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 on Palmer's list are 

 Oscillatoria (#2), Closterium (#16), Spirogyra (#21), Ulothrix (#30), Cladophora (#42), 

 Cosmarium (#53), and Tribonema (#55). Sites where one or more of these genera were frequent, 

 abundant, or dominant are: ANTLCOl, ELKR02, GAZLCOl, GAZLC02, and all sites on Blaine 

 Spring Creek. These sites are the ones that most likely receive the heaviest loads of organic 

 pollution. Genera on Palmer's list were common at the other two 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 good indicator algae. Tribonema, which is sensitive to organic pollution and prefers 

 cool waters, was a dominant in Blaine Spring Creek below the fish hatchery. Vaucheha, the 

 other chrysophyte, requires steady flows of cool water. Vaucheria was common in Gazelle 

 Creek (both sites) and frequent to abundant at the upper two sites on Blaine Spring 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 Madison River TMDL planning area, Mougeotia was found only in Elk River (both 

 sites), where it was common to frequent. 



■ 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 lower site on Gazelle Creek, 

 where it was abundant. 



• 



Diatoms (Table 5) 



Diatoms were present in all of the samples and ranked first in biomass at all sites except 

 the upper site on Blaine Spring Creek, where they ranked fourth. All of the 22 major diatom 



