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| activités | bourse | liens | membres | contact | ||
date |
Vendredi, 7 décembre 2007 |
lieu |
INRS-ETE,
salle 2417 |
| heure
|
12h15 |
| François
Guillemette UQAM
|
|
Les sources de carbone respirées par les bactéries en écosystème
d'eau douce à court et à long terme
|
The
sources of organic carbon being preferentially used by bacteria in
freshwater ecosystems are still today a matter of debate. It is now
clear that algae are not the sole source of carbon supporting bacterioplankton
metabolism, but the relative importance of other sources, such as
terrestrial carbon, is still uncertain. We used the newly-developed
ReCReS system that allows the recovery and subsequent isotopic analysis
of CO2 produced by aquatic bacterial respiration, to address two
fundamental questions: 1) Is algal-derived carbon preferentially
respired by lake bacteria, and 2) Do nutrients influence the patterns
of C utilization? The experiments were carried out in several lakes
in southern Québec, and followed the changes in respiratory
CO2 isotopic signature over time, with and without nutrient additions.
Our results suggest that algal carbon is preferentially used by bacteria
in the short-term, and that longer-term carbon consumption is supported
by terrestrially-derived carbon. Nutrients appear not only to enhance
bacterial respiration, but also to increase the range of sources
being used in the short-term. This study points to a sequential utilization
of dissolved organic carbon pools originating from different sources,
and to a modulation of this pattern of carbon consumption by nutrients. |
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