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| Titel |
Carbon dynamics in the Elbe land-ocean transition zone |
| VerfasserIn |
Thorben Amann, Andreas Weiss, Jens Hartmann |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250043041
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| Zusammenfassung |
| Recent model data reveal a discrepancy between the mobilisation of carbon from the
terrestrial system into the fluvial system and the amount of carbon reaching the ocean.
It is estimated that of 1.9 Pg C yr-1 total terrestrial input (Cole et al., 2007),
0.12-0.41 Pg C yr-1 are lost through CO2-evasion from inner and outer estuaries to
the atmosphere (Chen & Borges, 2009) while 0.9 Pg C yr-1 are exported to the
ocean (Cole et al., 2007). Therefore estuaries can be considered as significant CO2
sources.
To better understand temporal and spatial patterns of critical biogeochemical
transformations in the land-ocean transition zone (LOTZ), an extensive historical
hydrochemical dataset of the Elbe-river and –inner estuary system was analysed.
The LOTZ of the river Elbe can be distinguished into four zones with respect to changes
in carbon species abundance: the non-tidal river zone, the tidal harbour zone, the
maximum turbidity zone (MTZ) and the river mouth zone. The concentrations of
suspended matter and POC decrease from the non-tidal river zone reaching their
minima in the harbour zone. The MTZ is characterised by maximum SPM and
POC values, while both parameters decrease to a further minimum in the river
mouth.
Interestingly the POC concentration has nearly doubled in the period 1999-2007 if
compared to the period 1985-1998. A possible cause may be the decrease in the general
pollution of the river, despite of decreasing N and P loads in the past decades. This is
supported by the observed reduction of DOC concentrations by 50% in the earlier
period. In contrast the proportions of DOC and POC values within the four zones did
not change. The doubling of POC concentrations between the two periods is not
reflected in increasing SPM concentrations, resulting in higher POC (wt-% SPM)
values.
A decrease of POC (wt-% SPM) from the non-tidal river zone to the river mouth
indicates loss of organic carbon due to respiration processes. This is supported by an
increase of nitrate and phosphate concentrations as well as dissolved inorganic
carbon.
Presented analysis is used to develop a new spatial framework for quantification of carbon
dynamics especially addressing sinks and sources of carbon in the land-ocean transition zone
of the river Elbe.
References
Chen, C.-T.A. and Borges, A.V. (2009), „Reconciling opposing views on carbon cycling in
the coastal ocean: Continental shelves as sinks and near-shore ecosystems as sources of
atmospheric CO2”, Deep-Sea Research II (56), 578–590.
Cole, J. and Prairie, Y. and Caraco, N. and McDowell, W. and Tranvik, L. and Striegl, R.
and Duarte, C. and Kortelainen, P. and Downing, J. and Middelburg, J. and Melack, J. (2007),
"Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon
Budget", Ecosystems 10 (1), 172-185. |
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