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Zusammenfassung:
The sources and distribution of dissolved organic carbon (DOC), particulate organic carbon (POC) and dissolved inorganic carbon (DIC) in the Indian Sundarbans mangrove and Hooghly estuarine system were
examined during the pre-monsoon (summer) 2014. DOC is the dominant form of organic matter (OM) in
the studied estuarine waters and represents a mixture of mangrove and riverine sources. Microbial
degradation of land derived OM results in a high pCO2 in the Hooghly estuarine waters while enrichment
in d13C-DIC ascribes to CO2 uptake by phytoplankton in the Sundarbans water. Higher d15N in the particulate
organic nitrogen (PON) of the mangrove and marine zone could be associated with enhanced
phytoplankton production sustained by nitrate from mangrove derived OM decomposition and/or nitrate
imported from the Bay of Bengal. Low organic carbon contents and elemental ratios (TN/TOC) indicate an
intense mineralization and transformation of OM in the sediments, resulting insignificantly different OM
compositions compared to those of the three major sources: land derived OM, mangrove leaf litter
(Avicennia marina) and in situ phytoplankton production.
