792 BLAYLOCK AND FRANK 



Although the difference in survival time between doses of 1500 and 

 3000 rads was not significant, survival time was considerably reduced 

 at a dose of 5000 rads (Table 2). 



It is evident from this study that an acute dose of ionizing 

 radiation influences the thermal tolerance of Gambusia. A dose of 

 1500 rads, however, which was required to affect the thermal 

 tolerance of Gambusia, is much higher than the doses expected for 

 aquatic biota in the vicinity of a nuclear power station. On the other 

 hand, 500 rads, which is also much higher than doses expected nccir a 

 nuclear power station, did not cause a significant reduction of 

 thermal tolerance. Blaylock and Witherspoon (1976) estimated doses 

 of less than 1 rad/day to aquatic biota from routine releases of 

 radionuclides from nuclear power stations. Such doses could not be 

 expected to produce any effect on the thermal tolerance of fish. 



ACKNOWLEDGMENTS 



The research reported here was sponsored by the U. S. Depart- 

 ment of Energy under contract with Union Carbide Corporation. 

 Environmental Sciences Division Publication No. 1208. 



We wish to express our appreciation to G. E. Cosgrove, Biology 

 Division, Oak Ridge National Laboratory (ORNL), for histological 

 studies; to J. J. Beauchamp, Computer Sciences Division, ORNL, for 

 his advice on the statistical analysis of the data; and to Carol P. 

 Allen, Environmental Sciences Division, ORNL, for technical assis- 

 tance. 



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