Lobster Homarus gammarus: importance of different pathways of absorption and excretion. J. mar. biol. Ass. U.K. 66:175-199. Bryan, G. W., Potts, G. W., Forster, ...
Marine Biology116, 417-422 (1993)
Marine ==Biology 9 Springer-Verlag 1993
Accumulation and regulation of heavy metals by the intertidal snail Polinices sordidus Weimin Ying 1, M. Ahsanullah 1, G. E. Batley 2 1 Australian Nuclear Science and TechnologyOrganisation, Private Mail Bag 1, Menai, New South Wales 2234, Australia 2 Centre for Advanced AnalyticalChemistry,CSIRO Division of Coal and Energy Technology,Private Mail Bag 7, Menai, New South Wales 2234, Australia Received: 22 January 1993 / Accepted: 4 March 1993
Abstract. The gastropod Polinices sordidus was collected from an uncontaminated area in Quibray Bay, New South Wales, Australia, in 1990. The snails were exposed for 2 wk to polluted sediments collected from Port Kembla Harbour, Blackwattle Bay, Lake Illawarra, Lake Macquarie in New South Wales, Australia, and the Derwent River in Tasmania, Australia. Metal accumulation and regulation by this species were evaluated. Metal concentrations in snail tissues and total, EDTA and HCl-extractable metals in the sediments were compared. Copper concentrations were extremely varied in snails exposed to the same sediment. This was not the case for other metals tested. No accumulation of copper was found in snails exposed to different sediments. There was no zinc accumulation from sediments containing less then 10 mg Zn/g. P. sordidus could accumulate lead, manganese and iron from some of the sediments. Manganese concentrations in the snail tissues correlated with total, HCl-extractable and, more significantly, EDTA-extractable Mn in the sediments. P. sordidus was not considered to be a good bioindicator of copper and zinc contamination in sediments; however, this species could be used as an indicator of lead and manganese contamination.
Introduction In various studies, different types of animals have been used as bioindicators of metal pollution; among molluscs, bivalves have been extensively investigated but less emphasis has been given to gastropod species (Phillips 1980). Some of the gastropods that inhabit rocky shores or sediments fulfil most of the requirements of good bioindicators (Phillips 1980); however, it is important that they accumulate metals in proportion to metal concentrations in the environment. In the case of sedimentdwelling gastropods, only the bioavailable fraction of metals in sediments can have an impact on metal toxicity and accumulation. Attempts to quantify this fraction have been made using a wide variety of chemical extrac-
tion techniques (e.g. Tessier et al. 1979, F6rstner and Wittmann 1981, Batley 1987), but there have been limited comparisons of these techniques with accumulation by gastropods. Attention has been given to other species (e.g. Luoma and Jenne 1977, Luoma and Bryan 1978, 1982, Tessier et al. 1983, Tessier and Campbell 1990). Extraction with ethylenediaminetetraacetic acid (EDTA) and hydrochloric acid (HC1) have been used to quantify, in sediment, metals which are considered to be available to marine organisms (e.g. Ray et al. 1981, Batley 1987, Ying et al. 1992). One of the advantages of using EDTA is that it avoids the problem of readsorption experienced with other extraction procedures (Rendell et al. 1980). Dilute HC1 can dissolve metal associations in sediment, but without attacking the silicate matrix in which metals are considered to be not bioavailable. Metal concentrations in a marine organism do not depend on bioavailability alone, but also on the balance between uptake and excretion (Bryan and Hummerstone 1986, Rainbow 1990, Rainbow et al. 1990). The threshold concentrations where metal regulatory processes break down and metal accumulation or toxicity occurs must be also considered in any test of potential bioindicators. In the present investigation, the snail Polinices sordidus, an inhabitant of intertidal sandflats and mangroves, was selected as a test species. The aim of this study was to examine the possible use of this gastropod as an indicator of metal pollution in a laboratory microcosm, to test hypotheses of metal accumulation and regulation and to compare metal concentrations in snail tissues with EDTA and HCl-extractable metals in sediment.
Materials and methods Snails and sediment Mature individuals of Polinices sordidus used in this study were collected in late summer of 1990 from Quibray Bay (New South
418
Weimin Ying et al.: Heavy metals in Polinices sordidus e~
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Wales, Australia), placed in a fish box, and transported to the laboratory within 1 h. They were kept in glass tanks with sediment collected from the same site, and were acclimated to laboratory conditions in a continuously flowing seawater system (20 ~ _+1 C~ 32 4-1%0 S and > 4 rag/1 dissolved oxygen) for 1 wk. A series of contaminated sediments was collected from Port Kembla Harbour, Blackwattle Bay, Lake Illawarra, Lake Macquarie (New South Wales, Australia) and the Derwent River (Tasmania, Australia). At the northern margin of Lake Macquarie, sediment was significantly contaminated by a l e a d - z i n c smelter. The Derwent River had a similar type of contamination, and metal concentrations in sediment were extremely high. Port Kembla Hatbout, Blackwattle Bay and Lake Illawarra were contaminated by industrial and sewage discharges. The sediment collected from the same site as the snails was used as a control. All the above sediments were passed through a 2 m m sieve and stored at 4~ before use.
Exposure experiment Eight contaminated sediments plus one control sediment were used for the experiment. Nine 10-1itre Perspex tanks (25 x 25 x 18 cm), with lids, were filled with approximately equal amounts of sediment to a depth of ~- 10 era. After the addition of seawater, the sediments were allowed to settle for 24 h. Water was pumped into each tank separately and the overlying water level on sediment was held constant by a siphon system. Continuously flowing seawater was maintained for 2 d prior to introduction of snails. This was done to remove any contaminated seawater resulting from release of metals from the sediments. Snails were then randomly selected and introduced into the tanks. Each tank contained nine snails having dry tissue weights between 0.2 and 0.4 g. Snails were exposed for 2 wk. Air was bubbled into the seawater and dissolved oxygen was maintained at > 4 rag/1. Fresh seawater flowed continuously through the
Weimin Ying et al.: Heavy metals in Polinices sordidus
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tanks. Both air and seawater introduction positions were adjusted to avoid disturbance of sediment. The snails were not fed during the course of experiment. At the end of 2 wk, the snails were removed and transferred to clean seawater for 2 d to eliminate sediment particles present in their gut that might have interfered with analytical results.
Metals in all solutions were determined by inductively-coupled plasma atomic-emission spectrometry (ICPAES). The detection limits, calculated as twice the standard deviation of the reagent blanks, were 0.002, 0.003, 0.1, 0.002 and 0.1 rag/1 for copper, zinc, lead, manganese and iron, respectiely. High-purity water, obtained from a Milli-Q water purification system (Millipore Corporation, USA), was used for the preparation of all aqueous solutions, and all glassware cleaning was carried out using acid-leaching procedures.
Chemical analyses The shell was carefully removed from each snail and its soft tissue was oven-dried at 105 ~ for 2 d. The dried tissues were individually weighed and digested in hot concentrated nitric acid (3 ml/0A g dry tissue) for 8 h. Wet sediment samples taken from tanks were separately extracted by 0.05 M EDTA and 0.05 M HCI (Ying et al. 1992). Subsamples for total metal concentrations were dried, ground and completely digested with a hydrofluoric, nitric and perchloric acid mixture (1:3:1). The digests were then evaporated to near-dryness and reconstituted with 10% nitric acid for subsequent analysis.
Results
Sediment T h e c h e m i c a l a n d p h y s i c a l p r o p e r t i e s o f s e d i m e n t s used in this study, such as t o t a l o r g a n i c c a r b o n c o n t e n t a n d p a r t i c l e size d i s t r i b u t i o n , differed. Total m e t a l c o n c e n t r a tions r a n g e d widely, f r o m 3.3 to 1480 pg Cu/g, 25 to 67 000 ~g Z n / g , 10 to 2I 000 ~tg P b / g , 26 to 4300 ~tg M n / g a n d 3000 to 67 000 ~tg F e / g (Table 1).
420
Weimin Ying et al.: Heavy metals in Polinices sordidus
Table 1. Total metal concentrations and total organic carbon con-
tent (TOC) in test sediments. Sediment sources were: Control, Quibray Bay (NSW); 1, Port Kembla Harbour; 2, 3, Blackwattle Bay (NSW); 4, Lake Illawarra (NSW); 5, 6, 7, Lake Macquarie (NSW); 8, Derwent River (Tasmania) Sediment
Cu (~g/g)
Zn Pb Mn Fe TOC (~g/g) (~g/g) (gg/g) (~g/g) (%)
Control 1 2 3 4 5 6 7 8
3.3 25 13 370 110 580 180 I 150 19 320 370 7 100 79 1 050 74 2 200 1480 67000
10 26 37 280 240 180 520 460 74 140 990 1 600 270 140 460 360 21000 4300
3 000 22 000 33 000 62 000 17 000 44000 20 000 20 000 67000
0.9 1.3 6.0 7.5 0.4 2.5 2.2 2.0 6.4
Table 2. Polinicessordidus. Correlation coefficients between metals
in snail tissue. *: P 1 0 0 0 0 btg HCl-extractable Fe/g, snails could accumulate some iron into their tissues.
Cu
Zn Mn Fe
Discussion
Snails The uptake by Polinices sordidus of copper, zinc, manganese and iron is a function of extractable concentrations in the sediment, as shown in Fig. 1. In snails from the control tank, zinc and manganese accumulation (105 and 22 lag/g) with standard deviations of 8 and 30% respectively, was less variable than copper and iron accumulation (208 and 760 pg/g), which had standard deviations of up to 50%. Similarly, in the tanks containing contaminated sediments, copper concentrations were widely distributed, whereas zinc concentrations in snails were not very variable. No significant accumulation of copper by the snails was found in any tanks ( P > 0 . 0 5 ) compared with the control tank. Zinc and lead concentrations were significandy accumulated to 200 _+36 and 160_+ 50 gg/g, respectively, by snails exposed to the sediment from the Derwent River, which contained high metal concentrations. As the method used in this study could not detect less than 10 lag Pb/g in snail tissues, and lead concentrations in snails exposed to the other eight sediments were below this limit, lead accumulation is only presented for the Derwent River sediment. Manganese and iron were only accumulated from some of the contaminated sediments. Correlation coefficients between metals are shown in Table 2. The results demonstrate that there were significant correlations between zinc and manganese, zinc and iron and manganese and iron in snails. However, no correlation was found when metal concentrations in snails exposed to the Derwent River sediment were excluded.
Polinices sordidus, as a burrowing species, emerges from the sediment and actively searches for food at low tide and burrows back into sediment when the tide is high. Burrowing species are usually in close contact with the sediment and accmnulate metals principally from sediment. Earlier studies on the soldier crab Mictyris longicarpus revealed that > 80% of metal accumulation was derived from sediment (Ying et al. 1993). Observation of P. sordidus showed that it takes up fine sediment particles. It was therefore considered suitable for this study. Polinices sordidus was not considered to be a good bioindicator of copper and zinc contamination. The average copper concentrations in the snails did not increase with increasing extractable copper in the sediments. Evidence for the accumulation or regulation of copper by gastropod species is usually equivocal. Martoja et al. (1980) found that copper concentrations in the winkle Littorina littorea were independent of environmental exposure to copper and that this species stored copper sulfide in its tissues, while the whelk Busycon canaliculatum was considered to regulate copper poorly (Betzer and Pilson 1975). However, Mason and Simkiss (1983) compared L. littorea collected from clean and polluted sites and found that copper was accumulated eight times more by the gastropods from a polluted area than by those from a clean area. Hughes et al. (1987) reported that for P. sordidus the EDso (i.e., the concentration at which 50% of individuals would show the stress response) was 0.7 to 1.1 nag Cu/1 in seawater. These concentrations are high, and extremely rare in the natural environment. However, the results of Hughes et al. suggest that P. sordidus is highly tolerant of exposure to copper. The results of the present study provided some evidence of copper regulation by the snails, but copper concentrations in P. sordidus exposed to different metal-contaminated sediments, even to the control sediment, were sur-
Weimin Ying et al.: Heavy metals in Poliniees sordidus prisingly variable between snails, although these were collected from the same area and should also have been in the same reproduction state. The reason for this is unknown. On the other hand, zinc concentrations in the snails were less variable than concentrations of the other metals. As an essential element, zinc is usually regulated by gastropods, e.g. Littorina obtusata, Haliotis tuberculata and H. rufescens (Anderlini 1974, Bryan et al. 1977, Young 1977). In the present investigation, zinc was regulated by snails exposed to sediments containing up to 10 000 tag Zn/g. There is little evidence in the literature for the regulation by marine organisms of non-essential metals such as lead. Lead accumulated by the crab Mictyris longicarpus and the gastropods Vetacumantis australis and Pyrazus ebeninus was significantly correlated with EDTA- or HCl-extractable lead in the sediment (Ying et al. 1992, 1993). In the present study, tissue concentrations were < 1 0 gg Pb/g in snails exposed to concentrations of < 2000 ~tg Pb/g in the sediment, but lead was accumulated by snails exposed to sediment containing 21 000 gg Pb/g. As pointed out earlier ("Results - Snails") lead in most of the snails could not be detected by the method used, making interpretation difficult. However, the present limited results suggest that this snail could be a good indicator of lead pollution. There was obvious accumulation of iron by the snails exposed to iron concentrations of > 10 000 lag/g as EDTA- and HCl-extractable iron (Fig. 1). Iron in sediment is usually an important co-factor controlling the bioavailability of other metals ( L u o m a and Bryan 1978, Langston 1982, Tessier et al. 1983, Ying et al. 1993), but in the case of Polinices sordidus there was no obvious evidence that iron in the sediment affected the bioavailability of other metals. These results suggest that P. sordidus is not a good indicator o f iron bioavailability in the sediment. G a s t r o p o d species m a y be good indicators of manganese concentrations in the environment. Ireland and Wootton (1977) reported that Thais lapilus and Littorina obtusata accumulated manganese at nine sites around the coast of Wales, G r e a t Britain. Our results revealed evident manganese uptake by the snails, and the manganese concentration in the snails could be predicted by simply extracting manganese from the sediments by EDTA or HC1 (EDTA extractions produced better predictions than HC1 extractions), Other studies (e.g. L u o m a and Bryan 1978, L u o m a 1983, 1989, Tessier and Campbell 1990) have examined various invertebrates and have demonstrated significant correlations between metal concentrations in animals and metal concentrations extracted from the sediment by various extractants. Their results showed that correlations m a y be improved by normalizing with respect to other factors such as pH, and other sedimentary components such as iron or organic matter. As the sediments used in the present study were collected from different geographic sites, it can be concluded that the bioavailability of manganese to Polinices sordidus in the field m a y be predicted by measuring EDTA-extractable manganese in sediment regardless of other sedimentary components.
421 Acknowledgements. We are grateful to the Australian Research Council for financial support and would like to thank J. Buchanan of the CSIRO Centre for Advanced Analytical Chemistry for assistance with chemical analyses and S. Wilson of ANSTO for help with snail collection. Literature cited Anderlini, V. C. (1974). The distribution of heavy metals in the red abalone, Haliotis rufescens, on the California coast. Archs envir. Contain. Toxic. 2:253-265 Batley, G. E. (1987). Heavy metal speciation in waters, sediments and biota from Lake Macquarie, NSW Aust. J. mar. Freshwat. Res. 38:491-606 Betzer, S. B., Pilson, M. E. Q. (1975). Copper uptake and excretion by Busycon canaliculatum L. Biol. Bull. mar. biol. Lab., Woods Hole 148:1-15 Bryan, G. W, Hummerstone, L. G. (1986). Zinc regulation in the Lobster Homarus gammarus: importance of different pathways of absorption and excretion. J. mar. biol. Ass. U.K. 66:175-199 Bryan, G. W., Potts, G. W., Forster, G. R. (1977). Heavy metals in the gastropod mollusc Homarus tuberculata (L.). J. mar. biol. Ass. U.K. 57:379-390 F6rstner, U., Wittmann, G. T. W (1981). Metal pollution in the aquatic environment. 2nd edn. Springer-Verlag, Berlin Hughes, Jr. M., Chapman, H. F., Kitching, R. L. (1987). Effects of sublethal concentrations of copper and freshwater on behaviour in an estuarine gastropod Polinices sordidus. Mar. PoIlut. Bull. 18:127-131 Ireland, M. P., Wootton, R. J. (1977). Distribution of lead, zinc, copper and manganese in the marine gastropods around the coast of Wales. Envir. Pollut. 12:27-41 Langston, W. J. (1972). Distribution of mercury in British estuarine sediments and its availability to deposit-feeding bivalves. J. mar. biol. Ass. U.K. 62:667-684 Luoma, S. N. (1983). Bioavailability of trace metals to aquatic organisms - a review. Sci. total Envir. 28:1-22 Luoma, S. N. (1989). Can we determine the biological availability of sediment-bound trace elements? Hydrobiologia. 176/177: 379-396 Luoma, S. N., Bryan, G. W. (1978). Factors controlling the availability of sediment-bound lead to the estuarine bivalve Serobicularia plana. J. mar. biol. Ass. U.K. 58:793-802 Luoma, S. N., Bryan, G. W (1982). A statistical study of environmental factors controlling concentrations of heavy metals in the burrowing bivalve Scrobicularia plana and polychaete Nereis diversicolar. Estuar., cstl Shelf Sci. 15:95-108 Luoma, S. N., Jenne, E. A. (1977). The availability of sedimentbound cobalt, silver and zinc to a deposit-feeling clam. In: Wildung, R. E., Drucker, H. (eds.) The biological implications of metals in the environment. National Technical Information Services, Springfield, Virginia, USA, p. 213-231. (CONF750929) Martoja, M., Tue, V. T., Elkaim, B. (1980). Bioaccumulation de cuivre chez Littorina littorea (L.) (gasteropode prosobranche): signification physiologique et ecologique. J. exp. mar. Biol. Ecol. 43:251-270 Mason, A. Z., Simkiss, K. (1983). Interactions between metals and their distribution in tissues of Littorina littorea (L.) collected from clean and polluted sites. J. mar. biol. Ass. U.K. 63: 661672 Phillips, D. J. H. (1980). Quantitative aquatic biological indicators. Applied Science Publishers Ltd., London Rainbow, P. S. (1990). Heavy metal levels in marine invertebrates. In: Furncss, R. W, Rainbow, P. S. (eds.) Heavy metals in the marine environment. CRC Press, Inc. Boca Raton, Florida, p. 67-80 Rainbow, P. S., Phillips, D. J. H., Depledge, M. H. (1990). The significance of trace metal concentrations in marine invertebrates. Mar. Pollut. Bull. 21:321-324
422 Ray, S., McLeese, D. W., Peterson, M. R. (1981). Accumulation of copper, zinc, cadmium and tead from two contaminated sediments by three marine invertebrates - a laboratory study. Bull. envir. Contam. Toxic. 26:315-322 Rendell, P. S., Batley, G. E., Cameron, A. J. (1980). Adsorption as a control of metal concentrations in sediment extracts. Envir. Sci. Technot. 14:314-318 Tessier, A., Campbell, P. G. C. (1990). Partitioning of trace metals in sediments and its relationship to their accumulation in benthic organisms. In: Guer, S., Adams, E D., Izdar, E., Klockow, D. (eds.) Metal speciation in the environment. Springer-Verlag, Berlin, p. 545-569 Tessier, A., Campbell, P. G. C., Anclair, J. C. (1983). Relationship between trace metal partitioning in sediments and their bioaccumulation in fresh pelecypods. In: Proceedings of Fourth International Conference on Heavy Metals in the Environment. CEP Consultants Ltd., Edinburgh, Scotland, p. 1086-1089
Weimin Ying et al.: Heavy metals in Polinices sordidus Tessier, A., Campbell, P. G. C., Bisson, M. (1979). Sequential extraction procedure for the speciation of particulate trace metals. Analyt. Chem. 51:844-851 Ying, W., Batley, G. E., Ahsanullah, M. (1992). The ability of sediment extractants to measure the bioavailability of metals to three marine invertebrates. Sci. total Envir. 125:67-84 Ying, W., Batley, G. E., Ahsanullah, M. (1993). Metal bioavailability to soldier crab Mictyris longicarpus. Sci. total Envir. (in press) Young, M. L. (1977). The transfer of 65Zn and 59Fe along a Fucus serratus (L.) - Littorina obtusata (L.) food chain. J. mar. biol. Ass. U.K. 55:583-610
C o m m u n i c a t e d b y G. F. H u m p h r e y , S y d n e y
