SPATIAL AND TEMPORAL VARIATIONS OF MICROBIAL PROPERTIES AT DIFFERENT SCALES IN SHALLOW SUBSURFACE SEDIMENTS

Microbial abundance, activity, and community-level physiological profi les (CLPP) were examined at centimeter and meter scales in the subsurf ace environment at a site near Oyster, VA. At the centimeter scale, va riations in aerobic culturable heterotrophs (AGH) and glucose minerali zation rates (GMR) were highest in the water table zone, indicating th at water availability has a major effect: on variations in microbial a bundance and activity. At the meter scale, ACH and microaerophiles dec reased significantly with depth, whereas anaerobic GMR often increased with depth; this may indicate low redox potentials at depth caused by microbial consumption of oxygen. Data of CLPP indicated that the micr obial community (MC) in the soybean field exhibited greater capability to utilize multiple carbon sources than MC in the corn field. This di fference may reflect nutrient availability associated with different c rops (soybean vs corn). By using a regression model, significant spati al and temporal variations were observed for AGH, microaerophiles, ana erobic GMR, and CLPP. Results of this study indicated that water and n utrient availability as well as land use could have a dominant effect on spatial and temporal variations in microbial properties in shallow subsurface environments.