| The purpose of the study was to determine populations and activity of key petroleum degrading microorganisms inhabiting soils surrounding a capped well in a natural petroleum seepage area. Surface soils (0--30cm) were collected at 1.5, 2, 2.5, and 3m from well during three different sampling periods (November 2004, April 2005, and September 2005). Samples were serially diluted and plated on yeast extract peptone agar, glycerol casein agar, and potato dextrose agar, to determine total bacteria, actinomycetes, and fungi, respectively. The microbial activity for the September 2005 sampling period was determined using fluorescein diacetate hydrolysis (FDA). Enrichment cultures were performed to isolate potential hydrocarbon degraders which were subsequently tested for utilization of: benzene, toluene, ethyl benzene, xylene, naphthalene, and diesel. Populations of bacteria and fungi in soils collected during all three sampling periods were not significantly different in terms of distance away from the oil well. For the November 2004 and April 2005 sampling periods, actinomycete populations were significantly lower at the 1.5m distance compared to the other distances. The microbial activity determined by FDA was significantly lower in soils collected at the 1.5m distance than the greater distances. Several bacterial isolates were capable of degrading two or three of the hydrocarbons and 13 of the 15 isolates could degrade diesel. Results suggested that the natural microflora of the site contains hydrocarbon-degrading microorganisms. Crude oil seeping into the soil from the capped well has not impacted bacteria or fungi populations, but has affected the microbial functions at the 1.5m distance compared to 2 to 3m from the well. Also, the oil seepage is especially impacting the actinomycete populations close to the well, bacteria and fungi were not greatly affected. |
