E. coli is the number one cause for water quality impairments in rivers and streams in South Dakota and the United States. Stream bottom sediments can be a reservoir for bacteria, including pathogenic organisms and fecal indicator bacteria (FIB), due to the favorable conditions provided by sediments for survival. Despite this, little is known about the variability of E. coli in sediments which should be considered when developing a sampling regime. This study examines the spatial variability of E. coli in sediment across the stream cross-section, the temporal stability of E. coli in sediment samples, and the implications for sediment sampling and processing. Five locations were sampled for sediment E. coli along two tributaries to the Big Sioux River in eastern South Dakota, four along Skunk Creek (Sk1, Sk2, Sk3, and Sk4), and one in Sixmile Creek (SM). In Skunk Creek, site Sk1 has direct cattle access where the other three sites (Sk2, Sk3, and Sk4) are under Seasonal Riparian Area Management (SRAM), a strategy that limits the cattle access to the stream. E. coli concentrations in the sediment ranged from 4 to 997 CFU g⁻¹ (8.5 × 10² to 2.1 × 10⁵ CFU 100 mL⁻¹). The highest and lowest E. coli concentrations observed were at sites Sk1 and Sk4, respectively. The E. coli concentration decreased from the upstream cattle crossing site (Sk1) through the downstream SRAM sites. Analyzing the stream cross-section analysis revealed no significant difference in E. coli concentration between the edge and the middle of the stream. Sediment samples can be held up to 24 h after sample collection in refrigerated conditions (37 °F) in the majority of cases (80%) without significant changes in E. coli concentrations. The sample size analysis indicated the spatial variability of E. coli across the stream cross-section is high and a single grab sample may not be able to provide adequate representation of E. coli concentrations in sediment without substantial error. The findings provide insight for designing E. coli monitoring projects and promote the awareness of unconventional sources of microbiological water quality impairment which are often overlooked.

大肠杆菌是南达科他州和美国河流和溪流水质受损的第一大原因。由于沉积物为生存提供了有利条件，溪流底部沉积物可能是细菌的储存库，包括病原生物和粪便指示菌 (FIB)。尽管如此，人们对沉积物中大肠杆菌的变异性知之甚少，在制定采样制度时应考虑这些变异性。本研究探讨的空间变异大肠杆菌横跨流的横截面，的时间稳定性沉积物大肠杆菌沉积物样品中，以及用于沉积物采样和处理的影响。五个地点采样了沉积物大肠杆菌沿着南达科他州东部大苏河的两条支流，臭鼬溪（Sk1、Sk2、Sk3 和 Sk4）的四个支流，以及六英里溪 (SM) 的一个。在臭鼬溪，站点 Sk1 可以直接进入牛群，而其他三个站点（Sk2、Sk3 和 Sk4）则处于季节性河岸区域管理 (SRAM) 之下，该策略限制了牛群进入河流。沉积物中大肠杆菌的浓度范围为 4 至 997 CFU g ^-1 (8.5 × 10 ²至 2.1 × 10 ⁵  CFU 100 mL ^-1 )。观察到的最高和最低大肠杆菌浓度分别位于 Sk1 和 Sk4 站点。该大肠杆菌从上游牛穿越站点 (Sk1) 到下游 SRAM 站点，浓度降低。分析河流横截面分析表明，河流边缘和中间的大肠杆菌浓度没有显着差异。在大多数情况下 (80%)，在冷藏条件 (37 °F) 下收集样品后，沉积物样品可以保存长达 24 小时，而大肠杆菌浓度不会发生显着变化。样本大小分析表明，整个河流横截面的大肠杆菌的空间变异性很高，单个抓样可能无法在没有实质性错误的情况下充分代表沉积物中的大肠杆菌浓度。研究结果为设计提供了见解大肠杆菌监测项目并提高人们对经常被忽视的微生物水质损害的非常规来源的认识。