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A BASIN-WIDE ANALYSIS OF THE DYNAMICS OF FECAL CONTAMINATION AND FECAL SOURCE IDENTIFICATION IN TILLAMOOK BAY, OREGON
Citation:
SHANKS, O. C., C. T. NIETCH, M. SIMONICH, M. YOUNGER, D. REYNOLDS, AND K. G. FIELD. A BASIN-WIDE ANALYSIS OF THE DYNAMICS OF FECAL CONTAMINATION AND FECAL SOURCE IDENTIFICATION IN TILLAMOOK BAY, OREGON. L. N. Ornston (ed.), APPLIED AND ENVIRONMENTAL MICROBIOLOGY. American Society for Microbiology, Washington, DC, 72(8):5537-5546, (2006).
Description:
The objectives of this study were to determine if spatial and temporal dynamics exist in source-specific Bacteroidales 16S rRNA genetic marker data across a watershed, to study these in relation to fecal indicator counts, general measurements of water quality, and climatic forces, and to identify geographic areas of intense exposure to specific sources of contamination. 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 and source-specific primers for fecal source identification. We measured E. coli MPN by standard methods, and recorded temperature, turbidity, and 5-day precipitation. Climate and water quality data collectively supported a rainfall-runoff model for source loading 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. Ruminant livestock populations were estimated to generate roughly seven times more fecal source material than the human population, and there was a 40% greater probability of detecting a ruminant source marker than a human one across the basin. On a sample site basis, 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 freshwater rivers and the estuarine waters of the Bay suggested that the factors that control the quantity of fecal indicators in the water column are different than those influencing presence of Bacteroidales markers at specific times of the year in the Tillamook basin. These may be important if fecal indicator counts are used as a criterion for source loading potential in receiving waters.