Diatom species that prefer circumneutral (as opposed to alkaline) pH values were most 

 abundant in Monture Creek and Kleinschmidt Creek. These streams are likely to have lower pH 

 values than the other streams. 



Nitrogen autotrophs were in the majority at all sites except lower Deer Creek, where 

 facultative nitrogen heterotrophs accounted for the majority of the diatom cells. This site likely 

 receives heavier loads of organic nitrogen than other sites in the sample set. At site 20 on the 

 West Fork of the Clearwater River and site 10 on Rock Creek, most cells were represented by 

 species that have not been classified with regard to nitrogen uptake. 



The modal category for oxygen demand was "continuously high" at several sites. This is 

 the nominal category for mountain streams. Most diatoms were in the "fairly high" category in 

 Richmond Creek, Blanchard Creek, Wales Creek, the lower site on Washington Creek, and the 

 upper site on Jefferson Creek. Moderate oxygen demand was the modal category at most of the 

 remaining sites. Most cells were represented by species that have not been classified with regard 

 to oxygen demand in lower West Fork Clearwater River, upper Rock Creek, Buffalo Gulch, and 

 Seven-Up Pete Creek. 



Beta-mesosaprobous was the usual level of saprobity at most sites. This represents a 

 dissolved oxygen saturation level of 70-85% and a biochemical oxygen demand (BOD5) of 2-4 

 mg/L. However, saprobity levels were higher at three sites where most of the diatoms indicated 

 more organic loading (alpha-mesosaprobous): Youmame Creek, lower Deer Creek, and lower 

 Jefferson Creek. The alpha-mesosaprobous level corresponds to 25-70% saturation of dissolved 

 oxygen and 4-13 mg/L BOD5. Saprobity levels were unclassified for the majority of diatoms in 

 lower West Fork Clearwater River and upper Rock Creek. 



Most sites in the Blackfoot River TMDL planning area were dominated by eutraphentic 

 diatom species. Two sites — Wales Creek and Upper Deer Creek — were dominated by meso- 

 eutraphentic species. Meso-eutraphentic is the next trophic level below (less enriched than) 

 eutraphentic. Five sites were dominated by species that tolerate a wide range of trophic levels 

 ranging from oligotrophic to eutrophic: Monture Creek (all sites), Kleinschmidt Creek, and 



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