SUMMARY 



On June 20, 2001, periphyton samples were collected from two 

 stations on Ward Creek near Ovando, 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. 



Ward Creek heads in the foothills surrounding the Blackfoot 

 River Valley and flows for most of its length through a grassland 

 ecoregion. For this reason, Ward Creek metrics were compared to 

 criteria for both mountain streams and prairie streams. 



A large percent dominant species value indicated moderate 

 impairment at station 01. However, the "stress" indicated by the 

 dominant species is a lack of disturbance resulting from stable 

 flows, which is a natural phenomenon. The resulting low 

 diversity index at station 01 indicated minor impairment for a 

 mountain stream and moderate impairment for a prairie stream. 



When compared to biocriteria for mountain streams, the 

 siltation index indicated partial support of aquatic life uses at 

 station 02. When compared to criteria for plains streams, the 

 siltation index indicated no impairment at station 02 . 



A small number of teratological diatom cells indicated 

 possibile chemical toxicity or environmental stress at both 

 stations. The source of this toxicity or stress is unknown. 

 The non-diatom algal assemblages and the diatom pollution index 

 both indicated small increases in nutrient concentrations and 

 organic loading between stations 01 and 02 . The low similarity 

 index indicated that a moderate amount of environmental change 

 had occured between station 01 and station 02. 



