M22CTWDC01. The Oscillatoria in this sample comprised a 

 large, macroscopic mat; many loose filaments were also present 



M22CTWDC02. The Cladophora in this sample was senescent. 



NON- DIATOM ALGAE 



All three sites supported a normal algal flora consisting of 

 green algae, diatoms, and cyanobacteria (Table 4) . Unattached, 

 filamentous green algae ranked first in biovolume at all three 

 sites: Spirogyra ("pond scum") at sites 01 and 02, and Mougeotia 

 at site 03. A mat-forming species of Oscillatoria ranked second 

 at site 01 followed by diatoms. Diatoms ranked second in 

 biovolume at sites 02 and 03, where another filamentous green- - 

 Oedogonium- -ranked third. 



An abundance of unattached filamentous greens in Cottonwood 

 Creek is an indication of slower current velocities and elevated 

 nutrient concentrations. Audouinella, a red alga that prefers 

 cool waters and lower levels of nutrients, was common at site 01, 

 occasional at site 02, and absent at site 03 (Table 4). Nostoc, 

 a nitrogen- fixer that also prefers low nutrient levels and cool 

 water temperatures, was present at site 01 but absent from the 

 other two sites. 



The appearance of Euglena at site 03 (Table 4) may 

 signal an increase in organic loading at this site. Euglena is 

 very tolerant of decomposing organic matter. The appearance of 

 Merismopedia and Rivularia at site 03 indicates an increase in 

 dissolved solids here. AnaJbaena, which prefers warmer waters, 

 was absent from site 01, occasional at site 02, and frequent at 

 site 03, indicating an increase in water temperatures downstream. 

 However, Tribonema, which is a cool water genus, was also present 

 at site 03. 



8 



