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. 



Species/Metric' DOLTC01 DOLTC02 MCVYC01 MCVYC02 SWMPC01 SWMPC02 WRMSC01 



Achnanthidium affine 



Ach. minutissimum 7.54 



Aulacoseira alpigena 

 Cocconeis placentula 

 Diatoma mesodon 18.13 



Encyonema silesiacum 

 Epithemla sorex 

 FraQJIaria capucina 

 Fragilaria nitzschioides 



Fraqilaria vaucheriae 7.83 9.57 16.02 8.60 



Melosira varians 

 Meridian circulars 

 Navicula capitatoradiata 



Navicula minima 5.92 9.59 16.72 



Navicula reichardtiana 



Nitzschia archibaldii 18.63 



Nitzsctiia inconspicua 7.76 



Nitzschia linearis 



Nitzschia pales 17.07 



Nitzschia perminuta 9.82 



Planothidium spp. 8.01 5.03 8.74 



Pseudostaur. brevistriata 11.16 19.39 7.40 



Rhoicosphenia abbreviata 



Staurosira construens 10.45 10.71 28.90 8.18 8.28 



Staurosirella leptostauron 



Staurosirella pinnata 9.11 6.25 



Synedra ulna 



No. of Species Counted 64 59 75 55 67 57 61 



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 orgar 



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. 



