DIATOMS 



The major diatom species in the Redwater River were either 

 sensitive to organic loading (Pollution Tolerance Class 3) or 

 somewhat tolerant of organic loading (PTC 2) . The sensitive 

 species declined in abundance from above to below the Circle 

 lagoons, resulting in a lower pollution index. However, the 

 decline was not dramatic, indicating that discharges from the 

 lagoons did not have a major effect on water quality (Table 5) . 



With few exceptions, diatom association metrics indicated 

 good to excellent biological integrity at all sites (Table 5) . 

 The siltation index, which is based on the percentage of motile 

 diatoms in the diatom association, indicated moderate impairment 

 and partial support of aquatic life uses at RW-3 below the Circle 

 lagoons . The increase in motile diatoms here was due mainly to a 

 preponderance of Nitzschia species. Species of Nitzschia are 

 generally tolerant of organic loading. 



An unusually large number of teratological cells were 

 observed at all sites, resulting in ratings of fair biological 

 integrity and partial support of aquatic life uses (Table 5) . 

 Teratological cells were observed in diatom species that are 

 sensitive to pollution {Achnanthes minutissima, Cocconeis 

 placentula, Fragilaria brevistriata) , somewhat tolerant of 

 pollution [Mastogloia smithii, Nitzschia frustulum, Nitzschia 

 inconspicua, Nitzschia paleacea, Nitzschia valdestriata, Synedra 

 fasciculata) , and very tolerant of pollution {Navicula 

 duerrenbergiana) . . - 



The percentage of teratological cells more than doubled at 

 RW-3 below the Circle lagoons. Nitzschia inconspicua was the 

 dominant diatom at RW-3 and contributed eighty percent of the 

 teratological cells at this site. Nitzschia inconspicua is 

 characteristic of the mesosaprobic zone, where oxidation of the 



