The pollution index and the siltation index indicate minor impairment in Jennies Fork 

 from organic loading and sedimentation, respectively. Aside from A. minutissimum, the only 

 major diatom species recorded here were Fragilaria vaucheria, which is somewhat tolerant of 

 organic pollution, and Planothidium lanceolatum, which is both somewhat tolerant of organic 

 pollution and adapted to living on sand grains. Four teratological diatom cells were also 

 recorded at this site, which may indicate low background levels of heavy metals. 



Granite Creek. Granite Creek exhibited the best biological integrity of the three sites, 

 although both the pollution index and the siltation index approached their respective thresholds 

 for minor impairment (Table 4). The dominant diatom species here was Cocconeis placentula, 

 which, like A. minutissimum, is a pioneer adnate species adapted to living on hard substrates 

 (cobbles and coarse sand). 



Gomphonema rhombicum was also a major diatom species in Granite Creek. This 

 species is sensitive to organic pollution and grows on stalks that elevate the cells above the 

 understory layer of attached algae (e.g., Cocconeis placentula). An abundance o{ Gomphonema, 

 along with the abundance of Cladophora here, indicates a stable, mature periphyton community. 

 Another major species here was Rhoicosphenia abbreviata {=Rhoicosphenia curvata), which is 

 also sensitive to organic pollution and, like G. rhombicum, requires firm substrates for 

 attachment. The other major species here were Fragilaria vaucheriae (somewhat tolerant of 

 organic pollution) and Planothidium lanceolatum (pollution tolerant and adapted to living on 

 sand grains). Only one teratological diatom cell {of Fragilaria vaucheriae) was recorded in 

 Granite Creek. 



Modal Categories (Table 5) 



Several ecological attributes assigned by Stevenson and Van Dam et al. (1994) were 

 selected from the diatom reports in the appendix and modal categories of these attributes were 

 extracted to characterize water quality tendencies in Jennies Fork and in Jackson and Granite 

 Creeks (Table 5). 



10 



