-48-
SUMMARY
Trends with time in the beta redioactivity of invertebretes
and other organisms and substances were traced over a period of
about tvo years, from shortly before Nectar (May 14, 1954) to
April 1956.
Extensive observations at one locality, Belle, vere
supplemented by study at severe] other localities around the
atoll.
Absolute levele of radioactivity are summarized in Table 23.
Outstand
values expressed in disintegrations per minute per
grem (d/a/g) of wet tissue vere:
for pre-Nectar
coilections on
Anpt} 15, 1958, high valugs, tern feathers 3x10", clem kidney
727x105, and snail liver 10°; low values, fish muscle 200, and the
branching coral Acropora 600.
Maximum levels of 107 occurred within one veek post-Nectar
in plankton at Belle and Leroy, and in tern feathers at Belle.
Post-Nectar levels vere low for rat skin and suscle at Janet,
2 to 3x10 and for fyen muscle et Belle, 7000.
Acropora was
intermediate at 3xl0.
of 10°
py 700 days post-Nectar, the levels had decreased to maxima
for clam kidney and Coenobita (land hermit crab) carapace,
and minima of 100 for Acropora and estimated 30 to 40 for tern
gut and muscle.
The decrease in amount of radioactivity in a certain sub-
stance at a locality with the passage of time after detonation,
has been termed decline to distinguish it from the physical
decay of individual samples.
The declines and decays were plotted logarithmically for
comparison with the approximate theoretical decay rate,
for mixed fission products.
t-1.2,
Correlation coefficients at or
beyond the 1% level of P were demonstrated for the relationship
of log of activity to log of time after detonation in the cases
of survey meter readings, some island soils and beach sands
most sea vater samples, some plankton, most Halimeda (algae),
land plant leaves, Acropora, tridacnid clams, most spider snail
tissues, land hermit crabs. sea cucumbers, reef fish, tern, and
most rat tissues.
Levels of activity in the first few days were in some
cases too low to align with later points in logarithmic plot,
suggesting that @ preliminary pertod of build ‘p is required in
these organisms, part‘cularly coral, sea cucu...er, fish, and
tern, for the radioisotopes to attain equilibrium with the nonradioactive constituents of the tissues.