Project Area and Sampling Sites 



The project area is located mostly within the Middle Rockies Ecoregion (USEPA 2000). 

 Some of the north side tributaries of the Blackfoot River head in the Canadian Rockies 

 Ecoregion (USEPA 2000). The Blackfoot River begins at Rogers Pass north of Helena and 

 flows west for about 100 miles to its confluence with the Clark Fork River at Bonner, Montana. 

 The surface geology of the watershed is complex, consisting mostly of Precambrian Belt Series 

 Rocks in the uplands and Tertiary basin fill in the Blackfoot Valley (Renfro and Feray 1972). 

 Climax vegetation consists of alpine tundra at the highest elevations, mixed conifer forest at 

 intermediate elevations, and mixed grassland/sagebrush steppe in the Blackfoot Valley near 

 Ovando. The main land uses are recreation, logging, ranching, and mining. 



Periphyton samples were collected at 30 sites on 19 tributaries of the Blackfoot River 

 (Table 1). All sites are in USGS HUC 17010203 and are classified B-1 in the Montana Surface 

 Water Quality Standards. 



Methods 



Periphyton samples were collected following standard operating procedures of the 

 MDEQ Planning, Prevention, and Assistance Division. Using appropriate tools, microalgae 

 were scraped, brushed, or sucked from natural substrates in proportion to the importance of those 

 substrates at each study site. Macroalgae were picked by hand in proportion to their abundance 

 at the site. All collections of microalgae and macroalgae were pooled into a common container 

 and preserved with Lugol's (IKJ) solution. 



The samples were examined to estimate the relative abundance of cells and ranlc by 

 biovolume of diatoms and genera of soft (non-diatom) algae according to the method described 

 in Bahls (1993). Soft algae were idenfified using Smith (1950), Prescott (1962, 1978), John et al. 

 (2002), and Wehr and Sheath (2003). These books also served as references on the ecology of 

 the soft algae, along with Palmer (1969, 1977). 



