-microplankton to that in the iificant (on the average 0.00025 ial on the filter paper may be inorganic particulate matter. ' of the filter papers. kton per unit volume of sea kton volumes reported by the urveys made in 1956 and 1957 e volumes of water strained by with the volumes of plankton / ml of plankton was collected 7,800 and the carbonate/plankton ratio 28,000. The ratio of the total activity in the sea-water to that in the plankton increased by a factor of about 37/, during the 2'/,-month interval between the surveys. A greater increase in activity occurred during the time between the two surveys conducted in August and September 1958. The first survey was done aboard the USS Collett during the period 8-14 August 1958, and the ratio of activity associated with the particulate matter to that in the plankton was 1,500 and that for the soluble activity to that in the plankton 9,400. During the survey made three weeks later aboard the USS Silverstein, the ratios were 5,100 and 100,000 respectively. The total activity in the water compared to that in the plankton increased by a factor of about 9.5 during the three-week interval. The mechanism involved in the apparent increase of activity in the water with respect to that in the plankton is not known. In order to determine the factors involved, techniques must be devised to divide the particulate matter in the water into its organic and inorganic fractions and to separate tok Test Site in 1956 and 1958, m was low in comparison to ne dissolved material (Table IT). the colloidal and soluble fractions from each other. In addition, accurate measurements must be made of the total volume of water strained during each plankton haul. At the present time these problems have not been solved. Radioactivity in fish samples from Bikini and Eniwetok Atolls cannot be related to any specific date of origin of contamination, since the weapons test programme at the atolls has continued over a period of years and residual rIVITY IN PLANKTON Co, Filter paper + CO, jlankton plankton 7,600 28,000 10,500 4—23 days | 9,400 TABLE III RESULTS OF RADIOCHEMICAL ANALYSES ON ORGANS AND TISSUES OF FISH TAKEN IN AND NEAR THE ENIWETOK TEST SITE after detonation 10,900 at end of | Sample series 100,000 i Mnit || . Yellowfin tuna—Eniwetok Lagoon, June 1958 (during tests) Red muscle White muscle Fei? | Co? = 5 Co® |! | trace! . OO i | | | 4 Atoll, July 1957 (3 years post-shot**) i sea, July—Sept. 1958 (during tests) | White muscle i Tuna—Marshall Islands, open | Red muscle | : ol 0.2 0.3 | | 01) Bone | i OO 70 41 | | ! 0 0 ‘trace trace 1 Oo | 90 | 27 | ' 0 72. 86 35 26 Liver Skin | 4 1 l-1 Fish liver-—Eniwetok Lagoon, Sept. 1956 (six weeks post-shot) Reeffish liver—Ailinginae 1 material 7,600 times as much x | | trace ' 0 | | ! ‘ : 0 0 Coo | | [ Liver gt | ! Kidney Spleen \iddle two weeks of June 1956 ipling stations. Two centres of rea and were sampled 4-6 days 1e devices producing the fallout. articulate matter greater than Tee Te hy mame Fess | series 13,900 4 and 6 days post-shot 10,300 23 days postshot per litre of water. The samples t area resulting from contaminater shots, and (2) a contaminnts of calcium compounds from ble difference existed between iicroplankton nor the dissolved ‘oO areas. ie USS Marsh approximately iter paper/plankton ratio was Isotope * es 105,000 ~ 3 weeks after end of test 10,500 7,400 { after detonation 36,000 ~90 days . 38 : ; 22 | 1 17 2 Booc<dl 6 3 . 4 Zns 5| 1 I Nb# Po trace| 21 0 40 11 4 1 | zr || 5 | 5 | | | 36 8 26 4 1} 3 ' 7) <} | 47, trace . 3 40 0 0.2 87.0' ; 11.1 02 181 0.2 Ld 0.1; 06/<01'809 0 5.4 <0.1 05 0 6.9 6.1 0.3 12, 1.7 O38 0.4: O11 * Sr?—V9, Rul—Rhé Cgl37__Bat8?, Cel44—_Pr!4 not found in samples. ** Major contamination during March 1954. Recontaminated slightly during 1956. 90.5 91.5 | 905: O 0 0