• 



by various sources and causes of pollution (Bahls 1993). The biocriteria in Tables 2 and 3 are 

 valid only for samples collected during the summer field season (June 21 -September 21). 



The biocriteria in Tables 2 and 3 distinguish among four levels of stress or impairment 

 and three levels of aquatic life use support: (1) no impairment or only minor impairment (full 

 support); (2) moderate impainnent (partial support); and (3) severe impainnent (nonsupport). 

 These impairment levels correspond to excellent, good, fair, and poor biological integrity, 

 respectively. 



Quality Assurance 



Several steps were taken to assure that the study results are accurate and reproducible. 

 Upon receipt of the samples, station and sample attribute data were recorded in the Montana 

 Diatom Database and the samples were assigned a unique number. One of the sites that was 

 sampled in 2003 (Johnstone's) was also sampled in 2000 (Bahls 2001b). 



Sample observations and analyses of soft (non-diatom) algae were recorded in a lab 

 notebook along with information on the sample label. Portions of the two composite samples 

 were used to make duplicate diatom slides. The slide used for the diatom proportional count 

 will be deposited in the Montana Diatom Collection at the University of Montana Herbarium in 

 Missoula. The duplicate slide will be retained in the offices of Hannaea in Helena. Diatom 

 proportional counts have been entered into the Montana Diatom Database. 



Results and Discussion 



Results are presented in Tables 4, 5 and 6, which are located near the end of this report 

 following the references section. Appendix A consists of two diatom reports, one for each 

 composite sample. Each diatom report contains an alphabetical list of diatom species and their 

 percent abundances, and values for 65 diatom metrics and ecological attributes (Table 7). 



