~ 10 -
quickly taken by another.
There is here a perfect
economy of use of substances essential to life.
Available substances are rapidly taken up by
the biota,
never remaining
diluted and washed away.
long in the water to be
This is dramatically
demonstrated following an atomic test in which
radioactive materials are deposited in the water.
Within hours,
the great bulk of these materials to
is to be found in the living organisms.
Plankton
and some of the algae, which are the key organisms
in the food chain, may concentrate within themselves
more than a thousand times the amount of radioactive
substances found in the sea water.
The herbivorous
fish and invertebrates have lower concentrations of
radionuclides at any given time than do the plants
on which they feed,
and progressing along the food
chain to the carnivores the concentrations become
lower and lower.
Within each organism there is a
differential concentration from tissue to tissue,
the digestive organs having a higher concentration
than the other tissues, where a more selective
deposition as to specific isotopes has taken place.
More specifically, plankton, the oceanic plants
and animals that drift about passively with little or
no resistance to water movements, may influence greatly
the distribution of radioactive materials in the sea.
These forms include many groups of organisms from the
simple one-celled plants to the larval forms of vertebrates.
Plankton acquire radioisotopes by absorption,
adsorption, or both.
Plankton, especially phytoplankton,