Lower Teton River 



Genus richness of soft algae declined significantly 

 downstream from Highway 221 (Table 6) . The number of genera 

 declined from a Teton River high of 13 at Highway 221 to only 5 

 or 6 at Interstate 15, Kerr Bridge, and Dent Bridge. Only one 

 genus of non-diatom algae (Cladophora) was found in the sample 

 collected at the mouth of the river near Loma. Cladophora at the 

 Loma site was in poor condition and covered with an opaque floe. 

 Significantly, Audouinella disappeared downstream from Highway 

 221, to reappear in reduced numbers only at Dent Bridge. 



DIATOM ALGAE 



McDonald Creek 



Several species of tychoplanktonic diatoms (e.g., Rhopalodia 

 gibba, Mastogloia smithii, Fragilaria construens , and Fragilaria 

 pinnata) confirm the lacustrine origin and slow-moving nature of 

 McDonald Creek (Table 7) . McDonald Creek supported a rich diatom 

 flora commensurate with its exceptionally diverse non-diatom 

 algal flora. The lower site on McDonald Creek had slightly less 

 than half of its diatom flora in common with the upper site 

 (Similarity Index = 46.93%, Table 7), indicating no major 

 floristic changes between the two sites. 



With two minor exceptions, both related to the stream's 

 origin in McDonald Swamp, diatom metrics indicated excellent 

 water quality in McDonald Creek. The pollution index and the 

 percent dominant species both indicated minor impairment at the 

 upper site. The pollution index was probably depressed because 

 of natural organic loading from McDonald Swamp. The percent 

 dominant species was elevated because of the large number of 

 naturally occurring Mastogloia smithii at the upper site. 



12 



