342 ESCH AND HAZEN 



cooling reservoir, tentatively concluded that it could be related to 

 thermal effluent from a nuclear production reactor. 



From this brief overview^, we see clearly that red-sore disease is a 

 serious problem, that its epizootiology is not well understood, and 

 that, because of its impact on both commercial and sport fisheries, it 

 deserves rigorous study. An investigation of the problem was begun 

 in the fall of 1974. The initial objectives were (1) to ascertain the 

 identity of the causative agent, (e.g., is it Epistylis or Aeromonas)-, 

 (2) to follow the course of the disease seasonally and relate it, if 

 possible, to one or more water-quality parameters; (3) to determine 

 whether thermal effluent affects the course of the disease; and (4) to 

 develop a model for possible use in predicting when, where, and 

 under what circumstances an epizootic may occur in a given body of 

 water. During the first 2.5 years of the study, it became apparent 

 that the disease could be related to the stress phenomenon. This 

 notion has since been incorporated into the second and third 

 objectives listed. 



Description of the Study Site 



Par Pond, an 1120-ha reservoir located at the Savannah River 

 Plant near Aiken, South Carolina, serves as a cooling pond for a 

 nuclear production reactor. Extensive descriptions of the tempera- 

 ture and biotic characteristics have been given by Holland et al. 

 (1974), Lewis (1974), and Parker, Hirshfield, and Gibbons (1973). 

 Figure 5 shows the primary collecting sites. Most of the fish from the 

 thermally altered area were taken within 1 km of the point of entry 

 of thermal effluent from Pond C. Temperatures in this area varied 

 because of variability in reactor activity and season but generally 

 averaged between 5 and 10°C above ambient, depending on season 

 and distance from point of entry of thermal effluent into Par Pond. 



From the fall of 1974 through the present time, temperature, 

 dissolved oxygen, pH, redox potential, and conductivity have been 

 measured weekly, in profile, at several selected sites in the reservoir. 

 A depth profile for these parameters, measured in midwinter and 

 midsummer at representative ambient and thermal locations (Fig. 6), 

 clearly shows the monomictic nature of the impoundment. This is 

 characteristic of most impoundments in the southeastern United 

 States. Hazen (1978) provided a complete description of the 

 water-quality parameters in Par Pond during the course of this study. 



Identifying the Causative Agent for Red-Sore Disease 



As previously indicated, the literature is contradictory as to 

 whether Epistylis or Aeromonas is the etiological agent for red-sore 



