• 



array of diatom association metrics (Table 2) . A metric is a 

 characteristic of the biota that changes in some predictable way 

 with increased human influence (Barbour et al . 1999) . 



Metric values for the Redwater River were compared to 

 numeric biocriteria developed for streams in the Great Plains 

 Ecoregions of Montana (Table 3) . These criteria are based on 

 metric values measured in least-impaired reference streams (Bahls 

 et al . 1992) and on metric values measured in streams that are 

 known to be impaired by various sources and causes of pollution 

 (Bahls 1993) . 



The criteria in Table 3 distinguish among four levels of 

 impairment and three levels of aquatic life use support: no 

 impairment or only minor impairment (full support) ; moderate 

 impairment (partial support) ; and severe impairment (nonsupport) . 

 These impairment levels correspond to excellent, good, fair, and 

 poor biological integrity, respectively. 



QUALTIY ASSURANCE 



Several 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., 2008-01. The first part of this number (2008) designates 

 the sampling site (Redwater River upstream of the McCone County 

 Fairgrounds) ; the second part of the number (01) 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. 



