BIOASSESSMENT 



PROTOCOL I 



All diatom association metrics for UMC-1 indicated full 

 support of aquatic life uses when compared to least-impaired 

 reference streams elsewhere in eastern Montana (Table 5). Minor 

 impairment, but still full support, was indicated by two metrics: 

 Pollution index and percent abnormal cells. Full support of 

 aquatic life uses was also noted at UMC-1 in 1999 (Bahls 2000) . 



A very low pollution index and an exceptionally large 

 siltation index indicated only partial support of aquatic life 

 uses at LMC-7 when compared to prairie reference streams in 

 eastern Montana (Table 5) . The pollution index was lower and the 

 siltation index was higher in 2000 than they were at this site in 

 1999. This site also exhibited moderate impairment and partial 

 support of aquatic life uses in 1999 (Bahls 2000) . 



PROTOCOL II 



Metrics at LMC-7 were compared with those at the upstream 

 control site (UMC-1) following Protocol II and using the criteria 

 in Table 12 in Bahls (1993) . This comparison also indicated that 

 LMC-7 provided only partial support of aquatic life uses and was 

 moderately impaired. Impairment was due primarily to the very 

 low pollution index, indicating a high level of organic loading, 

 and to the dissimilarity between the two diatom associations. 

 Some of the organic loading here may be internal in origin, i.e., 

 resulting from the breakdown of aquatic plants. 



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