||k 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 21 on 

 Palmer's list are Euglena (#1), Oscillatoria (#2), Scenedesmus (#4), Stigeoclonium (#8), 

 Ankistrodesmus (#10), Phonnidium (U\2) Closterium (#16), and Spirogyra (#21). Euglena was 

 found in only one sample (DIVDCOl), where it was rare. Sites where one or more of the 

 remaining genera were frequent, abundant, or dominant are: WRMSC02, BGHNFOl and 02, 

 JERRCOl, PTNEC02, FOXC02, LMCHC02, ELKHC02, and DIVDCOl. These sites are the ones 

 that most likely receive the heaviest loads of organic pollution. Genera among the 21 most 

 pollution-tolerant algae were common at several more sites. 



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

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

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

 prefers cool waters, was most abundant in Fishtrap Creek. Vaucheria, another chrysophyte, 

 requires steady flows of cool water. Vaucheria was also abundant in Fishtrap Creek. A third 

 chrysophyte — Hydrurus foetidus — is a cold-water stenotherm that requires waters of constant 

 low temperature. Hydrurus was found only in upper Gold Creek, where it was abundant. 



Draparnaldia is a relatively rare filamentous green alga that is most often found in 

 pristine upland streams and springs. It also tends to be more abundant in cooler waters (Wehr 

 and Sheath 2003). Draparnaldia was found only at PfNECOl, where it was abundant. 



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 Big Hole TMDL planning area, Mougeotia occurred infrequently and was abundant 

 only at the lower site on Elkhom Creek (ELKHC02). 



The foliose, seaweed-like green alga Prasiola has been reported as abundant at sites that 

 are enriched with forms of organic nitrogen, such as bird droppings, as well as in cold mountain 

 streams (Wehr and Sheath 2003). Prasiola was found only at the upper site on Gold Creek, 

 IP where it was dominant. 



