Date of Award

5-1990

Document Type

Thesis

Degree Name

Master of Science

Department

Biology

First Advisor

Dr. Wilton Tenney

Second Advisor

Dr. R. Dean Decker

Third Advisor

Dr. John W. Bishop

Abstract

This study was based on the hypothesis that the populations of thermophilic, mesophilic, and psychrophilic bacteria in Westhampton Lake vary seasonally and are related to prevailing temperatures. It may be inferred that the kinds of bacteria present at a given season are those most directly involved in decomposition and recycling activities in the lake. Water samples were collected biweekly from September of 1986 through mid- August 1987 at three stations in Westhampton Lake. At each station, sample depths ranged from near the surface to near the bottom. Serial dilutions were plated in duplicate on nutrient agar and were incubated at 10,37, and 55 C. The number of CFU (colony forming units)/ml were calculated. Pure isolated colonies were subcultured as stock on nutrient agar slants. Experimentally, subcultures from the 10 C (psychrophilic) and 55 C (thermophilic) conditions were incubated at 37 C to check for facultative tendencies. Other subcultures were incubated under strictly anaerobic conditions to determine oxygen relationships. Standard staining methods were used to determine the gram staining reaction and the presence or absence of endospores for each isolate. Psychrophilic populations reached their maximum levels in winter during periods of minimum water temperatures while thermophile populations were at their maximum in the summer. No obligately thermophilic species were isolated, although several isolates of gram positive spore-forming rods were found that grew well at 55 C as well as at 37 C. Approximately 40-50% of the isolates originally obtained from plates cultured at 10 C proved to be obligately psychrophilic; of these, approximately two-thirds were gram-positive spore-forming bacilli. No strictly anaerobic forms were isolated. It is suggested that the diluting effect of rainfall and snow may affect both the temperature and the dissolved oxygen of the lake, resulting in immediately detectable effects on bacterial populations.

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