76 



Atomic Radiation and Oceanography and Fisheries 



oysters and other shellfish at the Radiation 

 Laboratory of the Fish and Wildhfe Service 

 (Chipman, unpublished data) it was found that 

 the rate of uptake was slowed down and the re- 

 tention time was extended when the animals 

 were kept in sea water at low winter tempera- 

 tures. Conversely, the rate of uptake was 

 speeded up and the retention time was short- 

 ened when the animals were kept at summer 

 temperatures. In other experiments at the same 

 laboratory, it was found that larvae of the win- 

 ter flounder {Pseudopleuronectes americanus) 

 took up strontium 89 much more rapidly at 

 higher water temperatures than at lower. 



So far as is known, there is no demonstrable 

 seasonal pattern of accumulation of radioma- 

 terials among the warm-blooded aquatic verte- 

 brates. It is generally believed that inasmuch as 

 the body temperatures of those animals remain 

 more or less constant throughout the year there 

 will be no marked seasonal changes in the up- 

 take of radiomaterials based on changes in rates 

 of metabolism. 



j . Effect of light 



Light affects the uptake and accumulation of 

 radioelements by plants. For example, it has 

 been clearly shown by Scott (1954) that the up- 

 take of radiocesium by the algae Fucus and 

 Rhodymenia was greatly enhanced in the pres- 

 ence of light. 



k. Radiation effects 



Many aquatic organisms have the ability to 

 concentrate radiomaterials in amounts deleteri- 

 ous to their well-being. These deleterious effects 

 range from those in which only the individual 

 is concerned to those in which the population 

 as a whole may be affected. Elsewhere in this 

 series of reports there is a paper on the effects 

 of radiation on aquatic organisms. 



Aspects of the accumtdation of radionuclides 

 through, the ecosystem 



For purposes of this paper, the aquatic bio- 

 sphere can be divided into three trophic levels 

 based on energy sources : 



1. Primary producers, such as the photosyn- 

 thetic plants. 



2. Primary consumers, the herbivores, such as 

 water fleas (cladocerans) . 



3. Secondary consumers, the carnivores, such as 

 the largemouth bass or the tunas. 



The community biomass (the total weight of 

 all organisms in the community) is unequally 

 divided between the three trophic levels. Usu- 

 ally there is a progressive decrease in both the 

 biomass and the number of organisms from the 

 first trophic level through the third, and a pro- 

 gressive increase in the size of the organisms. 

 However, most community populations are con- 

 stantly changing and are affected by seasonal, 

 diurnal, and other cycles of abundance. These 

 changes frequently have a profound effect on 

 the environment and any changes in the en- 

 vironment in turn affect the stability of the 

 community. 



Generally speaking, the smaller organisms 

 have a higher reproductive potential, a shorter 

 life span, and a shorter time between genera- 

 tions ; the length of the life span and the time 

 between generations usually give a fair indica- 

 tion of the length of the embryological period. 

 Furthermore, the smaller animals usually serve 

 as food for the larger ones. 



The discussion will consider the following 

 aspects of the accumulation of radiomaterials in 

 the three trophic levels: (1) the distribution 

 of elements among the three levels, (2) the 

 concentration factors in different organisms 

 within the same level, and (3) the transport of 

 radiomaterials from one trophic level to another. 

 Problems of the distribution of radionuclides 

 among the trophic levels and the degree of con- 

 centration of radionuclides by different organ- 

 isms can be approached most readily through 

 separate consideration of the effects from an 

 acute exposure and those from a chronic ex- 

 posure. 



A steady-state condition will be approximated 

 when the amounts of radiomaterials introduced 

 into the environment is equal to the amount 

 that disappears through physical decay. Any 

 organisms living in such an environment will 

 suffer chronic exposure to the radioactivity, the 

 level depending, of course, on their ability to 

 concentrate the radiomaterials introduced and 

 on the steady-state concentration of these ma- 

 terials in the surrounding medium. An approxi- 

 mation of the concentration factors for some 

 organisms is given in Table 4. 



Davis and co-workers (1952) showed that 

 there was a progressive decrease in the amount 

 of radioactivity found in the aquatic organisms 

 of the Columbia River downstream from the 

 Hanford Works. There, the principal radionu- 



