Figure 1 and the data in Table 5 also demonstrate that the 

 most significant changes in the diatom flora and in associated 

 diatom metrics occurred between the upstream reference site (#4) 

 and the culvert site (#3) . By comparison, changes between sites 

 #3 and #1 were quite small. These two sites had much more in 

 common with one another, in terms of floristics and diatom 

 community structure, than they did with the upstream reference 

 site (Figure 1 and Table 5) . 



Using Protocol II and the upstream site (#4) on Squirrel 

 Creek as the local reference site, biological integrity at the 

 two downstream sites was rated as "fair" with moderat? impairment 

 and partial support of aquatic life uses (Table 6) . These low 

 ratings were due to the low index of community similarity between 

 the reference site and the study sites. This assessment also 

 indicates that the most significant impairment of biological 

 integrity in Squirrel Creek occurs between site #4 and site #3, 

 and that little or no additional impairment occurs downstream 

 from site #3 . 



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