Albert, D. B. Univ. of North Carolina, albert@marine.unc.edu
Martens, C. B. Univ. of North Carolina, cmartens@marine.unc.edu

 
DETERMINATION OF ACETATE TURNOVER RATES IN SEDIMENTS: METHODOLOGICAL ARTIFACTS
 
Utilization of fermentation products in anaerobic sediments by sulfate reducers and methanogens is of interest to biogeochemists studying carbon cycling in sedimentary ecosystems. It represents the neck of the funnel through which organic carbon flows towards the ultimate products, CO2 and CH4. Acetate is the dominant fermentation product in most sediments and has thus received the most attention. Acetate turnover rate measurements using C-14 labeled acetate, however, have been plagued by recognized, but not well-understood problems. We have done a series of experiments investigating the validity of labeled acetate turnover rate measurements in homogenized and non-homogenized sediments. The use of non-homogenized sediments that are line-injected with label is preferable because the position of fermenters and terminal metabolizers relative to one another is unaltered. However, this technique yields turnover rate constants that may vary severalfold in response to the concentration of the labeled acetate solution injected. The low specific activity of C-14 substrates is often considered a problem in these measurements, however, dilute label injections (below the ambient concentration) generally yield erroneously high rate constants. This is most pronounced when ambient concentrations are low and turnover is fast relative to the time scale of diffusive processes near the injection point.
 
Day: Thursday, Feb. 4
Time: Poster
Location: Sweeney Center
 
Code: CS63TH0988S