578 ALSTON, LAWRENCE, BAYNE, AND CAMPBELL 



D's of the heated-water channels. The overall D's for the Ekman 

 dredge samples indicated that channels 1 and 2 were not significantly 

 different but that D in channel 3 was significantly lower. This 

 indicates that the floating heated-water plume had no effect on 

 bottom organisms. The mean D for plate samplers indicated that 

 each channel had a different D, 1 being highest ;_2, intermediate; and 

 3, lowest. The floating plume lowered the D of large fish-food 

 organisms in channel 2 but was not as severe as the effects measured 

 in channel 3. 



The prevalence of Branchiiira sowerbyi in channel 3 agrees with 

 results reported by Brinkhurst and Cook (1974), who found that 

 they attained large numbers and reached sexual maturity in heated 

 effluents. Our findings on mayfly populations corroborate results 

 reported by Howell and Gentry (1974), who stated that mayflies 

 increase in numbers of both individuals and species in a progression 

 from thermally affected to unheated waters. The floating plume in 

 channel 2 did not affect mayfly abundance. Large populations of 

 mayflies were found in the dredge samples. Channel 3 contained 

 numerous predaceous chironomids. Fish prey heavily upon larvae of 

 all chironomids, and, since these predaceous forms are not protected 

 by a silken case, they are more vulnerable than the case-building 

 chironomid larvae. Oligochaetes and ceratopogonids, which are also 

 prime fish food, had substantial populations in channel 3. 



Even though channel 3 was maintained as a heated -water habitat, 

 it appeared to have supported a substantial population of desirable 

 fish-food organisms. Channel 2 diversity was not affected as much as 

 that of channel 3 since mayflies were present. This was probably 

 because of the two separate environments in channel 2, a 

 heated-water layer and unheated-water layer. It appears that heated 

 water caused shifts in populations and changed the diversity of 

 channels 2 and 3, but enough organisms were present in both 

 channels to support a healthy fish population. 



ACKIMOWLEDGMEIMT 



Funding and field facilities for the research reported here were 

 provided by the Alabama Power Company. 



REFERENCES 



Aston, R. J., 1968, The Effect of Temperature on the Life Cycle, Growth and 

 Fecundity of Branchiiira sowerbyi (Oligochaeta: Tubificidae), J. Zool., 154: 

 29-40. 



