Date of Award

Summer 1981

Document Type


Degree Name

Master of Science (MS)


Biological Sciences



Committee Director

Carl W. Erkenbrecher, Jr.

Committee Member

Raymond W. Alden, III

Committee Member

Daniel M. Dauer

Committee Member

Paul W. Kirk, Jr.

Committee Member

Thomas P. Wallace

Call Number for Print

Special Collections LD4331.B46 S6


A silica gel-petroleum (SGP) medium was developed which is reliable, approximately the same cost as that of the corresponding agar-based petroleum medium, and can be made sufficiently firm to use in streaking or the spread-plate technique. Advantages of the medium include: the incorporation of all of the major ions of seawater in accordance with Dittmar's Law (the salinity of which can easily be varied from 0 to 35 parts per thousand); a wide workable pH range (5.5 to 11.6); negligable pH drift(~ 0.2 pH units after 166 days); the elimination of all but negligable amounts of syneresis, the ability to homogeneously incorporate a wide variety of liquid hydrocarbons including kerosene, motor oils, crude oils and Bunker C (#6) fuel oil into the medium without sonication; the elimination of all but negligable amounts of extraneous organic carbon; and the long shelf-life of the medium which is limited only by the chemical stability of the petroleum if a humid atmosphere is properly maintained.

To test the SGP medium, a study was undertaken in the Elizabeth River. The main objectives were to gather data on water quality, densities of aerobic heterotrophic and petroleumolytic bacteria and to establish the relationships between the occurrence of petroleumolytic bacteria and environmental factors.

Neither water temperature, pH, suspended solids, nitrates, nor nitrites presented a water quality problem in the Elizabeth River study area. Phosphates and, in late summer, dissolved oxygen were found to present severe water quality problems.

The mean densities of petroleumolytic bacteria on silica gel petroleum media in the Elizabeth River Surface waters were 17, 12 and 11 colony-forming units per 100 ml for Bunker C, South Louisiana crude and 20 weight motor oils, respectively. These densities were two to three orders of magnitude lower than estimates by the most probable number technique for the same hydrocarbons.

In general, petroleumolytic bacteria were correlated with dissolved oxygen, nitrate, nitrite, and oils and grease concentrations. Petroleumolytic bacteria were inversely correlated with water temperature, salinity, and total phosphate concentrations but were not affected by organic carbon concentrations. Bunker C-utilizing bacteria exhibited different relationships with environmental parameters, suggesting that they may be a unique population of petroleumolytic bacteria.


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