Project Area and Sampling Sites 



The project area is located in north central Montana in Chouteau County. Eagle Creek is 

 a tributary of the Missouri River. It heads in the Bearpaw Mountains and flows southwesterly, 

 entering the Missouri River downstream from Virgelle. Eagle Creek transects three ecoregions: 

 the Northern Rockies, Montana Valley and Foothill Prairies, and the Northwestern Glaciated 

 Plains (Woods et al. 1999). The upper sampling site is in the foothill ecoregion and the lower 

 site is in the plains ecoregion. 



Periphyton samples were collected at 2 sites on Eagle Creek (Table 1). 

 Elevations at the sampling sites range from about 3200 feet above mean sea level at the upper 

 site to about 2600 feet at the lower site. Vegetation in the study area is mainly mixed conifer 

 forest in the upper reaches of Eagle Creek and mixed grassland along the middle and lower 

 reaches (USD A 1976). Land use is primarily livestock grazing with some mining in the 

 headwaters. 



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 (LKJ) 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), 

 and Wehr and Sheath (2003). These books also served as references on the ecology of the soft 

 (|P algae, along with Palmer (1969, 1977). 



