Project Goals and Objectives: Protection of water resources is one of the most significant environmental challenges of the new millennium. Nonpoint sources (NPS) of pollution, including agricultural activities, can greatly impact water quality. One key component in effectively implementing a NPS pollution abatement program is the identification and assessment of sources of fecal pollution. Proper evaluation of these sources is needed to target best management practices (BMPs) and develop bacterial total maximum daily loads (TMDLs) or watershed protection plans (WPPs). This information may also be useful to properly assess risk in contact recreation, as many waterborne pathogens causing human illness do not colonize nonhuman hosts. According to the 2010 Texas Integrated Report, there are over 300 impairments due to excessive bacteria.
Fecal coliform bacteria have extensively been used as an indicator of fecal pollution and the potential presence of other pathogenic microorganisms in water. It has been established that the fecal coliform bacterium E. coli is more closely associated with fecal pollution than other fecal coliform bacteria, which may normally reside and multiply in the environment. E. coli is a common inhabitant of animal and human intestines and recent studies have shown that isolates from humans and various host animals (e.g., cattle, chickens, and pigs) may differ genetically and phenotypically. Use of genetic and biochemical tests may allow the original host species to be identified and is referred to as bacterial source tracking (BST).
The premise behind BST is that genetic and phenotypic tests can identify bacterial strains that are host specific so that the original host species and source of the fecal contamination can be identified. Often E. coli or Enterococcus spp. are used as the bacteria targets in BST, as this provides a direct link with water quality standards which are usually based on one of these two indicators (Parveen, Portier et al. 1999; Dombek, Johnson et al. 2000; Graves, Hagedorn et al. 2002; Field, Chern et al. 2003; Hartel, Summer et al. 2003; Kuntz, Hartel et al. 2003; Stoeckel, Mathes et al. 2004; Harwood, Levine et al. 2005). While there has been some controversy concerning host specificity and survival of E. coli in the environment (Gordon, Bauer et al. 2002), this indicator organism has the advantage that it is known to correlate with the presence of fecal contamination and is used for human health risk assessments. BST of E. coli, therefore, has the advantages of direct regulatory significance and availability of standardized culturing techniques for water samples, such as EPA Method 1603 (EPA 2005).
BST is a valuable tool for identifying human and animal sources of fecal pollution. Comprehensive BST has been completed by UTSPH EP (formerly with Texas A&M AgriLife Research) for (1) the Lake Waco and Belton Lake watersheds, (2) several San Antonio area watersheds, (3) the Lake Granbury watershed, (4) Buck Creek, and (5) the Leon and Lampasas Rivers watersheds. The Waco/Belton and Buck Creek studies were funded by the TSSWCB through Clean Water Act §319(h) NPS grants from the U.S. Environmental Protection Agency (EPA) (TSSWCB projects 02-10 and 06-11, respectively) and the Leon and Lampasas project through state general revenue funds (TSSWCB project 10-51); while the San Antonio study and Lake Granbury studies were funded by the Texas Commission on Environmental Quality (TCEQ). In addition, AgriLife SCSC has completed BST projects for the Little Brazos River tributaries and Big Cypress Creek watersheds (TSSWCB projects 09-52 and 09-55, respectively). Additionally, with TSSWCB funding, BST projects are currently under way in the Leona River and Attoyac Bayou watersheds to assess water quality impairments (projects 11-50 and 09-10, respectively). A Texas E. coli BST Library has been developed based on known source isolates from the Waco/Belton, San Antonio, Granbury, Buck Creek, Big Cypress, Little Brazos River, Attoyac Bayou, Leon River, Lampasas River, Upper Trinity River and Upper Oyster Creek watersheds. The Texas E. coli BST Library (ver. 8-12) currently contains 1,669 E. coli isolates obtained from 1,455 different domestic sewage, wildlife, livestock and pet fecal samples. While this represents a significant step towards development of a statewide E. coli BST library, continued expansion of the library to include additional known source isolates from different Texas watersheds and different animal hosts is still needed. This will allow continued evaluation of the library for geographical stability and the diversity of source specific isolates to identify specific needs for future expansion and refinement of the library. The use of the Texas E. coli BST Library will provide for significant cost and time savings for the identification of NPS pollution in the development of TMDLs and WPPs.
Project Location: Statewide
Project Cost: State Funds $454,098
Project Participants: Texas Water Resources Institute, University of Texas Health Science Center at Houston School of Public Health El Paso Regional Campus, Texas A&M AgriLife Research- Department of Soil and Crop Sciences and Texas A&M Institute of Renewable Natural Resources
Project Workplans: 13-50
Project QAPP: 13-50
Project Final Report: 13-50