Aquatic studies of Gable Mountain Pond

Studies of the biotic and abiotic components of the Gable Mountain Pond (HAPO cooling water disposal pond) ecosystem were undertaken to determine if there was a potential problem for off-site transfer of radioactivity to man originating with the aquatic food web. Most of the 137Cs in the pond is associated with the sediments which are probably the main source of 137Cs for uptake by the biota. Generally, highest concentrations of 137Cs and other radioisotopes were found in the upper two inches of sediments in the northwest end of the pond and in the deeper areas along the long-axis of the pond. Native goldfish had maximum and average 137Cs concentrations of about 340 and 170 pCi/g dry wt, respectively. Algae, macrophytes, and detritus comprised the main food items of the goldfish, and the 137Cs levels in the plants were usually higher than the 137Cs concentration in the fish. The 137Cs concentrations of wild experimental ducks restricted to Gable Mountain Pond were approximately the same as resident coots, but significantly higher than transient wild ducks. Neither the goldfish nor the waterfowl inhabiting the pond attained concentrations of 137Cs exceeding acceptable limits. Sediment, however, could be a source of high concentrations of radioactivity or radioactive contamination concern if the concentration of radiocontaminants increased and/or the pond dries up, and the contaminated sediments become windborne. (U.S.)