1. Amanda Garzio-Hadzick 1, Daniel Shelton 2, Yakov A. Pachepsky 2, Robert L. Hill 1, Andrey Guber 2, Randy Rowland 2, Zane Hadzick 1, 1 University of Maryland, College Park MD; 2 Environmental Microbial Safety Laboratory, USDA-ARS, Beltsville, MD Background E. coli are recommended by the EPA as indicator bacteria for fecal contamination and are currently used to evaluate water quality. Sediment has been identified as reservoirs for fecal bacteria; there has been a need to further study the relationships between E. coli and sediment. Sediment provides a hospitable secondary environment for E. coli due to the availability of nutrients and soluble organic matter, and protection from predators and UV light. Sediment texture and organic matter content effects on E. coli survival are no not well understood. Preliminary Reconnaissance Monitoring Laboratory Survival Study SedimentTexture% Sand% Silt% Clay Particle Density Organic Carbon % Saturated Water Content A Sand, Loamy Sand84.1 ± 0.85 11.5 ± 1.064.45 ± 0.292.61 ± 0.001.35 ± 0.180.56 ± 0.07 B Sandy Loam, Sandy Clay Loam59.9 ± 0.45 20.7 ± 0.5319.5 ± 0.412.55 ± 0.015.14 ± 0.801.99 ± 0.29 C Sand, Loamy Sand84.5 ± 0.19 9.59 ± 0.345.95 ± 0.152.61 ± 0.011.78 ± 0.120.64 ± 0.06 Location: First order stream of a riparian corridor bordering OPE3 field at USDA ARS Beltsville, MD Systematic in situ sampling occurred throughout 3 week period in summer 2008 E. coli concentrations remained relatively constant over time at all locations. Time and sampling position were found to be insignificant while sampling location was significant. Colilert-18 was used to quantify E. coli in water and sediment Flow chambers were constructed to simulate natural flow over sediment. Conclusions E. Coli die-off curves in sediment 4°C 14°C 24°C Chick’s Law (1908) was applied to the exponential decay portion of each curve. E. coli concentrations exponentially decreased with increasing depth at all locations. Most E. coli occurred in the upper 3 cm of sediment. Sediment ASediment BSediment C 4°C-0.02566-0.02002-0.02384 14°C-0.12775-0.07528-0.07890 24°C-0.34599-0.11986-0.24477 The slope of the exponential decay (μ) The T20 equation was then used to calculate θ (a temperature sensitivity parameter) and μ 20 (die off at temperature 20) Sediment ASediment BSediment C μ 20 0.22760.09670.1553 θ1.13891.09361.1235 Fine-textured sediment with high organic carbon content provided the most suitable environment for E. coli survival. This relationship was best represented by the lowest θ value, meaning E. coli was least sensitive to temperature in finer, high organic carbon content sediment, therefore having the slowest die-off. E. coli can persist in sediment for more than 3 months at 4°C, therefore they are capable of surviving the winter months. The persistence of E. coli in sediment was much greater than survival in water. E. Coli die-off curves in water above sediment 4°C 14°C 24°C Abstract Concentrations of E. coli bacteria are mandated by EPA for water quality evaluation in designating impaired surface waters, and for design of management practices to prevent fecal contamination of water. Many of these management practices reduce runoff from agricultural fields, implying that manure is the source of E. coli when it enters stream water. Recent studies have shown that stream sediment acts as a reservoir and potential source of fecal bacteria. This study was conducted to determine if (a) E. coli survival in the presence of dilute manure (i.e., simulated runoff) was effected by sediment particle size distribution and organic matter content, and (b) temperature affects E. coli survival in sediments the same way as it affects E. coli survival in other environmental media. Laboratory experiments were conducted at three temperatures (4, 14, and 24 ºC) using stream sediment from an agricultural stream mixed with a manure slurry from the USDA- ARS Beltsville dairy farm. Stream conditions were statistically simulated using innovative flow-through chambers. An oscillatory growth stage was observed during the first 4 to 7 days at all temperatures before the exponential inactivation stage began. The oscillation rhythm did not depend on temperature, but the population magnitude did. The E. coli inactivation rates slowed as the temperature decreased for the same sediment. The inactivation rates had the classical power law dependence on temperature during the exponential inactivation stages. Increases in both sediment clay content and in organic matter increased the initial E. coli growth and slowed the inactivation rates. At the lowest temperature, E. coli persisted for three months in sediment, suggesting that E. coli survival was possible in the stream sediment over winter. Sediment provides an effective hospitable secondary habitat for manure-borne E.coli with texture, organic matter content and temperature being the inactivation controls. Aerial photograph of study location. Blue circle represents location A, black square represents location B, and red triangle represents location C. Survival of E. coli Delivered with Manure to Stream Sediment Sediment was collected from the 3 locations along the stream and inoculated with a fresh manure slurry. The die-off of E.coli was monitored at 3 different temperatures: 4, 14, and 24°C.