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. tJnderlined 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) 



'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. 



