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Heavy metals in the aquatic environment of the Southern Adriatic Sea, Italy
Environment International 26 (2001) 505 ± 509
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Heavy metals in the aquatic environment of the Southern Adriatic Sea, Italy Macroalgae, sediments and benthic species M.M. Storelli*, A. Storelli, G.O. Marcotrigiano Section of Chemistry and Biochemistry, Pharmacal-Biologic Department, Medicine Veterinary Faculty, University of Bari, Strada Prov. le per Casamassima km 3, 70010 Valenzano (BA), Italy Received 13 June 1999; accepted 13 March 2001
Abstract Samples of sea urchins (Paracentrotus lividus), holothurians (Holothuria polii), green algae (Ulva lactuca, Codium vermilara and Enteromorpha prolifera) and sediments were collected from different coastal zones of the South Adriatic Sea (Italy). The occurrence of metals in macroalgae is poor especially if compared with that reported in other coastal areas affected by human activities, with the exception of Fe that showed high mean values (405 mg g 1 dry wt.). Likewise, relationships between metal concentrations in holothurians and sediments were found, demonstrating that H. polii could serve as bioindicator for Hg and Cu. D 2001 Elsevier Science Ltd. All rights reserved. Keywords: Metals; Macroalgea; Benthic species
1. Indroduction Urban and industrial activities introduce large amounts of pollutants into the marine environment, causing significant and permanent disturbances in marine systems and, consequently, environmental and ecological degradation. This phenomenon is especially significant in the coastal zones that are the main sinks of almost all anthropogenic discharges of pollutants. It has long been recognised that metals in the marine environment have a particular significance in the ecotoxicology, since they are highly persistent and can be toxic in traces (Langston, 1990; Claisse and Alzieu, 1993). Monitoring systems of the marine environmental are essential to track long-existing pollution processes (Waldman and Shevak, 1993), but the lack of them in many areas makes it very difficult to draw certain conclusion about the long-term results of human activities. In the framework of a wide monitoring programme for heavy metal distribution in the South Adriatic Sea, Hg, Cd, Pb, Zn, Cu and Fe concentrations were determined in macroalgae, sediments and in benthic organisms, such as sea * Corresponding author. Tel.: +39-80-5446066 to 67; fax: +39-805446063. E-mail address: [email protected] (M.M. Storelli).
urchins (Paracentrotus lividus) and holothurians (Holothuria polii) for the following purposes: 1. to provide information on the marine environmental quality throughout the use of macroalgae thought bioindicators of the pollution degree (Phillips, 1990, 1997); 2. to establish relationship between metal concentrations in sea urchin and macroalgae and between holothurians and sediments; 3. to determine whether Hg, Cd and Pb concentrations in P. lividus, species of wide food consumption, exceed the limits established by the Italian Legislation; 4. to determine whether H. polii could serve as a bioindicator of heavy metals.
2. Materials and methods Samples of sea urchins (P. lividus), holothurians (H. polii), green algae (Ulva lactuca, Codium vermilara and Enteromorpha prolifera) and sediments were collected in nine stations along the Apulian coast (South Adriatic Sea, Italy) (Fig. 1) in April 1998. Sea urchins, holothurians and seaweeds were caught by scuba diving. After collection, the
0160-4120/01/$ ± see front matter D 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 1 6 0 - 4 1 2 0 ( 0 1 ) 0 0 0 3 4 - 4
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M.M. Storelli et al. / Environment International 26 (2001) 505±509
and Cu were analysed using flame AA. Acid washed glassware, analytical grade reagents and double distilled deionized water were used in the sample analysis. In order to check on the purity of the chemical used, a number of chemical blanks were run; there was no evidence of any contamination in these blanks. Analytical quality control was achieved using TORT-1 Lobster Hepatopancreas (National Research Council of Canada) (Table 1). All data were computed on a microgram per gram dry weight basis. 3. Results and discussions
Fig. 1. Sampling stations along the Apulian coast.
samples were placed in polythene bags and transported to the laboratory in icebox. Seaweed samples were initially washed under a jet of tap water, then rinsed in distilled water. The samples were then washed three times in metalfree double distilled water and dried to constant weight (50°C). One thousand five hundred samples of sea urchins (length about 9 cm) and 500 holothurians (length about 20 cm) were classified according to their size. Composite samples of sea urchin gonads were taken. Holothurians dorsal and ventral body wall and gut contents were removed by dissection. All samples were dried to constant weight (50°C). Two hundred sediment samples to a depth of 2 cm were collected with a Van Veen type apparatus. After collection, sediment samples were air dried for 3 ± 4 days until to constant weight. Dried aliquots were ground using a mortar and pestle and sieved through a 0.5-mm screen. Samples (1 ±2 g of dried tissue) for quantitative analysis of heavy metals by atomic absorption spectrophotometry (Perkin Elmer 5000 Norwalk, USA) were digested into the reaction flask with 11 ml of the mixture HNO3 ±HClO4 (8:3) for Pb, Cd, Fe, Zn and Cu (Ciusa and Giaccio, 1984) and with 10 ml of the mixture H2SO4 ± HNO3 (1:1) for Hg (Gazzetta Ufficiale delle ComunitaÁ Europee, 1990). For Pb and Cd determination, a graphite furnace (HGA-500 Perkin Elmer Veberlinger, Germany) was used. Hg was determined by the cold vapour technique after reduction by SnCl2 (A.V.A. Thermo Jarrel Ash Franklin, USA), while Fe, Zn
Metal concentrations determined in the different species of macroalgae and in gonads of P. lividus from all sampling stations are given in Table 2. As regards macroalgae, among essential elements, metal concentrations were in the order Fe >Zn > Cu. The mean concentrations of Fe, Zn and Cu varied from 337.10 to 553.01, 58.79 to 127.27 and 10.33 to 12.07 mg g 1 dry wt., respectively. No significant differences of concentration were detected in the three species of algae examined (ANOVA test, Table 2), except for Zn that showed the highest mean values in U. lactuca (average: 127.27 mg g 1 dry wt.). As for the essential elements, the concentrations were in the order Pb > Cd > Hg. The mean levels of Pb, Cd and Hg varied from 0.84 to 2.55, 0.19 to 0.72 and 0.12 to 0.15 mg g 1 dry wt., respectively. Significant differences were observed solely for Cd that showed highest mean levels in E. prolifera (0.72 mg g 1 dry wt.). The high Fe concentration encountered in total seaweed as compared to the other trace metals, e.g., Zn and Cu, is probably due to several factors: the established need of Fe for normal growth of marine plants (Goldberg, 1952), ability of most algal species to biomagnify Fe from the surrounding environment and contamination from industrial and other operations (Eisler, 1981). Algae, in general, accumulate Zn and Cu readily from seawater (Ho, 1988). In benthic macrophytes, Zn levels not exceeding 100 mg g 1 are suggested as background for nonpolluted areas by Moore and Ramamurti (1987). In the opinion of these authors, higher concentrations are characteristic of the regions subjected to anthropogenic contamination. The Zn concentrations recorded in our study for algae may be considered to exceed the background level only in U. lactuca. In literature, Cu levels of 200 ± 300 mg g 1 have been recorded in species from polluted areas (Haug et al., 1974). The relatively low levels of Zn and Cu recorded in
Table 1 Metal concentrations in reference material (TORT-1), recovery and detection limit (DL) TORT-1 (mg/kg) Found values (mg/kg) No. of determinations % recovery DL (ng/g)
Hg
Pb
Cd
Fe
Zn
Cu
0.33 0.06 0.32 0.02 n = 10 97 50
10.4 2.0 9.9 0.83 n = 10 95 20
26.3 2.1 26.4 0.45 n = 10 100 2
186 11 174 9 n = 10 100 2
177 11 174 10 n = 10 100 0.2
439 22 419 20 n = 10 100 2.5
M.M. Storelli et al. / Environment International 26 (2001) 505±509
507
Table 2 Range, means S.D. of metal concentrations in the fronds of green algae U. lactuca, C. vermilara, E. prolifera and in P. lividus from all sampling stations and ANOVA test ANOVA1
ANOVA2
Metals
U. lactuca
C. vermilara
E. prolifera
F
P
P. lividus
Total seaweed
Hg
ND ± 0.18, 0.12 0.05 0.14 ± 0.60, 0.20 0.23 ND ± 1.23, 0.84 0.34 6.16 ± 26.05, 12.07 7.12 34.39 ± 192.17, 127.27 60.15 141.4 ± 849.4, 337.10 274.5
ND ± 0.26, 0.13 0.10 0.12 ± 0.29, 0.19 0.07 ND ± 4.12, 2.55 1.27 3.49 ± 15.24, 11.30 3.88 24.76 ± 104.17, 64.21 33.01 113.89 ± 1403.42, 553.01 434.41
ND ± 0.29, 0.15 0.12 0.30 ± 1.27, 0.72 0.36 ND ± 1.81, 1.15 0.46 6.07 ± 15.14, 10.33 3.48 32.63 ± 94.59, 58.79 22.26 139.49 ± 1970.68, 387.75 675.83
0.25
NS
9.58
***
2.32
NS
0.27
NS
9.28
***
0.03
NS
ND ± 0.16, 0.10 0.06 0.10 ± 0.65, 0.24 0.12 0.10 ± 2.65, 0.86 0.67 1.90 ± 14.60, 5.19 2.68 103.80 ± 294.90, 157.13 47.91 48.60 ± 622.70, 183.67 165.46
ND ± 0.29, 0.12 0.08 0.12 ± 1.27, 0.34 0.32 ND ± 4.12, 1.72 1.18 3.49 ± 26.05, 10.73 4.82 24.76 ± 192.17, 77.03 49.13 113.89 ± 1970.68, 405.10 494.62
Cd Pb Cu Zn Fe
F
P
0.95
NS
0.88
NS
6.17
NS
11.57
***
190.1
****
0.96
NS
(ANOVA1: comparison between different seaweeds, *** P < .005, NS: P > .05; ANOVA2: comparison between total seaweed and P. lividus, *** P < .02, **** P < .0001, NS: P >.05)
the present study indicated that contamination by these metals is small in this area. Hg, Pb and Cd concentrations recorded in this study are in the same order of magnitude of those reported for relatively contaminated areas (Hardisson et al., 1998; Hornung et al., 1992; Munda and Hudnik, 1991). Stenner and Nickless (1974), for the green algae from polluted fjord in Norway, reported extremely high Pb levels up to 1200 mg g 1 dry wt. Burdon-Jones et al. (1975) and Agadi et al. (1978) accounted Pb levels greater than 100 mg g 1 dry wt. from contaminated water; Hg high values of 20 mg g 1 dry wt. (Haug et al., 1974) and of 14 mg g 1 dry wt. (Matida and Kumada, 1969) were reported too from severally polluted environments. P. lividus, member of the echinoderm, class Echinoidea, is the most abundant inshore sea urchin, and it is one of the most ecologically important herbivores in this area. The examination of the intestinal content in samples collected from Adriatic Sea showed a diet rich in macroalgae, in particular a green alga U. lactuca (Serrazanetti et al., 1995). The trend of metals in P. lividus gonads is the same of those observed in algae. Fe showed highest concentrations followed by Zn, Cu, Pb, Cd and Hg. The comparison of Hg, Cd, Pb and Fe levels between total seaweed and gonads of P. lividus (ANOVA test, Table 2) showed similar values. As
for Cu, it exhibited higher levels in total seaweed respect to gonads, and this may reflects firstly the metabolic requirements of the plant for metals and secondly the capacity of the algae to take them up from the environment. Whereas Zn concentrations were two times higher in gonads than in total seaweed. The higher concentrations of this last metal in gonads, compared with algae, is in agreement with the findings of Catsiki et al. (1991). On the other hand, Zn has been reported to occur in high concentrations in gonads of different organisms (Phillips, 1980). P. lividus gonads are regarded as a delicacy in some parts of the world, including Japan, Chile, parts of Europe and the Mediterranean region. Along the Italian coasts, the presence of this echinoderm, once very copious, is decreasing due to an excessive exploitation. In order to safeguard this resort, the Ministry of the Alimentary Agricultural and Forestal Resources promulgated a Law Decree in 12 January 1995 (Gazzetta Ufficiale della Repubblica Italiana, 1995), forbidding the fishing along the Italian coast in the months of May and June. In the remaining months, fishing is allowed only for individuals of a minimum size of 7 cm of total diameter, aculei comprised, with a caught limit of 1000 individuals for professional fishers and 50 individuals for sporting fishers. The Italian legislation does not fix limits for cadmium and
Table 3 Range, mean value and standard deviation of metal concentrations in H. polii body wall, gut contents and sediments from all sampling stations and ANOVA test ANOVA Metals
Body wall tissue
Gut contents
Surface sediments
F
P
Hg Cd Pb Cu Zn Fe
0.40 ± 1.30, 0.96 0.22 0.02 ± 0.05, 0.04 0.01 1.12 ± 1.78, 1.26 0.12 40.30 ± 130.3, 70.60 50.7 31.99 ± 37.70, 34.58 2.49 595 ± 760, 669 60.02
0.27 ± 0.36, 0.30 0.04 0.09 ± 0.15, 0.11 0.05 1.97 ± 2.36, 2.12 0.15 10.72 ± 15.25, 13.60 1.58 44.84 ± 110.7, 87.76 30.7 7368 ± 9109, 8331 823.32
0.20 ± 0.40, 0.28 0.06 0.13 ± 0.24, 0.20 0.04 3.91 ± 6.69, 4.43 1.59 13.39 ± 20.18, 16.98 2.93 51.6 ± 151.2, 95.8 69.1 2599 ± 17805, 8838 5645
33.20 138.06 82.50 17.18 14.80 13.61
*** **** **** ** ** **
(ANOVA: comparison between body wall tissue and surface sediments, **** P < .0001, *** P < .002, ** P < .014)
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lead in fish products, except in mollusc cephalopods and in bivalve molluscs in which the limit established is 2 mg/kg wet wt. (Circolari del Ministero della SanitaÁ, 1986; Decreto Ministeriale, 1992), but it is customary to apply this limit as maximum tolerable value also in the other fish products. For total mercury, the European Commission Decision 93/351 of 19 May 1993 (Official Journal of the European Communities, 1994) asserts that the mean content of total mercury in edible parts of fish products should not exceed 0.5 and 1 mg/kg wet wt. for some species, reputed risky, because able to accumulate great quantities of this element. According to the rules in force, no sample showed concentrations exceeding the peak value of 2 mg/kg wet wt. for cadmium and lead and 0.5 mg/kg wet wt. for mercury. The levels of metals in body wall tissue in gut contents and surface sediment from all sampling stations are given in Table 3. The metal accumulation in sediments is related to different parameters, such as sediment characteristics, particle size and organic carbon content. More, the determination of metal concentrations in sediment provides information about the total content but not on the bioavailable fraction. Current research is addressing with some success to the chemical factors controlling trace metal bioavailability in sediments, not least the role of interstitial water pathways in the uptake of metals by burrowing organisms (Amiard, 1992; Decho and Luoma, 1994). Ideally, species to be chosen as biomonitors should fulfil several criteria (Phillips and Rainbow, 1993). Ideal biomonitors should be sedentary, easy to identify, abundant, long lived, available for sampling throughout the year, large enough to provide sufficient tissue for analysis, tolerant of exposure to environmental variation in physicochemical parameters and accumulators of the metals with a simple correlation between metal concentration tissues (body) and average ambient bioavailable metal concentration (Rainbow, 1995). Holothurians are numerically dominant members of the megafauna community in many sea areas, they are relatively easy to collect and their taxonomy is well known. In addition, deep-sea deposit feeding holothurians utilise large amounts of sediments, extracting organic matter as the sediment passes through the intestine and ejecting the remainder. Considering that the average life span of holothurians is about 4 years, and some species may live as long as 8 or 10 years, it is easy to understand as during their life cycle these organisms reworking of the surface sediment may accumulate pollutants eventually present in it. The close relationship between holothurians and sedimentary environment may presume the existence of a significant relationship between the concentrations of metals in tissue of the animals and those of sediments. In gut contents, the distribution order of metals was Fe>Zn>Cu>Pb>Cd>Hg. The same trend was observed in surface sediments, with levels generally closer to gut contents. In body wall tissue, the essential metal concentrations were in the order Fe>Cu>Zn. Among nonessential elements, Hg and Pb showed mean levels of the
same order of magnitude, while the Cd showed very low mean levels. A recent work highlighted the importance of holothurians as biomonitors of various metals (Moore et al., 1997). Moore et al. (1997) indicated the holothurians as potentially useful biomonitors of Cd and Cu, while Bargagli (1985) found the highest concentrations of mercury (from five to seven times) in muscle tissue respect to surface sediments. Comparison of body tissue metal burden with surface sediments (ANOVA test, Table 3) demonstrated elevated concentrations of Hg and Cu in the tissue. These observations suggest accumulation processes of these metals in holothurian tissue. For the other metals, the present data showed lower levels in the holothurians body wall tissue than in the surface sediments suggesting regulation of these metals. The results of this investigation lead to the following considerations: 1. The occurrence of metals in the investigated area is low especially if compared with that reported in other coastal areas affected by human activities, except for Fe that showed high values, probably due to antropogenic imput. 2. The presence of Hg, Cd, Pb and Fe in the gonads reflects those of the same metals in the algae, while the other metals are preferentially distributed in the gonads, e.g., zinc, or in macroalgae, e.g., Cu. 3. In P. lividus gonads, Hg, Cd and Pb levels do not show concentrations exceeding limits fixed by Italian legislation, and hence there are no health risks to humans consuming these seafood. 4. H. polii appears to be unable to regulate physiologically the uptake of Hg and Cu, and hence it can be considered as bioindicator of contamination by these metals in the environment.
References Agadi VV, Bhosle NB, Untawale AG. Metal concentration in some seaweeds of Goa (India). Bot Mar 1978;XXI:247 ± 50. Amiard JC. Bioavailability of sediment-bound metals for benthic aquatic organisms. In: Vernet JP, editor. Impact of heavy metals on the environment. Amsterdam: Elsevier, 1992. pp. 182 ± 202. Bargagli R. Il trasferimento del mercurio dai sedimenti agli organismi bentonici: osservazioni su Stichopus regalis (CUV.) e holoturia tubulosa GM. (Echinodermata ± Holothurioidea). Oebalia XI. 1985; 101 ± 13. Burdon-Jones C, Denton GRW, Jones GB, McPhic KA. Metal in marine organisms: Part I. Baseline survey. Progress report to the Water Qual. Queensland 4000: Council, Dept. Local Govt., 1975, p. 105. Catsiki VA, Papathanassiou E, Bei F. Heavy metal levels in characteristic benthic flora and fauna in the central Aegean Sea. Mar Pollut Bull 1991; 11:566 ± 9. Circolari del Ministero della SanitaÁ, Italia. n. 600.4/24992/AG 1808 del 31/ 05/'86, n. 600.4/24992/AG 3355 del 18/10/'86, n. 600.4/24992/AG 4011 del 23/12/'86, 1986. Ciusa W, Giaccio M. In: Cacucci F, editor, Bari, Italy. Il problema degli oligoelementi nelle specie ittiche dei mari italiani. 1984,227.
M.M. Storelli et al. / Environment International 26 (2001) 505±509 Claisse D, Alzieu C. Copper contamination as a result of antifouling paint regulations? Mar Pollut Bull 1993;26:395 ± 7. Decho AW, Luoma SN. Humic and fulvic acids: sink or source in the availability of metals to the marine bivalves Macoma balthica and Potamocorbula amurensis. Mar Ecol Prog Ser 1994;108:133 ± 45. Decreto Ministeriale no.° 131 del 27/01/1992. Limiti da rispettare per il piombo nei prodotti della pesca, 1992. Eisler RI. Trace metal concentrations in marine organisms Oxford: Pergamon, 1981. Gazzetta Ufficiale delle ComunitaÁ Europee. Metodi di riferimento per la ricerca di residui di metalli pesanti e arsenico, no.° L 286/33, 1990. Gazzetta Ufficiale della Repubblica Italiana, no.° 20 del 21/1/95, 1995. Goldberg ED. Iron assimilation by marine diatoms. Biol Bull 1952; 102:243 ± 8. Hardisson A, Frias I, de Bonis A, Lozano G, Baez A. Mercury in algae of the canary islands littoral. Environ Int 1998;24:945 ± 50. Haug A, Melsom S, Omang S. Estimation of heavy metal pollution in two Norwegian fjord areas by analysis of the brown alga Ascophyllum nodosum. Environ Pollut 1974;7:179 ± 92. Ho YB. Metal levels in three intertidal macroalgae in Hong Kong waters. Aquat Bot 1988;29:367 ± 72. Hornung H, Kress N, Friedlander M. Trace element concentrations intertidal algae collected along the Mediterranean shore, Israel. Fresenius Environ Bull 1992;1:84 ± 90. Langston WJ. Toxic effects of metals and the incidence of metal pollution in marine ecosystem. In: Furness RW, Rainbow PS, editors. Heavy metals in the marine environment. Boca Raton, FL: CRC Press, 1990. pp. 101 ± 22. Matida Y, Kumada H. Distribution of mercury in water, bottom mud, and aquatic organisms of Minamata Bay, the river Agano, and other water bodies in Japan. Bull Freshwater Fish Res Lab, Tokyo 1969;19:73 ± 9.
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Moore JV, Ramamurti S. Heavy metals in near-bottom water. Moscow. pp. 285 (in Russian). Moore HM, Roberts D, Harriot M, Burns DT. Holothurians, potential biomonitors for metal levels in deep-sea sediments. Fresenius J Anal Chem 1997;358:652 ± 6. Munda IM, Hudnik V. Trace metal content in some seaweeds from the northern Adriatic. Bot Mar 1991;34:241 ± 9. Official Journal of the European Communities L144 of 16 June 1994, 1994. Phillips DJH. The use of biological indicator organisms to monitor trace metal pollution in marine and estuarine environments Ð a review. Environ Pollut 1977;13:281 ± 317. Phillips DJH. Quantitative aquatic biological indicators: their use to monitor trace metal and organochlorine pollution. London: Applied Science, 1980. Phillips DJH. Use of macroalgae and invertebrates as monitors of metal levels in estuaries and coastal waters. In: Furness RW, Rainbow PS, editors. Heavy metals in the marine environment. Boca Raton, FL: CRC Press, 1990. pp. 81 ± 99. Phillips DJH, Rainbow PS. Biomonitoring of trace aquatic contaminants. Barking: Applied Science Publishers, 1993. Rainbow PS. Biomonitoring of heavy metal availability in the marine environment. Mar Pollut Bull 1995;31:183 ± 92. Serrazanetti GP, Pagnucco C, Conte LS, Cattani O. Hydrocarbons, Sterols and Fatty acids in sea urchin (Paracentrotus lividus) of the Adriatic Sea. Chemosphere 1995;30:1453 ± 61. Stenner RD, Nickless G. Distribution of some heavy metals in organisms in Hardangerfjord and Skjerstadfjord, Norway. Water Air Soil Pollut 1974;3:279 ± 91. Waldman M, Shevak Y. Biodegradation and leaching of pollutants: monitoring aspects. Pure Appl Chem 1993;65:1565 ± 603.
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Heavy metals in the aquatic environment of the Southern Adriatic Sea, Italy Macroalgae, sediments and benthic species M.M. Storelli*, A. Storelli, G.O. Marcotrigiano Section of Chemistry and Biochemistry, Pharmacal-Biologic Department, Medicine Veterinary Faculty, University of Bari, Strada Prov. le per Casamassima km 3, 70010 Valenzano (BA), Italy Received 13 June 1999; accepted 13 March 2001
Abstract Samples of sea urchins (Paracentrotus lividus), holothurians (Holothuria polii), green algae (Ulva lactuca, Codium vermilara and Enteromorpha prolifera) and sediments were collected from different coastal zones of the South Adriatic Sea (Italy). The occurrence of metals in macroalgae is poor especially if compared with that reported in other coastal areas affected by human activities, with the exception of Fe that showed high mean values (405 mg g 1 dry wt.). Likewise, relationships between metal concentrations in holothurians and sediments were found, demonstrating that H. polii could serve as bioindicator for Hg and Cu. D 2001 Elsevier Science Ltd. All rights reserved. Keywords: Metals; Macroalgea; Benthic species
1. Indroduction Urban and industrial activities introduce large amounts of pollutants into the marine environment, causing significant and permanent disturbances in marine systems and, consequently, environmental and ecological degradation. This phenomenon is especially significant in the coastal zones that are the main sinks of almost all anthropogenic discharges of pollutants. It has long been recognised that metals in the marine environment have a particular significance in the ecotoxicology, since they are highly persistent and can be toxic in traces (Langston, 1990; Claisse and Alzieu, 1993). Monitoring systems of the marine environmental are essential to track long-existing pollution processes (Waldman and Shevak, 1993), but the lack of them in many areas makes it very difficult to draw certain conclusion about the long-term results of human activities. In the framework of a wide monitoring programme for heavy metal distribution in the South Adriatic Sea, Hg, Cd, Pb, Zn, Cu and Fe concentrations were determined in macroalgae, sediments and in benthic organisms, such as sea * Corresponding author. Tel.: +39-80-5446066 to 67; fax: +39-805446063. E-mail address: [email protected] (M.M. Storelli).
urchins (Paracentrotus lividus) and holothurians (Holothuria polii) for the following purposes: 1. to provide information on the marine environmental quality throughout the use of macroalgae thought bioindicators of the pollution degree (Phillips, 1990, 1997); 2. to establish relationship between metal concentrations in sea urchin and macroalgae and between holothurians and sediments; 3. to determine whether Hg, Cd and Pb concentrations in P. lividus, species of wide food consumption, exceed the limits established by the Italian Legislation; 4. to determine whether H. polii could serve as a bioindicator of heavy metals.
2. Materials and methods Samples of sea urchins (P. lividus), holothurians (H. polii), green algae (Ulva lactuca, Codium vermilara and Enteromorpha prolifera) and sediments were collected in nine stations along the Apulian coast (South Adriatic Sea, Italy) (Fig. 1) in April 1998. Sea urchins, holothurians and seaweeds were caught by scuba diving. After collection, the
0160-4120/01/$ ± see front matter D 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 1 6 0 - 4 1 2 0 ( 0 1 ) 0 0 0 3 4 - 4
506
M.M. Storelli et al. / Environment International 26 (2001) 505±509
and Cu were analysed using flame AA. Acid washed glassware, analytical grade reagents and double distilled deionized water were used in the sample analysis. In order to check on the purity of the chemical used, a number of chemical blanks were run; there was no evidence of any contamination in these blanks. Analytical quality control was achieved using TORT-1 Lobster Hepatopancreas (National Research Council of Canada) (Table 1). All data were computed on a microgram per gram dry weight basis. 3. Results and discussions
Fig. 1. Sampling stations along the Apulian coast.
samples were placed in polythene bags and transported to the laboratory in icebox. Seaweed samples were initially washed under a jet of tap water, then rinsed in distilled water. The samples were then washed three times in metalfree double distilled water and dried to constant weight (50°C). One thousand five hundred samples of sea urchins (length about 9 cm) and 500 holothurians (length about 20 cm) were classified according to their size. Composite samples of sea urchin gonads were taken. Holothurians dorsal and ventral body wall and gut contents were removed by dissection. All samples were dried to constant weight (50°C). Two hundred sediment samples to a depth of 2 cm were collected with a Van Veen type apparatus. After collection, sediment samples were air dried for 3 ± 4 days until to constant weight. Dried aliquots were ground using a mortar and pestle and sieved through a 0.5-mm screen. Samples (1 ±2 g of dried tissue) for quantitative analysis of heavy metals by atomic absorption spectrophotometry (Perkin Elmer 5000 Norwalk, USA) were digested into the reaction flask with 11 ml of the mixture HNO3 ±HClO4 (8:3) for Pb, Cd, Fe, Zn and Cu (Ciusa and Giaccio, 1984) and with 10 ml of the mixture H2SO4 ± HNO3 (1:1) for Hg (Gazzetta Ufficiale delle ComunitaÁ Europee, 1990). For Pb and Cd determination, a graphite furnace (HGA-500 Perkin Elmer Veberlinger, Germany) was used. Hg was determined by the cold vapour technique after reduction by SnCl2 (A.V.A. Thermo Jarrel Ash Franklin, USA), while Fe, Zn
Metal concentrations determined in the different species of macroalgae and in gonads of P. lividus from all sampling stations are given in Table 2. As regards macroalgae, among essential elements, metal concentrations were in the order Fe >Zn > Cu. The mean concentrations of Fe, Zn and Cu varied from 337.10 to 553.01, 58.79 to 127.27 and 10.33 to 12.07 mg g 1 dry wt., respectively. No significant differences of concentration were detected in the three species of algae examined (ANOVA test, Table 2), except for Zn that showed the highest mean values in U. lactuca (average: 127.27 mg g 1 dry wt.). As for the essential elements, the concentrations were in the order Pb > Cd > Hg. The mean levels of Pb, Cd and Hg varied from 0.84 to 2.55, 0.19 to 0.72 and 0.12 to 0.15 mg g 1 dry wt., respectively. Significant differences were observed solely for Cd that showed highest mean levels in E. prolifera (0.72 mg g 1 dry wt.). The high Fe concentration encountered in total seaweed as compared to the other trace metals, e.g., Zn and Cu, is probably due to several factors: the established need of Fe for normal growth of marine plants (Goldberg, 1952), ability of most algal species to biomagnify Fe from the surrounding environment and contamination from industrial and other operations (Eisler, 1981). Algae, in general, accumulate Zn and Cu readily from seawater (Ho, 1988). In benthic macrophytes, Zn levels not exceeding 100 mg g 1 are suggested as background for nonpolluted areas by Moore and Ramamurti (1987). In the opinion of these authors, higher concentrations are characteristic of the regions subjected to anthropogenic contamination. The Zn concentrations recorded in our study for algae may be considered to exceed the background level only in U. lactuca. In literature, Cu levels of 200 ± 300 mg g 1 have been recorded in species from polluted areas (Haug et al., 1974). The relatively low levels of Zn and Cu recorded in
Table 1 Metal concentrations in reference material (TORT-1), recovery and detection limit (DL) TORT-1 (mg/kg) Found values (mg/kg) No. of determinations % recovery DL (ng/g)
Hg
Pb
Cd
Fe
Zn
Cu
0.33 0.06 0.32 0.02 n = 10 97 50
10.4 2.0 9.9 0.83 n = 10 95 20
26.3 2.1 26.4 0.45 n = 10 100 2
186 11 174 9 n = 10 100 2
177 11 174 10 n = 10 100 0.2
439 22 419 20 n = 10 100 2.5
M.M. Storelli et al. / Environment International 26 (2001) 505±509
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Table 2 Range, means S.D. of metal concentrations in the fronds of green algae U. lactuca, C. vermilara, E. prolifera and in P. lividus from all sampling stations and ANOVA test ANOVA1
ANOVA2
Metals
U. lactuca
C. vermilara
E. prolifera
F
P
P. lividus
Total seaweed
Hg
ND ± 0.18, 0.12 0.05 0.14 ± 0.60, 0.20 0.23 ND ± 1.23, 0.84 0.34 6.16 ± 26.05, 12.07 7.12 34.39 ± 192.17, 127.27 60.15 141.4 ± 849.4, 337.10 274.5
ND ± 0.26, 0.13 0.10 0.12 ± 0.29, 0.19 0.07 ND ± 4.12, 2.55 1.27 3.49 ± 15.24, 11.30 3.88 24.76 ± 104.17, 64.21 33.01 113.89 ± 1403.42, 553.01 434.41
ND ± 0.29, 0.15 0.12 0.30 ± 1.27, 0.72 0.36 ND ± 1.81, 1.15 0.46 6.07 ± 15.14, 10.33 3.48 32.63 ± 94.59, 58.79 22.26 139.49 ± 1970.68, 387.75 675.83
0.25
NS
9.58
***
2.32
NS
0.27
NS
9.28
***
0.03
NS
ND ± 0.16, 0.10 0.06 0.10 ± 0.65, 0.24 0.12 0.10 ± 2.65, 0.86 0.67 1.90 ± 14.60, 5.19 2.68 103.80 ± 294.90, 157.13 47.91 48.60 ± 622.70, 183.67 165.46
ND ± 0.29, 0.12 0.08 0.12 ± 1.27, 0.34 0.32 ND ± 4.12, 1.72 1.18 3.49 ± 26.05, 10.73 4.82 24.76 ± 192.17, 77.03 49.13 113.89 ± 1970.68, 405.10 494.62
Cd Pb Cu Zn Fe
F
P
0.95
NS
0.88
NS
6.17
NS
11.57
***
190.1
****
0.96
NS
(ANOVA1: comparison between different seaweeds, *** P < .005, NS: P > .05; ANOVA2: comparison between total seaweed and P. lividus, *** P < .02, **** P < .0001, NS: P >.05)
the present study indicated that contamination by these metals is small in this area. Hg, Pb and Cd concentrations recorded in this study are in the same order of magnitude of those reported for relatively contaminated areas (Hardisson et al., 1998; Hornung et al., 1992; Munda and Hudnik, 1991). Stenner and Nickless (1974), for the green algae from polluted fjord in Norway, reported extremely high Pb levels up to 1200 mg g 1 dry wt. Burdon-Jones et al. (1975) and Agadi et al. (1978) accounted Pb levels greater than 100 mg g 1 dry wt. from contaminated water; Hg high values of 20 mg g 1 dry wt. (Haug et al., 1974) and of 14 mg g 1 dry wt. (Matida and Kumada, 1969) were reported too from severally polluted environments. P. lividus, member of the echinoderm, class Echinoidea, is the most abundant inshore sea urchin, and it is one of the most ecologically important herbivores in this area. The examination of the intestinal content in samples collected from Adriatic Sea showed a diet rich in macroalgae, in particular a green alga U. lactuca (Serrazanetti et al., 1995). The trend of metals in P. lividus gonads is the same of those observed in algae. Fe showed highest concentrations followed by Zn, Cu, Pb, Cd and Hg. The comparison of Hg, Cd, Pb and Fe levels between total seaweed and gonads of P. lividus (ANOVA test, Table 2) showed similar values. As
for Cu, it exhibited higher levels in total seaweed respect to gonads, and this may reflects firstly the metabolic requirements of the plant for metals and secondly the capacity of the algae to take them up from the environment. Whereas Zn concentrations were two times higher in gonads than in total seaweed. The higher concentrations of this last metal in gonads, compared with algae, is in agreement with the findings of Catsiki et al. (1991). On the other hand, Zn has been reported to occur in high concentrations in gonads of different organisms (Phillips, 1980). P. lividus gonads are regarded as a delicacy in some parts of the world, including Japan, Chile, parts of Europe and the Mediterranean region. Along the Italian coasts, the presence of this echinoderm, once very copious, is decreasing due to an excessive exploitation. In order to safeguard this resort, the Ministry of the Alimentary Agricultural and Forestal Resources promulgated a Law Decree in 12 January 1995 (Gazzetta Ufficiale della Repubblica Italiana, 1995), forbidding the fishing along the Italian coast in the months of May and June. In the remaining months, fishing is allowed only for individuals of a minimum size of 7 cm of total diameter, aculei comprised, with a caught limit of 1000 individuals for professional fishers and 50 individuals for sporting fishers. The Italian legislation does not fix limits for cadmium and
Table 3 Range, mean value and standard deviation of metal concentrations in H. polii body wall, gut contents and sediments from all sampling stations and ANOVA test ANOVA Metals
Body wall tissue
Gut contents
Surface sediments
F
P
Hg Cd Pb Cu Zn Fe
0.40 ± 1.30, 0.96 0.22 0.02 ± 0.05, 0.04 0.01 1.12 ± 1.78, 1.26 0.12 40.30 ± 130.3, 70.60 50.7 31.99 ± 37.70, 34.58 2.49 595 ± 760, 669 60.02
0.27 ± 0.36, 0.30 0.04 0.09 ± 0.15, 0.11 0.05 1.97 ± 2.36, 2.12 0.15 10.72 ± 15.25, 13.60 1.58 44.84 ± 110.7, 87.76 30.7 7368 ± 9109, 8331 823.32
0.20 ± 0.40, 0.28 0.06 0.13 ± 0.24, 0.20 0.04 3.91 ± 6.69, 4.43 1.59 13.39 ± 20.18, 16.98 2.93 51.6 ± 151.2, 95.8 69.1 2599 ± 17805, 8838 5645
33.20 138.06 82.50 17.18 14.80 13.61
*** **** **** ** ** **
(ANOVA: comparison between body wall tissue and surface sediments, **** P < .0001, *** P < .002, ** P < .014)
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lead in fish products, except in mollusc cephalopods and in bivalve molluscs in which the limit established is 2 mg/kg wet wt. (Circolari del Ministero della SanitaÁ, 1986; Decreto Ministeriale, 1992), but it is customary to apply this limit as maximum tolerable value also in the other fish products. For total mercury, the European Commission Decision 93/351 of 19 May 1993 (Official Journal of the European Communities, 1994) asserts that the mean content of total mercury in edible parts of fish products should not exceed 0.5 and 1 mg/kg wet wt. for some species, reputed risky, because able to accumulate great quantities of this element. According to the rules in force, no sample showed concentrations exceeding the peak value of 2 mg/kg wet wt. for cadmium and lead and 0.5 mg/kg wet wt. for mercury. The levels of metals in body wall tissue in gut contents and surface sediment from all sampling stations are given in Table 3. The metal accumulation in sediments is related to different parameters, such as sediment characteristics, particle size and organic carbon content. More, the determination of metal concentrations in sediment provides information about the total content but not on the bioavailable fraction. Current research is addressing with some success to the chemical factors controlling trace metal bioavailability in sediments, not least the role of interstitial water pathways in the uptake of metals by burrowing organisms (Amiard, 1992; Decho and Luoma, 1994). Ideally, species to be chosen as biomonitors should fulfil several criteria (Phillips and Rainbow, 1993). Ideal biomonitors should be sedentary, easy to identify, abundant, long lived, available for sampling throughout the year, large enough to provide sufficient tissue for analysis, tolerant of exposure to environmental variation in physicochemical parameters and accumulators of the metals with a simple correlation between metal concentration tissues (body) and average ambient bioavailable metal concentration (Rainbow, 1995). Holothurians are numerically dominant members of the megafauna community in many sea areas, they are relatively easy to collect and their taxonomy is well known. In addition, deep-sea deposit feeding holothurians utilise large amounts of sediments, extracting organic matter as the sediment passes through the intestine and ejecting the remainder. Considering that the average life span of holothurians is about 4 years, and some species may live as long as 8 or 10 years, it is easy to understand as during their life cycle these organisms reworking of the surface sediment may accumulate pollutants eventually present in it. The close relationship between holothurians and sedimentary environment may presume the existence of a significant relationship between the concentrations of metals in tissue of the animals and those of sediments. In gut contents, the distribution order of metals was Fe>Zn>Cu>Pb>Cd>Hg. The same trend was observed in surface sediments, with levels generally closer to gut contents. In body wall tissue, the essential metal concentrations were in the order Fe>Cu>Zn. Among nonessential elements, Hg and Pb showed mean levels of the
same order of magnitude, while the Cd showed very low mean levels. A recent work highlighted the importance of holothurians as biomonitors of various metals (Moore et al., 1997). Moore et al. (1997) indicated the holothurians as potentially useful biomonitors of Cd and Cu, while Bargagli (1985) found the highest concentrations of mercury (from five to seven times) in muscle tissue respect to surface sediments. Comparison of body tissue metal burden with surface sediments (ANOVA test, Table 3) demonstrated elevated concentrations of Hg and Cu in the tissue. These observations suggest accumulation processes of these metals in holothurian tissue. For the other metals, the present data showed lower levels in the holothurians body wall tissue than in the surface sediments suggesting regulation of these metals. The results of this investigation lead to the following considerations: 1. The occurrence of metals in the investigated area is low especially if compared with that reported in other coastal areas affected by human activities, except for Fe that showed high values, probably due to antropogenic imput. 2. The presence of Hg, Cd, Pb and Fe in the gonads reflects those of the same metals in the algae, while the other metals are preferentially distributed in the gonads, e.g., zinc, or in macroalgae, e.g., Cu. 3. In P. lividus gonads, Hg, Cd and Pb levels do not show concentrations exceeding limits fixed by Italian legislation, and hence there are no health risks to humans consuming these seafood. 4. H. polii appears to be unable to regulate physiologically the uptake of Hg and Cu, and hence it can be considered as bioindicator of contamination by these metals in the environment.
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