SUMMARY 



On July 21, 2000, periphyton samples were collected from two 

 stations on Billman Creek near Livingston, Montana for the 

 purpose of assessing whether the creek is water-quality limited 

 and in need of TMDLs . The samples were collected following DEQ 

 standard operating procedures, processed and analyzed using 

 standard methods for periphyton, and evaluated following modified 

 USEPA rapid bioassessment protocols for wadeable streams. 



Billman Creek is unique among small streams in the area in 

 that it heads at a relatively low elevation, has a mud bottom, 

 and flows through agricultural land. For this reason, Billman 

 Creek metrics were compared to criteria for both mountain streams 

 and prairie streams . 



An unusually large percentage of motile diatoms indicated 

 that both sites on Billman Creek were impaired by sediment. The 

 upper site was severely impaired for a mountain stream and 

 moderately impaired based on criteria for prairie streams. The 

 lower site was moderately impaired for a mountain stream but only 

 slightly impaired for a prairie stream. All other diatom metrics 

 indicated no impairment or only minor impairment . 



Both sites showed signs of nutrient enrichment. However, 

 dominance by filamentous green algae, the presence of euglenoid 

 algae, and a lower value for the pollution index indicated that 

 Station 2 received more nutrient loading than Station 1. 



Both sites had a small number of teratological cells, 

 perhaps indicating small concentrations of toxic chemicals. And 

 both sites had only small percentages of diatoms in the family 

 Epithemiaceae, which may indicate that nitrogen concentrations 

 were not limiting to algal growth in Billman Creek. The two 

 sites had less than 40% of their diatom assemblages in common. 



