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| Titel |
Fe2+, Mn2+ and H2S as electron donors for benthic N-processes in lacustrine sediments |
| VerfasserIn |
Adeline Cojean, Jakob Zopfi, Elizabeth Robertson, Bo Thamdrup, Moritz F. Lehmann |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250144899
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| Publikation (Nr.) |
 EGU/EGU2017-8777.pdf |
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| Zusammenfassung |
| Intensive human activities have led to the increase of fixed N concentrations in many aquatic environments. Microorganisms help to mitigate N-loading in lakes by eliminating reactive nitrogen, mostly through anaerobic N$_2$ production within lacustrine sediments where bacterial densities are particularly high. The most important N sinks in lakes that transform fixed N (e.g. NO${^-_3$, NO${^-_2$, NH${^+_4$) to N$_2$ are denitrification and anammox. In contrast, dissimilatory nitrate reduction to ammonium (DNRA) retains bioavailable N within the system. The relative partitioning between nitrogen removal through denitrification and/or anammox, and its recycling via DNRA is an important modulator of internal eutrophication, and highly relevant for N balances in lakes. During canonical denitrification and DNRA, microorganisms use mainly organic matter for reducing nitrate, yet H$_2$S, Fe$^{2+}$, and/or Mn$^{2+}$ are potential alternative electron donors. Recent work on DNRA in estuarine sediments has revealed the coupling of nitrate reduction and iron oxidation, but the importance of Fe$^{2+}$-dependent DNRA in lacustrine sediments remains uncertain. Similarly, sulfide-dependent nitrate reduction has been found to occur in freshwater sediments, though this process remains under-investigated. To our knowledge, there is no clear evidence for nitrate reduction in association with the oxidation of reduced manganese in lakes. The goal of this study was to quantify benthic NO${^-_3$ reduction pathways in the lacustrine sediments of eutrophic Lake Lugano, and to investigate if, and to what extent, H$_2$S, Fe$^{2+}$, and/or Mn$^{2+}$ control denitrification, anammox and DNRA. Laboratory incubation experiments were conducted with benthic microbial biomass from the sediments, $^{15}$NO$_3$- (100 |
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