Watershed-Wide Analysis of Fecal Contamination and Fecal Source Identification in Santa Ana River Watershed Impacted by Differences Sources

Abstract

The Santa Ana River in Southern California is the primary water supply for about 2 m people. The river originates in the San Gabriel and San Bernardino Mountains at elevations of more than 10,000 feet and flows southwesterly for more than 100 miles before discharging into the Pacific Ocean at Huntington Beach. The watershed is home to more than 4 m people. The Regional Water Control Board has listed the Santa Ana River and its tributaries in Chino basin as impaired water bodies on the RWQCB 303(d) list. The main constituent of regulatory concern is pathogens that have impaired the use of waters for beneficial uses of warm freshwater habitat and non-contact water recreation. The objectives of this study were to elucidate spatial and temporal dynamics in source-specific E. coli genetic marker data across a watershed; to compare these dynamics to fecal indicator counts, general measurements of water quality, and to identify sampling points to specific sources of contamination. Samples were collected during a 12-month period throughout the watershed from 17 sites along four river tributaries and in Santa Ana River. Water and sediment samples were assessed to determine the occurrence of genetic markers for E. coli to identify fecal sources. Standard microbiological methods were used for the isolation of E. coli from water and sediment. Total bacterial DNA was extracted from water and sediment. UidA1939 gene was used as target genes for the non-library-based microbial source tracking. The uidA1939 marker was a good marker for microbial source tracking due to its sensitivity and discriminatory power.