Large Heronries Contribute E. coli and Nutrient Loads to Waterbodies

The impairment of watersheds by pathogens as indicated by the detection of high levels of Escherichia coli has been a problem in Texas for many years. Over half of the waterbodies designated for contact recreation in Texas are listed as impaired by bacteria. Herons and egrets are known to establish large colonies in close proximity to water. The objectives of this study were to determine the potential contribution of E. coli and nutrient loads from large heronries located near selected waterbodies in Texas. Three colonies were studied (Murphy Park (MP), Taylor, TX; Lake Conroe (LC), Conroe, TX; and Richland Creek (RC), Streetman, TX). Fecal material was collected from each colony and water samples were collected beneath and around them.  Samples were enumerated for E. coli and concentrations of nutrients were quantified.  E. coli concentrations in all water samples from MP and RC exceeded the criteria for primary contact recreation set by the Texas Commission on Environmental Quality. Nutrient concentrations in the fecal samples were found to be approximately 4 orders of magnitude greater than that of the water samples.  These preliminary results establish a foundation for improving our understanding of the potential contribution of E. coli and nutrients from heronries to Texas watersheds and clearly demonstrate the need for further investigation.  Such results will also contribute to the development of best management practices and other strategies to address bacterial and nutrient loads to Texas watersheds.