Samples were examined to estimate the relative abundance and 

 rank by biovolume of diatoms and genera of soft (non-diatom) 

 algae according to the method described in Bahls (1993) . Soft 

 algae were identified using Dillard (1999) , Prescott (1978) , 

 Smith (1950) , and Whitford and Schumacher (1984) . These books 

 also served as references on the ecology of the soft algae. 



After the identification of soft algae, raw periphyton 

 samples were cleaned of organic matter using sulfuric acid, and 

 permanent diatom slides were prepared in a high refractive index 

 mounting medium following Standard Methods for the Examination of 

 Water and Wastewater (APHA 1998) . For each slide, between 457 

 and 483 diatom cells (914 to 966 valves) were counted at random 

 and identified to species. The following were used as the main 

 taxonomic and autecological references for the diatoms : Krammer 

 and Lange-Bertalot 1986, 1988, •1991a, 1991b; Patrick and Reimer 

 1966, 1975. 



Lowe (1974) was also used as an ecological reference for the 

 diatoms. Eahls et al . (1984) provide, autecological information 

 on important diatom species that live in the Southern Fort Union 

 Coal Region of eastern Montana, including many of the diatom 

 species in Careless Creek and Lodgepole Creek. 



The diatom proportional counts were used to generate an 

 array of diatom association metrics (Table 2) . A metric is a 

 characteristic of the biota that changes in some predictable way 

 with increased human influence (Barbour et al . 1999) . 



One additional metric was calculated for this study: 

 percent of all diatom cells in the family Epithemiaceae . This 

 family is represented in streams by two genera, Epithemia and 

 Rhopalodia, that harbor endosymbiotic nitrogen- fixing bluegreen 

 algae (cyanobacteria) within their cells. A diatom association 

 that contains a large percentage of cells in these genera may 



