Modal categories at some other sites represent a significant improvement in water 

 quality. For example, most diatoms at East Redwater sites 01 and 03 and both sites on Pasture 

 Creek were "not motile". This is unusual for prairie streams and is due to the large percentages 

 of Rhoicosphenia abbreviata and other non-motile diatoms at these sites. At other sites, the 

 modal category was the more typical "highly motile". At most sites, the modal category for 

 salinity was "brackish" or "brackish-fresh", but it was "fresh" at East Redwater sites 01 and 03 

 and in lower Pasture Creek (PSTRCOl ). At the lower site on Horse Creek, the modal category 

 for pH was "circumneutral", whereas it was "alkaliphilous" at most of the remaining sites. 

 Nitrogen autotrophs (not heterotrophs) dominated the samples from lower East Redwater River 

 and lower Pasture Creek, confirming the lower levels of organic loading at these sites. Diatoms 

 at these sites also indicated higher concentrations of dissolved oxygen than the other sites. 



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. 

 EPAy841-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 w Stoermer, E.F., and J.P. Smol (eds.), The Diatoms: 

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



John, D.M., 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 DR. Dudley. 1981. Ecological perspectives on water quality goals. Environmental Management 

 5:55-69. 



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