Effect of Salinity on Denitrification Potential and Soil Microbial Community in Three Louisiana Coastal Wetlands.

Recent studies have shown difference in carbon gas emissions from the Mississippi River deltaic plain marshland and bottomland forest with relative to electron acceptors such as nitrate and sulfate.  To elucidate the underlying control mechanisms, soil microbial community and structure of these wetlands including forest swamp (FS), freshwater marsh (FM) and saline marsh (SM) were studied based on characterization of phosphorus lipid fatty acid (PLFA). The results showed that the PLFA profile changed along the salinity gradient toward the ocean, indicating the alteration of microbial community structure. Additionally, ratios of fungal: bacterial PLFAs (FBR) as well as ratios of cycle: mono-unsaturated PLFAs for stress evaluation were calculated. In general, these ratios were different between FS and FM/SM wetland ecosystems. The results and their implications with respect to CO₂ production will be discussed.