-18-
compared with that in algse and found to be quite similar as
would be expected in a species which is principally herbivorous.
The decline in the radioactivity of sea water is included
on a different scale to indicate the dependence or similarity
in the trends.
Algae are dependent on sea water for their radio-
activity, which they concentrate up to several thousand times
(Palumbo, 1957).
The surgeonfish take in considerable amounts
of radioactive material by feeding on the algae.
The data from
Belle Island (an area in which the supply of radioactive mater{al is only slowly decreasing)
indicate that,
for every micro-
curie of radioactive material ingested into the alimentary tract,
about 0.55 microcurtes are distributed to the skin, muscle,
bone
and liver combined.
In Figure 6, the decline of radioactivity in the liver tissue of omnivorous fishes is compared with that of the sea cucumber gut contents
(Bonham,
1957) and algae.
The similarities
appear to be marked during the early pertod of decline,
with
liver tissues of omnivorous fishes and sea cucumber gut averaging greater amounts of radioactivity than algae at 531 days.
Sea cucumber gut content is made up mostly of coral detritus, since this invertebrate obtains its food from this material.
Coral fragments are also found abundantly in the alimentary tract
of the mullet, a detritus feeder, along with plant and animal
material.
However,
comparisons of the decline in these two or-
ganisms in Figures 6 and 10 show marked differences in the trends
of radioactivity.
It will also be noted that the decline of
radioactivity in mullet tissues is considerably different from