Combining targeted sampling and bacterial source tracking (bst) during calm and stormy conditions

Abstract

In April 2004, high numbers of fecal enterococci triggered a beach advisory on Sea Island, GA. Targeted sampling, which finds fecal contamination much like the children’s game of “hot” and “cold,” was combined with three bacterial source tracking (BST) methods: Enterococcus speciation, the presence or absence of a human virulence factor in Enterococcus faecium, and fluorometry. During calm (i.e non-runoff) conditions, the likely contamination sources were wildlife feces and leaking sewer lines located on a creek of St. Simons Island, GA. Fluorometry quickly identified malfunctioning sewer lines. A test for human virulence factor was positive. During stormflow (i.e. runoff) conditions, the likely contamination sources were wildlife feces and effluent from two pipes. A test for human virulence factor was negative. Because the percentage of Ent. faecalis from the pipes was high (>30%), fecal contamination from wild birds was likely. This is the first report of targeted sampling during stormy conditions, and the first time fluorometry has been combined with targeted sampling.