- 21-
in Table 5, show that the ratio varied with the species of algae and
with the location of the collection site in the atoll.
In general
the
ratio was highest for the fleshy algae such as Lyngbya and Polysiphonia
and lowest for the coralline alga,
Halimeda.
The highest ratios or
concentration factors (80 to 86) were obtained from the samples collected shortly after the detonation in the southern portion of the atoll
(Fig.
1).
than unity,
Approximately one half of the samples
had ratios greater
indicating a concentration of radioactivity by these algae.
Comparison of Radioactive Decay Rates
The radioactive decay rates of four genera of algae collected at
Belle Island on different dates were determined and compared with
each other and with the decay rates of water samples obtained from the
same areas in order to determine whether there were any differences
in the radioisotopic content of the samples.
genera,
For algae of the following
Halimeda, Caulerpa, and Spyridia, the decay rates decreased
with time after the test of May 14, 1954,from a slope of -1.3 to -1.0
(Table 7).
For Udotea, a semi-calcareous alga, the slopes fluctuated
between -0.8 and -1.5.
In July and November,
1954, at least,
it
appears as though Udotea contained radionuclide mixtures different from
those taken up by the other algae.
The decay of algae collected in May and June, 1954, was slower
than the decay of water samples collected during the same period of time