The effect of the release of a thermal stressor on bluegill (Lepomis macrochirus) morphology and physiology.

摘要

Temperature is considered a very important abiotic factor in fish communities. An increase in water temperature, as is found with the use of nuclear production reactors, can act as a stressor in aquatic systems. The P-reactor, operational from 1954-1988, on the Savannah River Site near Aiken, South Carolina, utilized the Par Pond Reservoir System as part of its cooling mechanisms. During reactor operation, heated effluents were displaced into Pond C, causing the water to be heated to around 45° C. Fischer (1994) found that the bluegill population had adapted with changes to their morphology and physiology. The bluegill from the heated pond took on a fusiform shape with fin dimensions suited for open water. Fischer (1994) also observed a difference in lipid storage between bluegill from the ponds. When the reactor was periodically shut down for maintenance, he observed that bluegill from Pond C stored large amounts of lipids very quickly which acted as a buffer for when the reactor was again operational.;It has now been over 20 years since the P-reactor was permanently shut down, releasing the entire bluegill population in Pond C from the thermal stressor and its associated selection pressures. This study was aimed at determining how the bluegill would respond to the release of the selection pressures. Specifically, I addressed: 1) Will Pond C bluegill return to the original bluegill morphology? and 2) Will there be a difference between Pond C and Par Pond bluegill in the timing and amount of lipids stored?;Bluegill were collected from both ponds during the spring, summer, and fall of 2010, and then analyzed for both morphological and physiological differences. In the case of morphology, bluegill maintained the more streamlined bodies with propulsion fins, indicating that these changes are the result of rapid evolution and may be adaptive for Pond C bluegill under a series of different environmental conditions. As for lipid storage, lipid dynamics in Pond C bluegill seem to be influenced by seasonal changes and follow the typical cycles observed in southeastern bluegill, indicating that their previous response was an example of phenotypic plasticity.