to become insoluble and to precipitate on the stream bottom. 



Diatom floras at Carroll Trail, Spring Creek Colony and near 

 the mouth were even more unlike the flora at the upstream control 

 site below the hatchery (Table 5) . This is to be expected, 

 however, given the intervening tributaries and the change in 

 classification (from B-1 to B-2) that occurs between the control 

 site and these lower three stations. Pollution sources in this 

 reach would cause further divergence of floristic similarity from 

 the upstream control site. 



When diatom floras between adjacent sites are compared, 

 minor changes are indicated between between Burleigh' s Easement 

 and Carroll Trail, and between Carroll Trail and Spring Creek 

 Colony (Table 5) . The diatom floras at Spring Creek Colony and 

 near the mouth are essentially the same, indicating that no 

 significant perturbations (and no significant recovery) occurred 

 in this reach of the creek. 



ACKNOWLEDGEMENTS 



Carol Endicott of the Montana Department of Environmental 

 Quality, Monitoring and Data Management Bureau, provided the 

 author with copies of field data and with other helpful 

 information about station locations and sources and causes of 

 impairment along Big Spring Creek. 



LITERATURE CITED 



American Public Health Association. 1998. Standard Methods for 

 the Examination of Water and Wastewater. 20th Edition. 

 A.P.H.A., Washington, D.C. 



Bahls, L.L. 1993. Periphyton Bioassessment Methods for Montana 

 Streams (Revised) . Montana Department of Health and 

 Environmental Sciences, Helena. 



10 



