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| Titel |
Top-down control of methanotrophs regulates methane concentrations in a small humic lake |
| VerfasserIn |
Jatta Saarenheimo, Shawn Devlin, Jari Syväranta, Marja Tiirola, Roger Jones |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250089436
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| Publikation (Nr.) |
 EGU/EGU2014-3639.pdf |
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| Zusammenfassung |
| Many boreal lakes are known to be significant sources of methane (CH4), as methane
production in anaerobic layers of boreal stratified lakes often exceeds oxidation of
methane by methanotrophs, leading to methane fluxes to the atmosphere. In order to
investigate whether trophic interactions control methanotrophy via regulation of bacterial
community dynamics, we experimentally divided a small, humic, and fishless lake
with high zooplankton abundance into two treatment basins. We then established
either a) equal biomass of juvenile (12 cm) European perch
(Perca fluviatilis) or b) adult fish and no fish in the two basins. We hypothesized
that differences in predator presence and size would result in cascading trophic
interactions, altering the abundance of zooplankton (Daphnia sp.) which are known
to graze methanotrophic bacteria. Concurrently with zooplankton abundance and
methane concentration measurements, methanotrophic bacterial abundance was
assessed by quantitative PCR by targeting specific functional genes (pmoA). Fish
presence, regardless of size, exerted high grazing pressure on zooplankton dramatically
reducing their biomass. This shift in zooplankton density resulted in corresponding
changes in methanotrophic bacterial abundance. We found a clear difference between
epilimnetic methane concentrations for each treatment during the experiment, whereas
the hypolimnetic methane concentrations showed no differences. The observed
variation in epilimnetic methane concentrations was clearly linked to methanotrophic
abundance/activity, which, in turn, was regulated by Daphnia biomass. This illustrates that
cascading trophic interactions can be important regulators of methane concentration
in stratified humic lakes and that previously unrelated ecological properties, fish
abundance and atmospheric greenhouse gas concentrations, appear to be linked. |
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