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| Titel |
Spatio-seasonal variability in dissolved organic matter optical properties and its bioavailability in a subalpine lake |
| VerfasserIn |
Masumi Stadler, Elisabet Ejarque, Martin J. Kainz |
| 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 |
250140584
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| Publikation (Nr.) |
 EGU/EGU2017-3991.pdf |
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| Zusammenfassung |
| Allochthonous and autochothonous dissolved organic matter (DOM) in lakes mainly
originate from terrestrial and aquatic primary production, respectively. Due to their
differing biochemical composition the degradability of DOM by microorganisms is
expected to vary. The carbon use efficiency of bacteria and DOM biodegradability
determine whether the consumed DOM is incorporated into microbial biomass or
respired to CO2 and ultimately emitted into the atmosphere. Thus, understanding the
interaction of biodegradable DOM and its consumers is crucial to increase our
knowledge on the role of lakes in the global carbon cycling. However, interactions of
specific aquatic DOM signatures and the microbial population still remain widely
debated.
The aim of this study was to explore how DOM biodegradability changes along a
stream-lake continuum at different seasons of the year. We monitored DOM quantity and its
optical properties, inorganic nutrients, CO2 and bacterial growth over 20 days in dark
bioassays with water from the inflow, outflow and at three layers of an oligotrophic subalpine
lake. Preliminary results reveal highest microbial abundance in the metalimnion in winter and
summer (0.7 106 and 2.5 106 cells mL−1, respectively) and the inflow in spring and
autumn (1 106 and 1.4 106 cells mL−1, respectively) after 20 days. Surprisingly,
with the exception of winter samples final inflow bacterial abundance results high,
despite its lowest initial natural cell concentration, providing evidence for effective
utilisation of terrestrial DOM, even with its high humic signature as indicated by
the humification index (HIX). Nonetheless, after a microbial biomass peak with
the inflow yielding mostly highest after three days, at the final experimental stage
microbial biomass does only marginally differ between all sites with the exception of
autumn samples where outflow and metalimnion turn out most productive. Even
though the DOM of all lake sites and the lake outflow were characterised by lower
molecular weight (indicated by the slope ratio (SR)) and a higher autochthonous
signature (BIX) in all seasons, rapid growth of inflow bacteria highlight the potential of
terrestrially-derived DOM to support bacterial growth, and challenge previous ideas that
autchthonously-produced DOM would be more labile than DOM of terrestrial origin. |
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