Project Area and Sampling Sites 



The project area is located within the Montana extension of the Idaho Batholith 

 Ecoregion in Ravalli County, Montana. This ecoregion is mountainous, deeply dissected, 

 partially glaciated, and characteristically underlain by granitic rocks. Soils derived from 

 granitics are droughty and have limited fertility, and therefore provide only limited amounts of 

 nutrients to aquatic systems (McGrath et al. 2001). Vegetation in the project area is mixed 

 conifer forest at higher elevations and ponderosa pine, shrubs and grasses at lower elevations 

 (USDA 1976, Woods et al. 1999). The main land uses are logging, grazing, recreation, mining, 

 and wildlife production. Streams in this ecoregion are likely to suffer from increased loads of 

 fine sediments after disturbance by humans. In the Idaho portion of this ecoregion, logging has 

 caused slope instability (especially in granitic areas) and stream sedimentation. Placer gold 

 mining has heavily affected rivers in this ecoregion in the state of Idaho (McGrath et al. 2001). 



Periphyton samples were collected at 14 sites on 8 streams (Table 1). The study streams 

 are headwater tributaries of the Bitterroot River in USGS hydrologic unit 17010205. The 

 Bitterroot River is a tributary of the Clark Fork River. Streams in the project area are classified 

 B-l 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 (IKI) solution. 



The 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 

 4fe (1993). Soft algae were identified using Smith (1950), Prescott ( l l )(>:, 1978), John et al. (:i)02), 



