BIOACCUMULATION OF RADIOACTIVE GOLD USED AS A SEDIMENT 

 TRACER IN THE ESTUARINE ENVIRONMENT ' 



By Thomas W. Duke, John P. Baptist, and Donald E. Hoss 

 Fishery Biologists (Research), Bureau of Commercial Fisheries, Beaufort, N.C. 



ABSTRACT 



The accumulation of radioactive gold by selected 

 members of a marine animal community and sediment 

 material was followed under laboratory and field condi- 

 tions. In the laboratory an aqueous solution of radio- 

 active gold was placed directly in the gut of blue crabs, 

 toadfish, and croakers. There was little transfer of the 

 isotope to various tissues in these organisms. A group 

 of toadfish which were fed radioactive gold in an 

 aqueous solution retained more of the isotope than did 

 a group which were fed the same amount of radioactiv- 

 ity sorbed onto clay particles. Also, crabs, fish, clams, 

 and samples of bentonite clay were maintained for 25 

 days in 1,000 liters of cotton-filtered sea water contain- 

 ing radioactive gold. Crabs accumulated the most 



radioactivity followed, in descending order, by clams, 

 clay, and fish. A field experiment was conducted in 

 cooperation with the U.S. Army Corps of Engineers in 

 the Cape Fear River, N.C. Caged and indigenous free- 

 swimming organisms were exposed to sediment-sorbed 

 radioactive gold used as a sediment tracer by the Corps. 

 Oysters, crabs, and fish maintained in cages in the 

 experimental area were sampled periodically. The 

 maximum level of radioactive gold in the caged orga- 

 nisms (70.9 millimicrocuries per gram wet weight tissue) 

 was detected in oysters 17 hours after the isotope was 

 released. Indigenous organisms collected 41 hours 

 after the radioactivity was released contained no 

 detectable radioactive gold. 



The uncontrolled release of radioactivity into 

 estuarine waters could so contaminate marine 

 organisms that they would be unsafe for use as food 

 by man. However, with the use of basic data 

 from laboratory experiments to evaluate the quan- 

 tity and rates of release of radioactive materials, 

 and with sensitive instruments to measure the 

 resulting levels of radioactivity, radioisotopes can 

 be released into the natural environment without 

 adversely affecting seafood organisms. Also, when 

 released in this manner, radioisotopes can safely 

 be used in situ to investigate many ecological 

 problems. 



A study was made to determine the bioaccumu- 

 lation of sediment-sorbed radioactive gold re- 

 leased into the Cape Fear River. This study was 

 carried out with investigators of the U.S. Army 



Note.— Approved for publication Sept. 2, 1964. 



' The work upon which this report is bused was done under the cooperative 

 agreement between the Fish and Wildlife Service. U.S. Department of the 

 Interior and the U.S. Atomic Energy Commission. 



Corps of Engineers, who used this isotope to trace 

 sediment movement in the river. Prior to this 

 investigation, radioactive gold had been used 

 successfully as a sediment tracer by the Corps of 

 Engineers in several bays and harbor systems in 

 the United States. 



Determinations of gold in marine organisms 

 have been reported by Noddack (1939), Vino- 

 gradov (1944), and more recently by Fukai (1962). 

 Equilibrium values for the distribution of gold 

 between sea water and organisms have been cal- 

 culated by Krone (1959) using the data of both 

 Noddack and Vinogradov. The capacity of 

 marine organisms to accumulate radioactive gold 

 from contaminated sea water or from contami- 

 nated food organisms has not been determined. 



Since marine organisms could be exposed to 

 radioactive gold used in sediment tracer experi- 

 ments, an evaluation of the accumulation of this 

 isotope by several marine organisms was made by 

 (1) conducting laboratory experiments to deter- 



FISHERY BULLETIN: VOLUME 65, NO. 2 



427 



