Non-Diatom Algae (Table 3) 



Beaver Creek below Hilgard Creek. The sample from this site was dominated by 



Hydrurus foetidus: 



One of the most dramatic examples of a cold-water stenotherm is the mountain- 

 stream-dwelling chrysophyte Hydnirus foetidus . This macroscopic, brown, gelatinous, 

 unpleasant-smelling alga is relatively abundant in both the eastern and western mountain 

 streams of North America. The gelatinous envelope in which the cells are embedded is 

 exceedingly tough and the plant frequently covers the entire surface of submerged rocks 

 and has caused more than one hiker to lose his or her footing when crossing a stream. It 

 normally begins to disappear when water temperatures rise much above 10°C. . .Other 

 requirements for this species apparently include low pH and bright sunlight (Wehr and 

 - Sheath 2003). 



Diatoms were frequent in this sample and Hannaea arcus was the dominant diatom from a visual 

 standpoint. 



Beaver Creek at Highway 287. Diatoms were also frequent in this sample and ranked 

 first in biovolume. The filamentous green alga Ulothrix ranked second in biovolume, but only 

 occasional cells of this genus were observed. Ulothrix generally prefers cool, well-aerated 

 waters. Closterium, a desmid, ranked third and Oscillatoria, a filamentous cyanobacterium, 

 ranked fourth in biovolume. Both of these algae were represented by only occasional cells. 

 Hydrurus foetidus was absent from the sample collected at this site. 



Diatoms (Table 4) 



All six of the major diatom species from Beaver Creek are included in pollution tolerance 

 classes 3 or 2 and are either sensitive to organic pollution or only somewhat tolerant of organic 

 pollution (Table 4). None of the major diatom species are most tolerant of organic pollution 

 (pollution tolerance class =1). 



Some, if not all, of the stresses indicated at the two sites appear to be natural in origin. 

 High values for the disturbance index and percent dominant species and low values for the 



