Coordinates of the sampling sites are as follows: 



M22CTWDC01 46 57 46 N/109 29 02 W 

 M22CTWDC02 47 05 28 N/109 35 57 W 

 M22CTWDC03 47 07 34 N/109 34 18 W 



Land use in the Cottonwood Creek watershed is mostly 

 livestock and wildlife grazing and recreation. Cottonwood Creek 

 is classified B-1 in the Montana Surface Water Quality Standards 



METHODS 



Periphyton samples were collected by Rebecca Ridenour (Water 

 Monitoring Section, MDEQ Monitoring and Data Management Bureau) 

 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 rank of 

 those substrates at the 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 and preserved with Lugol's solution. 



The samples were examined to estimate the relative abundance 

 and rank by biovolume of diatoms and genera of soft (non-diatom) 

 algae according to the method described by Bahls (1993) . Soft 

 algae were identified using Dillard (1999) , Prescott (1978) , 

 Smith (1950) , and Whitford and Schumacher (1984) . These books 

 also served as references on the ecology of the soft algae, along 

 with Palmer (1977) . 



After the identification of soft algae, the raw periphyton 

 samples were cleaned of organic matter using sulfuric acid and 



