Spatial variability of sulfate reduction in a shallow aquifer.
The distribution and metabolic activity of sulfate-reducing bacteria (SRB) in a shallow, suboxic aquifer were studied. A radioimaging technique was used to visualize and quantify the activity of sulfate reducers in sediments at a centimetre-level scale. The distribution of SRB metabolic activity was heterogeneous with areas showing little activity far outnumbering areas with high activity. Variation in sulfate-reducing activity was not statistically correlated with variation in depth, bacterial numbers, or the following sediment properties: sediment type (sand, peat or silt), grain size, permeability and hydraulic conductivity. Sulfate-reducing bacteria activity did vary significantly with sediment porosity (multivariate analysis, r = 0.48). We hypothesized that the small pore sizes associated with sediments with low porosity restricted the ability of SRB to grow to high numbers as well as their access to nutrients. To further explore the relationship between pore size and microbial metabolic activity, columns with varying pore diameters were constructed. Sulfate-reducing bacteria in the columns with the smallest pore diameters had the lowest rates of metabolism and SRB metabolic rates increased as the pore diameter increased. For the aquifer studied, sediment porosities and pore sizes were the main factor controlling SRB activity.
Musslewhite
Chris L
CL
The University of Oklahoma, Department of Botany and Microbiology, 770 Van Vleet Oval, Norman, OK 73071, USA.
Swift
Don
D
Gilpen
Johnnie
J
McInerney
Michael J
MJ
D019342:Acetic Acid / Q000378:metabolism; D019015:Geologic Sediments / Q000382:microbiology*; D010084:Oxidation-Reduction; D010316:Particle Size; D010539:Permeability; D016062:Porosity; D013431:Sulfates / Q000378:metabolism*; D016999:Sulfur-Reducing Bacteria / Q000378:metabolism*; D014871:Water Microbiology
D013431:Sulfates; D019342:Acetic Acid