MOLECULAR EVALUATION OF CHANGES IN PLANKTONIC BACTERIAL POPULATIONS RESULTING FROM EQUINE FECAL CONTAMINATION IN A SUB-WATERSHED

Considerable emphasis has been placed on developing watershed-based strategies with the potential to reduce non-point-source fecal contamination. 16S-ribosomal-deoxyribonucleic-acid (rDNA) methods were used to examine a source of fecal contamination. Objectives: (1) to explore the use of denaturing-gradient-gel-electrophoresis (DGGE) with a primer set targeting a broad range of microorganisms for community perspective and (2) use a specific set to target a small portion of population to determine if there may be a useful alternative for source tracking. Fecal enterococci increased from (Log10) 1.4 CFU/ml upstream to 8.1 CFU/ml downstream. Upstream DGGE patterns varied more than downstream (Cs=42%±13). Downstream samples had greater pattern similarity (Cs=70%±11). Change in pattern similarity suggests that fecal bacteria altered microbial community structure locally and maintained downstream influence. Sequenced DGGE bands were Bacteroides, Prevotella, and uncultured rumen bacteria. Identification of bacteria within watersheds after fecal contamination may allow better selection of microorganism(s) for identifying fecal contamination sources to improve water quality.