Project Area and Sampling Sites 



The project area is located in north central Montana in Chouteau and Fergus Counties. 

 Both Dog Creek and Eagle Creek are tributaries of the Missouri River. Eagle Creek 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 sites are in the plains ecoregion. 



Dog Creek heads in the Moccasin Mountains north of Lewistown and flows 

 northwesterly, entering the Missouri River just below the mouth of the Judith River. Dog Creek 

 also transects the Northern Rockies and Montana Valley and Foothill Prairies Ecoregions, but for 

 most of its course it flows through the Northwestern Great Plains Ecoregion. The sampling site 

 on Dog Creek is located in the Northwestern Great Plains Ecoregion. 



Periphyton samples were collected at 3 sites on Eagle Creek and 1 site on Dog 

 Creek (Table 1, Maps 1-4). Elevations at the sampling sites range from about 4000 feet above 

 mean sea level at the upper site on Eagle Creek to about 2600 feet at the lower site on Eagle 

 Creek. The middle site on Eagle Creek and the site on Dog Creek are both at about 3000 feet 

 elevation. Vegetation in the study area is mainly mixed conifer forest in the upper reaches of 

 both streams and mixed grassland along the middle and lower reaches (USDA 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 



