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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 111,
G01009,
14 PP., 2006
doi:10.1029/2005JG000071
Ramifications of increased salinity in tidal freshwater sediments: Geochemistry and microbial pathways of organic matter mineralization
Department of Marine Science, University of Georgia, Athens, Georgia, USA
Department of Marine Science, University of Georgia, Athens, Georgia, USA
Department of Marine Science, University of Georgia, Athens, Georgia, USA
The effects of salinity intrusion on the anaerobic microbial and geochemical dynamics of tidal freshwater sediments were investigated using flow-through sediment reactors. In freshwater control sediments, organic matter mineralization was dominated by methanogenesis (62%), followed by sulfate reduction (18%), denitrification (10%), and iron reduction (10%). Upon salinity intrusion, nutrient (ammonium, silicate, phosphate) concentrations increased and rates of methanogenesis declined. Iron-oxide bioavailability increased and microbial iron reduction appeared to account for >60% of organic matter oxidation for several days after salinity intrusion. However, sulfate reduction was the dominant pathway (>50%) of organic matter oxidation within 2 weeks of salinity intrusion, and accounted for >95% of total organic matter mineralization after 4 weeks. Total in situ sediment organic matter mineralization doubled following salinity intrusion. Increased nutrient release, decreased methanogenesis and a rapid shift to sulfate reduction, with a coincident increase overall organic matter mineralization, accompanied salinity intrusion into previously freshwater riverine sediments.
Received 4 July 2005; accepted 13 December 2005; published 7 February 2006.
Citation: (2006), Ramifications of increased salinity in tidal freshwater sediments: Geochemistry and microbial pathways of organic matter mineralization, J. Geophys. Res., 111, G01009, doi:10.1029/2005JG000071.
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