Non-Diatom Algae (Table 4) 



Thirty-two genera representing five divisions of non-diatom algae were found in samples 

 that were collected from tributaries of the Blackfoot River (Table 4). Divisions represented by 

 the most genera were Chlorophyta or green algae (17 genera) and Cyanophyta or cyanobacleria 

 (10 genera). The Division Chr\'sophyta (yello\\'-green algae) was represented by Uvo genera and 

 the Divisions Rhodophyta (red algae) and Phaeophaeta (brown algae) were represented by one 

 genus each. 



Green algae were found in all but 5 samples and cyanobacteria were found in all but 5 

 samples. Yellow-green algae were found in 8 samples and the red alga Audoidnella was found 

 in 1 1 samples. Hehbaudiella fluviatilis, a rare freshwater brown alga [most other species of 

 brown algae are marine], was found in 7 samples and was abundant in Monture Creek, the West 

 Fork of the Clearwater Riven and upper Jefferson Creek. The number of genera of non-diatom 

 algae ranged from in lower Murray Creek to 1 5 at the lower site on the West Fork of the 

 Clearwater River. 



Nitrogen-fixing Algae. Cyanobacteria that possess a certain type of specialized cell 

 (heterocyst) are capable of fixing molecular or atmospheric nitrogen under aerobic conditions. 

 These algae have a competitive advantage in waters where nitrogen is in short supply relative to 

 phosphorus and other nutrients. Among tributaries of the Blackfoot River, blue-green algae with 

 heterocysts include Anabaena, Calothrlx, Nostoc, and Tolypothrix. Streams where one or more 

 of these genera were common, frequent, or abundant are: West Fork of the Clearwater River 

 (both sites), Deer Creek (both sites), Blanchard Creek, Buffalo Gulch (upper site), Washington 

 and Jefferson Creeks (upper sites), and Seven-Up Pete Creek. Nitrogen is most likely the 

 limiting nutrient at these sites. 



Mat-forming Filamentous Algae. Large standing crops of filamentous algae can 

 interfere with swimming, boating, fishing, and other water uses. Algal genera in tributaries of 



