the Blackfoot River that are known to produce nuisance growths in North American waters are 

 Cladophora, Oedogonium, Oscillatoria, Rhizocloniwn, Spirogyra, Stigeoclonium, and Ulothrix 

 (Wehr and Sheath 2003). Streams where one or more of these genera were dominant or 

 abundant in periphyton samples are: Monture Creek, Youmame Creek, West Fork Clearwater 

 River, Blanchard Creek, Rock Creek, Douglas Creek, and Braziel Creek. Among the streams 

 represented in this sample set, these are most likely to support nuisance growths of mat-forming 

 filamentous algae. 



Pollution-tolerant Algae. Palmer (1969) listed 60 algal genera that are most tolerant of 

 organic pollution. Genera of non-diatom algae in this sample set that are among the top 22 on 

 Palmer's list are Oscillatoria (#2), Scenedesmus (#4), Stigeoclonium (#8), Ankistrodesmus (#10), 

 Phormidiwn (#12) Closterium (#16), Spirogyra (#21), and Anabaena (#22). Streams where one 

 or more of these genera were abundant or dominant are: Monture Creek, West Fork Clearwater 

 River, Blanchard Creek, Rock Creek, and Douglas Creek. These streams are the ones that most 

 likely receive the heaviest loads of organic matter. Genera among the 22 most pollution-tolerant 

 algae were common or frequent at several more sites. 



Other Indicator Algae. When abundant, certain genera of algae can provide useful 

 clues about environmental conditions. The two genera of chrysophytes that were present in these 

 samples are both good indicator algae. Tribonema, which is sensitive to organic pollution and 

 prefers cool waters, was most abundant in upper Deer Creek, upper Monture Creek, and in the 

 West Fork of the Clearwater River. Vaucheria, another chrysophyte, requires steady flows of 

 cool water. Vaucheria was frequent in Buffalo Gulch (lower) and occasional in Frazier Creek 

 and lower Deer Creek. 



The filamentous green alga Mougeotia has often been reported to increase in abundance 

 in lakes that are subject to atmospheric deposition and undergoing acidification. Among study 

 sites in the Blackfoot River TMDL planning area, Mougeotia occurred infrequently and was 

 common only in the West Fork of the Clearwater River and in Rock Creek. 



