Project Area and Sampling Sites 



The project area is located in Dawson, McCone, and Richland Counties in northeastern 

 Montana. Horse Creek is a west side tributary of the upper Redwater River near Circle (HUC 

 10060002). Pasture Creek and the East Redwater River are east side tributaries of the Redwater 

 River near the lower end of the drainage. 



The streams are located in the Northwestern Great Plains and Northwestern Glaciated 

 Plains Ecoregions (Woods et al. 1999). The surface geology of the area consists of coal-bearing 

 sedimentary rocks of the Fort Union Formation and sandstones and shales of the Montana Group 

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

 summers. Upland vegetation is predominantly mixed grassland steppe (USDA 1976). The main 

 land uses are livestock grazing and dry land farming. 



Periphyton samples were collected at 4 sites on East Redwater River and 2 sites each on 

 Horse Creek and Pasture Creek (Table 1). Elevations at the sample sites range from about 2,500 

 to 2,000 feet. The streams are classified C-3 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 

 (1993). Soft algae were identified using Smith (1950), Prescott (1962, 1978), John et al. (2002), 



