Table 2. — Radioactivity content of toadfish tissues follow- 

 ing oral doses of gold 199 



pipetted into the stomachs of six fish. The fish 

 were then placed in flowing sea water. Three were 

 killed, dissected, and tissues were measured for 

 radioactive gold content after 78 hours and three 

 after 148 hours. 



Less than 1 percent of the dose was assimilated 

 by the tissue, about 99 percent having been elim- 

 inated within 78 hours (table 3). Of the rela- 

 tively small amount assimilated, kidney and gills 

 had the highest concentrations of gold 199 per 

 unit weight. After 148 hours the gills and spleen 

 had the highest concentrations. The increase in 

 gold 199 content in some of the tissues during the 

 period from 78 to 148 hours is probably the result 

 of continued assimilation from the digestive tract 

 and translocation of gold 199 from other tissues. 



EXPERIMENTAL ENVIRONMENT STUDY 



Since the planned application of radioactive 

 gold in the Cape Fear River would expose the 

 community of indigenous organisms further lab- 

 oratory studies were conducted with a marine 

 community maintained in a large tank. Data 

 obtained from tank experiments involving relatively 

 large volumes of sea water (1,000 1.) and a com- 

 munity of organisms have advantages over data 

 for individual species held in smaller volumes of 

 water. Increasing the volume of water enlarges 

 the experimental environment, and chronic as well 



as acute contamination can be observed since 

 observations can be made over longer periods of 

 time because of the improved physiological con- 

 dition of the organism. 



An experimental environment was established 

 to follow the movement of radioactive gold in a 

 marine community. The community, which con- 

 sisted of clams and clam shells, Mercenaria mer- 

 cenaria; blue crabs; and sheepshead minnow, 

 Cyprinodon variegatus; as well as sediment samples 

 of clay, was installed in a large (172 by 117 by 

 61 cm.) fiberglass tank containing 1,000 1. of 

 cotton-filtered sea water (table 4). Ten clams 

 were placed directly on the bottom of the tank, 

 and 10 in the sediment. Enough gold 199, as 

 AuCl 3 , was added to the water to give a con- 

 centration of 0.0142 juc/ml. After the gold was 

 added, the pH of the water was 8.1. Throughout the 

 experiment the water temperature was maintained 

 at 21°± 3° C. and the salinity at 32±0.10% o , 

 the latter by adding distilled water when nec- 

 essary to compensate for evaporation. A plastic 

 impeller pump circulated the water continuously. 



Clay sediment introduced into the tank was 

 first placed in glass bowls (3 cm. deep by 12.7 

 cm. in diameter) after being thoroughly wetted as 

 follows: 6 kg. of clay were suspended in 10 liters 

 of sea water for 48 hours, and the excess water 

 was decanted from the clay, leaving it with a 

 pastelike consistency. In each bowl, 200 g. of 

 the wet clay (125 g. dry weight) were placed 

 forming a smooth substrate that was not disturbed 

 by water circulation. 



The radioactivity content of whole animals and 

 sediment was measured periodically, with the 

 organisms afterward being returned to the tank. 

 Oysters, clams, and crabs were prepared for 

 radioactivity analysis by wrapping them in a thin 

 transparent plastic sheet. Fish were placed in 

 dark glass jars containing nonradioactive sea 

 water and counted for 3 minutes. Sediments 

 were removed from the tank with a small diameter 

 (2.5 cm.) core sampler and were not returned to the 

 tank. This procedure of measuring the activity 

 in a whole animal eliminated the need for killing 

 it, and the number of individuals was not reduced 

 with sampling. Also, uptake could be followed 

 on the same individual throughout the experiment. 



Appropriate corrections were made for decay, 

 geometry, and background on all radioactivity 

 measurements unless otherwise stated. 



430 



U.S. FISH AND WILDLIFE SERVICE 



