Molina, M. USEPA and University of Georgia, molina.marirosa@epa.gov
Cox, J. USEPA, cox.julia@epa.gov
Burke, R. A. USEPA, burke.roger@epa.gov

 
EXAMINATION OF SEDIMENTARY MICROBIAL LIPIDS USING COMPOUND SPECIFIC ISOTOPIC ANALYSIS TO DETERMINE CARBON TRANSFORMATION ALONG AN ESTUARINE CONTINUUM
 
Compound specific isotopic analysis (CSIA) of phospholipid fatty acids (PLFAs) was used to study the source of organic carbon available to the microbial community in surface sediments of the Altamaha and Savannah River estuaries. CSIA of PLFAs indicates the source of C that is actively metabolized by the microbial community. Altamaha water column bacteria incubated in the presence of different C sources demonstrated a 1-3 per mil depletion in 13C of PLFAs relative to the substrate. The del 13C of most PLFAs collected along a salinity gradient (0 to 25 per mil) during October 96, March 97, and October 97 reflected a terrestrial C3 source with a shift towards a marine or C4 influence downstream. However, light del 13C values obtained at the mouth of the Altamaha indicated that C3 sources are also utilized by bacteria closer to the ocean. No C3 terrestrial influence was observed at the mouth of the Savannah. In addition, PLFAs extracted from Savannah River sediments showed lighter del values during October than March. Highly 13C depleted del values (indicative of methanotrophic activity) were observed further downstream in the Altamaha during March (when freshwater discharge is maximal) and during October in the Savannah.
 
Day: Tuesday, Feb. 2
Time: 11:30 - 11:45am
Location: Eldorado Hotel
 
Code: SS32TU1130E