SUMMARY 



In 1998 and 1999, six composite periphyton samples were 

 collected from five sites on the East Boulder River near Big 

 Timber, Montana for the purpose of assessing whether this stream 

 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. 



Attached algae indicated cold, nutrient-poor, and fast- 

 flowing waters in the East Boulder River, especially at the upper 

 two sites. An increase in the number of non-diatom algal genera 

 and diatom species below Dry Fork Creek and below Elk Creek 

 probably indicates an increase in biologically available 

 nutrients below these tributaries. 



Low diatom diversity and high percent dominant species 

 indicated a moderate amount of stress at Stations 1 and 2, and 

 minor stress at Stations 3 and 4. This stress is probably 

 natural and caused by the cold, nutrient-poor, and rapidly- 

 flowing waters at these sites. This natural stress represents 

 the baseline condition for the upper East Boulder River. 



Minor siltation was noted near the mouth at Station 5, and 

 minor organic loading was indicated at Station 3 in 1999. Algae 

 samples collected by University of Montana researchers in 1998 

 indicated moderate siltation and minor organic loading below Elk 

 Creek and moderate siltation near the mouth of the East Boulder 

 River. Otherwise, aside from indicators of natural stress, 

 diatom metrics indicated excellent biological integrity, no 

 impairment, and full support of aquatic life uses at all sites on 

 the East Boulder River. 



