Effects of chronic low-level irradiation on Gambusia affinis. [White Oak Lake]

Abstract

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 1956 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 gaimia dose rate in this pond (measured at ten stations with thermoluminescent dosimeters) 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 does rates in WOL.

San Bernardino National Wildlife Refuge Well 10

“…Effects of exposure at similar levels to natural populations of fish include greater brood size and embryo mortality for mosquitofish (Gambusia aflhis) (Blaylock 1969;Trabalka and Allen 1977;Blaylock and Frank 1980) and lower fecundity and delay in spawning for roach (RutikJs rutihs) (Voronina et al 1974;Peshkov et al 1978).…”

“…Assuming the resultant concentration in an organism is only twice that of the concentration in water, the dose rate to a small fish would be as follows: A dose rate of 0.610 mGy/h exceeds the DOE recommended dose rate limit of 0.4 mGy/h; therefore, adverse effects to the three fish species of concern in Twin Pond~aqui chub (endangered), Yaqui topminnow (endangered), and beautiful shiner (threatened)], and possibly other organisms in the food web would be possible. Effects of exposure at similar levels to natural populations of fish are greater brood size and embryo mortality for mosquitofish (GarnbuskJ afink) (Blaylock 1969;Trabalka and Allen 1977;Blaylock and Frank 1980) and lower fecundity and delay in spawning for roach (RWUS rutilus) (Voronina et al 1974;Peshkov et al 1978).…”