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TRACKING FECAL CONTAMINATION WITH BACTEROIDALES MOLECULAR MARKERS: AN ANALYSIS OF THE DYNAMICS OF FECAL CONTAMINATION IN THE TILLAMOOK BASIN, OREGON
Citation:
SHANKS, O. C., C. T. NIETCH, M. SIMONICH, D. REYNOLDS, AND K. FIELDS. TRACKING FECAL CONTAMINATION WITH BACTEROIDALES MOLECULAR MARKERS: AN ANALYSIS OF THE DYNAMICS OF FECAL CONTAMINATION IN THE TILLAMOOK BASIN, OREGON. Presented at 106th General Meeting of the American Society of Microbiology, Orlando, FL, May 21 - 25, 2006.
Impact/Purpose:
To inform the public
Description:
Although amplification of source-specific molecular markers from Bacteroidales fecal bacteria can identify several different kinds of fecal contamination in water, it remains unclear how this technique relates to fecal indicator measurements in natural waters. The objectives of this study were to elucidate spatial and temporal dynamics of source-specific Bacteroidales 16S rRNA genetic marker data across a watershed, to compare these to fecal indicator counts, general measurements of water quality, and climatic forces, and to identify sites of intense exposure to specific sources of contamination. Biweekly sampling occurred over a two-year period in the Tillamook basin situated on the north central coast of Oregon, at 30 sites located along five river tributaries and in the Tillamook Bay. We performed Bacteroidales PCR assays with general, ruminant and human source-specific primers for fecal source identification. We measured E. coli MPN, and recorded temperature, turbidity, and 5-day precipitation. Results and Conclusions: Climate and water quality data collectively suggested a rainfall-runoff pattern for microbial source input in the Tillamook basin that mirrored the annual precipitation cycle. Fecal sources were statistically more linked to ruminants than humans on a basin-wide basis; there was a 40% greater probability of detecting a ruminant source marker than a human one across the basin. At individual sites, the addition of fecal source tracking data provided new information linking elevated fecal indicator bacteria loads to specific point and non-point sources of fecal pollution in the basin. Inconsistencies in E. coli and host-specific marker trends in the rivers and estuary suggested that the factors that control the quantity of fecal indicators in the water column are different than those influencing the presence of Bacteroidales markers at specific times of the year. This is important if fecal indicator counts are used as a criterion for source loading potential in receiving waters.