Preface ' 



Prior surveys of Yellowstone River algae (9, 14, 16) addressed 

 only a few stations in the middle and lower river during something 

 less than a full seasonal cycle. The most extensive of these studies 

 was accomplished by the Public Health Service (9) nearly a quarter of 

 a century ago when the river was receiving a much greater organic 

 load than it is today. To the author's knowledge, a seasonal analysis 

 of algae form the entire length of the river in Montana has not been 

 undertaken until this time. 



Proceeding with the business of impounding or allocating water 

 from the Yellowstone without knowledge or regard for the river's 

 primary producers--algae--is akin to applying water to an irrigated 

 pasture or field without knowing what kind of crop is being produced 

 or the water and nutrient requirements of that crop. Algae are a 

 significant resource that should not be overlooked. They provide 

 food for invertebrate animals, help keep the water aerated, regulate 

 the water's chemical balance and readily assimilate waste products 

 (ammonia) that may prove toxic to other organisms in the river. In 

 excess they can also be a nuisance, either physically or by causing 

 taste and odor problems. Moreover, algae are valuable indicators of 

 water quality conditions that may impair use of the water by fish or 

 for municipal, industrial or agricultural purposes. 



This report on the Yellowstone's non-diatom algae is a first 

 approximation, a crude sketch, of the plant life of one of Montana's 

 finest rivers. It is offered as a small step toward closing an inmense 



