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 Park County near Cooke City, 

 Montana. The Stillwater River heads on the Beartooth Plateau 

 (maximum elevation 12,799 feet) and flows northeasterly to the 

 Yellowstone River. The sampling sites, which lie at about 8,500 

 feet elevation, are within the Middle Rockies Ecoregion (Woods et 

 al. 1999) . 



The upper Stillwater River basin lies in a deep glaciated 

 canyon. The study area is upstream of the Beartooth-Absaroka 

 Wilderness. Vegetation is alpine tundra and spruce-fir forest 

 (USDA 1976) . The study area lies within the Beartooth Uplift, 

 which is composed of Precambrian granitic gneiss, amphibolite, 

 and subordinate metasedimentary rocks that are resistant to 

 erosion and dissolution and consequently generate groundwater and 

 runoff low in dissolved solids (Gurrieri 1998) . 



The New World Mining District at the headwaters of the basin 

 is dominated by Tertiary intrusive rocks that cross-cut Cambrian- 

 age sediments with localized Cu, Au, and Ag mineralization along 

 the contacts (Gurrieri 1998) . Oxidation of sulfide minerals by 

 groundwater migrating through the McLaren deposit and from 

 surface drainage from historic waste materials, produces water 

 with low pH, high acidity and sulfate, and high concentrations of 

 Al, Cu, Fe, Mn, and Zn that contaminate Daisy Creek (USEPA 1977) . 



Periphyton samples were collected at two sites on August 25, 



4 



