Percent community similarity values for 0' Fallon Creek 

 indicate that adjacent sites shared about half of their floras in 

 common (Table 6) . Adjacent sites became f loristically more 

 similar as one proceeded downstream. The upper site (OF- 7) and 

 the lowest site (BF-16) shared 43% of their floras. 



In September 1999, diatom metrics at Willard Crossing 

 indicated moderate impairment due to siltation and low diversity 



(Table 5, Bahls 2000) . In June 2001, diatom metrics at Willard 

 Crossing indicated moderate impairment due to pollution 



(salinity) and severe impairment due to siltation (Table 6) . 

 These different indications may result from sampling in different 

 seasons, i.e., early fall in 1999 and early summer in 2001. 



Tributaries. All of the major diatom species in tributaries 

 of 0' Fallon Creek are either tolerant (Class 2) or very tolerant 

 (Class 1) of pollution. As a result, the pollution index 

 indicated either moderate impairment (upper Pennel Creek) or 

 minor impairment (all other sites) in these streams (Table 7) . 



The dominant diatom species in Pennel Creek was Nitzschia 

 frustulum, which indicates alkaline fresh waters. Also common in 

 Pennel Creek was Nitzschia palea, which indicates substantial 

 organic loading and moderate impairment at the upper site. A 

 large percentage of motile diatoms also indicated moderate 

 impairment from siltation and partial support of aquatic life 

 uses at the upper site (Table 7) . A larger pollution index and a 

 smaller siltation index indicated some recovery and only minor 

 impairment at the lower site on Pennel Creek. The two sites on 

 Pennel Creek had over half of their diatom floras in common. 



The South Fork of Sandstone Creek at SS-3 was dominated by 

 two species of Synedra: S. fasciculata and S. pulchella (Table 

 7) . Both of these are brackish water species, occurring in salt 

 concentrations up to 30,000 mg/L (Lowe 1974). Hence, the very 



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