were calculated from these counts (Bahls 1980, Montana Diatom 

 Database) . 



A comparison of metrics generated from this year's samples 

 to those generated from the 1978-80 samples will help determine 

 whether and by how much biological integrity has changed at site 

 #1 over the intervening 20 years. Such comparison will also help 

 to ascertain whether pumped groundwater discharges were affecting 

 biological integrity when the samples were collected this year. 



The mean diatom species diversity index for 30 samples 

 collected at site #1 between 1978 and 1980 was 3.69, with a 

 standard deviation of 0.70. Although slightly lower, the 

 diversity index values calculated for the two samples collected 

 at site #1 in 2000 were both within one standard deviation of the 

 baseline mean (Figure 1) . One may conclude from this analysis 

 that there has been no measurable change in diatom species 

 diversity at site #1 from 1978-80 to this year. 



Other metrics generated from the 1978-80 Squirrel Creek 

 samples may also be compared with metrics generated from this 

 year's samples. For example, the nine samples collected at site 

 #1 during the Southern Fort Union study contained a maximum of 3 

 non-diatom genera, a minimum of genera, and an average of 1.7 

 genera (Bahls 1980) . In 2000, the two samples collected here had 

 5 and 4 genera of non-diatom algae (Table 4) . 



Moreover, in 1978-80 site #1 produced a maximum of 40 diatom 

 species, a minimum of 17 species, and an average of 32 species. 

 In 2000, the replicate samples collected at site #1 contained 44 

 and 55 species (Table 5) . By all of the above measures- -diatom 

 species diversity, non-diatom genus richness, and diatom species 

 richness- -there has been no decline in genetic diversity at the 

 lower Squirrel Creek station in the last 20 years. 



10 



