Project Area and Sampling Sites 



The project area is located within Level FV ecoregion 15f (Eastern Divide Mountains), 

 which is a part of the Northern Rockies Ecoregion in Lewis and Clark and Jefferson Counties, 

 Montana (Woods et al. 1999). This is a semiarid to sub-humid, largely forested region east of 

 the Continental Divide that is underlain by Precambrian Belt formations. The Eastern Divide 

 Mountains receive 12 to 25 inches of precipitation per year. The climax vegetation consists of 

 Douglas-fir and ponderosa pine forests, with subalpine fir occurring at the highest elevations. 

 The main land uses are logging, mining, recreation, and wildlife habitat. 



Periphyton samples were collected at one site each on Jackson Creek, Jennies Fork, and 

 Granite Creek (Table 1, Maps 1-3). All three streams are in upper Missouri River hydrologic 

 unit (USGS HUC 10030101). Jackson Creek is a tributary of McClellan Creek, which joins 

 Prickly Pear Creek near Montana City. Jennies Fork is a tributary of Silver Creek, which flows 

 into Lake Helena. Granite Creek is a tributary of Austin Creek, which is a tributary of 

 Greenhorn Creek, which is a tributary of Sevenmile Creek. Sevenmile Creek joins Tenmile 

 Creek northwest of Helena and Tenmile Creek joins Prickly Pear Creek just above Lake Helena. 

 All three streams are classified B-1 in the Montana Surface Water Quality Standards. Elevations 

 at the sampling sites range from about 5,000 feet at the mouth of Jackson Creek to 5,840 feet at 

 Jennies Fork downstream of the parking area for Great Divide Snowsports. 



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 collecfions of microalgae and macroalgae were pooled into a common container 

 and preserved with Lugol's (IKI) solution. 



