 |
| Titel |
Heterotrophic denitrification vs. autotrophic anammox – quantifying collateral effects on the oceanic carbon cycle |
| VerfasserIn |
W. Koeve, P. Kähler |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 7, no. 8 ; Nr. 7, no. 8 (2010-08-06), S.2327-2337 |
| Datensatznummer |
250004924
|
| Publikation (Nr.) |
 copernicus.org/bg-7-2327-2010.pdf |
|
|
|
|
|
| Zusammenfassung |
| The conversion of fixed nitrogen to N2 in suboxic waters is estimated
to contribute roughly a third to total oceanic losses of fixed nitrogen
and is hence
understood to be of major importance to global oceanic production and,
therefore, to the role of the ocean as a sink of atmospheric CO2. At
present heterotrophic denitrification and autotrophic anammox are considered
the dominant sinks of fixed nitrogen. Recently, it has been suggested that
the trophic nature of pelagic N2-production may have additional,
"collateral" effects on the carbon cycle, where heterotrophic
denitrification provides a shallow source of CO2 and autotrophic
anammox a shallow sink. Here, we analyse the stoichiometries of nitrogen and
associated carbon conversions in marine oxygen minimum zones (OMZ) focusing
on heterotrophic denitrification, autotrophic anammox, and dissimilatory
nitrate reduction to nitrite and ammonium in order to test this hypothesis
quantitatively. For open ocean OMZs the combined effects of these processes
turn out to be clearly heterotrophic, even with high shares of the
autotrophic anammox reaction in total N2-production and including
various combinations of dissimilatory processes which provide the substrates
to anammox. In such systems, the degree of heterotrophy
(ΔCO2:ΔN2),
varying between 1.7 and 6.5, is a function of the
efficiency of nitrogen conversion. On the contrary, in systems like the
Black Sea, where suboxic N-conversions are supported by diffusive fluxes of
NH4+ originating from neighbouring waters with sulphate reduction,
much lower values of ΔCO2:ΔN2 can be found.
However, accounting for concomitant diffusive fluxes of CO2, the ratio
approaches higher values similar to those computed for open ocean OMZs. Based on
this analysis, we question the significance of collateral effects concerning
the trophic nature of suboxic N-conversions on the marine carbon cycle. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|