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| Titel |
Ancient soil organic carbon in glaciers supports downstream metabolism in the European Alps |
| VerfasserIn |
C. Fasching, G. Singer, P. Steier, J. Niggemann, T. Dittmar, T. J. Battin |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063062
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| Zusammenfassung |
| Mountain glaciers and ice caps shrink at unprecedented pace with major implications for
macroscale runoff patterns and sea-level rise. Building evidence suggests that glaciers, beside
their prominent role in the hydrological cycle, are place for microbial and biogeochemical
processes. In the Gulf of Alaska, glacial runoff was shown to be a quantitatively important
source of ancient and labile organic carbon to marine ecosystems. However, both origin and
chemical composition of glacial organic carbon nurturing downstream ecosystems
remain elusive. This makes it difficult to understand the role of glaciers in carbon
cycling. Here we present first evidence from 26 Alpine glaciers that glacial dissolved
organic carbon (DOC), although very low in concentration (138±96 μg C L-1),
contributes to carbon cycling in pro-glacial streams. We found that the bioavailability
of glacial DOC (25 to 86 % labile) for microbial heterotrophs increased with its
proteinaceous content and with age. Black carbon did not explain the variation in DOC
age (600 to 8500 years), suggesting that ancient organic carbon other than black
carbon contributes to DOC bioavailability. Proteinaceous moieties from glacial
DOC were rapidly removed in the pro-glacial stream, where DOC bioavailability
rather than physical processes drove excess pCO2 (EpCO2) in the streamwater as
a proxy for in situ metabolism. Using mass loss data and carbon use efficiency
(19.4±7.2 %) data from glacial ice, we estimate that glaciers in the European Alps
deliver 340 tons C yr-1, of which 162 tons C are potentially respired as CO2 to
the atmosphere. These fluxes are small compared to those from high-mass-loss
glaciers, such in Alaska, but they are unexpected biogeochemical links between
low-DOC glaciers and the smallest of the headwaters in alpine fluvial networks. |
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