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| Titel |
Seasonal and spatial contrasts of sedimentary organic carbon in floodplain lakes of the central Amazon basin. |
| VerfasserIn |
Rodrigo Sobrinho, Jung-Hyun Kim, Gwenaël Abril, Claudia Zell, Patricia Moreira-Turcq, Jean-Michel Mortillaro, Tarik Meziane, Jaap Damsté, Marcelo Bernardes |
| 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 |
250086557
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| Publikation (Nr.) |
 EGU/EGU2014-447.pdf |
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| Zusammenfassung |
| Three-quarters of the area of flooded land in the world are temporary wetlands (Downing,
2009), which play a significant role in the global carbon cycle(Einsele et al., 2001; Cole et al.,
2007; Battin et al., 2009; Abril et al., 2013). Previous studies of the Amazonian floodplain
lakes (várzeas), one important compartment of wetlands, showed that the sedimentation of
organic carbon (OC) in the floodplain lakes is strongly linked to the periodical floods and to
the biogeography from upstream to downstream(Victoria et al., 1992; Martinelli et al., 2003).
However, the main sources of sedimentary OC remain uncertain. Hence, the study of the
sources of OC buried in floodplain lake sediments can enhance our understanding
of the carbon balance of the Amazon ecosystems. In this study, we investigated
the seasonal and spatial pattern of sedimentary organic matter in five floodplain
lakes of the central Amazon basin (Cabaliana, Janauaca, Canaçari, Miratuba, and
Curuai) which have different morphologies, hydrodynamics and vegetation coverage.
Surface sediments were collected in four hydrological seasons: low water (LW),
rising water (RW), high water (HW) and falling water (FW) in 2009 and 2010. We
investigated commonly used bulk geochemical tracers such as C:N ratio and stable
isotopic composition of organic carbon (δ13COC). These results were compared
with lignin-phenol parameters as an indicator of vascular plant detritus (Hedges
and Ertel, 1982) and branched glycerol dialkyl glycerol tetraethers (brGDGTs) to
trace the soil OC from land to the aquatic settings (Hopmans et al., 2004). Our
data showed that during the RW and FW seasons, the concentration of lignin and
brGDGTs were higher in comparison to other seasons. Our study also indicated that
floodplain lake sediments primarily consisted of a mixture of C3 plant detritus and
soil OC. However, a downstream increase in C4 plant-derived OC contribution
was observed along the gradient of increasingly open waters, i.e. from upstream to
downstream. We also identify the OC contribution from the seasonally flooded forests, i.e.
temporary wetlands as the most important source of sedimentary OC in floodplain
lakes. Accordingly, we attribute temporal and spatial difference in sedimentary
OC composition to the hydrological connectivity between the Amazon River and
its floodplain lakes and thus between the surrounding forests and the floodplain
lakes.
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Meziane, T., Kim, J.-H., Bernardes, M.C., Savoye, N., Deborde, J., Albéric, P., Souza,
M.F.L., Souza, E.L., Roland, F. Amazon River carbon dioxide outgassing fuelled by
wetlands. Nature accepted (2013).
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