-14The invertebrates,
or animals without backbones,
make up the great bulk of the animal life of an atoll.
The role of these animals in the cycling of radioactive
materials in an atoll is as varied as the invertebrate
forms.
Sea cucumbers have been compared with earth
worms in their ceaseless turning of the gravel and sand
as they obtain their nutriment from bacteria and algae.
Corals and clams remove microorganisms and particulate
matter from the water and also are host to the unicellular algae,
tissues.
Zooxanthellae, which are found in their
The Zooxanthellae may be thought of as a vast
reservoir of trapped plankton.
Their relationship to
their host is not completely understood but it is
probable that they play an important part in the removal
of phosphate wastes.
Corals and clams are eroded by
algae and sponges, which bore holes in the skeleton or
shell,
thus contributing to a return of carbonates to
the water.
Crabs,
sipunculid worms and others also
attack the skeleton of the corals.
Some of the land
crabs contribute to the deposition of radioisotopes from
the sea onto the islands by dragging fish and algae
ashore when feeding.
In short,
within the invertebrates
and their symbionts alone complete biological cycles
occur from land to sea and back again,
from inorganic
substances to organic and back again.
The fishes of the waters in and about the Marshall
Islands have received a major share of the attention in
the study of the biological cycling of radioactive
materials
UWFL-55).
(AECD-3446,
UWFL-46,
UWFL-47,
UWFL-49,
UWFL-51,
Despite detailed study, the great variety of