NON- DIATOM ALGAE 



0' Fallon Creek. Periphyton samples from 0' Fallon Creek 

 contained between 7 and 11 genera of non-diatom algae (Table 4) . 

 This is less than the average number of non-diatom algal genera 

 (13) reported from plains streams in Montana (Bahls 1993) . Five 

 algal divisions were represented in 0' Fallon Creek: Green algae 

 (Chlorophyta) , euglenoid algae (Euglenophyta) , golden algae 

 (Chrysophyta) , red algae (Rhodophyta) , and cyanobacteria 

 (Cyanophyta) . 



Diatoms ranked first in biovolume at all sites on 0' Fallon 

 Creek. Filamentous green algae ranked second in biovolume at all 

 sites, notably Rhizoclonium, which was present at all sites, 

 Microspora, and Cladophora (Table 4) . These algae are sessile 

 and attach by holdfasts, indicating the presence of suitable firm 

 substrates at all sampling sites on 0' Fallon Creek. Microspora, 

 which prefers cool water, was present only at the three upper 

 sampling sites. 



Euglenoid algae (Euglena and Phacus) were present, but not 

 common, at all sites. These algae are good indicators of organic 

 loading. The cool -water chrysophyte Tribonema was present at 

 Willard Crossing (OF-7) , but not at any of the downstream sites. 

 Audouinella, a red alga that is sensitive to organic loading, was 

 present only near the mouth of 0' Fallon Creek. Cyanobacteria 

 were present at all sites. With the exception of the rare genus 

 Romeria at BF-8, cyanobacteria were found only in small numbers. 



The station at Willard Crossing (OF-7) was also sampled in 

 September 1999 (Bahls 2000) . In both 1999 and 2001, diatoms and 

 green algae, particularly Rhizoclonium, dominated the algal flora 

 at this site. This site supported 10 genera of non-diatom algae 

 in 1999 and 9 genera in 2001. Stigeoclonium, an indicator of 

 organic loading, was present here in 1999 but not in 2001. 



