Non-Diatom Algae 



The sample from the upstream site above the county road was dominated by diatoms, 

 followed in abundance by the blue-green alga Oscillatoria and occasional cells of the 

 filamentous green alga Rhizoclonium (Table 3). Rhizoclonium was dominant at the downstream 

 site, followed by diatoms, the filamentous green alga Schizomeris, and the desmid Closterium. 

 Rhizoclonium is a common mat-forming and nuisance alga in streams of the western United 

 States. Schizomeris is most common in eutrophic waters, including polluted environments such 

 as sewage sludge or shallow lakes close to discharges from sewage treatment plants (Wehr and 

 Sheath 2003). It grows in quiet waters as dark green, coarse clumps and is widespread but not 

 common. 



Diatoms 



Five of the major diatom species in Lake Creek are sensitive to organic pollution and 

 were present at both sites (Table 4). Six of the major species are somewhat tolerant of organic 

 pollution and most of these were also present at both sites. Navicula veneta, Nitzschia palea, and 

 Nitzschia pusilla are very tolerant of organic pollulion. Each site supported the same total 

 percent abundance of these very tolerant species (16.1%). 



Lake Creek above count}' road. Diatom metrics indicate moderate impairment from 

 sedimentation and minor impairment from organic loading at this site (Table 4). Otherwise, 

 diatom metrics indicate no impairment and full support of aquatic life uses. 



Lake Creek above Hevron Road. This site supported fewer species than the upstream 

 site and had a lower diversity index value. The pollution index value was nearly identical to the 

 upstream site and indicates minor impairment from organic loading. The sedimentation index 

 was somewhat lower than upstream and indicated minor impairment. A large percent abundance 

 of Nitzschia inconspicua indicated minor stress. Since Nitzschia inconspiciia is a highly motile 

 diatom and a faculatative nitrogen heterotroph (Van Dam et al. 1994), this stress is probably due 

 to sedimentation and elevated levels of organic nitrogen. This site shared only about one-third of 



