and indicate either beta-mesosaprobous or alpha-mesosaprobous/polysaprobous conditions. 

 Most diatoms in these streams tolerate a wide range of trophic conditions (Table 11). 



Most diatoms at plains sites in the Two Medicine drainage are non-motile and indicate 

 fresh-brackish waters (Table 12). Beyond this, much less can be said about ecological conditions 

 at plains sites in the Two Medicine drainage. For most of these sites and ecological attributes, 

 the modal category is of diatoms that have not been classified with respect to their ecological 

 affinities. There are two reasons why these diatoms have not been classified. One reason is 

 because many of the common diatoms found in these streams (Table 9) have not been reported 

 from The Netherlands (Van Dam et al. 1994) nor have they been covered in the other major 

 autecological summaries (Lowe 1974, Beaver 1981, Lange-Bertalot 1996). The other reason is 

 that some of these taxa (Encyonopsis krammeri, E. minuta, E. subminuta) have been described 

 only within the last few years (Krammer 1997b) and after publication of Van Dam et al. (1994). 



References 



APHA. 1998. Standard Methods for the Examination of Water and Wastewater. 20"' Edition. American Public 

 Health Association, Washington, D.C. 



Bahls, L.L. 1979. Benthic diatom diversity as a measure of water quality. Proceedings of the Montana 

 Academy of Sciences 38:1-6. 



Bahls, L.L. 1993. Periphyton Bioassessment Methods for Montana Streams (revised). Montana Department of 

 Health and Environmental Sciences, Helena. 



Bahls, L.L. , Bob Bukantis, and Steve Tralles. 1992. Benchmark Biology of Montana Reference Streams. Montana 

 Department of Health and Environmental Sciences, Helena. 



Barbour, M.T., J. Gerritsen, B.D. Snyder, and J.B. Stribling. 1999. Rapid Bioassessment Protocols for Use 

 In Streams and Wadeable Rivers: Periphyton, Benthic Macroinvertebrates and Fish. Second Edition. 

 EPA/84 l-B-99-002. U.S. Environmental Protection Agency, Office of Water, Washington, D.C. 



Beaver, Janet. 1981. Apparent Ecological Characteristics of Some Common Freshwater Diatoms. 

 Ontario Ministry of The Environment, Technical Support Section, Don Mills, Ontario. 



Johansen, J.R. 1999. Diatoms of Aerial Habitats. Chapter 12 (>i Stoermer, E.F., and J.P. Smol (eds.). The Diatoms: 

 Applications For the Environmental and Earth Sciences, Cambridge University Press, New York. 



John, DM., B.A. Whitton, and A.J. Brook (eds.). 2002. The Freshwater Algal Flora of the British Isles: An 

 Identification Guide to Freshwater and Terrestrial Algae. Cambridge University 



Karr, J.R. , and D.R. Dudley. 1981. Ecological perspectives on water quality goals. Environmental Management 

 5:55-69. 



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