| For the past 35 years heated effluent has entered Pond C at approximately 50{dollar}spcirc{dollar}C causing at least 90% of the water to reach lethal temperatures for almost all plants and animals during long periods of reactor operation. Bluegill have survived the severe and unpredictable heating of the reservoir by occupying one of four relatively small and distinct refuge areas containing cooler water, reduced food availability, virtually no habitat structure, and increased interactions with predators. A comparison of morphology, physiology, and life history traits between bluegill from a normal reservoir (Par Pond) and bluegill from a severely impacted reservoir (Pond C) has provided us with an understanding of how an organism responds to severe and chronic changes to their environment.; A comparison of morphology between sites revealed that overall body length increased and body depth decreased in Pond C bluegill compared to bluegill from Par Pond. In addition, both the pectoral and anal fins changed, with fin bases increasing and fin lengths decreasing in Pond C bluegill compared to Par Pond bluegill. Thus, morphological changes in Pond C bluegill indicate that body form has been modified from that of a maneuvering specialist towards that of a cruising or accelerating specialist.; In examining lipid and reproductive cycles we observed that Pond C bluegill had twice the amount of percent body lipids and exhibited a 3 month delay in reproduction compared to Par Pond bluegill. In addition, during prolonged reactor down periods, percent body lipids of Pond C bluegill increased at a rate of approximately 3% of body weight per week compared to an increase of less than one percent per week in Par Pond bluegill.; An examination of life history patterns showed that bluegill from the heated site matured at a younger age, had a slower growth rate, a higher reproductive investment (increased egg number), and a shorter life span than did bluegill from Par Pond. Thus bluegill from the heated site (Pond C) have altered their morphology, physiology, and life histories either genetically or phenotypically in response to unpredictable thermal perturbation. |
