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| Titel |
Tracing organic matter sources in a tropical mangrove ecosystem (Pichavaram, India) - a stable isotopic approach |
| VerfasserIn |
Swati Mohan Sappal, Tim Jennerjahn, Alagappan Ramanathan |
| 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 |
250095172
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| Publikation (Nr.) |
 EGU/EGU2014-10619.pdf |
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| Zusammenfassung |
| Mangroves are among the most productive ecosystems on earth and thus highly
efficient carbon sinks with most of the carbon stored in the sediments. These are the
sites for accumulation and preservation of both autochthonous and allochthonous
organic matter (OM) due to their strategic location at the interface between land and
sea and prevailing reducing environment. Recent studies suggest that vegetated
coastal habitats are more important quantitative carbon sinks than previously thought.
However, for global carbon budgets it is important to know whether the carbon buried is
freshly fixed from atmospheric CO2 or relocated, and possibly very old, carbon from
another reservoir. Therefore, the identification of OM sources is a critical issue for
constructing the carbon budget in mangrove ecosystems so as to differentiate between the
recent autochthonous or relocated allochthonous carbon that gets accumulated in the
sediments.
In this context the Pichavaram mangrove complex (comprising of a core mangrove area
and the Vellar and Coleroon rivers) in the South of India was sampled along the estuarine
gradient and in its different environmental settings, as these influence the carbon dynamics
through differences in tidal flushing and relative importance of allochthonous versus
autochthonous inputs. A total of 11 sediment cores, 18 surface sediments, 18 suspended
sediment samples, 13 true mangrove plant species, 2 mangrove associate plants, 4 marsh
shrub samples and 4 algae samples were collected from the Pichavaram mangrove complex in
January 2012 and January 2013. The samples were analysed for carbon (C), nitrogen (N),
stable carbon (δ13Corg) and stable nitrogen (δ15N) isotope composition. Our results highlight
the relative abundance of terrestrial and mangrove derived organic matter over the marine
dominated organic matter in the mangrove sediments. The sites with dense mangrove
vegetation showed higher sediment carbon content as compared to the sites with
degraded vegetation or estuarine sites thus indicating mangrove plants to be the
dominant source of carbon to the sediments. Depth distributions of biogeochemical
parameters in sediment cores indicate a shift from a terrestrial/mangrove carbon
dominance to a present-day marine carbon dominance at some sites and vice versa at
other sites. Our preliminary results suggest that variations in hydro- and sediment
dynamics and in vegetation cover and composition appear to be the responsible factors. |
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