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 othier values indicate no stress and full support of aquatic life uses wtien compared to biocriteria 

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



Species/Metric 



FRANC02 DIVDC01 DIVDC02 SOAPC01 SOAPC02 MCLNC01 GROSC01 



Achnanthidium affine 

 Ach. minutissimum 

 Aulacoseira alpigena 

 Cocconeis placentula 

 Diatoma mesodon 

 Encyonema silesiacum 

 Epithemia sorex 

 Frapilaria capucina 

 Fragilaria nitzschioides 

 Frapilaria vaucheriae 

 Melosira varians 

 Meridian circulare 

 Navicula capitatoradiata 

 Navicula minima 

 Navicula reichardtiana 

 Nitzschia archibaldii 

 Nitzschia inconspicua 

 Nitzschia linearis 



19.11 



10.45 



10.41 



11.67 



5.20 



24.76 



14.67 



7.53 



7.83 



7.22 



9.98 



8.74 



6.08 



'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 show/n 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. 



