Project Area and Sampling Sites 



The project area is located in Garfield County in east central Montana. Little Dry Creek 

 heads west of Cohagen at an elevation of about 3,500 feet, then flows east and north to meet Big 

 Dry Creek about 25 miles east of Jordan and just north of Montana Highway 200 near the Van 

 Norman community. The combined flows of Little Dry and Big Dry Creeks then continue north 

 into the Big Dry Arm of Fort Peck Reservoir on the Missouri River. 



The project area is within the Northwestern Great Plains Ecoregion (Woods et al. 1999). 

 The surface geology of the area consists of sandstone and shales of the Hell Creek Formation and 

 rocks of the coal-bearing Fort Union Formation (Renfi-o and Feray 1972). The climate is 

 semiarid and continental, with cold winters and hot, dry summers. Upland vegetation is 

 predominantly mixed grassland (USDA 1976). The main land use is livestock grazing. 



Periphyton smples were collected at three sites on Little Dry Creek (Table 1). Elevations 

 at the sampling sites range from about 3,000 feet at Cohagen to about 2,400 feet at the Van 

 Norman School. 



Methods 



Periphyton samples were collected following standard operating procedures of the 

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

 were scraped, bmshed, 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. 



