96
is adsorbed are shown entering sea water from the air.
of the zinc-65,
is dissolved.
Some
which forms soluble compounds in sea water,
Mixing, by means of turbulent diffusion and
advection, brings about almost infinite isotopic dilution by
the stable zine present in sea water.
It is ultimately carried
out of the lagoon in the exchange of water from the open ocean.
Much of the zinc-65 is prevented from going into solution by
the formation of an insoluble shell of Mg(OH)2 around the particles which either sink or remain suspended,
their size and density.
depending on
The particles then either settle to
the bottom or are taken up by the plankton either by adsorption
or ingestion,
primarily the latter.
The zinc-65 associated
with these particles thereupon enters the several food cycles
indicated in Figure 8.
lines in the figure.
Major pathways are suggested by heavy
Inorganic and organic particles which set-
tle directly on the bottom are either
animals,
(1) ingested by benthic
(2) carried out of the lagoon by bottom currents, or
(3) incorporated into the bottom sediments.
Much of the material
ingested by benthic animals is returned to the focd cycles of the
overlying water by benthos feeding carnivorous fish such as goatfish.
Losses from the food cycles occur in three ways:
(1)
iso-
topic dilution of soluble fractions derived from excreta or local
reduction by bacterial processes on the bottom,
(2)
sedimentation
Joe