Only periphyton samples collected in summer (i.e., June 21- 

 September 21) can be compared with confidence to reference stream 

 samples because metric values change seasonally and summer is the 

 season in which reference streams and impaired streams were 

 sampled for the purpose of biocriteria development . 



QUALITY ASSURANCE 



Se-'-'eral steps were taken to assure that the study results 

 are accurate and reproducible. 



Upon receipt of the samples, station and sample information 

 were recorded in a laboratory notebook and samples were assigned 

 a unique number compatible with the Montana Diatom Database, 

 e.g., 0364-22. The first part of this number (0364) designates 

 the sampling site (Tongue River above Prairie Dog Coulee near 

 Pyramid Butte) ; the second part of the number (22) designates the 

 number of periphyton samples that have been collected at this 

 site to date for which data have been entered into the Montana 

 Diatom Database. 



Sample observations and analyses of soft (non-diatom) algae 

 were recorded in a lab notebook along with station and sample 

 information provided by MDEQ . A portion of the raw sample was 

 used to make duplicate diatom slides. 



On completion of the project, station information, sample 

 information, and diatom proportional count data will be entered 

 into the Montana Diatom Database. One set of diatom slides will 

 be deposited in the University of Montana Herbarium in Missoula. 

 The other set of slides will be retained by Hannaea in Helena. 



RESULTS AND DISCUSSION 

 7 



