Te
9
samples it was less than 5%. Silicification appears to
be associated particularly with the yellow-green
algae, the Chrysophyta™”, Thus the residue might
derive, in part, from epiphytic diatoms.“!) The insoluble residues might also represent mechanically en‘ trapped contamimants. It would be expected that
those algae which have a mat- or sponge-like struc-
t in
und
ore,
was
ave
‘ac
wn
ted
the
shows that, depending on collection location, the sand
can consist of from 60% to 90% of calcium carbonate
and other acid soluble components. It may be further
noted from the data in Table 2 that the concentra-
tions of radium, uranium, and calcium in sand are
very similar to those reported for the samples of
Halimeda opuntia or Penicillus capitatus (Table 1
also}. This is consistent with the observations that
ture, and which grow where there is considerable sus-
pended material of land origin, would show the greatest
degree of such entrapment. It is of interest, therefore,
that the spongy Aurainvillea rawsoni shows the greatest degree of variation in insoluble residue, its soluble
the sands in the region of collection are made up
largely of the mineral residues of calcareous orga-
nisms, particularly Halimeda."*) Thus, it is possible
that calcareous contamination might have contributed
to the extent of variance found for some of the analy-
fraction varying between 0.98 and 0.48 for different
samples. Laurencia papillosa and Dictyota divaricata
ses.
For those species where samples were collected in
also show a large variation in their soluble fractions.
The degree of contamination by silica would also
depend on the nature of the bottom sediments where
the algae are growing. The importance of this factor
may be inferred from the variability in the values of
sufficient number in 1961 and again in 1967 or 1968,
there were no significant differences between the two
groups in their concentrations of calcium, radium,
uranium or nitrogen. An insufficient number of sam-
ples from each location precludes an evaluation of
the analyses for calcium and insoluble matter in the
samples of sand from different locations (Table 2).
the effect of the environment at each collection site or
Even the limited sampling represented by Table 2
°-20/
'
of location dependent differences for the various spe-
O
]
oO
O CHLOROPHYCEAE
O RHODOPHYCEAE
& PHAEOPHYCEAE
0.15
A
o
—
SS apa
Qo
oO
A
_
oO
E
an
=
2
o
= 0.10
ole
A
A
oO
A
A
=
oS
A
a
oc
oO
a
AA
A
A
Do
oOo
Oo
o.oo
a
oo
o|
0
A
=
Oo
oO
CA
Oo
o
oO
Oo
©
4o
oOo
—
Oo
A
0.05f—
A
oO
A
o
oO
oO
0
co
oO
oO
°
a
J
0.1
]
0.2
|
0.3
0.4
CALCIUM (qm/gm)
Fig. 4.—The variation in the concentration of radium with the degree of calcification of the algae