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 Fergus County near the city 

 of Lewistown, Montana (pop. 6,368). Casino Creek heads in the 

 foothills of the Big Snowy Mountains at an elevation of about 

 5,000 feet and flows north for about 15 miles to where it enters 

 Big Spring Creek just south of Lewistown. 



The Casino Creek watershed is within the Montana Valley and 

 Foothill Prairies Ecoregion (Woods et al . 1999) . The surface 

 geology consists of metamorphic rocks of the Kootenai Formation 

 overlain by Quaternary gravel deposits (Renfro and Feray 1972) . 

 Vegetation is mixed forest and grassland in the headwaters and 

 grassland at lower elevations (USDA 1976). 



Periphyton samples were collected at two sites on August 8, 

 2000 (Table 1) . The upper site (C 1) is located just downstream 

 of the road to Cottonwood Creek at an elevation of about 5,000 

 feet (Map 1) . The lower site (C 2) is located at an elevation of 

 about 4,100 feet just upstream of the reservoir near the mouth of 

 Casino Creek (Map 2) . 



Land use in the Casino Creek watershed is mostly livestock 

 and wildlife grazing. Casino Creek is classified B-1 in the 

 Montana Surface Water Quality Standards. Several hundred gallons 

 of used motor oil were released into Casino Creek near the end of 

 February 1999. This oil did not appear to have an immediate 

 effect upon the periphyton community (Bahls 1999) . 



