Vilas County, WI is home to more than 1300 inland lakes and recreational beach use is a large contributor to tourism dollars brought into the area. Thus, beach closures can be extremely costly in terms of lost tourism revenue. The indicator organism of fecal contamination used in beach monitoring in Wisconsin is Escherichia coli , as high levels of this organism have been correlated with recent fecal contamination events. It has been hypothesized that stands of aquatic macrophytes may harbor high concentrations of E. coli . The objective of this project was to assess the relationship between aquatic macrophytes and the persistence of the fecal indicator organism, E. coli in beach water using both field studies and laboratory studies. The laboratory study consisted of microcosms containing three different densities of Sagittaria, Myriophyllum or a plastic plant used in combination with lake water and a strain of environmental E. coli . Water from the microcosms was sampled to enumerate the E. coli concentrations in each of the microcosms for seven days. The laboratory study found that E. coli survival was not dependent on the presence of living plant matter. The field studies observed E. coli concentrations at four inland lakes with high tourist activity during the summers of 2005 and 2006. The field studies found that dense mats of aquatic macrophytes have an increased amount of E. coli when compared to two, five and ten meters from the mat.
