Old Maids Coulee. Filamentous green algae (Microspora at the upstream site, 

 Cladophora at the downstream site) dominated periphyton samples collected from Old Maids 

 Coulee (Table 4). Diatoms were frequent at both sites and Vaucheria, a coenocytic alga that 

 indicates steady flows of cool water, was common at the downstream site. Cyanobacteria were 

 absent from Old Maids Coulee. The upper and lower sites supported 5 and 7 genera of non- 

 diatom algae, respectively. 



Two Medicine River. Stigeoclonium-a branched filamentous green alga that is 

 sometimes associated with nutrient enrichment-ranked first in biovolume at both sites on the 

 South Fork of the Two Medicine River (Table 5). Diatoms ranked second at the upper site and 

 Nostoc, a nitrogen-fixing cyanobacterium, ranked third. At the lower site, Mougeotia ranked 

 second in biovolume and diatoms ranked third. Mougeotia is a filamentous green alga that 

 prefers cool waters of good quality. The upper and lower sites supported 3 and 4 genera of non- 

 diatom algae, respectively. 



Mougeotia was the most abundant alga in Railroad Creek, followed by diatoms (Table 5). 

 Railroad Creek supported 6 genera of non-diatom algae, including 2 genera of cyanobacteria and 

 4 genera of green algae. 



The diatoms were the most abundant algal group at the mouth of the Two Medicine River 

 (Table 6). This site supported 5 genera of non-diatom algae, including the filamentous 

 cyanobacteria Oscillatoria and Phormidium, and the non-filamentous green algae Closterium, 

 Cosmarium, and Scenedesmus. 



Birch Creek. The chrysophyte Hydrurus foetidus ranked first in biovolume at the site on 

 the South Fork of Birch Creek (Table 5). This slimy, yellow-green alga often dominates the 

 periphyton community in undisturbed mountain streams exposed to full sunlight, especially in 

 the spring and the fall. Diatoms ranked second at this site, followed by the cyanobacterium 

 Oscillatoria and the red alga Audouinella. Audouinella indicates cool waters of good quality. 



