-
ll -
present a greater absorptive surface to the environment
than any other group of marine organisms.
Thus,
the
major initial concentration of radioactive isotopes
probably occurs in the phytoplankton--the same
organisms which comprise the foundation of the food
chain in the sea.
The isotopes especially concen-
trated by these forms are,
for the most part,
repre-
sentatives of those elements which tend to form strong
complexes with organic material.
They include most of
the anionic radioisotopes,with the exception of iodine,
and the cationic radioisotopes produced by neutron
induction including radioactive
manganese.
zinc,
cobalt,
iron and
All of the cationic radioisotopes concen-
trated in the plankton are biologically important
elements comprising the essential parts of enzyme
systems and,
in one case at least,
an essential vitamin.
The levels of radioisotopes present in the plankton
vary with time after release of the radioactive materials,
mainly because of the variation in availability due to
physical decay of the individual radioisotopes
In general,
however,
(UWFL-53).
plankton contain the three radio-
active isotopes of cobalt.
Co57, Co°8 and co69, at a
level of 11 to 50 percent of the total radioactivity.
zn©> is present at a level of 12 to 47 percent; Fe°25-59
at a level of 1 to 40 percent; Mn54 in trace amounts,
and the fission products Zr95_Nb95 at levels of 3 to 44
percent; Rul06_pnl06 from 0 to 7 percent; Cel44-prl44,
0 tol3 percent; and Csl37 in trace amounts, if present
at all
(UWFL-54).
plankton.
Sr?9-y99 has not been found in