A number of factors are known to cause abnormalities in 

 diatom cells, including heavy metals (McFarland et al . 1997) . 

 Salinity and ammonia are other possible causes. Salinity is not 

 the likely cause of teratological cells in the Redwater River 

 because most of the major diatom species that are present (Table 

 5) indicate fresh to somewhat brackish water. Heavy metals are 

 also an unlikely cause. Deformities caused by hea-vy metals have 

 been reported only from poorly buffered circumneutral waters 

 (McFarland et al . 1997). ■ 



Although abnormal cells were observed at all stations in 

 this study, they were more than twice as common below the Circle 

 lagoons than at any other site. In May of 1999, problematic 

 numbers of abnormal cells were observed only below the Circle 

 lagoons. In August 2000, the percentage of deformed cells below 

 the Circle lagoons (3.97%) exceeded the percentage observed at 

 other sites on the Redwater River by a ratio of two to one. 



In summer, with decreased flows, higher temperatures, and 

 decompositon of algae and aquatic macrophytes, a certain amount 

 of internal organic loading may occur. Some of the abnormalities 

 observed in August may have been caused by ammonia generated from 

 this internal organic loading. Thus, the percentage of deformed 

 cells at three of the four stations (1.56% to 1.73%) may be 

 within the normal range for prairie streams in summer. 



Two additional diatom metrics show a significant change in 

 water quality below the Circle lagoons. The minimum value for 

 the percentage of diatoms in the family Epithemiaceae indicates 

 nitrogen enrichment at RW-3. Diatoms in this family typically 

 harbor nitrogen-fixing cyanobacteria within their cells and are 

 adapted to living in waters that are nitrogen-poor. Similarity 

 index values between adjacent stations in this reach of the 

 Redwater River indicate that the greatest change in diatom 

 species composition, hence water quality, occurred between sites 



11 



