As expected, the pollution index fell slightly from Station 

 1 to Station 2, indicating a small increase in nutrients between 

 the two sites (Table 5) . The siltation index also increased, but 

 both values were within acceptable limits for mountain streams. 

 Station 1 supported a few deformed valves of Achnanthes 

 winutissiwa and Synedra rumpens, but the number of abnormal 

 valves was within acceptable limits. The two sites had almost 

 two-thirds of their diatom floras in common, indicating only a 

 minor change in water quality between the sites. 



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Bahls, L.L. 1993. Periphyton Bioassessment Methods for Montana 

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