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Cd, Mn, and Zn concentrations in vertebrae of blue shark and shortfin mako in Australian coastal waters
Volume 2 l / N u m b e r 4/April 1990 McLaughlin, P. A., Treat, S. F., Thorhaug, A. & Lemaitre, R. (1983). A restored seagrass (Thalassia) bed and its animal community. Enu Conserv. 10,247-254. Phillips, R. C. (1982). Seagrass Areas. In Creation and restoration of coastal plant communities (Lewis, R. R., ed.), pp. 173-201. CRC Press, Florida (USA). Pollard, D. A. (1985). A review of ecological studies on seagrass-fish communities, with particular reference to recent studies in Australia. Aquat. Bot. 18, 3-42. Thomas, R. I. (1983). Seagrass bedforms, their erosion and implica-
tions for coastal management of the Adelaide Metropolitan shoreline. Sixth Aust. Conf. Coastal and Ocean. Eng. Gold Coast, Queensland, Australia. 13-15 July, 1983. Thorhaug, A. (1983). Habitat restoration after pipeline construction in a tropical estuary: seagrasses. Mar. Pollut. Bull. 14,422-425. Thorhaug, A. (1985). Large-scale seagrass restoration in a damaged estuary. Mar. Pollut. Bull 16, 55-62. West, R. J. (1980). A study of growth and primary productivity of the seagrass Posidonia australis Hook. f. M.Sc. Thesis, University of Sydney (Australia).
Edited by E. I. Hamilton 0025-326X/90 $3.00+0,00 © 1990PergamonPressplc
Marine Polh~tionBulletil~,Volume21. No. 4. pp 203 206. 1990. Printed m Great Britain.
The objective of BASELINE is to publish short communications for the concentration and distribution of elements and compounds in the marine environment. Only those papers which clearly identify the quality of the data will be considered for publication. Contributors to Baseline should refer to 'Baseline--A Record of Contamination Levels" (Mar. Pollut. Bull. 13,217-218).
Cd, Mn, and Zn Concentrations in Vertebrae of Blue Shark and Shortfin Mako in Australian Coastal Waters The blue shark (Prionace glauca L.) and the shortfin mako (Isurus oxyrinchus Rafinesque) are large pelagic predators with worldwide oceanic distributions in warm-temperate seas (Compagno, 1985). Both species occur regularly off the Australian coast, and are amongst the most abundant species taken by sport fishermen off New South Wales (Stevens, 1984), but little is known of their trace metal content in these waters. Ontogenetic changes in trace metal content have been noted for many species of marine vertebrate (Eisler, 1984), but few studies have examined this phenomenon for sharks (Eisler, 1967; Stevens & Brown, 1974). The uptake of some trace metals has been linked with calcium metabolism (Bryan, 1979). Consequently, trace metals are often incorporated into various skeletal or cartilaginous tissues such as fish scales (Bonwick, unpublished data), vertebrae and skin (Pentreath, 1973; Vas, 1987). Vertebrae were obtained from 41 shortfin makos and 33 blue sharks taken off the coast of New South Wales between October 1979 and January 1984. Complete length-weight data was available for only 17 shortfin makos and 13 blue sharks. For the remainder, either the
length or weight alone was reported. Total lengths and weights for these specimens were derived from the length-weight equations of Stevens (1984). Calculated lengths and weights did not differ significantly from the observed data. A single cervical vertebra was selected from the same location from each shark, and was analysed for Mn, Cd, and Zn using atomic absorption spectrophotometry (I.L. Model S l l AAS), following wet digestion with HNO 3 and HCIO4 (Vas, 1987). Standards were made up from 1000 ppm stock solutions by serial dilution with 20% H N O 3 with C%(PO4)2 added as a matrix modifier. Analysis of blank samples gave readings at or below the detection limits of the method (<0.05 gg g-l). Analysis of standard reference material (Kodak TEC-50-B gel) gave results within 5% of the certified values. With low sample numbers for each sex, the results were pooled for analysis, and thus no distinction was made between male and female specimens for either species.
Prionace glauca The blue sharks sampled ranged from 218-326.3 cm total length, and thus were probably all sexually mature fish (Pratt, 1979). Of the three metals for which the vertebrae were analysed, the order of occurrence ( C d < M n < Z n ) was the same in all 33 specimens, irrespective of size, sex, or date of capture. Observed Cd concentrations ranged from 0.84-3.13 gg g-t (dry wt), with 22 of the 33 samples (67%) being in the range 2-3 p.g g-t, and only 3 samples (9%) being < 1 tag g-1. Although such a small range of concentrations was encountered, a significant change with length was apparent (Table 1). Vertebral Cd concentrations were observed to decrease with increasing length (Fig. 1). Mn concentrations were observed to range from 1.72-22.69 gg g-l, but were most frequently in the range 10-20 gg g-1 (Fig. 1). Although there was some suggestion of decreasing Mn concentrations with 203
Marine PollutionBulletin length, the relationship was not statistically significant (Table 1). Vertebral Z n concentrations were found to be considerably higher than either those of Mn or Cd, ranging from 32.16-210.74 ~tg g-a, with 27 of the 33 samples (82%) being in the range 6 0 - 1 3 0 ~tg g-1 (Fig. 1). The vertebra from a 236 cm shark was found to have a Zn content of 264 ~tg g-L As this was almost 50 ~tg g-~ greater than the next lowest sample, it was considered likely that this sample had been contaminated at some point, and this data point was excluded from the analysis. Overall, the data for Zn was highly scattered (Fig. 1), and no significant relationship with length was found (Table 1). Three of the blue sharks were pregnant females. The vertebral metal contents of these three sharks ( 2 4 7 265.7 cm) were compared with those of five nonpregnant sharks of similar length ( 2 4 6 - 2 6 4 cm). Although Zn levels were found to be slightly higher in the pregnant sharks, the difference was not significant. No significant differences were found for either Mn or Cd (Table 2).
lsurus oxyrinchus The shorffin mako sample included sharks of all sizes from a 74 cm neonatal male to a 333.5 cm fully grown female. As with P. glauca, the order of occurrence of metals was C d < M n < Z n . However, the observed metal levels were much lower than those of P. glauca. Cd concentrations ranged from 0.42-8.81 gg g-l, with 63% of the samples being < 1 gg g-L Mn concentrations ranged from 1.3-10.3 gg g-l, only a single sample being > 1 0 gg g-1. And Z n concentrations
ranged from 5.04-127 ~tg g-l, only 2 samples being > 100 ~tg g-1. The levels of all 3 metals (Cd, Mn, and Zn) were observed to decrease significantly with length (Fig. 2, Table 1). In addition, the data for Mn and Zn showed wider variation in sharks < 190 cm (Fig. 2). The order of accumulation of the metals was the same in both species, and also the same as that reported by Glover (1979) for other sharks from the same area. This suggests that the internal concentration of these elements reflects their relative occurrence in the environment (Lee & Duffield, 1979; Brewer, 1975). The concentrations of both Mn and Zn found in this study were similar to those reported for other shark species (Eisler, 1981; Lowman et al., 1966; Pentreath, 1973; Stevens & Brown, 1974), although the concentrations of Z n were higher than those reported by Glover (1979) for sharks from the same locale. Cd concentrations in shark tissues rarely exceed 0.3 gg g-a (Eisler, 1981), and are most frequently reported as < 0 . 0 5 gg g-~ (Stevens & Brown, 1974; Vas, 1987; Vas & Gordon, 1988); in this study, concentrations of 2-3 gg g-~ were common. Although these levels are much higher than many previous studies, high values have occasionally been reported (ol
25
Mn 2O
o• o E 0 U
a••
10
0
TABLE
• •
[_ 240
200
Length
Changes in vertebral metal concentration with length in Prionace and Isurus from south-easternAustralia. Species Metal r P Relationship
(crn)
Cd
I
•
eee
%
21~
•o•
g ~
1.5
05
I 240
200
Zn
180
Mn
Cd
Zn
~2 sd
13.15 2.97
2.42 0.62
99.41 20.49
Non-pregnant
~ sd
14.65 6.00
2.57 0.44
87.81 24.53
t-test
t p
0.81 ns
0.43 ns
0.70 ns
T o~ o•
120
204
(cm)
(c)
TABLE 2
Comparison of vertebralmetal concentrationsin pregnant and non-pregnant specimensof Prionace glauca.
l
I 32O
1
280 Length
i - mean concentrationin Bagg-1 (dry wt). sd standard deviation. n s - - n o t significant.
320
(bl
3.5
Prionace glauca
Pregnant
{
I 280
1
Cd -0.423 <0.05 log h= 3.59-1.341og L Mn -0.128 ns Zn 0.059 ns lsurus oxyrinchus Cd -0.824 <0.001 1og h = 3 . 4 0 - 1 . 4 0 logL Mn -0.704 <0.001 logh--3.11-1.131ogL Zn -0.529 <0.002 loghffi3.87-1.061ogL r - corelationcoefficientfor logarithmicallytransformeddata. h-- metal concentration(Mn, Cd, or Zn) in ~tgg-1 (drywt). L -- total length in cm. ns--not significantat the 95% confidencelevel.
•
•
dc
Ol •g
%.
•
•
60
0
z00
1
I
l
Z40
Z80
320
__
Length (crn)
Fig. 10ntogenetic changes in vertebral metal concentrations in Prionace glauca. (a) Mn, (b) Cd. (el Zn.
Volume 2 1 / N u m b e r 4/April 1990
elsewhere (Windom et al., 1973; Denton & BurdonJones, 1986). Vertebral concentrations of both Mn and Zn were found to be significantly higher in P. glauca than in L oxyrinchus (Table 3). As both species have similar spatial and temporal distributions off the Australian coast (Stevens, 1984), this difference is unlikely to be a function of locale. Because cephalopods are a more important dietary component for P. glauca than L oxyrinchus (Stevens, 1984), and the fact that molluscs can accumulate high concentrations of trace metals (Bryan, 1973; Martin & Flegal, 1975), it is suggested •12
(o)
Mn
IC~)
8
o• o
II
4
•
0
•
•
I 150
50
•
o•
I 25O
I 350
Length (cm) (b)
10
Cd 8 t
6 :L
d
4
LJ
O0
#•
I 50
•l 250
150
that the difference between the two species is a function of diet. Several studies have shown that the concentration of various trace metals in fish tissues decreases with age (Chernoff & Dooley, 1979; Eisler, 1967; Milner, 1979), though no single satisfactory explanation was put forward to account for the decrease. In this study, the concentration of Cd in P. glauca, and Cd, Mn, and Zn in I. oxyrinchus were similarly observed to decrease with size. The decrease in metal concentration with size may be explained in terms of changes in the rate of uptake of the metals with age. If the rate of uptake is related to the rate of growth, then the faster and more variable growth rates of young sharks means that they will accumulate more metals than older sharks. Because the vertebral centra of sharks continually increase in size throughout life (Casey et al., 1985; Cailliet et al., 1983; Branstetter, 1987), then as the rate of uptake slows or ceases in larger sharks, so the relative concentration of the metal in the vertebrae (in p.g metal g-~ vertebra) will fall as both the shark and its vertebrae get larger. The experimental work of Pentreath (1973) with the thornback ray, Raja clavata, lends credence to this hypothesis. Metal concentrations in the tissues were observed to increase with both exposure time and concentration until a maximum value was obtained. After this, no further increase in tissue concentration was observed. The factors controlling ontogenetic changes in metal concentrations in sharks are not clearly understood. And more experimental evidence is required to investigate this phenomenon.
PHILIP VAS** JOHN D. STE VENS* G R A H A M A. BONWICK§ OMAR A. TIZINI§
I
350
Length (cm) (c) •
*South-East Fisheries Center, Miami Laboratory, NOAA/NMPS, 75 Virginia Beach Dr., Miami, Florida 33149, USA
Zn
120
8O
d
*CSIRO Marine Laboratories, GPO Box 1538, Hobart, Tasmania 7001
c o qD •
4O
g
0 5O
I
I
150
250
I 350
Length I c m )
Fig. 2 0 n t o g e n e t i c changes invertebral metal concentrations in lsurus oxyrinchus. (a) Mn, (b) Cd, (c) Zn. TABLE 3 Comparison of mean vertebral metal concentrations in Prionace glauca and Isurus oxyrinchus.
Prionace glauca Isums oxyrinchus t-test
Mn
Cd
Zn
~ sd
12.55 4.86
2.36 0.63
94.74 43.77
5~ sd
4.11 2.26
2.07 1.41
35.78 27. l 1
t p
38.64 <0.001
1.07 ns
26.89 <0.001
,~= mean concentration in gg g-~ (dry wt). sd = standard deviation. ns = not significant.
~Department of Biological Sciences, University of Salford, Salford, M5 4WT, UK *To whom correspondence should be addressed. Branstetter, S. (1987). Age, growth and reproductive biology of the silky shark (Carcharhinus falciformis) and the scalloped hammerhead (Sphyrna lewini) from the northwestern Gulf of Mexico. Environ. Biol. Fish. 19, 161-173. Brewer, P. G. (1975). Minor elements in sea water. In Chemical Oceanography, Volume 2. (J. P. Riley & G. Skirrow, eds), pp. 415-496. Academic Press, London. Bryan, G. W. (1973). T h e occurrence and seasonal variation of trace metals in the scallops Pecten rnaximus (L.) and Chlamys opercularis (L.). J. Mar. Biol. Assoc. UK. 4 9 , 2 2 5 - 2 4 3 . Bryan, G. W. (1979). Bioaccumulation of marine pollutants. Phil. Trans. R. Soc. Lond. B. 2 8 6 , 4 8 3 - 5 0 5 . Cailliet, G. M., Martin, L. K., Harvey, J. T., Kusher, D. & Welden, B. A. (1983). Preliminary studies on the age and growth of blue, Prionace glauca, c o m m o n thresher, Alopias vulpinus, and shortfin mako, lsurus oxyrinchus, sharks from California waters. N O A A Tech. Rep. NMF8 8: 179-188.
205
Marine Pollution Bulletin Casey, J. G., Pratt, H. L. & Stillwel[, C. E. (1985). Age and growth of the sandbar shark (Carcharhinus plumbeus) from the western North Atlantic. Can. J. Fish. Aquat. Sci. 42,963-975. Chernoff, B. & Dooley, J. K. (1979). HeaW metals in relation to the biology of the mummichog, Fundulus heteroclitus. J. Fish Biol. 14, 309-328. Compagno, L. V. J. (1985). FAO Species Catalogue. Sharks of the World: an annotated and illustrated catalogue of shark species known to date. FAO Fisheries Symposia No. 125, Vol. 4, Pt. 2, pp. 251-655. Denton, G. R. W. & Burdon-Jones, C. (1986). Trace metals in fish from the Great Barrier Reef. Mar. Pollut. Bull. 17,201-209. Eisler, R. (1967). Variations in mineral content of sandbar shark vertebrae ( Carcharhinus milberti). Naturaliste Can. 94,321-326. Eisler, R. (1981). Trace Metal Concentrations in Marine Organisms. Pergamon Press, New York. Eisler, R. (1984). Trace metal changes associated with age of marine vertebrates. Biol. Trace Element Res. 6, 165-180. Glover, J. W. (1979). Concentrations of arsenic, selenium and ten heavy metals in school shark, Galeorhinus australis (Macleay), and gummy shark, Mustelus antarcticus (Gunther), from south-eastern Australian waters. Aus. 3. Mar. Frshw. Res. 30, 505-510. Lee, R. E. & Duffield, F. V. (1979). Sources of environmentally important metals in the atmosphere. In Ultratrace Metal Analysis in Biological Sciences and Environment (T. H. Risby, ed.), pp. 146-171. American Chemical Society (Advances in Chemistry Series 172). Lowman, F. G., Phelps, D. K., Ting, R. Y. & Escalara, R. M. (1966).
Progress Summary Report No. 4, Marine Biology Program June 1965-June 1966, Puerto Rico Nucl. Cen. Rep. PRNC 85. Martin, J. H. & Flegal, A. R. (1975). High copper concentrations in squid livers in association with elevated levels of silver, cadmium and zinc. Mar. Biol. 35, 91-104. Milner, N. J. (1979). Zinc concentrations in juvenile flatfish. J. Mar. Biol. Assoc. U.K. 59,761-775. Pentreath, R. J. (1973). The accumulation from sea water of 65in, S"Mn, SSCo, and 59Fe by the thornback ray, Ra]a clavata L. J. Exp. Mar. Biol. Ecol. 121,327-334. Pratt, H. L. (1979). Reproduction in the blue shark, Prionace glauca. Fish Bull. 77,445-470. Stevens, J. D. (1984). Biologicalobservations on sharks caught by sport fishermen off New South Wales. Aust. J. Mar. Freshm Res. 35,573590. Stevens, J. D. & Brown, B. E. (1974). The occurrence of heaW metals in the blue shark, Prionace glauca, and other pelagics in the northeast Atlantic. Mar. Biol. 26,287-293. Vas, P. (1987). Observations on trace metal concentrations in a carcharhinid shark, Galeorhinus galeus, from Liverpool Bay. Mar. Pollut. Bull 18,153-154. Vas, P. & Gordon. J. D. M. (1988). Trace metal concentrations in the scyliorhinid shark Galeus melastornus from the Rockall Trough. Mar. Pollut. Bull. 19,396-398. Windom, H., Stickney, R., Smith, R., White, I3. & Taylor, F. (1973). Arsenic, cadmium, copper, mercury and zinc in some species of north Atlantic finfish.Z Fish. Res. Bd. Can. 30. 275-279.
Kuwait Convention Protocol
t e n d e r s from suppliers who m a d e such i n f o r m a t i o n available w o u l d be viewed m o r e favourably. Details of toxicity tests were then f o r t h c o m i n g . O t h e r s have had similar experiences. T h e r e are still difficulties. I u n d e r s t a n d that some suppliers insist that such i n f o r m a t i o n is accepted in c o n f i d e n c e , a n d that may conflict with the duty of the p e r s o n or a u t h o r i t y which seeks it. Not all suppliers, however, insist o n strict confidentiality. If weight is given to requests for i n f o r m a t i o n , by such organizations as R O P M E (the O r g a n i z a t i o n established u n d e r the Kuwait C o n v e n t i o n ) , covering sea areas with m a n y installations, the practice of releasing i n f o r m a t i o n is likely to b e c o m e m o r e general. M y o w n h o p e is that R O P M E will be able to compile a data b a n k o n a c c e p t a b l e p r o d u c t s which will benefit the o p e r a t o r s in the area, a n d facilitate better protection of the m a r i n e e n v i r o n m e n t there.
Sir,
In the J a n u a r y issue of M a r i n e P o l l u t i o n B u l l e t i n , y o u p u b l i s h e d a review of the n e w P r o t o c o l o n p o l l u t i o n from offshore o p e r a t i o n s , p r e p a r e d u n d e r the Kuwait C o n v e n t i o n . A s the c o n s u l t a n t who p r e p a r e d the initial draft for that Protocol, a n d advised t h r o u g h o u t the meetings at which the final text was agreed, I f o u n d it a g e n e r o u s review, of which I have n o c o m p l a i n t . T h e r e is o n e point, however, o n which I w o u l d like to offer a word of e x p l a n a t i o n . T h e reviewer refers to the p r o v i s i o n b y which water b a s e d drilling m u d s which c o n t a i n persistent systemic toxins must n o t be discharged to the sea. H e u n d e r s t a n d a b l y adds that, as the c o m p o s i t i o n of such m u d s is part of i n d u s t r i a l secrecy, that p r o v i s i o n will be difficult to enforce. My e x p e r i e n c e has b e e n that if sufficient pressure is put o n suppliers, details of toxicity tests carried out o n their p r o d u c t s will be m a d e available. U n d e r a c o n t r a c t o n which I was engaged recently, it was m a d e clear that
206
J. M c L O U G H L I N J. M c L o u g h l i n a n d A s s o c i a t e s , 17 B e c k Yeat, Coniston, Cumbria LA21 8HT, UK
tions for coastal management of the Adelaide Metropolitan shoreline. Sixth Aust. Conf. Coastal and Ocean. Eng. Gold Coast, Queensland, Australia. 13-15 July, 1983. Thorhaug, A. (1983). Habitat restoration after pipeline construction in a tropical estuary: seagrasses. Mar. Pollut. Bull. 14,422-425. Thorhaug, A. (1985). Large-scale seagrass restoration in a damaged estuary. Mar. Pollut. Bull 16, 55-62. West, R. J. (1980). A study of growth and primary productivity of the seagrass Posidonia australis Hook. f. M.Sc. Thesis, University of Sydney (Australia).
Edited by E. I. Hamilton 0025-326X/90 $3.00+0,00 © 1990PergamonPressplc
Marine Polh~tionBulletil~,Volume21. No. 4. pp 203 206. 1990. Printed m Great Britain.
The objective of BASELINE is to publish short communications for the concentration and distribution of elements and compounds in the marine environment. Only those papers which clearly identify the quality of the data will be considered for publication. Contributors to Baseline should refer to 'Baseline--A Record of Contamination Levels" (Mar. Pollut. Bull. 13,217-218).
Cd, Mn, and Zn Concentrations in Vertebrae of Blue Shark and Shortfin Mako in Australian Coastal Waters The blue shark (Prionace glauca L.) and the shortfin mako (Isurus oxyrinchus Rafinesque) are large pelagic predators with worldwide oceanic distributions in warm-temperate seas (Compagno, 1985). Both species occur regularly off the Australian coast, and are amongst the most abundant species taken by sport fishermen off New South Wales (Stevens, 1984), but little is known of their trace metal content in these waters. Ontogenetic changes in trace metal content have been noted for many species of marine vertebrate (Eisler, 1984), but few studies have examined this phenomenon for sharks (Eisler, 1967; Stevens & Brown, 1974). The uptake of some trace metals has been linked with calcium metabolism (Bryan, 1979). Consequently, trace metals are often incorporated into various skeletal or cartilaginous tissues such as fish scales (Bonwick, unpublished data), vertebrae and skin (Pentreath, 1973; Vas, 1987). Vertebrae were obtained from 41 shortfin makos and 33 blue sharks taken off the coast of New South Wales between October 1979 and January 1984. Complete length-weight data was available for only 17 shortfin makos and 13 blue sharks. For the remainder, either the
length or weight alone was reported. Total lengths and weights for these specimens were derived from the length-weight equations of Stevens (1984). Calculated lengths and weights did not differ significantly from the observed data. A single cervical vertebra was selected from the same location from each shark, and was analysed for Mn, Cd, and Zn using atomic absorption spectrophotometry (I.L. Model S l l AAS), following wet digestion with HNO 3 and HCIO4 (Vas, 1987). Standards were made up from 1000 ppm stock solutions by serial dilution with 20% H N O 3 with C%(PO4)2 added as a matrix modifier. Analysis of blank samples gave readings at or below the detection limits of the method (<0.05 gg g-l). Analysis of standard reference material (Kodak TEC-50-B gel) gave results within 5% of the certified values. With low sample numbers for each sex, the results were pooled for analysis, and thus no distinction was made between male and female specimens for either species.
Prionace glauca The blue sharks sampled ranged from 218-326.3 cm total length, and thus were probably all sexually mature fish (Pratt, 1979). Of the three metals for which the vertebrae were analysed, the order of occurrence ( C d < M n < Z n ) was the same in all 33 specimens, irrespective of size, sex, or date of capture. Observed Cd concentrations ranged from 0.84-3.13 gg g-t (dry wt), with 22 of the 33 samples (67%) being in the range 2-3 p.g g-t, and only 3 samples (9%) being < 1 tag g-1. Although such a small range of concentrations was encountered, a significant change with length was apparent (Table 1). Vertebral Cd concentrations were observed to decrease with increasing length (Fig. 1). Mn concentrations were observed to range from 1.72-22.69 gg g-l, but were most frequently in the range 10-20 gg g-1 (Fig. 1). Although there was some suggestion of decreasing Mn concentrations with 203
Marine PollutionBulletin length, the relationship was not statistically significant (Table 1). Vertebral Z n concentrations were found to be considerably higher than either those of Mn or Cd, ranging from 32.16-210.74 ~tg g-a, with 27 of the 33 samples (82%) being in the range 6 0 - 1 3 0 ~tg g-1 (Fig. 1). The vertebra from a 236 cm shark was found to have a Zn content of 264 ~tg g-L As this was almost 50 ~tg g-~ greater than the next lowest sample, it was considered likely that this sample had been contaminated at some point, and this data point was excluded from the analysis. Overall, the data for Zn was highly scattered (Fig. 1), and no significant relationship with length was found (Table 1). Three of the blue sharks were pregnant females. The vertebral metal contents of these three sharks ( 2 4 7 265.7 cm) were compared with those of five nonpregnant sharks of similar length ( 2 4 6 - 2 6 4 cm). Although Zn levels were found to be slightly higher in the pregnant sharks, the difference was not significant. No significant differences were found for either Mn or Cd (Table 2).
lsurus oxyrinchus The shorffin mako sample included sharks of all sizes from a 74 cm neonatal male to a 333.5 cm fully grown female. As with P. glauca, the order of occurrence of metals was C d < M n < Z n . However, the observed metal levels were much lower than those of P. glauca. Cd concentrations ranged from 0.42-8.81 gg g-l, with 63% of the samples being < 1 gg g-L Mn concentrations ranged from 1.3-10.3 gg g-l, only a single sample being > 1 0 gg g-1. And Z n concentrations
ranged from 5.04-127 ~tg g-l, only 2 samples being > 100 ~tg g-1. The levels of all 3 metals (Cd, Mn, and Zn) were observed to decrease significantly with length (Fig. 2, Table 1). In addition, the data for Mn and Zn showed wider variation in sharks < 190 cm (Fig. 2). The order of accumulation of the metals was the same in both species, and also the same as that reported by Glover (1979) for other sharks from the same area. This suggests that the internal concentration of these elements reflects their relative occurrence in the environment (Lee & Duffield, 1979; Brewer, 1975). The concentrations of both Mn and Zn found in this study were similar to those reported for other shark species (Eisler, 1981; Lowman et al., 1966; Pentreath, 1973; Stevens & Brown, 1974), although the concentrations of Z n were higher than those reported by Glover (1979) for sharks from the same locale. Cd concentrations in shark tissues rarely exceed 0.3 gg g-a (Eisler, 1981), and are most frequently reported as < 0 . 0 5 gg g-~ (Stevens & Brown, 1974; Vas, 1987; Vas & Gordon, 1988); in this study, concentrations of 2-3 gg g-~ were common. Although these levels are much higher than many previous studies, high values have occasionally been reported (ol
25
Mn 2O
o• o E 0 U
a••
10
0
TABLE
• •
[_ 240
200
Length
Changes in vertebral metal concentration with length in Prionace and Isurus from south-easternAustralia. Species Metal r P Relationship
(crn)
Cd
I
•
eee
%
21~
•o•
g ~
1.5
05
I 240
200
Zn
180
Mn
Cd
Zn
~2 sd
13.15 2.97
2.42 0.62
99.41 20.49
Non-pregnant
~ sd
14.65 6.00
2.57 0.44
87.81 24.53
t-test
t p
0.81 ns
0.43 ns
0.70 ns
T o~ o•
120
204
(cm)
(c)
TABLE 2
Comparison of vertebralmetal concentrationsin pregnant and non-pregnant specimensof Prionace glauca.
l
I 32O
1
280 Length
i - mean concentrationin Bagg-1 (dry wt). sd standard deviation. n s - - n o t significant.
320
(bl
3.5
Prionace glauca
Pregnant
{
I 280
1
Cd -0.423 <0.05 log h= 3.59-1.341og L Mn -0.128 ns Zn 0.059 ns lsurus oxyrinchus Cd -0.824 <0.001 1og h = 3 . 4 0 - 1 . 4 0 logL Mn -0.704 <0.001 logh--3.11-1.131ogL Zn -0.529 <0.002 loghffi3.87-1.061ogL r - corelationcoefficientfor logarithmicallytransformeddata. h-- metal concentration(Mn, Cd, or Zn) in ~tgg-1 (drywt). L -- total length in cm. ns--not significantat the 95% confidencelevel.
•
•
dc
Ol •g
%.
•
•
60
0
z00
1
I
l
Z40
Z80
320
__
Length (crn)
Fig. 10ntogenetic changes in vertebral metal concentrations in Prionace glauca. (a) Mn, (b) Cd. (el Zn.
Volume 2 1 / N u m b e r 4/April 1990
elsewhere (Windom et al., 1973; Denton & BurdonJones, 1986). Vertebral concentrations of both Mn and Zn were found to be significantly higher in P. glauca than in L oxyrinchus (Table 3). As both species have similar spatial and temporal distributions off the Australian coast (Stevens, 1984), this difference is unlikely to be a function of locale. Because cephalopods are a more important dietary component for P. glauca than L oxyrinchus (Stevens, 1984), and the fact that molluscs can accumulate high concentrations of trace metals (Bryan, 1973; Martin & Flegal, 1975), it is suggested •12
(o)
Mn
IC~)
8
o• o
II
4
•
0
•
•
I 150
50
•
o•
I 25O
I 350
Length (cm) (b)
10
Cd 8 t
6 :L
d
4
LJ
O0
#•
I 50
•l 250
150
that the difference between the two species is a function of diet. Several studies have shown that the concentration of various trace metals in fish tissues decreases with age (Chernoff & Dooley, 1979; Eisler, 1967; Milner, 1979), though no single satisfactory explanation was put forward to account for the decrease. In this study, the concentration of Cd in P. glauca, and Cd, Mn, and Zn in I. oxyrinchus were similarly observed to decrease with size. The decrease in metal concentration with size may be explained in terms of changes in the rate of uptake of the metals with age. If the rate of uptake is related to the rate of growth, then the faster and more variable growth rates of young sharks means that they will accumulate more metals than older sharks. Because the vertebral centra of sharks continually increase in size throughout life (Casey et al., 1985; Cailliet et al., 1983; Branstetter, 1987), then as the rate of uptake slows or ceases in larger sharks, so the relative concentration of the metal in the vertebrae (in p.g metal g-~ vertebra) will fall as both the shark and its vertebrae get larger. The experimental work of Pentreath (1973) with the thornback ray, Raja clavata, lends credence to this hypothesis. Metal concentrations in the tissues were observed to increase with both exposure time and concentration until a maximum value was obtained. After this, no further increase in tissue concentration was observed. The factors controlling ontogenetic changes in metal concentrations in sharks are not clearly understood. And more experimental evidence is required to investigate this phenomenon.
PHILIP VAS** JOHN D. STE VENS* G R A H A M A. BONWICK§ OMAR A. TIZINI§
I
350
Length (cm) (c) •
*South-East Fisheries Center, Miami Laboratory, NOAA/NMPS, 75 Virginia Beach Dr., Miami, Florida 33149, USA
Zn
120
8O
d
*CSIRO Marine Laboratories, GPO Box 1538, Hobart, Tasmania 7001
c o qD •
4O
g
0 5O
I
I
150
250
I 350
Length I c m )
Fig. 2 0 n t o g e n e t i c changes invertebral metal concentrations in lsurus oxyrinchus. (a) Mn, (b) Cd, (c) Zn. TABLE 3 Comparison of mean vertebral metal concentrations in Prionace glauca and Isurus oxyrinchus.
Prionace glauca Isums oxyrinchus t-test
Mn
Cd
Zn
~ sd
12.55 4.86
2.36 0.63
94.74 43.77
5~ sd
4.11 2.26
2.07 1.41
35.78 27. l 1
t p
38.64 <0.001
1.07 ns
26.89 <0.001
,~= mean concentration in gg g-~ (dry wt). sd = standard deviation. ns = not significant.
~Department of Biological Sciences, University of Salford, Salford, M5 4WT, UK *To whom correspondence should be addressed. Branstetter, S. (1987). Age, growth and reproductive biology of the silky shark (Carcharhinus falciformis) and the scalloped hammerhead (Sphyrna lewini) from the northwestern Gulf of Mexico. Environ. Biol. Fish. 19, 161-173. Brewer, P. G. (1975). Minor elements in sea water. In Chemical Oceanography, Volume 2. (J. P. Riley & G. Skirrow, eds), pp. 415-496. Academic Press, London. Bryan, G. W. (1973). T h e occurrence and seasonal variation of trace metals in the scallops Pecten rnaximus (L.) and Chlamys opercularis (L.). J. Mar. Biol. Assoc. UK. 4 9 , 2 2 5 - 2 4 3 . Bryan, G. W. (1979). Bioaccumulation of marine pollutants. Phil. Trans. R. Soc. Lond. B. 2 8 6 , 4 8 3 - 5 0 5 . Cailliet, G. M., Martin, L. K., Harvey, J. T., Kusher, D. & Welden, B. A. (1983). Preliminary studies on the age and growth of blue, Prionace glauca, c o m m o n thresher, Alopias vulpinus, and shortfin mako, lsurus oxyrinchus, sharks from California waters. N O A A Tech. Rep. NMF8 8: 179-188.
205
Marine Pollution Bulletin Casey, J. G., Pratt, H. L. & Stillwel[, C. E. (1985). Age and growth of the sandbar shark (Carcharhinus plumbeus) from the western North Atlantic. Can. J. Fish. Aquat. Sci. 42,963-975. Chernoff, B. & Dooley, J. K. (1979). HeaW metals in relation to the biology of the mummichog, Fundulus heteroclitus. J. Fish Biol. 14, 309-328. Compagno, L. V. J. (1985). FAO Species Catalogue. Sharks of the World: an annotated and illustrated catalogue of shark species known to date. FAO Fisheries Symposia No. 125, Vol. 4, Pt. 2, pp. 251-655. Denton, G. R. W. & Burdon-Jones, C. (1986). Trace metals in fish from the Great Barrier Reef. Mar. Pollut. Bull. 17,201-209. Eisler, R. (1967). Variations in mineral content of sandbar shark vertebrae ( Carcharhinus milberti). Naturaliste Can. 94,321-326. Eisler, R. (1981). Trace Metal Concentrations in Marine Organisms. Pergamon Press, New York. Eisler, R. (1984). Trace metal changes associated with age of marine vertebrates. Biol. Trace Element Res. 6, 165-180. Glover, J. W. (1979). Concentrations of arsenic, selenium and ten heavy metals in school shark, Galeorhinus australis (Macleay), and gummy shark, Mustelus antarcticus (Gunther), from south-eastern Australian waters. Aus. 3. Mar. Frshw. Res. 30, 505-510. Lee, R. E. & Duffield, F. V. (1979). Sources of environmentally important metals in the atmosphere. In Ultratrace Metal Analysis in Biological Sciences and Environment (T. H. Risby, ed.), pp. 146-171. American Chemical Society (Advances in Chemistry Series 172). Lowman, F. G., Phelps, D. K., Ting, R. Y. & Escalara, R. M. (1966).
Progress Summary Report No. 4, Marine Biology Program June 1965-June 1966, Puerto Rico Nucl. Cen. Rep. PRNC 85. Martin, J. H. & Flegal, A. R. (1975). High copper concentrations in squid livers in association with elevated levels of silver, cadmium and zinc. Mar. Biol. 35, 91-104. Milner, N. J. (1979). Zinc concentrations in juvenile flatfish. J. Mar. Biol. Assoc. U.K. 59,761-775. Pentreath, R. J. (1973). The accumulation from sea water of 65in, S"Mn, SSCo, and 59Fe by the thornback ray, Ra]a clavata L. J. Exp. Mar. Biol. Ecol. 121,327-334. Pratt, H. L. (1979). Reproduction in the blue shark, Prionace glauca. Fish Bull. 77,445-470. Stevens, J. D. (1984). Biologicalobservations on sharks caught by sport fishermen off New South Wales. Aust. J. Mar. Freshm Res. 35,573590. Stevens, J. D. & Brown, B. E. (1974). The occurrence of heaW metals in the blue shark, Prionace glauca, and other pelagics in the northeast Atlantic. Mar. Biol. 26,287-293. Vas, P. (1987). Observations on trace metal concentrations in a carcharhinid shark, Galeorhinus galeus, from Liverpool Bay. Mar. Pollut. Bull 18,153-154. Vas, P. & Gordon. J. D. M. (1988). Trace metal concentrations in the scyliorhinid shark Galeus melastornus from the Rockall Trough. Mar. Pollut. Bull. 19,396-398. Windom, H., Stickney, R., Smith, R., White, I3. & Taylor, F. (1973). Arsenic, cadmium, copper, mercury and zinc in some species of north Atlantic finfish.Z Fish. Res. Bd. Can. 30. 275-279.
Kuwait Convention Protocol
t e n d e r s from suppliers who m a d e such i n f o r m a t i o n available w o u l d be viewed m o r e favourably. Details of toxicity tests were then f o r t h c o m i n g . O t h e r s have had similar experiences. T h e r e are still difficulties. I u n d e r s t a n d that some suppliers insist that such i n f o r m a t i o n is accepted in c o n f i d e n c e , a n d that may conflict with the duty of the p e r s o n or a u t h o r i t y which seeks it. Not all suppliers, however, insist o n strict confidentiality. If weight is given to requests for i n f o r m a t i o n , by such organizations as R O P M E (the O r g a n i z a t i o n established u n d e r the Kuwait C o n v e n t i o n ) , covering sea areas with m a n y installations, the practice of releasing i n f o r m a t i o n is likely to b e c o m e m o r e general. M y o w n h o p e is that R O P M E will be able to compile a data b a n k o n a c c e p t a b l e p r o d u c t s which will benefit the o p e r a t o r s in the area, a n d facilitate better protection of the m a r i n e e n v i r o n m e n t there.
Sir,
In the J a n u a r y issue of M a r i n e P o l l u t i o n B u l l e t i n , y o u p u b l i s h e d a review of the n e w P r o t o c o l o n p o l l u t i o n from offshore o p e r a t i o n s , p r e p a r e d u n d e r the Kuwait C o n v e n t i o n . A s the c o n s u l t a n t who p r e p a r e d the initial draft for that Protocol, a n d advised t h r o u g h o u t the meetings at which the final text was agreed, I f o u n d it a g e n e r o u s review, of which I have n o c o m p l a i n t . T h e r e is o n e point, however, o n which I w o u l d like to offer a word of e x p l a n a t i o n . T h e reviewer refers to the p r o v i s i o n b y which water b a s e d drilling m u d s which c o n t a i n persistent systemic toxins must n o t be discharged to the sea. H e u n d e r s t a n d a b l y adds that, as the c o m p o s i t i o n of such m u d s is part of i n d u s t r i a l secrecy, that p r o v i s i o n will be difficult to enforce. My e x p e r i e n c e has b e e n that if sufficient pressure is put o n suppliers, details of toxicity tests carried out o n their p r o d u c t s will be m a d e available. U n d e r a c o n t r a c t o n which I was engaged recently, it was m a d e clear that
206
J. M c L O U G H L I N J. M c L o u g h l i n a n d A s s o c i a t e s , 17 B e c k Yeat, Coniston, Cumbria LA21 8HT, UK