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| Titel |
Carbon dynamics in highly heterotrophic subarctic thaw ponds |
| VerfasserIn |
T. Roiha, I. Laurion, M. Rautio |
| 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 ; 12, no. 23 ; Nr. 12, no. 23 (2015-12-10), S.7223-7237 |
| Datensatznummer |
250118208
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| Publikation (Nr.) |
 copernicus.org/bg-12-7223-2015.pdf |
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| Zusammenfassung |
| Global warming has accelerated the formation of permafrost thaw ponds in
several subarctic and arctic regions. These ponds are net heterotrophic as
evidenced by their greenhouse gas (GHG) supersaturation levels (CO2 and
CH4), and generally receive large terrestrial carbon inputs from the
thawing and eroding permafrost. We measured seasonal and vertical variations
in the concentration and type of dissolved organic matter (DOM) in five
subarctic thaw (thermokarst) ponds in northern Quebec, and explored how
environmental gradients influenced heterotrophic and phototrophic biomass
and productivity. Late winter DOM had low aromaticity indicating reduced
inputs of terrestrial carbon, while the high concentration of dissolved
organic carbon (DOC) suggests that some production of non-chromophoric
dissolved compounds by the microbial food web took place under the ice
cover. Summer DOM had a strong terrestrial signature, but was also
characterized with significant inputs of algal-derived carbon, especially at
the pond surface. During late winter, bacterial production was low (maximum
of 0.8 mg C m−3 d−1) and was largely based on free-living
bacterioplankton (58 %). Bacterial production in summer was high (up to 58 mg C m−3 d−1), dominated by particle-attached bacteria (67 %),
and strongly correlated with the amount of terrestrial carbon. Primary
production was restricted to summer surface waters due to strong light
limitation deeper in the water column or in winter. The phototrophic biomass
was equal to the heterotrophic biomass, but as the algae were mostly
composed of mixotrophic species, most probably they used bacteria rather
than solar energy in such shaded ponds. Our results point to a strong
heterotrophic energy pathway in these thaw pond ecosystems, where
bacterioplankton dominates the production of new carbon biomass in both
summer and winter. |
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