TABLE V RATIO OF OBSERVED Sr°° TO EXPECTED Sr*° IN PLANKTON BASED ON OBSERVED LEVELS OF Mo*®—Te®™, Te!32?——[192, Zr5—Nb*, Cel4i—Pri and Ba't?—Lal?? ‘(AMPLES IN AND NEAR THE 40_yoo [m/z % . 5.9 Cali? ! djmjg % | 242 119 | 2.0 7.9 | i 667 $3,303 100 7.3 3.8 jours. after 3 | 86 86.8 Mo** | - 83 Plankton 2k 36 . large ~ small large large | . | , | 0 0.16 O14 0.07 | Tel? Zs 0 0 0.23 0.06 0.05 Celtt | 0.42 0.06 0.02 | — » : Bal | Average |: | 0 0 0.18 0.06 0.01 1.18 0.08 0.02 0 0.43 0.06 0.03 85 wee ee that expected. This steady decrease in the expected levels of Sr®° with increased | time is probably caused by a combination of two mechanisms: one, there 26.7 4.6 3.1 71.4 33.7 95.4 3.5 28.6 6.5 0.37 32.4 5.4 92.6 1.2 49.2 4.6 i 7.00 1.6 | 77.0 1.4 was active concentration of the radioisotopes used for comparison, and two, there waslittle or no concentration of the Sr. Since Sr* was not detected in any plankton samples collected six weeks after contamination, although in many of the samples the total amount of rad#pactivity was high, Sr%? was probably not concentrated in plankton organisms, and discrimination against its uptake may have occurred. Strontium-90 is also found at low levels in marine invertebrates collected at the Eniwetok Test Site (Table VI) (South, unpublished). In spider-snail muscle and mantle, Sr®° accounted for 0.03% and 0.01% of the total activity. In sea-cucumber gonad, Sr® contributed 0.06% of the total radioactivity. However, in the hermit crab, which lives on land and derives its food therefrom, Sr® contributed 4.9%, of the total radioactivity in the muscle and 40°, of that in the carapace. TABLE VI PERCENTAGE OF TOTAL RADIOACTIVITY IN INVERTEBRATES FROM ENIWETOK ATOLL CONTRIBUTED BY Cs187, Sr°° AND Ce'* (South, unpublished) 7—-Ba!37m accounted for the ; of strontium and caesium iificant fraction of the total in the sea, although these y importance in the contam- | Eniwetok | Spider-snail muscle Spider-snail mantle Hermit-crab muscle | Hermit-crab carapace Sea-cucumber gonad Eniwetok Test Site in 1958 f observed Sr® to expected 9m, TelS2_J132 7795_Np95, The results are shown in ‘contamination, no Srwas in the nannoplankton was, of the levels of the above‘tectable difference in ratios the small plankton. At 21 id, and at 36 hours 0.03 of Date | gl3? 2/9/55 2/9/55 2/9/55 — | notdone not done 84.7% | not done Sr? | Celts 0.03% 0.01% 4.9% | | | 54° 57% 1%, 0.06%, | 66%, pn nefee pn : ; | 2/9/55 2/9/55 | J not done | | | ° | 40.0 °% | ! | 1% Neither is Sr°°—Y® found in high amounts in marine fishes collected in the contaminated area near the Eniwetok Test Site. Nacasawa et al (25), in an analysis of muscle of yellowfin tuna collected at N 4° E 140° on 8 July 1954, found only 0.003 d/m of Sr®/g of wet tissue. Sr®° accounted for 0.2% of the total activity. In the kidney of the same animal no Sr*° was detected. KawaBaTa (35) reported in a study on contaminated fish tissues collected near the Eniwetok Test Site: “It is a noticeable fact that the activity detected in various samples of Group IV was slight or even negligible.”’ This group includes strontium. o* 131