The two Stillwater River sites shared 58.27% of their diatom 

 floras (Table 4) . This indicates that the two communities are 

 somewhat similar and that a small amount of environmental change 

 (recovery) occurred between the two sites. 



Periphyton samples were collected from these same two sites 

 in August 1994 (Bahls 1995) . A bioassessment based on these 

 samples, using the same methods used here, resulted in the same 

 ratings of biological integrity: "Fair" (moderate impairment) 

 below Daisy Creek and "Good" (minor impairment) above the 

 Wilderness boundary. In both cases, low diatom diversity was the 

 reason for the less than excellent ratings. 



REFERENCES 



APHA. 1998. Standard Methods for the Examination of Water and 

 Wastewater. 20th Edition. American Public Health 

 Association, Washington, D.C. 



Bahls, L.L. 1979. Benthic diatom diversity as a measure of 

 water quality. Proc . Mont. Acad. Sci . 38:1-6. 



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

 Streams (Revised) . Montana Department of Health and 

 Environmental Sciences, Helena. 



Bahls, L.L. 1995. An Assessment of Biological Integrity in the 

 Stillwater River Based on Analysis of the Periphyton 

 Community. Water Quality Division, Montana Department of 

 Environmental Quality, Helena. 



Bahls, L.L., E.E. Weber, and J. 0. Jarvie. 1984. Ecology and 

 Distribution of Major Diatom Ecotypes in the Southern Fort 

 Union Coal Region of Montana. U.S. Geological Survey 

 Professional Paper 1289, U.S. Government Printing Office, 

 Washington. 



Bahls, L.L., Bob Bukantis, and Steve Tralles. 1992. Benchmark 



Biology of Montana Reference Streams . Montana Department of 

 Health and Environmental Sciences, Helena. 



10 



