-24-
after the Dominic test series to determine the radionuclide
content in pelagic fish, plankton and sea water.
Analyses of 107 yellowfin tuna and 62 other species of
pelagic fishes showed that during this period there was little
change,
if any,
in levels of radioactivity in samples of light
muscle,
dark muscle,
and liver tissue.
More of the liver samples
were radioactive and the liver tissue contained a greater number
of radionuclides than the muscle tissue, but the amount of any
one radionuclide in a sample was the same for all tissues.
The levels of radioactivity of these radionuclides averaged
less than the potassium-40 content of the tissues and in most
cases were barely detectable.
Plankton samples collected during the latter part of the
Operation contained slightly higher levels of radioactivity,
especially zirconium-niobium-95 and cerium-141,144,
as a greater variety of radionuclides.
able, but very low levels,
as well
It appears that measure-
of comparatively short-lived radio-
nuclides in the plankton were due to fallout from the tests
at Christmas Island.
Analysis of sea water samples revealed no increase in
either the number of radionuclides present in each sample or
in the levels of radioactivity during the period of study.