RADIONUCLIDES IN PLANKTON NEAR THE 
MARSHALL ISLANDS, 1956 
Introduction 
During the summer and fall of 1956 members of the 
Applied Fisheries Laboratory conducted two surveys in the 
region of the Pacific Ocean bounded by the Marshall, 
Caroline, and Marianas Islands. The purpose of the surveys 
was to measure the levels of radioactivity in the water, 
plankton, and fish and to determine the westward boundary 
of the contaminated area. 
The first survey was made June 11-21, 1956, during the 
weapons testing period and included 53 collection stations 
in the ocean 11° N to 14° N and 159° E to 166° FE. The re- 
sults were reported in U. S. Atomic Energy Commission report 
UWFL-46 (6). The second survey conducted from September 1- 
20, 1956, about six weeks after the conclusion of the weapons 
tests, included 74 stations between 9° N and 15° N and 
approximately 145° E and 1669 E (Fig. 1). The findings were 
published in U. S. Atomic Energy Commission report UWFL-47 
(21). 
Chemical separations for fission products, cobalt, and 
zinc were made on a limited number of samples from both surveys, 
the results of which were reported in the latter report (21). 
According to these data fission products contributed a major 
