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The rate of decay of radioactivity in the samples of algae collected
at Leroy and Henry Islands was faster than that at other islands of the
atoll.
Samples collected in February 1955 (nine months after detonation)
decayed at rates much faster than would be expected on the basis of mixed
fission product decay,
an indication that these algae must have been con-
centrating short-lived radioisotopes.
is not known,
The identity of these radioisotopes
nor is it known why the algae in these
two areas should
take up short-lived isotopes and algae at other islands take up different
ones.
Studies of the levels of radioactivity of the algae and bottom sediment at different locations in the lagoon at Eniwetok Atoll showed that
high amounts of radioactivity can be expected at depths up to 140 feet at
any location in the atoll months after a nuclear detonation.
The radio-
activity present in the bottom of the lagoon, miles from the site of detonation,
could be deposited there either by direct fallout or by transport
by water currents.
Once the radioactivity is deposited on the bottom of
the lagoon after settling out of the water, it probably remains near its
deposition site.