are presented in Standard Methods (American Public Health Association et al 

 1975). This was done to clean the diatom frustules for the purpose of facili- 

 tating the essential taxonomic work, and the cleansing technique resulted in 

 the production of three randomly strewn mounts that are directly amenable to a 

 microscopic evaluation. These slides were then surveyed microscopically in a 

 preliminary fashion in order to develop taxa listings of the stations' diatom 

 assemblages. This particular analytical step required the application of a 

 taxonomic keying effort by referencing the appropriate literature sources 

 (e.g., Patrick and Reimer 1966), and the diatoms were identified to the 

 generic, specific, and varietal systematic levels as this proved to be 

 feasible in any particular case. 



Following such preliminary applications, the diatoms on each of the 

 slides were partially and randomly counted by taxa in a formal manner until a 

 total of about 415 frustules had been tabulated for each of the preparations. 

 The modified short-count approach that was used has been described by Weber 

 (1973), and PRA values were ultimately calculated for each of the diatom taxa 

 that had been formally counted from any one of the permanent slides. However, 

 a "trace" designation had to be assigned to those diatoms of a mount that were 

 spotted in the various preliminary scans but then not actually tabulated 

 during the formal counts. 



The raw data of the inventory's periphyton community analyses therefore 

 consist of the diatom and non-diatom taxa listings plus the diatom's PRA 

 values and the qualitative abundance estimates of the soft-bodied forms. 

 These raw data can be obtained from the collecting agency. But as a final 

 analytical step, the project's diatom count data were later reduced and 

 refined for the interpretive and descriptive needs of this report by calcu- 

 lating Shannon-Wiener diversity and index values for each of the station's 



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