Dynamic of Fecal Indicator Bacteria in the St Lucie River Watershed, FL.

The Florida legislature designated St. Lucie Estuary a high priority area in the Indian River Lagoon Surface Water Improvement and Management plan. Previous report showed that higher concentration of fecal coliform was measured in the surface water runoff from agricultural lands than from unban area in the St Lucie River (SLR) watershed, indicating that some agricultural practices may serve as potential source of water pollution and posing health hazard to local communities. The objective of this study was to characterize fecal pollution affecting water quality from different agricultural practices in the SLR watershed.  Surface water samples from the 12 selected sites representing major soil types and land use modes in the SLR watershed were collected monthly over a period of one year.  Physical and chemical properties of water samples were measured on the spot. Samples were assessed for E coli, fecal coliform and enterococci using USEPA standard membrane filtration methods. A PCR based assay targeting the human specific marker esp (enterocucci surface protein) was conducted to track the source of the fecal pollution. High levels of fecal indicator bacteria were detected during the raining season from all monitoring sites. E coli levels were always lower than or equal to the fecal coliform level. Fecal coliform level exceeding Florida freshwater bacteria criteria (FFBC) were more frequently detected under storm conditions than dry weather. Fecal indicator bacteria levels tend to decrease during the cold seasons. Relatively high indicator bacteria levels were continuously determined from lands of specific agricultural practices. Microbial source tracking using esp marker will also be detailed and discussed.