RADIATION EFFECTS PROGRAM 



Joseph W. Angelovic, Chief 



Radioactivity has become an increasingly 

 important determinant in the ecology of many 

 estuaries due to expanding use of nuclear 

 reactors. Because radiation now is an environ- 

 mental factor, like temperature and salinity, 

 interactions between radiation and other en- 

 vironmental factors may have a great impact 

 on the growth, reproduction, and survival of 

 estuarine organisms. This year we observed 

 how the interactions of radiation, salinity, and 

 temperature affect the metabolismof the eury- 

 haline crustacean, the brine shrimp. In addi- 

 tion, we determined how chronic exposure to 

 low levels of radiation interacts with tempera- 

 ture and salinity to affect the growth of post- 

 larval pinfish. 



INTERACTIONS OF CHRONIC GAMMA 



RADIATION, SALINITY, AND TEMPERATURE 



ON THE MORPHOLOGY OF YOUNG PINFISH 



John C. White, Jr. 



Estuarine organisms have always been ex- 

 posed to chronic low levels of ionizing radi- 

 ation from cosmic rays and naturally occur- 

 ring radioisotopes. Inaddition, these organisms 

 have been exposed to widely fluctuating tem- 

 peratures and salinities. The animals inhabit- 

 ing the estuaries and lower reaches of rivers 

 have, of necessity, become a hardy breed, 

 readily adapting to these natural changes in 

 their environment. Since 1942, man has in- 

 creased the existing levels of background 

 radiation many hundreds of times by testing 

 nuclear weapons andbuilding nuclear reactors, 

 power plants, ships, and submarines. Water 

 usage by reactors, powerplants, cities, and 

 industry has increased the temperature in 

 rivers and estuaries and has caused upstream 

 penetration of the estuarine salt wedge. Possi- 

 ble effects of exposures to increased levels of 

 chronic ionizing radiation, temperature, and 

 salinity on aquatic species are largely unknown 

 and have become a subject of increasing con- 

 cern. 



Estuaries are unstable environments char- 

 acterized by perpetual tidal cycles and annual 

 weather cycles that cause wide variations in 

 temperature and salinity. In the study area, 

 Beaufort, N.C., for example, daily estuarine 

 water temperatures may vary as much as 5 C. 

 and salinity may vary 10 p.p.t. Seasonal water 

 temperatures may range from 2 to 30 C, 

 and shallow tide pools have an even wider 

 range; salinity may vary as much as 20 p.p.t. 

 If the effects of any one environmental factor 

 on an organism were independent of other fac- 

 tors, existing levels of radioactivity in the 

 environment probably would not be detrimental. 



Any single environmental factor, however, is 

 rarely independent of all others. Rather, an 

 interaction exists among environmental factors 

 that we know little about. Hence, as many fac- 

 tors as possible have to be considered simul- 

 taneously to determine synergistic or antago- 

 nistic effects of interactions. 



The purpose of the present study was to 

 determine the effects of low levels of chronic 

 gamma radiation, salinity, and temperature, 

 and their possible interactions, on the mor- 

 phology of an estuarine teleost, the pinfish, 

 during its critical transformation from post- 

 larva to juvenile. 



Experimental Design and Procedures 



The experiment was a 3 completely ran- 

 domized factorial design. The design consisted 

 of three temperatures (15°, 20°, 25° C), three 

 salinities (10, 20, 30 p.p.t.), three radiation 

 exposure levels (0, 0.83, 1.28 rads/hour), and 

 three replications at each combination. The 

 fish received either no radiation (controls), 

 865 rads, or 1,335 rads during the experiment 

 which lasted 45 days. 



The design made use of 81 aquaria, each 

 containing 30 fish and 14 1. of water. Random 

 samples of five fish were taken from each 

 aquarium at 15, 30, and 45 days after irradi- 

 ation had begun. These five fish made up one 

 replication for any combination of radiation, 

 salinity, and temperature. 



Experimental conditions were maintained 

 within the following limits or in the following 

 manner: temperature ( + 1° C), salinity ( t 1 

 p.p.t.), day length (12 hours light; 12 hours 

 dark), food supply (daily feeding), oxygen con- 

 tent (saturation by aeration), and metabolite 

 buildup (charcoal filtration in each aquarium). 

 The irradiation room was maintained at a tem- 

 perature of 15° +1° C. Aquaria in the irradi- 

 ation room that required 20° and 25° C. were 

 insulated with 5 cm. of plastic-covered fiber- 

 glass, and a 100-w Supreme Thermostatic 

 Heater was immersed in each one. Animals 

 receiving no radiation (controls) were housed 

 in three constant-temperature rooms adjacent 

 to the irradiation room. Salinity of the water was 

 adjusted daily, and 90 percent of the water was 

 changed every 10 days. Pinfish were fed daily 

 with fresh or frozen nauplii of the brine shrimp, 

 and the diets were supplemented about once a 

 week with commercially prepared fish food. To 

 obtain a better estimate of true weight, we did 

 not feed the fish on the day before sampling. 



Postlarval pinfish were irradiated with a 

 5-c. cobalt 60 source for an average of 23.17 

 hours a day for 45 days. Aquaria were placed 

 at random in two concentric circles around 



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