~ J4 . 185 we | 055 100 ) 8 0057 .12 90 80 A - Silverstein plankton B - Collett plankton 70 60 Activity 50 ho 30 20 10 Fig. 4. Gamma spectrum curves of combined plankton samples of the Collett and of the Stiverstein_ survey which was conducted three weeks Tater. WIO5 was present at a high level in the plankton from the Collett survey but was absent in the plankton from the Silverstein survey. The Collett sampies contained higher levels of radioactivity than did the Silver- stein samples and the gamma curves are not indicative of the relative gamma activity in the two samples.