Nelson Creek. Nelson Creek was dominated by 4 species of diatoms that are very 

 tolerant of elevated organic loading and/or salinity. The pollution index indicates severe 

 impairment from organic loading, which resulted in depressed diatom species richness and 

 diversity. Sedimentation was only a minor problem in Nelson Creek. Nelson Creek supported a 

 large percentage of nitrogen-fixing diatoms (Rhopalodiales), which indicates probable nitrogen 

 limiting conditions. 



Prairie Elk Creek. Prairie Elk Creek (and the lower site on Sand Creek) had the best 

 overall biological integrity of all the sites in this sample set. Diatom metrics indicate only minor 

 impairment from organic loading and sedimentation. Diatom species richness and diversity 

 values were somewhat depressed, but still within the range of minor impairment. This was the 

 only site where the pollution sensitive diatom Achnanthidium minutissimum was a major species. 



Redwater River. Diatom metrics indicate severe organic loading and moderate 

 sedimentation at the upper (Fairgrounds) site on the Redwater River (Table 4). This site was 

 dominated by Navicula durrenbergiana, a motile diatom that tolerates elevated concentrations of 

 organic nutrients and dissolved solids. Although diatom species richness and non-diatom genus 

 richness were normal for a prairie stream, diatom diversity and equitability were low and 

 indicate a moderate amount of stress. Two abnormal diatom cells were counted at this site. This 

 is within the normal range for an unimpaired prairie stream. No abnormal cells were obser\'ed at 

 the other 10 sites that were sampled for this project. 



The Cemetery Road and airport sites showed moderate stress from organic loading and 

 sedimentation, respectively. The salinity tolerant species Navicula salinarum dominated the 

 diatom assemblage at Cemetery Road, indicating that elevated dissolved solids were also a 

 stressor here. This site shared about a third of its diatom assemblage with the upstream site, 

 indicating that a moderate amount of environmental change occurred between the two sites. 

 Nitzschia frustulum was the dominant diatom species at the airport site. This species is highly 

 motile and tolerates elevated concentrations of both orsanic and inorganic nutrients. This site 



