low species diversity and species richness at this site and the 

 large percentage of the dominant species {S. fasciculata) were 

 likely caused by elevated levels of salinity. Salinity resulted 

 in severe impairment and non- support of aquatic life uses in the 

 South Fork of Sandstone Creek. Siltation, on the other hand, was 

 very low in South Sandstone Creek and caused no impairment. 



As in Pennel Creek, all three sites on Sandstone Creek were 

 dominated by Nitzschia frustulum, which indicates alkaline fresh 

 water. However, low diatom diversity, a large percentage of the 

 dominant species, and a large siltation index all indicate 

 moderate impairment and partial support of aquatic life uses in 

 upper Sandstone Creek (Table 7) . Downstream in Sandstone Creek, 

 diatom diversity increased and the percentage of N. frustulum 

 decreased. Nevertheless, the percentage of motile diatoms in 

 lower Sandstone Creek remained high, resulting in moderate 

 impairment from siltation at all three sites on this stream. The 

 three sites on Sandstone Creek had over 60% of their diatom 

 floras in common (Table 7) . 



13 



