(Lange-Bertalot 2001). It was abundant only at the lower site on Eagle Creek. The tolerance of 

 this species to organic pollution is unknown. 



Dog Creek. The major diatom species in Dog Creek were either somewhat tolerant of 

 organic pollution or very tolerant of organic pollution (Table 4). The dominant species here was 

 Nitzschia inconspicua. This is a facultative nitrogen heterotroph and a species that prefers 

 eutrophic waters with moderate BOD loads and oxygen content (Van Dam et al. 1994). Diatom 

 metrics for Dog Creek indicated severe impairment from sedimentation. Depressed diatom 

 species diversity indicated moderate impairment and partial support of aquatic life uses. This 

 stress was probably due to excess nutrients, primarily nitrogen, which resulted in an unusually 

 large population of Nitzschia inconspicua. 



Eagle Creek. The upper site on Eagle Creek had excellent biological integrity for a 

 prairie stream (Table 4). Even when compared to criteria for a mountain stream (Bahls 1993), 

 diatom metrics at this site indicated only minor impairment from organic loading and 

 sedimentation. Diatom species richness and diversity were excellent. The major diatom species 

 here were mostly sensitive to or only somewhat tolerant of organic pollution. The most abundant 

 species at sites 1 and 2 was Stanrosira construens, a non-motile araphid species that indicates 

 stable flows and little physical disturbance. 



Diatom metrics at the middle site on Eagle Creek indicated good biological integrity for a 

 prairie stream (Table 4). Only a few abnormal cells ofDiatoma vulgaris kept this site from 

 having excellent biological integrity. Abnormal cells of this species are a common occurrence, 

 even in unpolluted waters (personal observation). Diatom species richness and diversity were 

 excellent here. This site shared about half of its diatom flora with the upper site on Eagle Creek, 

 but only about 13% with the downstream site near the mouth. This indicates a major change in 

 the diatom flora and in ecological conditions between this site and the lower site on Eagle Creek. 



Moderate impairment from sedimentation and partial support of aquatic life uses was 

 indicated at Eagle Creek site 3 (Table 4). A somewhat depressed pollution index also indicated 

 minor loading of organic pollutants at this site. Diatom species richness and diversity were less 



