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| Titel |
Partial coupling and differential regulation of biologically and photochemically labile dissolved organic carbon across boreal aquatic networks |
| VerfasserIn |
J.-F. Lapierre, P. A. del Giorgio |
| 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 ; 11, no. 20 ; Nr. 11, no. 20 (2014-10-31), S.5969-5985 |
| Datensatznummer |
250117660
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| Publikation (Nr.) |
 copernicus.org/bg-11-5969-2014.pdf |
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| Zusammenfassung |
| Despite the rapidly increasing volume of research on the biological and
photochemical degradation of DOC (dissolved organic carbon) in aquatic environments, little is known
of the large-scale patterns in biologically and photochemically degradable DOC
(BDOC and PDOC, respectively) in continental watersheds, and on the links
that exist between these two key properties that greatly influence the flow
of carbon from continents to oceans. Here we explored the patterns in the
concentrations and proportions of BDOC and PDOC across hundreds of boreal
lakes, rivers and wetlands spanning a large range of system trophic status and
terrestrial influence, and compared the drivers of these two reactive pools
of DOC at the landscape level. Using standardized incubations of natural
waters, we found that the concentrations of BDOC and PDOC covaried across
all systems studied but were nevertheless related to different pools of
dissolved organic matter (DOM; identified by fluorescence analyses) in
ambient waters. Concentrations of nutrients and protein-like fluorescent DOM
(FDOM) explained nearly half of the variation in BDOC, whereas PDOC was
exclusively predicted by DOM optical properties, consistent with the
photochemical degradability of specific FDOM pools that we experimentally
determined. The concentrations of colored DOM (CDOM), which we use here as a
proxy of terrestrial influence, almost entirely accounted for the observed
relationship between FDOM and the concentrations of both BDOC and PDOC. The
concentrations of CDOM and of the putative biolabile fluorescence component
shifted from complete decoupling in clear-water environments to strong
coupling in darker streams and wetlands. This suggests a baseline
autochthonous BDOC pool fueled by internal production that is gradually
overwhelmed by land-derived BDOC as terrestrial influence increases across
landscape gradients. The importance of land as a major source of both
biologically and photochemically degradable DOC for continental watersheds
resulted in a partial coupling of those carbon pools in natural freshwaters,
despite fundamental contrasts in terms of their composition and regulation. |
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