Project Area and Sampling Sites 



The project area is located in Fergus County in central Montana. Beaver Creek, Casino 

 Creek, and Cottonwood Creek are tributaries of Big Spring Creek, which is a principal tributary 

 of the Judith River. These streams head south of Lewistown on the north side of the Big Snowy 

 Mountains, which is an outlier of the Middle Rockies Ecoregion (USEPA 2000). 



Periphyton samples were collected at three sites on Beaver Creek (Table 1). Elevations 

 at the sampling sites range from about 4400 feet above mean sea level at the upper site to about 

 3840 feet at the lower site. Vegetation in the study area is mainly mixed conifer forest in the 

 upper reaches of Beaver Creek and mixed grassland along the middle and lower reaches (USDA 

 1976). Land use is primarily livestock grazing. Samples of conspicuous algae were also 

 collected from nearby Casino Creek and Cottonwood Creek (Table 1). 



Methods 



Periphyton samples were collected from Beaver Creek following standard operating 

 procedures of the MDEQ Planning, Prevention, and Assistance Division. Using appropriate 

 tools, microalgae were scraped, bnished, 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. Grab samples of conspicuous 

 macroalgae (for identification only) were collected from Casino Creek and Cottonwood Creek 

 and preserved with Lugol's solution. 



The Beaver Creek 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), and Wehr and Sheath (2003). These books also served as references on the ecology of 

 the soft algae, along with Palmer (1969, 1977). 



