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| Titel |
The dual role of lakes as buffers and amplifiers of dissolved organic matter temporal dynamics: Buffering transport and amplifying transformation |
| VerfasserIn |
Elisabet Ejarque, Jakob Schelker, Samiullah Khan, Lisa-Maria Hollaus, Gertraud Steniczka, Martin Kainz, Tom Battin |
| 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 |
250133915
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| Publikation (Nr.) |
 EGU/EGU2016-14580.pdf |
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| Zusammenfassung |
| Lakes that disrupt the flow of water and its constituents within the fluvial continuum can
modify the downstream dynamics of dissolved organic matter (DOM). Potential causes of
this change may include the hydrological buffering capacity of lakes relative to streams and
rivers and the amplification of biotic processes. To test this hypothesis, we measured DOM
quantity and quality at the inflow and outflow of sub-alpine Lake Lunz (Lower Austria)
during one year. DOM quality was characterised using optical metrics indicative of the
humic-like composition (fluorescence peak C), humification (HIX), and aromaticity (SUVA)
degree, predominance of autochthonous components (BIX), and average molecular weight
(E2:E3).
Total annual variability was found to be lower in the outflow compared with the inflow
(SDout:SDin < 1) for dissolved organic carbon (DOC) concentration and HIX. These
variables showed a minimal seasonal variation in both inflow and outflow, together with a
more accentuated response to hydrology in the inflow. Mean DOC concentration
was significantly higher in the outflow (1.70 ± 0.14 mg L−1) than in the inflow
(1.3 ± 0.25 mg L−1), and this pattern was only occasionally reversed during high
flow.
By contrast, the total annual variability of peak C, SUVA, BIX and E2:E3 was
higher in the outflow than in the inflow (SDout:SDin > 1). This was due to the large
seasonal variability in the outflow, which contrasted with a reduced temporal dynamics
in the inflow. Combined, this created a shift from similar inflow-outflow DOM
characteristics during winter, to uncoupled DOM characteristics during summer. This
uncoupling consisted in a higher signal of the autotrophic origin of DOM, a lower
average molecular weight, as well as a lower aromatic and humic-like content in the
outflow.
Overall, these results highlight the role of the Lake Lunz as a DOC source and as a buffer
of hydrological pulses of DOC export. Moreover, results emphasise the capacity of the lake to
amplify the seasonal variability of DOM quality, creating a maximum uncoupling between
the inflow and the outflow during the months of increased biotic processing in the
lake. |
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