- Email: [email protected]
PCB and DDT contamination in cultivated and wild sea bass from Ria de Aveiro, Portugal
Chemosphere 54 (2004) 1503–1507 www.elsevier.com/locate/chemosphere
PCB and DDT contamination in cultivated and wild sea bass from Ria de Aveiro, Portugal q Paulo Antunes, Odete Gil
*
INIAP/IPIMAR, Av. de Brasılia, 1449-006 Lisboa, Portugal Received 25 November 2002; received in revised form 28 July 2003; accepted 21 August 2003
Abstract Polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) and metabolites were quantified in muscle and liver of sea bass (Dicentrarchus labrax) collected in Ria de Aveiro and in two fish farms. Sea bass from natural environment showed lower levels than fish from farming, which may be partly attributed to the higher lipid content of cultivated fish. PCB congener distribution in tissues of sea bass from the two farms resembled that of diet pellets suggesting that commercial diet is a major source of PCBs. However, fish in the two sites were fed with diet of similar PCB and DDT contamination but showed distinct levels in its tissues not explained by lipid content. 2003 Elsevier Ltd. All rights reserved. Keywords: Organochlorines; Dicentrarchus labrax; Wild fish; Fish farming
1. Introduction PCBs and DDTs are known to occur in aquatic systems and fish accumulate these substances either directly from the surrounding environment or from their diet. Some studies have shown that food is the major contributor for PCB bioaccumulation (Thomann and Connolly, 1984; Loizeau et al., 2001a,b). Therefore, the use of commercial diets, in fish farming and its levels of micro-contaminants, may influence pollutant concentration in cultivated fish (de Boer and Pieters, 1991). Besides the artificial diet, in these systems of culture, fish also consumes natural preys produced in the ponds, which also contributes to the contamination burden. The characteristics of organochlorine compounds and
of the aquatic environment as well as the lipid content influence also the bioaccumulation (Herbert and Keenleyside, 1995; Bentzen et al., 1996; Pastor et al., 1996). Ria de Aveiro is a coastal lagoon, located in the northern of Portugal that receives inputs from agriculture, urban and industrial activities where fish farming has been significantly developed. In this study the concentration of eighteen PCB congeners and of DDT compounds were compared in muscle and liver of wild and cultivated sea bass (Dicentrarchus labrax, Linnaeus, 1758) and the importance of diet as source of contamination was evaluated.
2. Materials and methods q
Paper presented in Dioxin 2002––22nd International Symposium on Halogenated Environmental Organic Pollutants and POPs, August 11–16, Barcelona, Spain. * Corresponding author. Fax: +351-213-011-5948. E-mail address: [email protected] (O. Gil).
2.1. Sampling Sea bass samples were collected in 1998 in Ria de Aveiro and in January 1999 in two farms located at the sampling area. These production systems are
0045-6535/$ - see front matter 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2003.08.029
1504
P. Antunes, O. Gil / Chemosphere 54 (2004) 1503–1507
semi-intensive and based on water supply controlled by the tides. After measuring both length and weight, 10 individuals of similar length were selected from each site. The muscle and liver of individual fish as well as the commercial feed pellets sub-samples supplied to fish farming were taken for chemical analysis. 2.2. Materials Solvents––Acetone and n-hexane distilled in the laboratory. Dichloromethane (Merck). Sodium sulphate–– Anhydrous (Merck), heated at 440 C overnight. Florisil––60–100 mesh (Merck), activated at 440 C overnight, and partially deactivated with 1% distilled water. Standards––PCB congeners were obtained, as crystals, from Promochem, Germany (99% of purity), and p,p0 -DDT, p,p0 -DDD, p,p0 -DDE from Supelco (99.2%, 98.5%, 99.5% of purity, respectively).
m · 0.25 mm i.d., 0.25 lm film thickness) and operating at an electron impact energy of 70 eV. The column was held at 60 C for 1 min, then programmed at 20 C min1 to 210 C (8 min); at 2 C min1 to 250 C (5 min). Compounds were determined by selected ion monitoring (SIM) at m=z 256, 290, 324, 358, 392, 426, and 318 for tri-, tetra-, penta-, hexa-, hepta-, octachlorobiphenyl and p,p0 -DDE, respectively. Extraction efficiency was tested by re-extracting the sample with fresh solvents. Concentrations of the second extraction were less than 10% of the value determined previously. The recovery of the Florisil column was evaluated with a standard solution and more than 85% of each compound was obtained. Procedural blanks were also analysed in each batch of 10–16 samples. One way analysis of variance was used to compare concentrations (Zar, 1996). A 5% significance level was used for the statistical tests.
2.3. Chemical analyses 3. Results and discussion PCBs and DDTs were extracted from freeze-dried tissues and from diet pellets with hexane using Soxhlet apparatus for 6 h. Fat content was determined gravimetrically from aliquots of the extracts. The remaining extracts were concentrated and passed through a 2.5 g Florisil-packed glass column for separation of the compounds. The first fraction eluted with n-hexane contained PCBs and p,p0 -DDE, the second fraction eluted with dichloromethane:hexane (30:70) contained p,p0 -DDD and p,p0 -DDT. The extracts were subjected to a further clean up with sulphuric acid. After concentration, each sample was injected into a Hewlett-Packard 5890 series II gas chromatograph equipped with an electron capture detector. A DB-5 (J&W Scientific, Folsom, CA) capillary column (60 m · 0.25 mm i.d., 0.25 lm film thickness) was used. The column was held at 60 C for 1 min, then programmed in three levels: at a rate of 20 C min1 to 210 C (8 min); 2 C min1 to 250 C (17 min) and 4 C min1 to a final temperature of 260 C (15 min). The injector temperature was kept at 270 C and the detector was maintained at 320 C. Helium and argonmethane were used as the carrier and the make up gases, respectively. Concentrations of CBs and DDT compounds were quantified from the peak heights using a six-point multilevel calibration curve. A mixture of 18 individual CBs (IUPAC Nos. 18, 26 tri-, 52, 49, 44 tetra-, 101, 118, 105 penta-, 151, 149, 153, 138, 128 hexa-, 187, 183, 180, 170 hepta-, 194 octachlorobiphenyl), p,p0 -DDE, p,p0 -DDD and p,p0 -DDT was used as external standard for quantification. Compounds analysed by GC–ECD were confirmed in some samples with high levels by GC–MS using a Finningan Mat GCQ instrument, equipped with a DB5MS (J&W Scientific, Folsom, CA) capillary column (30
3.1. Organochlorine concentrations The concentrations of total PCB (calculated as the sum of individual CBs) and total DDT (calculated as the sum of concentrations of p,p0 -DDE, p,p0 -DDD and p,p0 DDT) in muscle and liver of sea bass collected in Ria de Aveiro and in two farms are presented in Table 1. The results show that the concentrations of total PCB in tissues of sea bass from Ria was more than the double of total DDT. However, sea bass from farming showed similar levels of these contaminants (Student test, p < 0:05). The muscle concentrations (Table 1) obtained in our study (155 ± 49 to 294 ± 104 ng g1 lipid for total PCB and 108 ± 43 to 336 ± 132 ng g1 lipid for total DDT), were lower than those reported by Pastor et al. (1996), respectively, 800 ± 50 and 513 ± 97 ng g1 lipid, for sea bass from the Ebro Delta, in western Mediterranean. Table 1 also shows that total PCB and total DDT concentrations on a dry weight basis were lower in wild sea bass (13 and 5.4 ng g1 in muscle; 65 and 26 ng g1 in liver) than in fish from farming, presenting the farming 2 generally the highest values (36 and 39 ng g1 in muscle; 179 and 194 ng g1 in liver). Lipid content of an organism may influence its organochlorine concentrations (Herbert and Keenleyside, 1995; Pastor et al., 1996; Bayarri et al., 2001). The observed differences in concentrations may be attributed partly to higher lipid content in fish from farms 1 and 2 (17%, 66% and 12%, 44%, respectively, in muscle and liver) than those from Ria (5%, 26%). Normalization of concentrations to lipid content reduced, in general, the variability between Ria and farms, but not that between the two fish farms. In fact, tissues of sea bass from farm 2 showed lower lipid content and higher dry weight total PCB and total DDT
P. Antunes, O. Gil / Chemosphere 54 (2004) 1503–1507
1505
Table 1 Mean concentrations of total PCB and total DDT (ng g1 ) ± SD, in muscle and liver of sea bass from Ria de Aveiro and from farms 1 and 2 Concentration (ng g1 dry weight)
Concentration (ng g1 lipid)
Total PCB
Total DDT
Total PCB
Total DDT
Muscle Ria Farming 1 Farming 2
13 ± 2.5a 26 ± 9.5b 36 ± 13b
5.4 ± 2.3a 22 ± 7.0b 39 ± 13c
275 ± 84b 155 ± 49a 294 ± 104b
108 ± 43a 125 ± 22a 336 ± 132b
Liver Ria Farming 1 Farming 2
65 ± 32c 106 ± 33d 179 ± 22e
26 ± 13c 88 ± 14d 194 ± 22e
329 ± 231c 159 ± 30d 405 ± 62d
121 ± 67c 135 ± 17c 449 ± 67d
Different letters represent significant differences (p < 0:05) between Ria and farms, according to ANOVA followed by Scheffe test.
concentrations than tissues of fish from farm 1. So, the lipid content does not explain the difference in dry weight concentrations of fish from these two sites. This cannot also be attributed to a different contamination of the diet pellets, because the fish were fed with diet of similar total PCB (26 and 25 ng g1 dw, respectively, for farming 1 and 2) and total DDT (19 and 26 ng g1 dw) levels. The natural preys carried by the water and also produced inside the earth ponds are, however, an important component of the diet. The observed variability in levels between the two fish farms may be related to differences in contamination of the natural component of the diet and to other factors such as differences in physiological condition of the individuals (Loizeau et al., 2001a,b; Norstrom, 2002). 3.2. Composition From the DDT compounds, DDE was present in the highest concentration in tissues of all the analysed organisms and in pellet diet (Table 2), representing more than 79% of total DDT. The relative distribution of PCB congeners may differ in aquatic organisms because the contamination sources have different congener patterns. The patterns of PCBs would become enriched in more hydrophobic congeners
in predators relative to their prey as a result of digestive fractionation (Kucklick and Backer, 1998). In our study PCB patterns, determined as the concentration ratios between individual congener and total PCB, did not vary among wild and cultivated sea bass. The pattern of PCBs in muscle and liver of all individuals was very similar and CBs 153 and 138 (hexachlorobiphenyls) were the dominant congeners (Fig. 1). This congeners are usually reported as dominant in marine fishes (Bayarri et al., 2001; Loizeau et al., 2001a,b). The overall PCB congener distribution in tissues of sea bass from farms resembled that of diet pellets (Fig. 1) being the relative proportions of individual chlorobiphenyl congeners both in fish tissues and in diet significantly correlated (Table 3). These results imply that commercial diet is a major source of PCBs and a fractionation of PCB congeners, between sea bass and diet pellets, in farms was not significant. This is in accordance with findings of Kucklick and Backer (1998) for other species and contrasts with other works of the same author that found a selective accumulation of more hydrophobic PCB congeners in food chain transfer. In cultivated sea bass the relative proportions of PCB congeners were similar to those in its diet pellets, which may indicate that assimilation efficiency may not systematically vary with the hydrophobicity.
Table 2 Mean concentrations (SD) of DDT compounds (ng g1 dry weight) in muscle and liver of sea bass and in diet pellets Sea bass
Diet pellets
Muscle DDE DDD DDT a
Liver
Ria
Farming 1
Farming 2
Ria
Farming 1
Farming 2
Farming 1
Farming 2
4.8 (2.4) 0.4 (0.2) 1.7 (0.9)
19 (6.4) 2.8 (1.0) 1.1 (1.4)
35 (13) 3.9 (2.0) nda
19 (9.2) 4.7 (6.1) 1.9 (2.6)
77 (13) 12 (3.0) 7.7 (8.9)
170 (16) 16 (4.4) 9.3 (4.3)
18 (1.7) 1.0 (0.9) 0.6 (0.3)
24 (2.6) 1.9 (0.4) nda
nd: not detected.
1506
P. Antunes, O. Gil / Chemosphere 54 (2004) 1503–1507
Ria
Muscle
Farming 1
Farming 2
% total PCB
25 20 15 10 5 0 Liver
% total PCB
25 20 15 10 5 0 Diet pellets
% total PCB
25 20 15 10 5 194
170
180
128
183
187
138
105
153
118
149
151
101
44
49
52
26
18
0 Congener Fig. 1. PCB congener patterns in sea bass collected in Ria de Aveiro and in two fish farms and in diet pellets.
Table 3 Correlation coefficients (r2 ) of relative proportions of PCB congeners (n ¼ 18) in pellet diet with those in muscle and liver of sea bass from fish farms Muscle Liver
Farm 1/diet 1
Farm 2/diet 2
0.98 0.95
0.97 0.96
Acknowledgements We thank to M. Sobral for collecting fish samples. This work was co-financed through ‘‘EICOS’’ project (PRAXIS XXI 2.2.2.MAR/1750/95).
References Bayarri, S., Baldassarri, L.T., Iacovella, N., Ferrara, F., di Domenico, A., 2001. PCDDs, PCDFs, PCBs and DDE in edible marine species from the Adriatic Sea. Chemosphere 43, 601–610.
Bentzen, E.D., Lean, R.S., Taylor, W.D., Mackay, D., 1996. Role of food web structure on lipid and bioaccumulation of organic contaminants by lake trout (Salvelinus namaycush). Can. J. Fish. Aquat. Sci. 53, 2398–2407. de Boer, J., Pieters, H., 1991. Dietary accumulation of polychlorinated biphenyls, chlorinated pesticides and mercury by cultivated eels, Anguilla anguilla L. Aquacult. Fish. Manag. 22, 329–334. Herbert, C.E., Keenleyside, K.A., 1995. To normalize or not to normalize? Fat is the question. Environ. Toxicol. Chem. 14, 801–807. Kucklick, J.R., Backer, J.E., 1998. Organochlorines in Lake Superior’s food web. Environ. Sci. Technol. 32, 1192–1198. Loizeau, V., Abarnou, A., Cugier, P., Jaouen-Madoulet, A., Le Guellec, A.-M., Menesguen, A., 2001a. A model of PCB bioaccumulation in the sea bass food web from the Seine Estuary (eastern English Channel). Mar. Pollut. Bull. 43, 242–255. Loizeau, V., Abarnou, A., Menesguen, A., 2001b. A steadystate model of PCB bioaccumulation in the sea bass (Dicentrarchus labrax) food web from the Seine Estuary, France. Estuaries 24, 1074–1087. Norstrom, R., 2002. Chemical, biological, ecological and environmental properties fundamental to understanding bioaccumulation of POPs in food webs. Organohalogen Compd. 55, 5–10.
P. Antunes, O. Gil / Chemosphere 54 (2004) 1503–1507 Pastor, D., Boix, J., Fernandez, V., Albaiges, J., 1996. Bioaccumulation of organochlorinated contaminants in three estuarine fish species (Mullus barbatus, Mugil cephalus and Dicentrarchus labrax). Mar. Pollut. Bull. 32, 257– 262.
1507
Thomann, R.V., Connolly, J.P., 1984. Model of PCB in the Lake Michigan lake trout food chain. Environ. Sci. Technol. 18, 65–71. Zar, J.H., 1996. Biostatistical Analysis, 3rd ed. Prince-Hall Int. Inc., London.
PCB and DDT contamination in cultivated and wild sea bass from Ria de Aveiro, Portugal q Paulo Antunes, Odete Gil
*
INIAP/IPIMAR, Av. de Brasılia, 1449-006 Lisboa, Portugal Received 25 November 2002; received in revised form 28 July 2003; accepted 21 August 2003
Abstract Polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) and metabolites were quantified in muscle and liver of sea bass (Dicentrarchus labrax) collected in Ria de Aveiro and in two fish farms. Sea bass from natural environment showed lower levels than fish from farming, which may be partly attributed to the higher lipid content of cultivated fish. PCB congener distribution in tissues of sea bass from the two farms resembled that of diet pellets suggesting that commercial diet is a major source of PCBs. However, fish in the two sites were fed with diet of similar PCB and DDT contamination but showed distinct levels in its tissues not explained by lipid content. 2003 Elsevier Ltd. All rights reserved. Keywords: Organochlorines; Dicentrarchus labrax; Wild fish; Fish farming
1. Introduction PCBs and DDTs are known to occur in aquatic systems and fish accumulate these substances either directly from the surrounding environment or from their diet. Some studies have shown that food is the major contributor for PCB bioaccumulation (Thomann and Connolly, 1984; Loizeau et al., 2001a,b). Therefore, the use of commercial diets, in fish farming and its levels of micro-contaminants, may influence pollutant concentration in cultivated fish (de Boer and Pieters, 1991). Besides the artificial diet, in these systems of culture, fish also consumes natural preys produced in the ponds, which also contributes to the contamination burden. The characteristics of organochlorine compounds and
of the aquatic environment as well as the lipid content influence also the bioaccumulation (Herbert and Keenleyside, 1995; Bentzen et al., 1996; Pastor et al., 1996). Ria de Aveiro is a coastal lagoon, located in the northern of Portugal that receives inputs from agriculture, urban and industrial activities where fish farming has been significantly developed. In this study the concentration of eighteen PCB congeners and of DDT compounds were compared in muscle and liver of wild and cultivated sea bass (Dicentrarchus labrax, Linnaeus, 1758) and the importance of diet as source of contamination was evaluated.
2. Materials and methods q
Paper presented in Dioxin 2002––22nd International Symposium on Halogenated Environmental Organic Pollutants and POPs, August 11–16, Barcelona, Spain. * Corresponding author. Fax: +351-213-011-5948. E-mail address: [email protected] (O. Gil).
2.1. Sampling Sea bass samples were collected in 1998 in Ria de Aveiro and in January 1999 in two farms located at the sampling area. These production systems are
0045-6535/$ - see front matter 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2003.08.029
1504
P. Antunes, O. Gil / Chemosphere 54 (2004) 1503–1507
semi-intensive and based on water supply controlled by the tides. After measuring both length and weight, 10 individuals of similar length were selected from each site. The muscle and liver of individual fish as well as the commercial feed pellets sub-samples supplied to fish farming were taken for chemical analysis. 2.2. Materials Solvents––Acetone and n-hexane distilled in the laboratory. Dichloromethane (Merck). Sodium sulphate–– Anhydrous (Merck), heated at 440 C overnight. Florisil––60–100 mesh (Merck), activated at 440 C overnight, and partially deactivated with 1% distilled water. Standards––PCB congeners were obtained, as crystals, from Promochem, Germany (99% of purity), and p,p0 -DDT, p,p0 -DDD, p,p0 -DDE from Supelco (99.2%, 98.5%, 99.5% of purity, respectively).
m · 0.25 mm i.d., 0.25 lm film thickness) and operating at an electron impact energy of 70 eV. The column was held at 60 C for 1 min, then programmed at 20 C min1 to 210 C (8 min); at 2 C min1 to 250 C (5 min). Compounds were determined by selected ion monitoring (SIM) at m=z 256, 290, 324, 358, 392, 426, and 318 for tri-, tetra-, penta-, hexa-, hepta-, octachlorobiphenyl and p,p0 -DDE, respectively. Extraction efficiency was tested by re-extracting the sample with fresh solvents. Concentrations of the second extraction were less than 10% of the value determined previously. The recovery of the Florisil column was evaluated with a standard solution and more than 85% of each compound was obtained. Procedural blanks were also analysed in each batch of 10–16 samples. One way analysis of variance was used to compare concentrations (Zar, 1996). A 5% significance level was used for the statistical tests.
2.3. Chemical analyses 3. Results and discussion PCBs and DDTs were extracted from freeze-dried tissues and from diet pellets with hexane using Soxhlet apparatus for 6 h. Fat content was determined gravimetrically from aliquots of the extracts. The remaining extracts were concentrated and passed through a 2.5 g Florisil-packed glass column for separation of the compounds. The first fraction eluted with n-hexane contained PCBs and p,p0 -DDE, the second fraction eluted with dichloromethane:hexane (30:70) contained p,p0 -DDD and p,p0 -DDT. The extracts were subjected to a further clean up with sulphuric acid. After concentration, each sample was injected into a Hewlett-Packard 5890 series II gas chromatograph equipped with an electron capture detector. A DB-5 (J&W Scientific, Folsom, CA) capillary column (60 m · 0.25 mm i.d., 0.25 lm film thickness) was used. The column was held at 60 C for 1 min, then programmed in three levels: at a rate of 20 C min1 to 210 C (8 min); 2 C min1 to 250 C (17 min) and 4 C min1 to a final temperature of 260 C (15 min). The injector temperature was kept at 270 C and the detector was maintained at 320 C. Helium and argonmethane were used as the carrier and the make up gases, respectively. Concentrations of CBs and DDT compounds were quantified from the peak heights using a six-point multilevel calibration curve. A mixture of 18 individual CBs (IUPAC Nos. 18, 26 tri-, 52, 49, 44 tetra-, 101, 118, 105 penta-, 151, 149, 153, 138, 128 hexa-, 187, 183, 180, 170 hepta-, 194 octachlorobiphenyl), p,p0 -DDE, p,p0 -DDD and p,p0 -DDT was used as external standard for quantification. Compounds analysed by GC–ECD were confirmed in some samples with high levels by GC–MS using a Finningan Mat GCQ instrument, equipped with a DB5MS (J&W Scientific, Folsom, CA) capillary column (30
3.1. Organochlorine concentrations The concentrations of total PCB (calculated as the sum of individual CBs) and total DDT (calculated as the sum of concentrations of p,p0 -DDE, p,p0 -DDD and p,p0 DDT) in muscle and liver of sea bass collected in Ria de Aveiro and in two farms are presented in Table 1. The results show that the concentrations of total PCB in tissues of sea bass from Ria was more than the double of total DDT. However, sea bass from farming showed similar levels of these contaminants (Student test, p < 0:05). The muscle concentrations (Table 1) obtained in our study (155 ± 49 to 294 ± 104 ng g1 lipid for total PCB and 108 ± 43 to 336 ± 132 ng g1 lipid for total DDT), were lower than those reported by Pastor et al. (1996), respectively, 800 ± 50 and 513 ± 97 ng g1 lipid, for sea bass from the Ebro Delta, in western Mediterranean. Table 1 also shows that total PCB and total DDT concentrations on a dry weight basis were lower in wild sea bass (13 and 5.4 ng g1 in muscle; 65 and 26 ng g1 in liver) than in fish from farming, presenting the farming 2 generally the highest values (36 and 39 ng g1 in muscle; 179 and 194 ng g1 in liver). Lipid content of an organism may influence its organochlorine concentrations (Herbert and Keenleyside, 1995; Pastor et al., 1996; Bayarri et al., 2001). The observed differences in concentrations may be attributed partly to higher lipid content in fish from farms 1 and 2 (17%, 66% and 12%, 44%, respectively, in muscle and liver) than those from Ria (5%, 26%). Normalization of concentrations to lipid content reduced, in general, the variability between Ria and farms, but not that between the two fish farms. In fact, tissues of sea bass from farm 2 showed lower lipid content and higher dry weight total PCB and total DDT
P. Antunes, O. Gil / Chemosphere 54 (2004) 1503–1507
1505
Table 1 Mean concentrations of total PCB and total DDT (ng g1 ) ± SD, in muscle and liver of sea bass from Ria de Aveiro and from farms 1 and 2 Concentration (ng g1 dry weight)
Concentration (ng g1 lipid)
Total PCB
Total DDT
Total PCB
Total DDT
Muscle Ria Farming 1 Farming 2
13 ± 2.5a 26 ± 9.5b 36 ± 13b
5.4 ± 2.3a 22 ± 7.0b 39 ± 13c
275 ± 84b 155 ± 49a 294 ± 104b
108 ± 43a 125 ± 22a 336 ± 132b
Liver Ria Farming 1 Farming 2
65 ± 32c 106 ± 33d 179 ± 22e
26 ± 13c 88 ± 14d 194 ± 22e
329 ± 231c 159 ± 30d 405 ± 62d
121 ± 67c 135 ± 17c 449 ± 67d
Different letters represent significant differences (p < 0:05) between Ria and farms, according to ANOVA followed by Scheffe test.
concentrations than tissues of fish from farm 1. So, the lipid content does not explain the difference in dry weight concentrations of fish from these two sites. This cannot also be attributed to a different contamination of the diet pellets, because the fish were fed with diet of similar total PCB (26 and 25 ng g1 dw, respectively, for farming 1 and 2) and total DDT (19 and 26 ng g1 dw) levels. The natural preys carried by the water and also produced inside the earth ponds are, however, an important component of the diet. The observed variability in levels between the two fish farms may be related to differences in contamination of the natural component of the diet and to other factors such as differences in physiological condition of the individuals (Loizeau et al., 2001a,b; Norstrom, 2002). 3.2. Composition From the DDT compounds, DDE was present in the highest concentration in tissues of all the analysed organisms and in pellet diet (Table 2), representing more than 79% of total DDT. The relative distribution of PCB congeners may differ in aquatic organisms because the contamination sources have different congener patterns. The patterns of PCBs would become enriched in more hydrophobic congeners
in predators relative to their prey as a result of digestive fractionation (Kucklick and Backer, 1998). In our study PCB patterns, determined as the concentration ratios between individual congener and total PCB, did not vary among wild and cultivated sea bass. The pattern of PCBs in muscle and liver of all individuals was very similar and CBs 153 and 138 (hexachlorobiphenyls) were the dominant congeners (Fig. 1). This congeners are usually reported as dominant in marine fishes (Bayarri et al., 2001; Loizeau et al., 2001a,b). The overall PCB congener distribution in tissues of sea bass from farms resembled that of diet pellets (Fig. 1) being the relative proportions of individual chlorobiphenyl congeners both in fish tissues and in diet significantly correlated (Table 3). These results imply that commercial diet is a major source of PCBs and a fractionation of PCB congeners, between sea bass and diet pellets, in farms was not significant. This is in accordance with findings of Kucklick and Backer (1998) for other species and contrasts with other works of the same author that found a selective accumulation of more hydrophobic PCB congeners in food chain transfer. In cultivated sea bass the relative proportions of PCB congeners were similar to those in its diet pellets, which may indicate that assimilation efficiency may not systematically vary with the hydrophobicity.
Table 2 Mean concentrations (SD) of DDT compounds (ng g1 dry weight) in muscle and liver of sea bass and in diet pellets Sea bass
Diet pellets
Muscle DDE DDD DDT a
Liver
Ria
Farming 1
Farming 2
Ria
Farming 1
Farming 2
Farming 1
Farming 2
4.8 (2.4) 0.4 (0.2) 1.7 (0.9)
19 (6.4) 2.8 (1.0) 1.1 (1.4)
35 (13) 3.9 (2.0) nda
19 (9.2) 4.7 (6.1) 1.9 (2.6)
77 (13) 12 (3.0) 7.7 (8.9)
170 (16) 16 (4.4) 9.3 (4.3)
18 (1.7) 1.0 (0.9) 0.6 (0.3)
24 (2.6) 1.9 (0.4) nda
nd: not detected.
1506
P. Antunes, O. Gil / Chemosphere 54 (2004) 1503–1507
Ria
Muscle
Farming 1
Farming 2
% total PCB
25 20 15 10 5 0 Liver
% total PCB
25 20 15 10 5 0 Diet pellets
% total PCB
25 20 15 10 5 194
170
180
128
183
187
138
105
153
118
149
151
101
44
49
52
26
18
0 Congener Fig. 1. PCB congener patterns in sea bass collected in Ria de Aveiro and in two fish farms and in diet pellets.
Table 3 Correlation coefficients (r2 ) of relative proportions of PCB congeners (n ¼ 18) in pellet diet with those in muscle and liver of sea bass from fish farms Muscle Liver
Farm 1/diet 1
Farm 2/diet 2
0.98 0.95
0.97 0.96
Acknowledgements We thank to M. Sobral for collecting fish samples. This work was co-financed through ‘‘EICOS’’ project (PRAXIS XXI 2.2.2.MAR/1750/95).
References Bayarri, S., Baldassarri, L.T., Iacovella, N., Ferrara, F., di Domenico, A., 2001. PCDDs, PCDFs, PCBs and DDE in edible marine species from the Adriatic Sea. Chemosphere 43, 601–610.
Bentzen, E.D., Lean, R.S., Taylor, W.D., Mackay, D., 1996. Role of food web structure on lipid and bioaccumulation of organic contaminants by lake trout (Salvelinus namaycush). Can. J. Fish. Aquat. Sci. 53, 2398–2407. de Boer, J., Pieters, H., 1991. Dietary accumulation of polychlorinated biphenyls, chlorinated pesticides and mercury by cultivated eels, Anguilla anguilla L. Aquacult. Fish. Manag. 22, 329–334. Herbert, C.E., Keenleyside, K.A., 1995. To normalize or not to normalize? Fat is the question. Environ. Toxicol. Chem. 14, 801–807. Kucklick, J.R., Backer, J.E., 1998. Organochlorines in Lake Superior’s food web. Environ. Sci. Technol. 32, 1192–1198. Loizeau, V., Abarnou, A., Cugier, P., Jaouen-Madoulet, A., Le Guellec, A.-M., Menesguen, A., 2001a. A model of PCB bioaccumulation in the sea bass food web from the Seine Estuary (eastern English Channel). Mar. Pollut. Bull. 43, 242–255. Loizeau, V., Abarnou, A., Menesguen, A., 2001b. A steadystate model of PCB bioaccumulation in the sea bass (Dicentrarchus labrax) food web from the Seine Estuary, France. Estuaries 24, 1074–1087. Norstrom, R., 2002. Chemical, biological, ecological and environmental properties fundamental to understanding bioaccumulation of POPs in food webs. Organohalogen Compd. 55, 5–10.
P. Antunes, O. Gil / Chemosphere 54 (2004) 1503–1507 Pastor, D., Boix, J., Fernandez, V., Albaiges, J., 1996. Bioaccumulation of organochlorinated contaminants in three estuarine fish species (Mullus barbatus, Mugil cephalus and Dicentrarchus labrax). Mar. Pollut. Bull. 32, 257– 262.
1507
Thomann, R.V., Connolly, J.P., 1984. Model of PCB in the Lake Michigan lake trout food chain. Environ. Sci. Technol. 18, 65–71. Zar, J.H., 1996. Biostatistical Analysis, 3rd ed. Prince-Hall Int. Inc., London.