Some algae, such as the filamentous greens, are conspicuous 

 and their excessive growth may be aesthetically displeasing. 

 Algae may also deplete dissolved oxygen, interfere with fishing 

 and fish spawning, clog water filters and irrigation intakes, 

 create tastes and odors in drinking water, and generate toxins 

 that may be lethal to livestock and other animals. 



Plafkin et al . (1989) and Stevenson and Bahls (1999) list 



several advantages for using periphyton in biological assessments 



of streams: 



Algae are universally present in large numbers in all 

 streams and unimpaired periphyton assemblages typically 

 support a large number (>30) of species; 



Algae have rapid reproduction rates and short life cycles, 

 making them useful indicators of short-term impacts; 



As primary producers, algae are most directly affected by 

 physical and chemical factors, such as temperature, 

 nutrients, dissolved salts, and toxins; 



Sampling is quick, easy and inexpensive, and causes minimal 

 damage to resident biota and their habitat; 



Standard methods and criteria exist for evaluating the 

 composition, structure, and biomass of algal associations; 



Identification to species is straightforward for the 

 diatoms, for which there is a large body of taxonomic and 

 ecological literature; 



Excessive algae growth in streams is often correctly 

 perceived as a problem by the public. 



Periphyton and other biological communities reflect the 

 biological integrity^ of waterbodies; restoring and 

 maintaining the biological integrity of waterbodies is a 

 goal of the federal Clean Water Act; 



Periphyton and other biological communities integrate the 



^ 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 composition, 

 diversity, and functional organization comparable to that of 

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



