Some algae, such as the filamentous greens, are conspicuous 

 and their excessive growth may be aesthetically displeasing, 

 deplete dissolved oxygen, interfere with fishing and fish 

 spawning, clog water filters and irrigation intakes, create 

 tastes and odors in drinking water, and cause other problems. 



PROJECT AREA AND SAMPLING SITES 



The project area is located in Sweet Grass County in 

 southcentral Montana. The East Boulder River heads on the East 

 Boulder Plateau in the Absaroka-Beartooth Wilderness at an 

 elevation of about 10,000 feet. The East Boulder River is a 

 third-order tributary of the Boulder River, which is a tributary 

 of the Yellowstone River. 



The East Boulder River begins in the Middle Rockies 

 Ecoregion and enters the Montana Valley and Foothill Prairies 

 Ecoregion about midway through the study reach (Woods et al . 

 1999) . The surface geology of the upper watershed consists of 

 high-grade Precambrian metamorphic rocks of various lithologies 

 (Renfro and Feray 1972) . Vegetation is alpine tundra at the 

 highest elevations, conifer forest at middle elevations, and 

 grassland below the mouth of the East Boulder Canyon (USDA 1976) . 



Periphyton samples were collected at five sites on The East 

 Boulder River in 1998 and 1999 (Maps 1 and 2, Table 1) . The ■ 

 upper site above Dry Fork Creek is located at an elevation of 

 about 6,300 feet. Elevation at the lowest site near the mouth of 

 the river is about 5,000 feet. The East Boulder River is 

 classified B-l in the Montana Surface Water Quality Standards. 



