habitat alteration, and sedimentation (MDEQ 1998; Carol Endicott, 

 MDEQ, personal communication) . 



The headwaters of the Teton River begin in the Overthrust 

 Belt of the Northern Rocky Mountains . Here the surface geology- 

 consists of faulted blocks of Madison limestone alternating with 

 sandstones, shales, and mudstones of the Kootenai Formation. At 

 the base of the Rocky Mountain Front the Teton River flows across 

 a band of Bearpaw Shale that is about 20 miles wide. The lower 

 reaches of the river are underlain by Colorado Shale (Taylor and 

 Ashley, undated) . 



Vegetation in the headwaters is mostly mixed conifer forest 

 dominated by douglas-fir and lodgepole pine, with mixed fescue 

 and wheatgrass grassland in the foothills, and shorter grasses 

 (e.g., needleandthread and related species) on the plains (USDA 

 1976) . The main land uses in the watershed are recreation, 

 waterfowl and wildlife production, livestock grazing, hay 

 production, and dryland farming. Choteau (pop. 1,729) is the 

 largest town in the watershed. 



Periphyton samples were collected at 3 sites on the Forks of 

 the Teton River and 3 sites on the mainstem Teton River in July 

 and August 199 8 (maps; Table 1) . The 3 sites on the mainstem 

 extend from just below the forks to near the mouth. Elevations 

 at the sampling sites range from about 6,000 feet at the upper 

 sites on the North and South Forks to about 3,000 feet near the 

 mouth of the Teton River near Loma, Montana. 



METHODS 



Periphyton samples were collected following standard 

 operating procedures of the MDEQ Planning, Prevention, and 

 Assistance Division. Using appropriate tools, microalgae were 



