filamentous alga Oedogonium was abundant. .Ajnong sites represented by this sample set, lower 

 Stony Creek is 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), Ankistrodesmus (#10), Closterium (#16), Spirogyra (#21), and 

 Anabaena (#22). One or more of these genera were abundant or dominant only in lower 

 McCormick Creek, where the blue-green alga Anabaena was abundant. On this basis, lower 

 McCormick Creek most likely receives the heaviest load of organic matter among streams in the 

 sample set. Genera among the 22 most pollution-tolerant algae were common or frequent in 

 lower Stony Creek and lower Josephine Creek. 



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

 clues about envirorunental conditions. The chrysophyte Tribonema, which is sensitive to organic 

 pollution and prefers cool waters, was common in lower McCormick Creek and lower Josephine 

 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 Ninemile Creek TMDL planning area, cells of Mougeotia were frequent in lower 

 Josephine Creek and occasional in McCormick Creek (both sites). The presence of the rare and 

 pollution sensitive brown alga Heribaudiella indicates that upper McCormick Creek retains 

 vestiges of the native algal flora and remains relatively unaffected by human disturbance. 



Diatoms (Table 5) 



Diatoms were frequent, abundant, or dominant and ranked first in biovolume in all of the 

 samples (Table 4). All of the 16 major diatom species in tributaries of Ninemile Creek are either 

 sensitive to organic pollution or only somewhat tolerant of organic pollution. None of the major 

 diatom species is most tolerant of organic pollution (Table 5). 



