Effects of Chronic Low-Level Irradiation on Gambusia Affinis

摘要

Since 1944, White Oak Lake (WOL), located on the Oak Ridge Reservation, has served as a final settling basin for low-level radioactive effluents from the Oak Ridge National Laboratory. Organisms inhabiting the lake have been exposed for many generations to chronic low-level radiation significantly higher than background. During the past decade, studies on Gambusia affinis from WOL have been carried out to relate estimated radiation doses to effects on the fitness of the Gambusia population. Results of studies on fecundity, temperature tolerance, and embryonic mortality have led to the conclusion that the Gambusia population in White Oak Lake has an increased frequency of deleterious and recessive lethal genes which may be attributed to the radiation exposure history. The frequency of nonviable embryos from WOL Gambusia did not change significantly from 1966 to 1978; however, it was still significantly greater than that of a control population. In July 1977, Gambusia from a control population were stocked into a 0.45-ha pond which had served as a low-level waste settling basin. The beta and gamma dose rate in this pond averaged from 37 rad/yr at the water surface, 394 rad/yr at mid-depth, and 1150 rad/yr at the surface of the sediments. Preliminary results from samples taken in August 1978 showed that although the frequency of nonviable embryos increased, the frequency was not significantly greater than that of the control parent population. Additional sampling of future generations of Gambusia in this pond will determine whether the frequency of nonviable embryos increases as succeeding generations are exposed to dose rates that are higher than the dose rates in WOL. (ERA citation 05:007689)