Beta-mesosaprobous was the usual level of saprobity at most sites. This represents a 

 dissolved oxygen saturation level of 70-85% and a biochemical oxygen demand (BOD5) of 2-4 

 mg/L. However, saprobity levels were higher at both sites on Josephine Creek, where most of 

 the diatoms were alpha-mesosaprobous. The alpha-mesosaprobous level corresponds to 25-70% 

 saturation of dissolved oxygen and 4-13 mg/L BOD5. Most diatoms at upper Stony Creek were 

 in the oligosaprobous category. This is the lowest level of organic loading and represents >85% 

 oxygen saturation and a BOD5 concentration of <2 mg/L. 



Most sites in the Ninemile Creek TMDL plarming area were dominated by eutraphentic 

 diatom species. One site — lower Stony Creek — was dominated by mesotraphentic species. 

 Mesotraphentic is the next trophic level below (less enriched than) eutraphentic. Upper Stony 

 Creek was dominated by oligotraphentic diatoms, which prefer even smaller concentrations of 

 inorganic nutrients than mesotraphentic species. Two sites — Big Blue Creek and Cedar Creek — 

 were dominated by species that tolerate a wide range of trophic levels ranging from oligotrophic 

 to eutrophic. 



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. Striblmg. 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 m 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. Whinon, and A.J. Brook (eds.). 2002. The Freshwater Algal Flora of the British Isles: An 

 Identification Guide to Freshwater and Terrestrial Algae. Cambridge University Press, Cambndge, U.K. 



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