Titel |
Nitrogen cycling and N2O production in the water column of the ferruginous meromictic Lake La Cruz (Spain) |
| VerfasserIn |
Jana Tischer, Jakob Zopfi, Caitlin H. Frame, Corinne Jegge, Kirsten Oswald, Andreas Brand, Maria R. Miracle, Eduardo Vicente, Moritz F. Lehmann |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250135526
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| Publikation (Nr.) |
 EGU/EGU2016-16404.pdf |
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| Zusammenfassung |
| Ferruginous meromictic lakes are rare systems, considered potential modern analogues for an
ancient Archean ferruginous Ocean. They may therefore represent valuable model
ecosystems to study biogeochemical processes of early Earth history, in particular, the
interaction between the iron (Fe) and other element cycles such as the complex nitrogen (N)
cycle. In context of its exceptional water chemistry, we studied the N-cycling in
the meromictic, ferruginous Lake La Cruz in the Central Iberian Ranges in Spain,
combining i) general water column chemistry and detailed N speciation ii) stable isotope
composition and intramolecular 15N distributions (site preference) of dissolved N2O
and iii) 15N-isotope label incubation experiments, to identify and quantify biotic
and abiotic N2O and N2 production pathways. Nitrification was identified as the
main N2O production mechanism in the oxic zone, based on the N2O concentration
profile and the isomeric composition of N2O (site preference = 24.7) at the depth
of maximum concentration relative to the surface water. A second N2O peak of
23 nmol/L was observed within the chemocline, and relatively low values for the
δ15N-N2O (-1.1) and a site preference of 16.1‰ with respect to the oxic water column
suggest that here incomplete (nitrifier) denitrification is the dominant N2O production
pathway. However, based on the bulk dual N-versus-O isotope signature, other
production mechanisms cannot be excluded at this point. Within the anoxic water
column, N2O is consumed quantitiatively to N2, consistent with 15N-NO3− incubation
experiments, showing denitrification (and anammox) activity below the redox transition
zone. The overlap of Fe and N-species (N2O, NO2−) in the water column is small,
therefore abiotic N2O production is most likely negligible. The planned analysis of the
NO3− and NH4+ isotopic signatures will provide further insight into the origin of
N2O. Additionally, molecular biological analyses will provide information on the
microbial community structure, particularly of nitrifying, denitrifying and anammox
bacteria.
Walter, X. A., Picazo-Mozo, A., Miracle, M.R., Vicente, E., Camacho, A., Aragno, M. &
Zopfi, J. 2014: Phototrophic Fe(II)-oxidation in the chemocline of a ferruginous meromictic
lake, Frontiers in Microbiology, 5, 1-9. |
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