62 



This computed hypothetical distribution (similar to what might have been 

 exi>ected on land) may now be compared with actual concentrations measured in 

 l!JtJG along the tracks of ships going westward to Honolulu and northward to 

 Kodiak. Observed (5) concentration magnitudes were plotted as amplitudes to 

 the right-hand of the ships' tracks. 



This suggests that large amounts of radioactivity that fell most intensely 

 near 45°N were displaced by the California Current to a region near the 

 International boundary. This conclusion has been supported by many other 

 radiometric measurements of fallout. 



SOME ANNUAL ENVIRONMENTAL REPORTS FROM THE TUNAS 



Biological systems often are extremely effective in accumulating easily 

 measurable amounts of radionuclides (and certain other trace contaminants) 

 even when their environment contains concentrations that are very diflScult 

 to detect with the most sensitive modern equipment. We have found that 

 certain tissues of the albacore tuna are especially effective in indicating 

 changes in concentrations of certain metallic nuclides in the open ocean. Other 

 marine indicator species that are more convenient to use near the coasts will be 

 discussed further below. 



Figure 4 points out the long oceanic route covered by the albacore each 

 year (6). 



Figure 5 illustrates several of the organs (7) that are convenient and effective 

 as sources of radionuclide concentrates whose levels api)ear to follow proportion- 

 ately the concentrations in the environment. Comparisons between tissue and 

 environmental concentrations are shown in Figure 6(8) . 



The advantage of the fish method is that it is extremely sensitive, and that it 

 integrates average concentrations in the environment selected by the fish. 

 The disadvantage include the limitations of sampling only at definite places 

 and seasons, and the present knowledge of the area that has been integrated. 

 Too little is known about biological "turnover rates". 



Figure 6 shows however that both biological and direct water measure- 

 ments have indicated consistently that fallout cesium has been retained for long 

 periods in the eastern N. Pacific. 



Table 1 lists the apparent residence half-times for different nuclides. It is 

 notable, but not unexi)ected, that plutonium from fallout is not retained in the 

 upper layers as long as radiocesium. 



In passing, it should be said that although albacore, because of their habits, 

 are convenient for monitoring a number of radionuclides in the sea, the levels of 

 artificial radioactivities found in their tissues are always exceedingly 

 low, threatening no hazard to humans. This is likewise true of radioactive 

 concentrations which we have sought out in certain sessile algae and used for 

 monitoring extremely small changes in radioactivity in the coastal marine 

 environment. 



COMPLICATIONS TO OCEANIC BIOLOGICAL SURVEYS 



Figure 7 is offered for comparison with Figure 2 to illustrate the greatly 

 different depts to which faUout penetrates at diagonally opposite sides of the 

 Pacific. Thes both are extremes. However, both indicates that trace element 

 concentrations may very greatly with depth, indicating one or more striking 

 maxima at shallow depths. A description of conditions at these stations, such 

 as shown in Figure 7, can scarcely be complete without tabulating or graphing 

 a dozen or more concentrations. 



When it is recognized that the thin strata carrying these concentration 

 maxima probably have been moving laterally, even more than a thousand miles, 

 it can be understood how diflicult it is to make .sure that a reprodu.nble 

 characteristic of a given environment has been determined, even by jiurely 

 physical means. losing biological indicators may add other unknown factors ; 

 on the other hand, there is also a simplification afforded by the fact that 

 many .species seek out and prefer to dwe'l in a limite<l number and presumably 

 definite classes of habitats. Each might be used, therefore, as a reiKirter 

 representing its own environment, what ever that is. 



Figure 8 is offered as a reminder of how much is involvetl when environ- 

 mental conditions near I.os Angeles, San Diego and Ensenada. for exami)le. are 

 to be compared. It is now recognized that the large, oceanic California 



