69
To emphasize the probable role of diet in the distribution of gamma radioactivity in the fish of the lagoon,
the
histogram in Figure 5 was plotted from the data of Table 2,
showing gamma radioactivity in the stomachs of fish classified
according to feeding habit.
It is apparent from
the figure
that the gamma radioactivity was concentrated in the carnivores,
gomewhat more heavily in those of benthic feeding
in those which feed on pelagic fauna.
fish are,
in the strictest sense,
Although
habits than
coral-feeding
benthic carnivores,
it is
apparent from the figure that, with respect to the accumulation
of
radioactivity from the diet,
fish which feed on coral are
rather conspicuously different from those which feed on motile
fauna.
The higher levels of radioactivity in carnivorous rather
than in omnivorous or herbivorous fish may be due to the binding of induced,
transition element radionuclides from airborne
fallout to a solid phase in sea water, which when ingested by
heterotrophic plankton organisms,
to the carnivorous
becomes available,
principally,
food cycle.
The greater concentration of radiomaterials in the benthic
than in the pelagic carnivores may be due to the
effects of
gravity on the solid phase in the sea water; the particles tend-
ing to settle to the bottom where they present a higher density