organic load is proceeding and where nitrogen is present as 

 ammonia (Krammer and Lange-Bertalot 1988) . Nitzschia inconspicua 

 (misidentif ied as N. epiphytica) was the dominant diatom species 

 in the East Gallatin River immediately below the old Bozeman 

 wastewater treatment plant in the late 1960s (Bahls 1973) . 



It is unlikely that the Nitzschia inconspicua cells found in 

 the Redwater River, including the teratological cells of this 

 species, originated in the Circle lagoons. This species requires 

 oxygenated waters where the breakdown of organic nitrogen is 

 nearly complete. Unlike Nitzschia palea and other species of 

 Nitzschia that thrive under anaerobic conditions and heavy 

 organic loading, Nitzschia inconspicua has not been reported from 

 sewage treatment ponds (Palmer 1969) . 



Moreover, the Circle lagoons are flushed in the spring, well 

 before the samples for the present study were collected (in 

 August) . Any algae released in the flush would have been carried 

 downstream or decomposed. Diatoms that might have been living in 

 the Circle lagoons would not survive for long in the Redwater 

 River, at least not in large numbers. In alkaline waters such as 

 the Redwater River, dead (empty) diatom frustules likely would 

 not persist for more than a few weeks. 



In May of 1999, a large number of teratological cells of 

 Diatoma tenue resulted in a similar rating of partial support in 

 the Redwater River below the Circle lagoons (Bahls 1999) . At 

 that time, Diatoma tenue was the dominant diatom species both 

 above and below the Circle wastewater effluent. No teratological 

 cells of this species were observed above the wastewater lagoons. 

 Diatoma tenue is a cool season diatom (Bahls et al . 1984); it 

 tolerates about the same amount of organic loading as Nitzschia 

 inconspicua (Lowe 1974) ; and it has not been reported from sewage 

 stabilization-ponds (Palmer 1977). 



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