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

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

 the most genera were Chlorophyla or green algae (18 genera) and Cyanoph>ta or cyanobacteria 

 (1 1 genera). The Division Chrysophyta (yellow-green algae) was represented by three genera 

 and the Divisions Rhodophyta (red algae) and Euglenophyta (euglenoid algae) were represented 

 by one genus each. 



Green algae were found in all but 10 samples and cyanobacteria were found in all but 12 

 samples. Yellow-green algae were found in 15 samples and the red alga Audouinella was found 

 in 10 samples. Euglena, a pollution tolerant euglenoid alga, was found in only one sample 

 (DFVDCOl). The number of genera of non-diatom algae ranged from in Soap Creek (01) and 

 Lost Creek (02) to 1 1 in the North Fork of the Big Hole 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 Big Hole River, algae with heterocysts 

 include Anahaena, Calothrix, Nodularia. Nostoc, and Tolypothrix. Sites where one or more of 

 these genera were common, frequent, or abundant are: DOLTCOl, SWMPCOl, WRMSCOl, 

 WRMSC02, PINECOl and 02, FOXCOl and 02, FSHTC02, ELKHCOl and 02, and DIVDC02. 

 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 

 the Big Hole River that are known to produce nuisance growths in North American waters are 

 Cladophora, Oedogonium, Oscillatoria. Spirogyra, Stigeoclonium, and Ulolhrix (Wehr and 

 Sheath 2003). Sites where one or more of these genera were dominant or abundant in periphyton 

 samples are: BGHNFOl and 02, JERRCOl, LMCHC02, FRANC02, and DIVDCOl. Among 

 sites in this sample set, these are the sites that are most likely to support nuisance growths of 

 filamentous algae. 



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