Project Area and Sampling Sites 



The project area is located in McCone County in northeastern Montana. Both Sand 

 Creek and Prairie Elk Creek are south side tributaries of the Missouri River. Prairie Elk Creek 

 heads northwest of Circle in central McCone County and flows north to meet the Missouri River 

 just south of Wolf Point. Sand Creek, the ne.xt drainage to the east of Prairie Elk Creek, heads 

 north of Circle and enters the Missouri River a few miles downstream. 



The headwaters of Prairie Elk Creek are in the Northwestern Great Plains Ecoregion and 

 the lower reaches are in the Northwestern Glaciated Plains Ecoregion (Woods et al. 1999). The 

 Sand Creek drainage is entirely within the Northwestern Glaciated Plains. The surface geology 

 of the area consists of coal-bearing sedimentary rocks of the Fort Union Formation in the 

 headwaters of both streams and sandstones and shales of the Montana Group in the lower 

 reaches (Renfro and Feray 1972). The climate is semiarid and continental, with cold winters and 

 hot, dry summers. Upland vegetation is predominantly mi.xed grassland steppe (USDA 1976). 

 The main land uses are livestock grazing and dr>'land farming. 



Periphyton samples were collected at five sites on Prairie Elk Creek and one site on Sand 

 Creek (Table 1). Elevations at the sampling sites range from 2,300 feet at Garoutte's to 2,000 

 feet near the mouths of Sand Creek and Prairie Elk Creek 



Methods 



Periph>lon 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. 



