Ritchie D Taylor

Water quality of effluent-dominated ecosystems: ecotoxicological, hydrological, and management considerations

In arid and semi-arid regions of the southwestern United States and other parts of the world, flows of historically ephemeral streams are now perennially dominated by municipal and/or industrial effluent discharges, particularly in urbanized watersheds. Because effluent-dominated and dependent water bodies have previously received limited scientific study, we reviewed select contemporary topics associated with water quality of ephemeral streams receiving effluent flows. Our findings indicate that these ecosystems present numerous challenges to aquatic scientists and water resources managers, including: 1) appropriate ecosystems or upstream conditions used reference sites in biomonitoring are difficult to locate or do not exist; 2) water quality criteria, particularly for metals, are dramatically influenced by unique site-specific stream and land use conditions; 3) effluent-dominated streams represent worse-case scenarios for evaluating and predicting aquatic responses to emerging contaminants (e.g., pharmaceuticals and personal care products); 4) low-flow and drought conditions often preclude effective biomonitoring and water quality interpretation, or skew ambient assessment results; 5) chemical-physical water quality parameters (e.g., dissolved oxygen, conductivity, temperature) are dramatically altered by effluent and stormwater characteristics; and 6) beneficial reuse of reclaimed effluent waters potentially conflict with sustainability of ecological integrity. Subsequently, we recommend several water quality research priorities for effluentdominated water bodies.

Using the agricultural environment to select better surrogates for foodborne pathogens associated with fresh produce

Despite continuing efforts to reduce foodborne pathogen contamination of fresh produce, significant outbreaks continue to occur. Identification of appropriate surrogates for foodborne pathogens facilitates relevant research to identify reservoirs and amplifiers of these contaminants in production and processing environments. Therefore, the objective of this study was to identify environmental Escherichia coli isolates from manures (poultry, swine and dairy) and surface water sources with properties similar to those of the produce associated foodborne pathogens E. coli O157:H7 and Salmonella enterica serotype Typhimurium. The most similar environmental E. coli isolates were from poultry (n=3) and surface water (n=1) sources. The best environmental E. coli surrogates had cell surface characteristics (zeta potential, hydrophobicity and exopolysaccharide composition) that were similar (i.e., within 15%) to those of S. Typhimurium and/or formed biofilms more often when grown in low nutrient media prepared from lettuce lysates (24%) than when grown on high nutrient broth (7%). The rate of attachment of environmental isolates to lettuce leaves was also similar to that of S. Typhimurium. In contrast, E. coli O157:H7, a commonly used E. coli quality control strain and swine isolates behaved similarly; all were in the lowest 10% of isolates for biofilm formation and leaf attachment. These data suggest that the environment may provide a valuable resource for selection of surrogates for foodborne pathogens.