PARENT SESSION
Oral Session #27: Aquatic Ecology: Lake structure and function. Presiding: L.A. Hansson.
Tuesday, August 7, 2001. 8:00 AM to 11:30 AM. Hall of Ideas I.

Fecal Coliforms: Where do they come from and where do they go?

THOMAS, CAROLYN¹, ¹

ABSTRACT- Fecal coliforms have long been considered a human health problem but have only recently been identified as a health problem associated with lakes and streams. In Smith Mountain Lake, VA and its tributaries fecal coliform populations have been studied for 6 years (1995-2000). In efforts to determine the source of fecal coliforms, their populations were measured using "Standard Methods" for fecal coliforms and fecal streptococci populations. Marina and non-marina coves of the lake were compared and found to be significantly different but not in violation of state standards. DNA fingerprinting of fecal coliforms and bacterial source tracking (antibiotic resistance assay) were used to determine the animal sources of these bacteria. In at least one tributary 86% of the colonies came from a human source. An intensive 96-hour study was done during a rain event at 6 sites along a major lake tributary to determine the input and variability of nonpoint source runoff on fecal coliform populations. The fecal coliform population peak was observed at time intervals consistent with its movement down the tributary until the bacteria reached the lake and the population peak was no longer detectable. A similar population study was done in a lake cove comparing fecal coliform population variability with site, depth and time of day. All three variables were found to be significant in their effect on fecal coliform populations.

KEY WORDS: bacteria, quality, antibiotic, lake