In the main stem of Birch Creek, Oscillatoria ranked first in bio\olume at the upstream 

 site and diatoms ranked first at the other 3 sites (Table 6). Besides diatoms, all 4 sites supported 

 green algae and cyanobacteria. In addition, the site near the mouth of Birch Creek supported the 

 xanthophyte Vaucheria, which may indicate the upwelling of cool water at this site. The number 

 of genera of non-diatom algae declined fi-om 9 at the Heart Butte Road to 3 near the mouth of 

 Birch Creek. 



Dupuyer Creek. Diatoms ranked first in biovolume in the North Fork of Dupuyer Creek 

 and the filamentous green alga Ulothrix ranked first in biovolume in the South Fork (Table 5). 

 UlothrLx is sometimes associated with nitrogen enrichment. The North Fork also supported 

 cyanobacteria (Oscillatoria) and green algae, including the filamentous genus Mougeotia. Both 

 sites supported 3 genera of non-diatom algae. 



The filamentous green alga Cladophora dominated the sample ft"om the upstream site on 

 the main stem of Dupu\-er Creek (Table 6). Cladophora requires relatively cool waters that are 

 rich in nutrients. Diatoms ranked second here and were abundant. This site supported 10 genera 

 of non-diatom algae, including 3 genera of cyanobacteria, the red alga Audouinella, and 6 genera 

 of green algae, 5 of which are filamentous. Diatoms ranked first in biovolume at the middle and 

 lower sites on Dupuyer Creek. The middle site supported only 3 genera of non-diatom algae, all 

 of them green algae. The lower site supported 8 genera of non-diatom algae, all but one of them 

 green algae. The filamentous green alga Spirogyra ("pond scum") ranked second in biomass at 

 the middle and lower sites. Spirogyra, along with Zygnema, another filamentous green that was 

 fi-equent at the lower site, indicates warmer water temperatures at the middle and lower sites than 

 at the upstream site. 



Diatoms 



All but 2 of the major diatom species from the Cut Bank — Two Medicine planning area 

 are either sensitive to organic pollution or only somewhat tolerant of organic pollution (Tables 7, 

 8, and 9). The 2 exceptions are Gomphonema parvulum and Nitzschia palea. These diatom 

 species accounted for more than 5% of the cells at only 2 sites: the upstream site on Old Maids 

 Coulee (Table 7) and the middle site on Dupuyer Creek (Table 9). 



