nutrients, and toxins; 



• Sampling is easy and inexpensive, and causes minimal impact 

 to resident biota and their habitat; 



• Standard methods and criteria exist for evaluating the 

 composition, structure, and biomass of algal associations; 

 and 



• Excess algae in streams is often perceived as a problem by 

 the public. 



For several reasons, biological surveys are superior to 

 water quality analyses for determining use support (Plafkin et 

 al . 1989): (1) Biological communities measure our success at 

 protecting the biological integrity of waterbodies, which is a 

 goal of the Clean Water Act; (2) biological communities integrate 

 the effects of different pollutants and provide a holistic 

 measure of their aggregate impact; (3) routine biological 

 monitoring can be relatively inexpensive; (4) the status of 

 biological communities is of direct interest to the public; and 

 (5) biological communities may be the only practical means to 

 evaluate certain types of impacts, such as nutrient enrichment or 

 habitat degradation from non-point sources. 



Biological integrity is defined as "the ability of an 

 aquatic ecosystem to support and maintain a balanced, integrated, 

 adaptive community of organisms having a species composision, 

 diversity, and functional organization comparable to that of the 

 natural habitats within a region" (Karr and Dudley 1981) . It is 

 an objective of the federal Clean Water Act, and of the state 

 agencies that implement the Act, to "restore and maintain the 

 chemical, physical, and biological integrity of the Nation's 

 waters" (Section 101) . In response to this directive, the state 

 of Montana has developed methods and criteria for evaluating 



