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| Titel |
Linkage between the temporal and spatial variability of dissolved organic matter and whole-stream metabolism |
| VerfasserIn |
S. Halbedel, O. Büttner, M. Weitere |
| 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. 8 ; Nr. 10, no. 8 (2013-08-19), S.5555-5569 |
| Datensatznummer |
250085303
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| Publikation (Nr.) |
 copernicus.org/bg-10-5555-2013.pdf |
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| Zusammenfassung |
Dissolved organic matter (DOM) is an important resource for microbes, thus
affecting whole-stream metabolism. However, the factors influencing its
chemical composition and thereby also its bio-availability are complex and
not thoroughly understood. It was hypothesized that whole-stream metabolism
is linked to DOM composition and that the coupling of both is influenced by
seasonality and different land-use types. We tested this hypothesis in a
comparative study on two pristine forestry streams and two non-forestry
streams. The investigated streams were located in the Harz Mountains (central
Europe, Germany). The metabolic rate was measured with a classical
two-station oxygen change technique and the variability of DOM with
fluorescence spectroscopy. All streams were clearly net heterotrophic,
whereby non-forestry streams showed a higher primary production, which was
correlated to irradiance and phosphorus concentration. We detected three CDOM
components (C1, C2, C3) using parallel factor (PARAFAC) analysis. We compared
the excitation and emission maxima of these components with the literature
and correlated the PARAFAC components with each other and with fluorescence
indices. The correlations suggest that two PARAFAC components are derived from
allochthonous sources (C1, C3) and one is derived autochthonously (C2). The
chromophoric DOM matrix was dominated by signals of humic-like substances
with a highly complex structure, followed by humic-like, fulfic acids,
low-molecular-weight substances, and with minor amounts of amino acids and
proteins. The ratios of these PARAFAC components (C1 : C2, C1 : C3,
C3 : C2) differed with respect to stream types (forestry versus
non-forestry). We demonstrated a significant correlation between gross
primary production (GPP) and signals of autochthonously derived, low-molecular-weight
humic-like substances. A positive correlation between P / R
(i.e. GPP/daily community respiration) and the fluorescence index FI suggests
that the amount of autochthonously produced DOM increased overall with
increasing GPP. In accordance with the coupling between DOM and the
metabolism, our data also indicate that the composition of DOM is subject to
seasonal fluctuations.
We concluded that temporal and spatial differences in DOM composition are
driven by whole-stream metabolism, in addition to pronounced effects coming
from allochthonous sources. |
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