Vol.1 part 4-5 - Department of Invertebrate Zoology

consumed by man, any accumulation of toxic metal pollutants
by these species may be detrimental to human
health .
Other species may be food sources for animals
higher in trophic order . As these species are consumed,
their trace metal burdens could be magnified as they are
passed up the food chain, eventually affecting man
(Windon et al ., 1976) .
It has been shown (Pringle et al ., 1968) that some
marine organisms which accumulate high concentrations
of toxic trace metals (e .g ., Cd) will purge themselves
and return to ambient levels once the source of exposure
is removed . This capability can complicate any
consideration of a species as an indicator for trace metal
pollution .
Another important factor in considering a potential
monitoring species is the partitioning of trace metals
among different tissues of the animal . Horowitz (1977)
showed that there can be several orders of magnitude
difference in the concentration of metals in different tissues
of the same animal . Pertinent points about each tissue
analyzed are : (1) the liver provides a "filtering"
mechanism for the circulatory system and should show
the accumulative effect of exposure to high metal concentrations
; (2) the gills are in intimate contact with the
external environment of the fish and should indicate exposure
to soluble and suspended particulate trace metals
; (3) the gonads exposed to high concentrations of
certain trace metals may prevent or inhibit the normal
reproductive cycle of the individuals and thus reduce the
species population with time ; and (4) muscle tissue is the
principle tissue consumed by humans - exposure to elevated
concentrations of toxic trace metals in muscle
would have an immediate impact on human health .
1 . Archosargus probatocephalus
Table 7 summarizes the mean trace metal
concentrations in Archosargus probatocephalus
(sheepshead) tissues . Data from the BGOF (Tillery,
1980a) are included for comparison .
Trace metal concentrations in sheepshead muscle
tissue from this study are very similar to those from the
BGOF study . This is to be expected since the sheepshead
habitats (i .e ., petroleum production platforms) in both
studies are similar . Concentrations of Cu, Fe, and Ni,
however, appear to be higher in sheepshead from the
Louisiana oil fields (p=0.01) .
Different tissues showed significant differences
in trace metal concentrations . Liver tissue concentrates
higher levels of Cd, Cu, Fe, Pb, and Zn than the other
tissues . Higher concentrations of Cu, Fe, and Zn may
be explained on the basis of their biochemical functions .
However, there are no known biochemical requirements
for Cd and Pb, and the higher levels in the liver probably
reflect the age of the fish and the detoxification
function of the liver . Cadmium, Cr, Cu, Fe, Ni, Pb, and
Zn concentrate in the gills . The gonads appear to concentrate
Cd, Cr, and Pb even though the last three elements
have no known biochemical function.
2. Chaetodipterus faber
Mean concentrations of trace metals in Chaetodipterus
faber (spadefish) tissues are given in Table 8 .
Comparisons are also made with spadefish data from
the BGOF study. There appear to be significantly
(p=0 .01) higher Cu and Fe concentrations in spadefish
muscle from the present study . Since these were collected
during summer (1978), differences may reflect either
spacial or exposure variations .
Liver tissues contained higher concentrations of
Cd, Cu, and Fe than other tissues . Concentrations of
Cu and Fe may reflect biochemical requirements for
these metals . The high Cd concentrations, however,
may reflect the detoxification function of the liver and
age of the fish .
Higher concentrations of Cd, Cr, Cu, Fe, Ni,
and Zn in the gill tissues were also observed in this species
and the gonads had higher levels of Cd, Cu, Fe, Ni,
Pb, and Zn as compared to muscle tissue . No other literature
values were found for these particular tissues .
The muscle tissues of sheepshead (Table 7) and
spadefish have similar concentrations of all metals except
Pb . Except for Ni, Pb, and Zn, gill tissue metal
concentrations are also similar, probably reflecting the
similarity in the water columns from which both species
were taken . The differences in Ni, Pb, and Zn concentrations
may reflect differences in the water column
concentrations of these metals .
The gonadal tissue of spadefish had higher concentrations
of Cd, Cu, Fe, Ni, Pb, and Zn than that of
the sheepshead . Liver tissues in sheepshead were higher
in Cu, Pb, and Zn, whereas livers of spadefish were
higher in Cd . These variations may reflect the different
abilities of the species to accumulate certain metals, exposure
levels or possible age differences .
3. Micropogon undulates
Comparisons of trace metal concentrations in
Micropogon undulates (Atlantic croaker) muscle tissue
with similar data from other studies in the Gulf are
given in Table 9. Concentrations of Cd, Cr, Ni, and Pb
from this study are lower than those reported by Horowitz
and Presley (1977) but higher than those reported
by Shokes (1978) . The concentrations of the remaining
metals (Cu, Fe, and Zn) are similar in all three studies .
The differences in Cd, Cr, Ni, and Pb may be due to
spacial and temporal variations or possibly due to analytical
variability. Horowitz and Presley (1977) thought
their Cr and Ni values may be influenced by contamination
from the stainless steel instruments used in sample
dissection .
Trace metal concentrations in muscle tissues of
croaker, sheepshead (Table 7) and spadefish (Table 8)
are very similar . Metal concentrations in gills and gonads
of croaker are more closely matched to those in
spadefish than to those in sheepshead . Liver concentrations
of Cr, Cu, Fe, Pb, and Zn are similar to those of
spadefish while Cd and Ni concentrations are closer to
those of sheepshead . The number of croaker gills, gonads
and liver samples available were not sufficient to
make more than estimates of their trace metal ~concentrations
.
4. Lutjanus campechanus
Table 10 is a comparison of the mean trace metal
concentrations in Lutjanus campechanus (red snapper)
tissues with data from the STOCS study (Presley and
Boothe, 1979) . This is the only fish species for which
comparisons with another location can be made for tissues
other than muscle .
Concentrations of Cr, Fe, Ni, and Pb are higher
in snapper muscle samples from this study while Cd,
24