genera are motile and capable of maintaining their position on 

 top of aggrading substrates. 



A small number of teratological cells was counted at sites 

 02 and 03, indicating minor impairment of aquatic life uses. 

 Salinity, heavy metals, and organic loading are three of several 

 factors that have been shown to cause diatom deformities. 



No diatoms in the family Epithemiaceae were counted at site 

 01 (Tables 5 and 6) . On the other hand, exceptionally large 

 numbers of diatoms in this family were recorded at sites 02 and 

 03. Diatoms in the family Epithemiaceae harbor nitrogen-fixing 

 cyanobacteria within their cells. Hence, the large number of 

 diatoms in this family indicate that nitrogen is likely the 

 limiting nutrient at sites 02 and 03. 



Adjacent sites on Cottonwood Creek shared between 40% and 

 50% of their diatom floras (Similarity Index, Tables 5 and 6) . 

 This level of similarity indicates only minor change in 

 environmental conditions between adjacent sites. 



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