Abstract
Arabian medium crude oil was applied to historically exposed estuarine sediments contained in a controlled laboratory environment and intrinsically remediated for 56 days. In situ microbial and petroleum dynamics were monitored via Most Probable Number (MPN) statistical analysis, Gas Chromatography-Mass Spectroscopy (GC-MS) and denaturing gradient gel electrophoresis of polymerase chain reaction-amplified 16S rRNA gene fragments (PCR-DGGE). The microbial community was monitored to determine (i) the extent of intrinsic remediation and (ii) if hydrocarbon contamination caused structural changes to chronically exposed microbial communities. MPN statistical analysis revealed that the addition of oil caused 3-fold increases in both aliphatic and aromatic-degrading bacteria. Petroleum chemistry demonstrated a concomitant decrease of aliphatic and aromatic hydrocarbon fractions. Therefore, an inverse relationship between hydrocarbon-degrading bacterial populations and hydrocarbon concentrations was observed throughout the experiment, illustrating that oil was being intrinsically remediated. Kinetic analysis showed that the aliphatic and aromatic hydrocarbons had a half-life of 18 and 56 days, respectively. While MPN and GC-MS analysis showed that microbial populations were increasing and hydrocarbon concentrations were decreasing, PCR-DGGE analysis revealed that the addition of oil to a complex microbial community had no detectable effect upon the microbial structure. Community changes that occurred in sediments with oil were consistent with those observed in unoiled sediments. Band pattern analysis revealed that microbial community dynamics were independent of oil contamination. Therefore, when historically contaminated sediments are re-exposed to hydrocarbon pollution, the overall structure of the microbial community as detected by PCR-DGGE is negligibly affected, however dominance of specific subpopulations (i.e. aliphatic and aromatic hydrocarbon-degraders) can change significantly.
Thornburg, Nathaniel David (2001). Microbial dynamics during intrinsic remediation of oil contaminated coastal wetland sediments (a microcosm study). Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2001 -THESIS -T467.