Table 5. Percent abundance of major diatom species^ and values of selected diatom association metrics 

 for periphyton samples collected from the Big Hole River TMDL Planning Area in 2003. Underlined values 

 indicate minor stress; bold values indicate moderate stress; underlined and bold values indicate severe 

 stress; all other values indicate no stress and full support of aquatic life uses when compared to biocriteria 

 (thresholds) in Table 2. Observed stress may be natural or anthropogenic, (continued) 



Species/Metric' WRMSC02 BGHNF01 BGHNF02 GOLDC01 GOLDC02 JERRC01 PINECo7 



Achnanthidium affine 



Ach. minutissimum 25.30 7.00 



Aulacoseira alpigena 

 Cocconeis placentula 

 Diatoma mesodon 

 Encyonema silesiacum 

 Epithemia sorex 

 Frapilaha capucina 

 Fragilaria nitzschioides 



Fraqilaria vaucheriae 6.36 11.96 19.52 25.50 7.36 



Melosira varians 8.00 



Meridian circulare 8.59 



Navicula capitatoradiata 

 Navicula minima 

 Navicula reichardtiana 



Nitzscliia arciiibaldii 20.67 6.60 



Nitzschia inconspicua 

 Nitzschia linearis 

 Nitzschia palea 



Planothidium spp. 13.40 12.52 



Pseudostaur brevistriata 7.81 12.43 18.04 14.19 9.39 7.25 16.41 



Rhoicosplienia abbreviata 



Staurosira construens 6.23 9.57 10.85 12.21 12.88 



Staurosirella leptostauron 5.10 9.84 



Staurosirella pinnata 6.62 5.00 13.56 



Synedra ulna 



No. of Species Counted 58 64 56 44 49 47 52 



Species Diversity 



Pollution Index 



Siltation Index 



Disturbance Index 



% Dominant Species 



% Abnormal Cells 



Similarity Index'' 



A major diatom species accounts for 9.0% or more of the cells at one or more stations in a sample set. 



Values for major species are shown only where they equal or exceed 5.0% of the cells in that sample. 

 ^Species that are sensitive to organic pollution are in italics ; species that are somewhat tolerant of organic 



pollution are underlined : species that are very tolerant to organic pollution are in bold face type. 

 ^Percent Community Similarity (Whittaker 1952) when compared to the diatom assemblage at the 



adjacent station on the same stream. 



