New approaches and technologies for quantifying fecal contamination in tidal creek and coastal receiving waters
Creators: name: Stumpf, Curtis Hubert
Publisher: name: University of North Carolina at Chapel Hill
Year: 2011

description: The coastal waters of North Carolina (NC) are important recreational areas for bathing, fishing, and shellfish harvesting. However, much of these coastal waters are contaminated with fecal indicator bacteria (FIB) (Escherichia coli (EC) and Enterococcus spp. (ENT)) which are used as proxies for pathogens of fecal origin. This fecal contamination largely occurs from improperly functioning septic systems, illicit discharges from wastewater treatment plants, and overland transport to water bodies during rainfall events. Little is known about loading concentrations and characteristics (transport) of FIB in tidal creeks of the New River Estuary, NC. FIB frequently exceeded regulatory standards for fecal contamination in headwater portions of tidal creeks. Total loads of 109 -1012 EC and ENT cells occurred over the course of storm events, and storm loading was as much as 30 to 37 times greater than baseflow loading for EC and ENT, respectively. Within the first 30% of creek storm volume for all storms and all creeks combined, a mean cumulative load of only 37% and 44% of the total EC and ENT cells, respectively, were discharged, indicating these creeks are not demonstrating first flush loading characteristics. Understanding source of contamination (human vs. wildlife) of these fecal indicators is useful for understanding risk from exposure to contaminated waters and developing mitigation strategies to improve water quality. A “toolbox” approach including conventional indicators, three alternative fecal indicator Bacteroides assays, and optical brighteners was utilized to make more robust source estimates of fecal contamination in four tidal creeks. Indicators of human contamination were found in all creeks despite relatively undeveloped land surfaces. One creek (Southwest) in particular had suggestive human fecal contamination, as determined by agreement among the entire suite of indicators. Alternative indicator testing methods using Bacteroides spp. DNA assays and Quantitative Polymerase Chain Reaction (QPCR) proved useful at distinguishing human from animal fecal contamination. However, QPCR for monitoring fecal indicators in complex tidal creek water matrices were less practical due to confounding factors. The future of water quality monitoring will likely involve the use of rapid biosensors. However, current biosensor technologies are often limited by sensitivity and specificity of analysis. Methods were developed to concentrate, purify, and capture EC, ENT, and Bacteroides spp. from marine and freshwater samples. Methods were optimized to concentrate 5 L samples by factors of 221 – 317, with average recovery from concentration of 58.6 ± 20.0%, 48.3 ± 25.5 %, and 27.5 ± 19.1 % for EC, ENT, and B. thetaiotaomicron, respectively. An immunomagnetic separation (IMS) technique was also optimized to selectively recover EC and ENT from samples using antibody labeled magnetic beads. IMS resulted in moderate recoveries of nearly 40% of EC and ENT from marine water samples, enabling detection in biosensor platforms. Overall, this research provides approaches for calculating and characterizing FIB loading in headwater tidal creeks, using a multiple indicator approach for robustly determining sources of fecal contamination, and optimized methods for sample processing for downstream application of emerging biosensor technology. Results indicate the need for improved assessment of fecal contamination in order to inform mitigation strategies for reduction of fecal contamination in tidal creeks and marine waters.