LEVLES AND SITES OF CONCENTRATION OF TRACE METALS
IN INSHORE FISHES OF MONTEREY BAY
ABSTRACT
The sites of concentration of the trace metals
cadmium, lead, silver, copper, chromium, manganese, and
zinc were determined for five species of inshore marine
fishes. Generally, zinc and lead accumulate in the gills;
copper, cadmium, and zinc accumulate in liver; and silver,
zinc, manganese, chromium, and cadmium concentrate in bone.
Flesh dosen't noticeably concentrate any of these elements.
Concentration levels with regard to trophic levels were
also examined, and it was found that manganese in the
liver, and zinc in flesh and bone decrease in concentration
with increasing trophic level. Cadmium in the liver may
show a direct relationship of concentration with higher
trophic levels.
119
LEVELS AND SITES OF CONCENTRATION OF TRACE METALS
IN INSHORE FISHES OF MONTEREY BAY
By James Prickett
Hopkins Marine Station of Stanford University
14
INTRODUCTION
Most public attention and much of the research
involving pollution has centered around the introduction
of pesticides, especially DDT and its derivatives, into
the environment. Only recently, with the government's
release of mercury levels in swordfish, has public awareness
focussed on another source of pollution, that of the trace
metals.
Using calculations of the total amount of an element
mined each year as compared to the amount of that element
added to the oceans each year, Bowen (1966) has classified the
pollution potential of many of the trace metals. Silver (Ag),
cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), and
zinc (Zn) are all classified as having a very high potential
of pollution. Manganese (Mn) is classified as having a
high potential of pollution.
The detrimental effects of many of the trace metals
have been known for years. Silver is highly poisonous,
and copper, which is used in large amounts in some areas
as a fungicide, is also toxic. The toxicity of manganese
is reported to be moderately high. Chromium, although it
may be important in activating some enzymes, is suspected
of being carcenogenic. Stock's study (1960) of zinc pol-
luton in industrial smoke indicates that this metal may
4/4
induce lung disease (Bowen).
Cadmium, which is used extensively by man in such
varied items as automobile parts, laundry equipment, and
dental fillings, has been responsible for many human deaths.
In Japan alone, since 1962, fifty-six deaths have resulted
from "Ouchi-Ouchi" disease, which is linked to cadmium-
polluted rice in areas adjacent to mining operations. On
a molecular level, cadmium binds to essential SH-groups
to block the functioning of many enzyme systems (Nillson, 1970).
Lead has long been known to be highly toxic, and yet
in 1965 alone, about 6,000 tons of lead were introduced
into the air of Los Angeles as a result of the use of
tetraethyl lead in gasoline (Lead in the Environment and
its Effects on Humans, 1967). Lead readily co-ordinates
with organic ligands, and is generally toxic to enzyme
systems (Brooks and Rumsby, 1965). Both lead and cadmium
are cumulative poisons, so that exposure to low levels
over an extended period can allow undesirable levels to
accumulate (Bowen).
In an effort to determine the extent to which these
metals are accumulating in marine fishes, a study was made
of the concentration of Ag, Cd. Cr. Cu, Mn, Pb, and Zn
in inshore fishes of Monterey Bay. It was felt that the
inshore water mass, due to its proximity to pollution sources,
would tend to accumulate metal pollutants at higher levels
ao
than those found in open ocean, and give a clearer picture
of what metals are involved as pollutants.
The question of trace metal accumulation was approached
from two points of view. First, for each fish studied,
levels of the seven metals were measured in the flesh,
liver, bone, and gills to determine the principle sites
of concentration of each metal. Flesh was chosen because
of its use in several of the species studied as food by
man. The liver, because of its use as a filtering organ,
and because of its many physiological roles, might be
expected to act as an accumulation site. Bone was chosen
since due to its mineral composition, it might offer a
matrix suitable for the concentration of an entirely dif-
ferent group of metals than those found in the other
tissues. Finally, gills, because of their large surface
area and use as an exchange organ, would be predicted to
be another site of concentration.
The second focus of attention involved trace metal
behavior in food chains. Although the fishes used in this
study do not lie necessarily in the same food chain, they
do fall into general trophic levels. The fish studied
were the top smelt, Atherinops affinis; shiner perch,
Cymatogaster aggregata; starry flounder, Platichthys
stellatus; striped bass, Roccus saxatilis; and the leopard
shark, Triakis semifasciata.
The food of these fishes are
444
found in Table 1, along with an indication of the approximate
trophic level of each fish.
MATERIALS AND METHODS
The geographic location of this study is shown in
Figure 1. Elkhorn Slough enters into the central portion
of Monterey Bay. Although there is a small amount of fresh
water entering the slough, generally the physical character-
istics are those of an inshore marine environment (Rote, 1968).
The Pajaro River enters into Monterey Bay about three miles
north of Elkhorn Slough, and is a typical estuarine environ-
ment, with salt water intrusion occuring up to two miles
above the mouth of the river.
The shiner perch (12-14 cm; all were females with young)
and the leopard sharks (100 cm) were captured using gill
nets at Kirby Park in Elkhorn Slough, shown as station 1
in Figure 1. The starry flounder (22-26 cm) were captured
with a beach seinein the yacht harbor of the slough, shown
as station 2. Finally, the top smelt (22-25 cm; all were
females with young) and striped bass (24 cm) were taken
using gill nets, about one mile up from the mouth of the
Pajaro river at station 3.
Tissues were either dissected on the day of capture,
or the whole fish was frozen in a plastic bucket for later
dissection. It should be noted that due to the small
14
size of the gills in some of these fishes, the whole gill
basket, including bone, had to be used. Thus, gills can
be said to accumulate a metal only when that metal's con-
centration in the gills is greater than its concentration
in the bone of the same fish.
Samples were prepared for analysis using a modification
of the wet digestion procedure of Middleton and Stuckey
as described in Christion and Feldman (1970). Samples
were dried at 90'C and powdered with mortar and pestle.
one gram aliquot was dissolved in 5 ml of 90% HNO3 and
refluxed at low temperature. HCl was used to dissolve
any remaining calcareous particles. Two ml of 30% Ho09
were added and the sample was refluxed again before
bringing to volume with distilled water.
All samples were analyzed on a Perkin-Elmer Model 303
atomic absorption spectrophotometer using an air-acetylene
flame. Standard conditions were followed for each element.
For each set of tissues, the mean value was calculated,
and all variation was reported in terms of one standard
deviation. Those tissues for which N = 1 or N = 2 represent
a composit value of five samples which were too small
to be run individually.
RESULTS AND DISCUSSION
The concentrations found for each of the metals by
1/66
species are given in Tables 2A-20. Values determined by
Ting (1967) for albacore and skipjack tunas are found
in Table 3. Ting's values are given as a comparison, since
his fish were pelagic and from a different region (Peru).
His values generally compare closely with the values found
by this study of inshore fishes, with the exception of
manganese. The inshore fishes were often one order of
magnitude higher for manganese than the tunas. This could
possibly be due to manganese accumulation in the inshore
waters, since manganese levels would be expected to be
approximately equal if they were only involved with natural
systems. Veith's study of trace metal introduction into
Monterey Bay (1971) shows that manganese is one of the
principle trace metals found in the sewage effluent. In
addition, he found manganese to be the highest of the metals
studied in sediments near the Monterey sewage outfall.
Manganese concentrations in the two water bodies would
have to be determined before any definite hypotheses could
be made.
The concentrations of each metal by tissue are plotted
in Figure 2 - Figure 8. From these, it can be seen that
certain tissues are accumulating much more of particular
metals than others. Flesh is the site of lowest concentration
for all of the metals. Lead and zinc concentrate in the
4/
gills at levels above those found in bone, so that the
gill filaments themselves may be said to accumulate these
metals. Ting's data also shows this trend. Manganese
is possibly accumulating in the gills, but the values are
too close to those of bone to make a definite statement.
These observations are similar to those made in studies
by Pringle, et. al. (1968) and Brooks, et. al. (1965),
which indicate that the gills of bivalves, due to their
mucous secretions, tend to be sites of concentration of
Cutt, Zn, and Mnt. One theory for the toxicity of
the trace metals upon fish attributes them with causing
asphyxiation. When in high enough concentrations, the
metals have been found to precipitate in the mucous
layers of the gills, blocking respiratory transfers
(Pringle, et. al.).
The liver seems to be accumulating cadmium, zinc,
and copper. The copper levels are especially interesting,
since they range from two to twenty times the levels of
copper in the other tissues. Among the catalytic trace
elements, Bowen includes copper, manganese, and zinc. Thus,
considering the many enzymatic functions of the liver,
the relatively high levels of zinc and copper would be
expected.
Bone concentrates the largest number of the elements
studied, including silver, zinc, manganese, chromium, and
44
cadmium. Chromium and silver especially are found in bone
as opposed to the other tissues. Since much of bone is
inorganic material, concentration of these generally non-
enzymatic elements is not unusual. However, no definite
explanation can be found for the high manganese and zinc
levels. These, too, could be accumulating in the inorganic
fractions of the bone, or they could be involved in some
physiological functions of bone cells. No information
could be found in the literature which could distinguish
between these or other hypotheses.
No general conclusions can be made concerning the
behavior of trace metals as a class in regard to food chain
magnification. As a whole, no single pattern emerged,
with most of the elements in each tissue showing much
scatter between different trophic levels. Hovever, a few
patterns for specific elements in specific tissues are
seen in Figure9- Figure 12. Manganese in the liver,
and zinc in the flesh and bone all show decreasing concen-
trations with increasing trophic levels. This is the same
pattern ovserved in an experiment by Baptist and Lewis (1969)
for both 2n65 and Cr5l in an artificial food chain of
four levels. Although at first this inverse relationship
might appear to be due to decreasing surface/volume ratios
with increasing size, this does not explain the scattered
behavior of most of the other elements with regard to
trophic level.
2/0
A rather interesting behavior is observed for cadmium
in the liver, shown in Figure 12. Of the twenty-eight
metal-organ systems studied with regard to food chains,
only cadmium showed any kind of direct relationship
between trophic level and concentration. Although the
uncertainty of Figure 12 is rather large, due to the high
toxicity of cadmium in enzymatic reactions, and the essential
physiological role of the liver, this trend of cadmium to
accumulate at higher trophic levels deserves further study.
Although some conclusions have been reached concerning
the two questions set forth in this study, no definite
statement can be made concerning the more important and
general question: Is trace metal pollution occuring in
these marine fishes? To draw such a conclusion, base-
lines of natural concentrations must exist for comparison.
Ting's study on tuna was used to partially fill this need,
and indeed, as mentioned earlier, there is the possibility
that manganese is acting as a pollutant. Perhaps cadmium
and silver, since they have no known physiological
functions are also occuring due to pollution. But no
such conclusions can be made for the other four metals,
and it is quite possible that all of the levels measured
are simply natural levels. Hopefully, the data obtained
in this study will be of use to other investigators as
comparison values, so that some idea of natural levels
450
can be obtained. Knowing these, more conclusive measure-
ments can be made of trace metal pollution of marine fishes.
SUMMARY
The sites of concentration of the trace metals
cadmium, lead, silver, copper, chromium, manganese, and
zinc were determined for five species of inshore marine
fishes. Generally, zinc and lead accumulate in the gills;
copper, cadmium, and zinc accumulate in liver; and silver,
zinc, manganese, chromium and cadmium concentrate in bone.
Flesh dosen't noticeably concentrate any of these elements.
Concentration levels with regard to trophic levels were
also examined, and it was found that manganese in the
liver, and zinc in flesh and bone decrease in concentration
with increasing trophic level. Cadmium in the liver may
show a direct relationship of concentration with higher
trophic levels.
ACKNOWLEDGEMENTS
This work was made possible by Grant GY-8950 of the
Undergraduate Research Participation Program of the
National Science Foundation. I would like to thank James
Rote for his help throughout the project, and Dr. John Martin
and George Knauer for their help with atomic absorption
analysis. Also, I would like to thank Gary Kukowski of
45
Moss Landing Marine Lab for his aid in collecting materials
for this study.
REFERENCES
Ackerman, L. T. 1970. Variations in food habits with
length of leopard sharks in Elkhorn Slough.
From an unpublished paper at Moss Landing Marine Lab.
Baptist, J. P., and C. W. Lewis. 1969. Transfer of 65-
Zn and 51- Cr through an estuarine food chain, p. 420-
430. In D. J. Nelson and F. C. Evans (eds.), Proc.
2nd. Natl. Symp. on Radioecology, Ann Arbor.
Baxter, J. L. 1966. Inshore Fishes of Californea. State
of Calif., The Resources Agency, Dept. of Fish and
Game. 80 p.
Trace elements in biochemistry.
Bowen, H. J. M. 1966.
Academic Press. 241 p.
Brooks, R. R., and M. G. Rumsby. 1965. The biogeochemistry
of trace element uptake by some New Zealand bivalves.
Limnol. Oceanogr., 10: 521-537.
Christian, G. D., and F. J. Feldman. 1970. Atomic
Absorption Spectroscopy: Applications in Agriculture,
Biology, and Medicine. John Wiley & Sons, New
York, 490 p.
Lead in the Environment and its Effects on Humans. Air
Resources Board, Sacramento, Calif. 1967.
Nilsson, R. 1970. Aspects on the toxicity of cadmium
and its compounds. Swedish Natural Science Research
Council, Ecological Research Committee Bull. No. 7.
Pringle, B. H., D. E. Hissong, E. L. Katz, and S. T. Mulawka.
1968. Trace metal accumulation by estuarine mollusks.
J. Sanit. Eng. Div., 94: 355-475.
Rote, J. W., 1968. Ecological Studies of the Cirratulid
Worm Cirriformia Spirabrancha at Elkhorn Slough.
Paper submitted to Hopkins Marine Station, Pacific
Grove, California, for Biol. 175h.
450
Ting, R. Y. 1967. Appendix A. p. A-1 - A-191. In
F. G. Lowman, D. K. Phelps, R. Y. Ting. J. H. Martin.
D. J. Swift, R. M. Escalera. Puerto Rico Nuclear
Center Marine Biology Program Progress Summary
Report No 5, 1967.
Veith, R. 1971. Trace Metals in Monterey Peninsula
Sewerage. Paper submitted to Hopkinc Marine Station,
Pacific Grove, California, for Bio. 175h.
6
TABLE LEGEND
Food and Trophic Levels of Five Species of
Table 1.
Inshore Fishes.
Table 2A. Trace Metal Concentrations in ug/gram Dry Weight.
Table 2B. Trace Metal Concentrations in ug/gram Dry Weight.
Table 20. Trace Metal Concentrations in ug/gram Dry Weight.
Table 3. Trace Metal Concentrations in ug/gram Dry Weight
as reported by Ting, 1967.
Table 4. Key to Figures.
TASLE
FOOD AND TROPHIC LEVELS OF FIVE SPECIES
OF INSHORE FISHES
Top Smelt: Small planktonic crustacea.
1 carnivore (Baxter, 1966).
Shiner Perch:
Small crustacea and invertebrates.
2° carnivore (Baxter).
Starry Flounder:
Small crustacea, clams; small fish.
2° - 3° carnivore (Baxter).
Striped Bass:
Shrimp, anchovies, small fish.
30 carnivore (Baxter).
Leopard Shark:
Crabs, Urechis; fish (scavenger).
3+ carnivore (Ackerman, 1971).
TABLE àA
TRACE METAL CONCENTRATIONS
IN ug/gram DRY WEIGHT
Species: Atherinops affinis, Top Smelt
N = 3
N = 3
N = 3
liver
flesh
bone
O.8 + 0.2
O.9 + 0.2
N.D.
Pb
N. D.
0.5 + 0.7
N.D.
2.0 f 0.1
Ag
N.D.
3.4 + 0.3
4.9 + 0.2
90.0 + 20
Cu
0.8 + 0.1
N.D
N.D
3.9 + 1.5
0.7 + 0.1
15.0 + 4.5
71.0 + 9
Mn
66.0 + 6
98.0 + 10
146.0 + 12
Species:
Cymatogaster aggregata, Shiner Perch
N = 1
N = 10
N = 2
liver
flesh
bone
O.3 +O
0.2 + 0.3
0.2
1.6
1.4 + 1.4
1.3 f 0.1
Pb
2.7 + 0.2
0.2 + 0.2
N.D.
5.1 f 1.4
Cu
3.6 + 1.7
16.0
8.5 + 0.5
Cr
N.D.
3.7 + 6.7
2.0 + 0.7
7.6
30.0 + 4
13.0 + 13
Zn
103.0
118.0 + 4
N = 3
gill
0.5 + 0.2
2.5 + 2.0
2.0+ 0.8
4.1 + 0.9
3.5 + 0.9
73.0 + 10
102.0 + 13
N = 2
gill
0.2 + 0.1
3.7 + 3.1
1.7 + 0
6.0 + 0.5
10.0 + 1.3
30.0 + 6
108.0 + 9
16
Species:
Cd
Pb
Ag
Mn
Zn
Species:
Pb
Cu
Cr
Mn
Zn
TABLE 2B
TRACE METAL CONCENTRATIONS
IN ug/gram DRY WEIGHT
Platichthys stellatus, Starry Flounder
N = 5
N = 5
N = 5
lag
flesh
liver
bone
0.5 +0.2
1.6 + 0.8
O.9 + 0.7
N.D.
N.D.
0.5 + 0.1
N.D.
N.D.
2.7 + 0.7
4.3 + 1.3
111.0 + 14
1.5f0.2
1.3 + 1.2
6.4 + 2.0
7.0 + 3.7
1.0 +0.2
38.0 + 15
5.8 + 0.8
N.D.
238.0 + 6
112.0 + 18
Roccus saxatilis, Striped Bass
N = 3
N = 3
N =
liver
bone
flesh
N.D.
1.0 f0.2
1.5 +O.1
N.D.
N.D.
5.1 + 1.3
2.5 + 0.2
N.D.
N.D.
1.2 + 0.4
5.0 +0.2
11.0 + 2
N.D.
N.D.
3.4 + 2.4
46.0 + 4
1.5+0.6
7.1 + 0.8
20.0 + 2
94.0 + 11
73.0 f 11
N = 5
gill
0.9 + 0.6
3.6 + 2.5
1.0 +0.1
2.7 + 0.9
2.5 + 1.1
15.0 + 6
194.0 + 18
N =
gill
0.5 + O.1
4.8 + 0.3
1.3 + 0.4
4.7 + 2.1
1.4 + 0.8
32.0 + 3
73.0 + 10
465
Species:
Cd
Pb
Ag
Cu
Cr
Mn
Zn
TASLE ac
TRACE METAL CONCENTRATIONS
IN ug/gram DRY WEIGHT
riakis semifasciata, Leopard Shark
N = 5
N = 5
N = 3
liver
cartilage
flesh
N.D.
7.0 + 6.0
0.9 + 0.2
4.0 + 0.3
N.D.
N.D.
1.3 + 0.2
N.D.
0.1 + 0.1
1.6 + 0.6
1.6 + 0.5
3.8 + 1.2
12.3 + 8.7
N.D.
N.D.
0.5 + 0.5
2.5 + 1.2
15.0 + 3
44.0 + 3
19.0 + 2
33.0 + 13
N = 5
gill
0.7 + 0.3
N.D.
0.2 + 0.1
4.2 + 0.9
3.4 + 1.8
6.7 + 0.6
61.0 + 3
4
C
Species:
cd
Pb
Cu
Mn
Zn
Species:
Cd
Pb
Cu
Mn
Zn
TABLE 3
TRACE METAL CONCENTRATIONS
IN ug/gram DRY WEIGHI
(Taken from Ting, 1967)
Thunnus albacares, Albacore
N = 10
N = 20
N = 10
flesh
bone
gill
1.0 f O
1.8 + 0.5
1.5 + 0.5
4.7 + 0.5
N.D.
9.8 + 6.2
1.7 + 0.4
1.8 + 0.4
2.9 + 0.1
O.4+0.5
8.5 + 0.7
7.0 +0.8
65.0 + 2.7
156.0 + 9
134.0 + 36
Katsuwonus
pelamis, Skipjack
N =10
N -10
N = 10
bone
flesh
gill
0.9 + 0.3
3.0 f 1.0
3.2 + 0.4
8.4 + 3.4
N.D.
14.0 + 6
1.6 f 0.7
5.4 + 1.2
6.6 + 0.5
0.9 + 0.3
2.5 + 1.3
5.4 + 0.4
24.0 + 3
142.0 + 6
55.0 + 9
169
e
TABLE A
Key to Figures
= Top Smelt
P = Shiner Perch
= Starry Flounder
B = Striped Bass
= Leopard Shark
flesh
= liver
- bone
g = gill
660
FIGURE LEGEND
Fig. 1. Map of Monterey Bay area.
Fig. 2. Sites of concentration of cadmium in ug/g.
Fig. 3. Sites of concentration of lead in ug/g.
Fig. 4. Sites of concentration of silver in ug/g.
Fig. 5. Sites of concentration of copper in ug/g.
Fig. 6. Sites of concentration of chromium in ug/g.
Fig. 7. Sites of concentration of manganese in ug/g.
Fig. 8. Sites of concentration of zinc in ug/g.
Fig. 9. Concentration of manganese in liver.
Fig.10. Concentration of zinc in flesh.
Fig.11. Concentration of zinc in bone.
Fig.12. Concentration of cadmium in liver.
2o
Santa Cryz
Monterey
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46
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