39 SUMMARY A survey to determine the amount of radioactivity in the waters about Bikini and Eniwetok Atolls was made during the period June 11 to 21, 1956. A grid of stations about 45 miles apart covering 78,000 square miles of ocean between 10° 15' N to 14° N and 159° to 166° E was covered by the survey. The distance traveled was 3,300 miles. Radioactive materials were found in the plankton samples from every station. The highest plankton counts, 1,100,000 d/m/g ( wet weight) were obtained near Bikini Atoll, and the lowest, 1,300 d/m/fg, in the northwestern part of the survey area. The average value for plankton was 71,000 d/m/g which was 7,100 times the average surface water value. Water samples were collected at surface and at depths of 25, 50, 75 and 100 meters. The average radioactivity of water was 10,000 d/m/. at the surface and 3,900 d/mfAi at 100 meters. A scintillation probe was used to continuously record the radioactivity of the surface water. This method has interest- ing possibilities if problems of contamination, vibration, and static electricity can be overcome. The survey successfully demonstrated the usefulness of the various methods in evaluating the amount and distribution of radioactivity in the sea. | oye LTVES “f2