partial support of aquatic life uses . 



The diatom association at Paulson Road (PR2-1) was very- 

 different from the diatom association upstream at Lehf eldt . The 

 two sites had only about 15 percent of their diatom associations 

 in common (Table 5) . The dominant diatoms here- -Rhoicosphenia 

 curvata and Achnanthes minutissima- -are freshwater species that 

 do not tolerate large amounts of salt. They also prefer firm 

 attachment sites such as bare rock or other algae {Cladophora) . 

 Diatom metrics at Paulson Road indicated minor impairment but 

 full support of aqxiatic life uses. 



The sites at the Buffalo Highway (PR2-3) and near the mouth 



of Painted Robe Creek (PR2-14) had similar diatom floras, both 

 dominatated by species of Synedra that tolerate moderate amounts 

 of salt (Bahls and Bahls 1976) . These brackish water diatoms-- 

 Synedra famelica, S. fasciculata, and S. pulchella- -indicate 

 increasing salt concentrations in the lower reaches of Painted 

 Robe Creek. Nevertheless, diatom metrics at these sites 

 indicated full support of aquatic life uses with only minor 

 impairment (Table 5) . 



LITERATURE CITED 



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



Biology of Montana Reference Streams. Montana Department of 

 Health and Environmental Sciences, Helena. 



Bahls, L.L., and P. A. Bahls. 19 76. An Algal Survey of Surface 



