We are now studying the trace element 

 composition of estuarine organisms, with par- 

 ticular reference to those organisms known 

 to concentrate envirormnental radioactivity. 

 Mineral metabolism in the American oyster 

 is being studied with special emphasis on 

 protein-metal interactions. Anatomical and 

 subcellular distribution and the physiological 

 function of various minerals are being analyzed. 

 Soluble metalloproteins are chromatographed, 

 and the protein fractions are characterized by 

 ultraviolet absorption, nitrogen content, min- 

 eral content, and enzymatic activity. 



Estuarine organisms and sediments must 

 also be characterized chemically before con- 

 clusions on accumulation or exchange of radio- 

 isotopes can be drawn. Estuarine organisms 

 are being systematically collected and analyzed 

 for naturally occurring gamma activity; bio- 

 logical indicators of radioactivity are identified 

 and studied to determine the physiological 

 characteristics which cause them to accumulate 

 specific radionuclides. Environmental samples 

 collected for radioassay are analyzed for con- 

 tent of various trace metals by atomic absorp- 

 tion spectrophotometry. This project is being 

 expanded to include facilities for additional 

 elements so that our knowledge of the cycling 

 of elements and their radionuclides in the 

 estuarine environment can be correlated with 

 compositional data. 



Pollution Studies 



Experiments are conducted in this program 

 to explore the routes and rates by which radio- 

 activity released into the estuarine environ- 

 ment might be returned to man and to deter- 

 mine the rates by which nutrients move through 

 the biotic and abiotic phases in the environ- 

 nnent. Scope of research ranges from experi- 

 ments in the natural environment with com- 

 munities of organisms to those conducted 

 in the laboratory with single species of 

 organisms maintained in small volumes of 

 water. 



Observations are made on the cycling of 

 radionuclides released in artificial tidal ponds 

 and other more natural environments. By fol- 

 lowing the uptake of the radioisotopes by the 

 biota, we can compare the rates of accumula- 

 tion by the different species of organisms be- 

 cause they are all exposed to the same en- 

 vironmental factors. The rates should be 

 approximately those which would occur in the 

 sea because the physiological condition of the 

 organisms should be similar to their normal 

 conditions. Sannples of the biota, sediment, 

 and water are removed from the pond periodi- 

 cally and analyzed for radioactivity. Organisms 

 are analyzed alive and returned to the pond so 

 that the ecology of the pond will be unchanged. 

 At the end of the experiment, components of the 

 pond are analyzed for content of stable ele- 



ments so that their specific activity can be 

 calculated. 



All processes in anestuary cannot be studied 

 in situ; therefore, experiments also are con- 

 ducted under controlled conditions in the labo- 

 ratory. For example, the interaction of en- 

 vironmental factors such as pH, temperature, 

 salinity, and stable element concentration on 

 the exchange of radionuclides and nutrients 

 between sediments and sea water and the 

 accumulation of these materials by estuarine 

 organisms is determined by varying one of 

 these factors while the others remain con- 

 stant. Other experiments in the laboratory 

 include studies of the retention of radio- 

 nuclides by fish and shellfish and the passage 

 of radionuclides from water to phytoplankton 

 to organisms of other trophic levels. Analyses 

 of related stable element content of the orga- 

 nisms in each trophic level are made so that 

 the passage of a radionuclide through the food 

 chain can be related to the specific activity 

 of the organisms and their environment. 



Radiation Effects 



Research on the effects of ionizing radiation 

 on marine organisms is a logical sequel to the 

 investigations of the fate of radioactive ma- 

 terials in the marine environment. Our main 

 objectives are to determine the influence of 

 environmental factors on the response of 

 estuarine organisms to ionizing radiation and 

 to characterize the physiological effects of 

 radiation on these organisms. We are now in- 

 vestigating the influences of temperature, sa- 

 linity, population, number of organisms per 

 volume, and food on the responses of estuarine 

 organisms to radiation. In an estuary, salinity 

 and temperature largely characterize the phys - 

 icochemical properties of the water and control 

 the fauna. Effects of temperature upon the re- 

 sponse of mammals and fresh-water fish to 

 radiation are well documented, but data are few 

 concerning the effects of temperature on the 

 response of marine organisms to radiation and, 

 to our knowledge, no data exist on the influence 

 of salinity. 



We are describing the interactions of radia- 

 tion, salinity, and temperature by subjecting 

 various developmental stages of resident es- 

 tuarine species to combinations of the three 

 factors and nneasuring changes in their LD-50's 

 (dose of radiation (in roentgens) required to kill 

 50 percent), growth, and respiration. Prelimi- 

 nary work indicates salinity can modify L.D-50's 

 of estuarine species. Newly hatched brine 

 shrimp, exposed to different doses of radiation, 

 are reared in various combinations of popula- 

 tion sizes and water volumes to determine the 

 influence of radiation on their growth and sur- 

 vival. Similarly designed experiments will test 

 the influence of food supply. Results fronn 

 constant low-level irradiation are to be com- 

 pared with those fronn acute doses. 



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