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Trace element levels in some commercially valuable fish species from coastal waters of Mediterranean Sea, Egypt
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Journal of Marine Systems 73 (2008) 114 – 122 www.elsevier.com/locate/jmarsys
Trace element levels in some commercially valuable fish species from coastal waters of Mediterranean Sea, Egypt Maha Ahmed Mohamed Abdallah National Institute of Oceanography and Fisheries, Kayet Bey, Alexandria, Egypt Received 18 December 2006; received in revised form 9 September 2007; accepted 12 September 2007 Available online 12 October 2007
Abstract Concentrations of 5 trace elements (Cd, Pb, Cu, Cr, Zn) were determined in muscle of fishes collected from two coastal areas of the Egyptian coast of the Mediterranean Sea west of Alexandria (El-Mex Bay and Eastern Harbour). Sardinella aurita, Alepes djedaba, Siganus luridus, Siganus rivulatus, Sphyraena chrysotoenia, and Scomberomorus commerson were collected from ElMex Bay. While Boops boops, Lithognathus mormyrus, Sparisoma cretense, Serranus cabrilla and Synodus saurus were collected from the E.H. In all fishes zinc was highest (up to 57 mg/kg) followed by Cr, Cu, Pb and Cd. The concentrations of several metals in fishes were significantly different among the species in each area. For all trace element examined, the concentrations decreased significantly with body weight of some fishes. In contrast, a positive correlation with body weight was found especially for Zn and Cu concentrations in 5 fish species and for Pb in 4 fish species. The concentrations of Cd, Pb and Zn were higher in fishes from El-Mex Bay (3.76, 6.49 and 57.21 mg/kg) than those from Eastern Harbour, whereas the opposite trend was observed for Cu and Cr, revealing the direct sources of trace metal pollution present in El-Mex coastal area. Levels of Cr surpassed the Maximum Permissible Concentration in most fish tissues, followed by Pb and Cd in some species. Cu and Zn presented concentrations below the maximum permissible levels in fish tissues. © 2007 Elsevier B.V. All rights reserved. Keywords: Trace elements; Fish; Growth-variation; MPC; El-Mex Bay; Eastern Harbour
1. Introduction Accumulation of trace elements in aquatic organisms is one of the most striking effects of pollution in aquatic system. Some trace metals are necessary in small amounts for individual metabolic processes, being assimilated by marine organisms. However, their capacity to form complexes with organic substances can result in concentrations up to 1000 times higher than their assimilation and fixation in tissues, becoming toxic to organisms (CETESB, 1982). The northwest coast of Egypt has been subjected to high inputs of anthropogenic E-mail address: [email protected]. 0924-7963/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jmarsys.2007.09.006
contamination over the past decades, mainly contributed by Alexandria City. El-Mex Bay and the Eastern Harbour (E.H.) are two parts of Alexandria coast on the Mediterranean Sea, they consider as the two main fishing sources in the City and its adjacent areas. As a semi-enclosed environment (E.H.), various pollutants have accumulated in the E.H due to effluents from coastal catchment's areas and several land-based sources. Levels of trace elements in water of huge drain (6 × 106 m3/day) called Omoum Drain (El-Rayis and Abdallah, 2006), have increased over the past 15 years (El-Rayis et al., 1997; Abouldahab et al., 1990). Furthermore, elevated concentrations of some trace elements have been reported in sediments (El-Sabarouti
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et al., 1997; Abdel-Moati, 2001). Since sediments act as sinks for contaminants, which can persist in the aquatic environment for decades, changes in sediment in fauna activity and water chemistry allow these persistent contaminants to enter food chain, and thus into fish tissues (Kirby et al., 2001a,b). Many studies have been conducted on the human health effects of metals due to consumption of contaminated fish flesh (Chan et al., 2003; Alquezar et al., 2006). However only a few studies have been conducted to reveal the status of trace element contamination in bony fishes from El-Mex Bay and Eastern Harbour (El-Rayis et al., 1997). The two sample sites chosen for this study, El-Mex Bay and the Eastern Harbour (E.H.), all fishing areas in Alexandria City, are shown in Fig. 1. They were selected on the basis of potentially different pollution input levels. El-Mex Bay is considered to be a site of high industrial point source pollution associated with the activities of a chloroalkali plant, tanneries, petroleum refining and also an iron and steel factory. In addition, this Bay is an estuarine zone, it receives primary agricultural runoff by rate of 2547.7 × 106 m3/year from huge drain called Omoum Drain (El-Rayis and Abdallah, 2006). The downstream part of this drain receives considerable amounts of Alexandria domestic and industrial wastes prior to discharging to the Bay. The E.H. is a relatively shallow semi-enclosed basin, sheltered from the Mediterranean Sea by an artificial breakwater leaving two openings. The Harbour has been
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subject to high levels of pollution due to municipal waste disposal in addition, it is also affected by the waste products and (fuel) spills resulted from the ships anchored at its western side. El-Mex Bay and E.H. represent an area with complex urban, agricultural and industrial influences including industrial and urban storm water runoffs, treated sewage effluents associated with shipping, docking and manufacturing. The present study seeks to evaluate the present levels of 5 trace elements (Cd, Pb, Cu, Cr, Zn) in the edible parts (muscles and fillet) of 11 commercially used fish species from two polluted Bays, which is situated on the southeast Mediterranean Sea coast of Egypt, discusses the species and growth related variation of trace element levels and also establish comparisons with the Maximum Permissible Concentration standard. 2. Materials and methods 2.1. Samples Fish samples were collected along two coastal areas of El-Mex Bay and E.H. in 2005 and 2006 (Fig. 1). Round Sardinella (Sardinella aurita, n = 22), Shrimp Scad (Alepes djedaba, n = 10), Dusky Spinefoot (Siganus luridus, n = 9), Marbled Spinefoot (Siganus rivulatus, n = 10), Obtuse Barracuda (Sphyraena chrysotoenia, n = 10) and Spanish Mackerel (Scomberomorus
Fig. 1. The study area of El-Mex Bay and Eastern Harbour.
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variance (ANOVA) and Duncan's test (p = 0.05) were used to access whether trace elements concentrations varied significantly. All statistical calculations were performed with SPSS 9.0 for windows. Dependence of trace elements concentration on body weight was examined using Spearman rank correlation test. A p value of less than 0.05 was considered to indicate statistical significance.
commerson, n = 8) were caught from El-Mex Bay. Bogue (Boops boops, n = 13), Striped Seabream (Lithognathus mormyrus, n = 10), European Parrotfish (Sparisoma cretense, n = 8), Comber (Serranus cabrilla, n = 15) and Atlantic Lizardfish (Synodus saurus, n = 10) were caught from the E.H. Body weight and length of fishes were measured prior to dissection (Table 1). Muscle samples taken and stored at − 20 °C until chemical analysis.
3. Results and discussion 2.2. Chemical analysis 3.1. Species dependent variations of trace elements levels in fishes from Alexandria coastal areas
The procedure used for measuring concentrations of trace elements has been described previously (Anan et al., 2001). Tissue samples were dried for 12 h at 80 °C and then weighed and digested in a microwave oven using nitric acid in a Teflon PTFE tube. Concentrations of five trace elements (Cd, Pb, Cu, Cr and Zn) were measured using AAS (Varian Spectra 220 Fast Spectrometry). Results were expressed as milligram of element per dry weight kilogram of fish. The Maximum Permissible Concentrations (MPC) were established by FAO (1983). Accuracy of this analysis was examined using standard reference materials SRM Dorm-2 (National Research Council Canada). Recoveries of all the elements ranged from 93% to 109%. In the present study, concentrations are expressed on a dry weight basis. Moisture content of the muscle samples was 71.5 ± 2.3%. In order to compare our data to published values reported on a wet weight basis, we have converted the latter to dry weight basis using a conversion factor 3.51 (including FAO and MPCs).
Concentrations of five elements in the muscle of fishes from El-Mex Bay and Eastern Harbour (E.H) are shown in (Table 2). Zinc was highest in muscle of all species analyzed in this study, followed by Cr, Cu, Pb and Cd. The concentrations of several metals in fishes were significantly different among the species in each area. Concentrations of Cd, Pb and Zn were higher in muscle of S. rivulatus and S. aurita than in the rest species from El-Mex Bay (p b 0.01). In contrast, concentrations of Cr and Cu (p b 0.01) were higher in muscle of S. luridus than in the other species from the same Bay. Among the five species collected from the E.H, the levels were different between species for all the elements. The highest concentration of Cd, Pb and Cu were found in S. saurus and S. cabrilla (p b 0.05), while the highest concentrations of Cr and Zn were found in B. boops species. In contrast, Cr was below the detection limit in three species (L. mormyrus, S. cretense and S. saurus). Trace element levels are known to vary in fishes depending on various factors such as its habitat, feeding behavior and migration even in the same area (Andres et al., 2000; Canli and Atli, 2003). The ecological
2.3. Statistical analysis Non-parametric tests were used for statistical analysis to improve normality (because some of the variables were not normally distributed). One way analysis of
Table 1 Biometric data (mean ± S.D. and range) of fishes from El-Mex Bay and Eastern Harbour Location
Species
n
Body weight (g)
Body length (cm)
El-Mex Bay
Sardinella aurita Alepes djedaba Siganus rivulatus Siganus luridus Sphyraena chrysotoenia Scomberomorus commerson Boops boops Lithognathus mormyrus Sparisoma cretense Serranus cabrilla Synodus saurus
22 10 10 9 10 8 13 10 14 15 10
15.3 ± 1.7 (12.7–17.9) 34.7 ± 1.2 (33.5–36.8) 44.6 ± 9.9 (30.6–53.7) 40.7 ± 0.99 (39.2–41.2) 41.1 ± 4.9 (36.1–47.3) 106.9 ± 11.8 (93.6–115.9) 32.3 ± 1.2 (31.2–34.1) 57.7 ± 1.4 (57.8–60.5) 73.7 ± 14.7 (54.4–85.8) 50.8 ± 10.6 (35.1–66.3) 84.4 ± 16.6 (64.2–114.5)
9.1 ± 1.4 14.9 ± 1.7 13.5 ± 3.1 11.3 ± 1.3 13.6 ± 1.0 28.2 ± 5.8 15.2 ± 1.8 14.8 ± 1.4 21.4 ± 4.6 15.9 ± 3.4 20.8 ± 6.6
Eastern Harbour
(7.2–11.5) (13–16.2) (9.5–12.5) (12–14.5) (12–15.2) (25.3–30.8) (13.4–17.0) (13.0–16.4) (18.5–24.4) (14.1–17.4) (18.4–22)
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Table 2 Concentrations (range and average ± S.D. on mg/kg dry weight) of trace elements in muscle of fishes from coastal waters of El-Mex Bay and Eastern Harbour Area
Species
n
Cd
Pb
Cu
Cr
Zn
El-Mex
Sardinella aurita
22 10
2.46–4.93 4.0 ± 1.4 b0.003
Siganus luridus
9
Siganus rivulatus
10
Sphyraena chrysotoenia
10
Scomberomorus commerson
8
Boops boops
13
2.72–6.49 4.7 ± 1.9 1.4–3.2 2.1 ± 0.9 1.09–1.69 1.33 ± 0.32 0.96–1.30 1.2 ± 0.2 0.94–2.04 1.5 ± 0.6 0.98–2.52 1.9 ± 0.8 b0.02
b0.005
Alepes djedaba
0.16–1.49 1.2 ± 0.8 b0.0006
Lithognathus mormyrus
10
Sparisoma cretense
8
Serranus cabrilla
15
Synodus saurus
10
28.1–54.4 42.0 ± 10.9 13.3–31.1 20.4 ± 9.4 4.4–15.2 10.4 ± 5.5 30.0–57.2 43.9 ± 13.6 19.7–28.3 22.9 ± 4.7 17.7–31.0 22.4 ± 7.5 12.6–29.5 19.3 ± 8.9 15.9–19.9 17.8 ± 2.0 3.9–14.1 7.4 ± 4.7 8.6–17.1 14.1 ± 4.8 9.9–22.2 16.7 ± 6.2
E.H.
b0.002–0.42 0.3 ± 0.2 2.23–3.76 2.8 ± 0.8 1.87–2.93 2.34 ± 0.54 b0.0006–0.19 0.14 ± 0.1 b0.0006 1.37–1.57 1.50 ± 0.11 0.09–0.93 0.6 ± 0.4 b0.0006 0.44–2.65 1.9 ± 0.3
characteristics of eleven fish species analyzed in the two studied areas, El-Mex Bay and E.H are shown in (Table 3). The studied fishes could be grouped, according to their feeding habits, into three groups. The first one is filter feeders on phytoplankton (including S. aurita and B. boops) the second group is carnivores on macrofauna (including A. djedaba, S. chrysotoenia, S. commerson and L. mormyrus), while S. cabrilla and S. saurus are classified as carnivores on fish and crustacea. The third group is deposit feeders on detritus and organic materials (including S. luridus, S. rivulatus and S. cretense). These species-specific characteristics
1.66–1.78 1.72 ± 0.06 0.88–1.76 1.2 ± 0.5 0.92–3.27 2.1 ± 1.2 0.90–2.53 1.4 ± 0.9
4.12–8.25 5.9 ± 2.1 1.35–4.56 2.7 ± 1.7 1.98–3.24 2.8 ± 0.7 b0.003 3.36–7.87 5.2 ± 2.4 1.63–3.08 2.28 ± 0.74 b0.003–0.48 0.4 ± 0.1 7.49–9.69 8.3 ± 1.2 2.49–5.73 4.0 ± 1.6
3.6–8.4 4.5 ± 2.6 3.7–14.4 8.4 ± 5.5 b0.005 b0.005 5.9–6.9 6.4 ± 0.5 13.1–30.6 20.1 ± 9.3 b0.005 b0.005 7.1–20.4 12.2 ± 7.2 b0.005
may result in the variation of trace element accumulation between the species from the two areas. Growth-dependent variations were found in concentrations of several trace elements in muscle of fishes from El-Mex Bay and E.H. Since significant correlations between body weight and length were found in most fish species (p b 0.01), only relationships between body weight and trace element concentrations are reported here. Representative relationships are shown in Fig. 2. Significant negative correlations with body weight were found for Zn (0.01) concentrations in A. djedaba and S. rivulatus, and for Cu (0.05) in S. aurita, S. chrysotoenia
Table 3 Fish species examined and their ecological characteristics English name
Scientific name
Feeding habits
Biotope complex
Round Sardinella Shrimp Scad
Sardinella aurita Alepes djedaba
Filter feeders on phytoplankton and zooplankton Carnivores on macrofauna and zooplankton
Dusky Spinefoot Marbled Spinefoot Obtuse Barracuda Spanish Mackerel Bogue Striped Seabream European Parrotfish Comber Atlantic lizardfish
Siganus luridus Siganus rivulatus Sphyraena chrysotoenia Scomberomorus commerson Boops boops Lithognathus mormyrus Sparisoma cretense Serranus cabrilla Synodus saurus
Deposit feeders on detritus and organic materials Deposit feeders on detritus and organic materials Carnivores on macrofauna Carnivores on macrofauna Filter feeder on selective plankton Carnivores on macrofauna and zoobenthose Deposit feeders on detritus and organic materials Carnivores on macrofauna, zoobenthose, cephalopods and fish Carnivores on fish and crustacean
Pelagic (water column) Rock associate (schools near shore, reef) Rock associate (reef) Rock associate (reef) Pelagic (water column) Pelagic and rock associate Demersal and pelagic Seagrass bed Rock associate (reef) Pelagic (water column) Demersal and pelagic
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Fig. 2. Growth-dependent variation of trace element concentrations in the muscle of fishes from El-Mex Bay and E.H.
and L. mormyrus, for Cd (0.01) in S. luridus, S. rivulatus, S. chrysotoenia and S. commerson, for Pb (0.01) in A. djedaba and S. commerson and for Cr (0.05) in A. djedaba and S. luridus. Until now, growth (body weight, length and age) dependent decrease in trace elements level has been reported for many fish species (Anan et al., 2005). Honda et al. (1983) found that the concentrations of Cu, Cd and Pb in muscle decreased with an increase in body weight in Antarctic fish Pagothenia borchgrevinki. Generally, the growth-dependent variations of trace element levels are known to be influenced by various factors such as metabolic rate, and growth dilution of elements (Langston and Spencer 1995). In contrast, positive significant correlations with body weight were found in El-Mex Bay for Zn (0.05) in S. chrysotoenia, Cu (0.05) in S. luridus and S. rivulatus, Pb (0.05) in S. aurita and S. chrysotoenia, for Cr (0.05) in S. commerson.
Similarly in E.H. area, positive correlation with body weight were found for Zn (0.05) L. mormyrus, S. saurus and S. cretense, Cu (0.05) in S. saurus, Cd (0.05) in S. cretense and S. saurus, Pb (0.05) in L. mormyrus and S. cabrilla and Cr (0.05) in S. cabrilla. 3.2. Accumulated trace elements and Maximum Permissible Concentration (MPC) 3.2.1. Cadmium Cadmium concentrations (Fig. 3) were below MPC, except for muscles of S. rivulatus and S. chrysotoenia in El-Mex Bay and S. saurus in the E.H. As humans commonly consume muscles (edible parts) Cd toxicity via fish ingestion is unlikely. However, Cd is not an essential element, it is difficult to excrete once ingested, it presents high toxicity, and in both El-Mex Bay and E.H it is very widespread (concentration in sediments
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Fig. 3. Concentrations of Cd, Pb, Cu, Cr and Zn in fish muscles from El-Mex Bay and Eastern Harbour, MPC, Maximum Permissible Concentration.
were 8.09 and 3.8 μg/g respectively, Abdallah (2007) and Abdallah and Abdallah, 2007). 3.2.2. Lead Concentrations of Pb (Fig. 3) exceeding MPC were found in S. aurita, A. djedaba and S. commerson from El-Mex Bay, and S. cabrilla from E.H. The other species had concentrations below MPC, Pb does not present beneficial or nutritional effects to organisms and is extremely toxic (CETESB, 1982). Overall it occurs in very low concentrations in the biota, even when there are high concentrations in the abiotic environment (De
Souza Lima Jr. et al., 2002). This metal is used in several industrial processes and is a common residue from gasoline combustion (Evangelista, 1984). It ranks as the metal of largest diffusion through the atmosphere (SEMA, 1998). 3.2.3. Copper Overall Cu levels (Fig. 3) were below the MPC for human consumption in all studied fish tissues. This metal accumulates by several means, depending on environmental conditions and habits of species (Saward et al., 1975; Rosenthal and Alderdice, 1976).
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Copper is essential for animals and plants, as it takes part in enzyme formation and participates in respiratory processes, with accumulation levels varying widely among aquatic organisms. Variations in Cu concentration are related to levels of tolerance and toxicity symptom outbreaks, depending on species and period of passive accumulation (CETESB, 1984). 3.2.4. Chromium Concentrations of Cr (Fig. 3) exceeded MPC in most fish species tissues studied, for both bays. This metal is used in the leather industry, in inks and in processing of steel, among other uses (Evangelista, 1994). In El-Mex Bay there are several of those types of industries (Abdallah, 2007). 3.2.5. Zinc Concentrations of Zn (Fig. 3) were below the MPC for human consumption in all studied fish muscles. Most of the samples with slightly high Zn concentrations were from El-Mex Bay. The present work agrees with CETESB (1982), that the highest Zn concentrations occurred in S. rivulatus, which associated with substrate. While S. aurita, species less related to substrate than the others, had also high Zn concentrations, it could be due to the filter feeder habits of this fish (feeds upon plankton organisms, mainly diatoms and copepods). Phytoplankton is the most likely biota compartment for Zn and Cu concentration (EPA, 1972), along with sediments, due to great capacity of Zn and Cu for precipitation. Therefore, this may interpret the high concentrations of Zn being found in S. aurita. 3.3. Comparison of trace element levels in El-Mex Bay and Eastern Harbour fishes with those in other regions Levels of trace elements in muscle of fishes from ElMex Bay and E.H were compared with those reported
for fishes in other regions (Table 4). In general, the concentrations of all trace elements in muscle of El-Mex Bay and E.H fishes were higher than the values reported for fishes around the world (Tamira et al., 2001; Anan et al., 2005; Dalman et al., 2006; Türkman et al., 2005; Topcuoğlu et al., 2002; Canli and Atli, 2003; Kwon and Lee, 2001). Except for Cd, Pb and Zn levels that were reported by Türkman et al. (2005), Tamira et al. (2001) and Anan et al. (2005), Table 4 were higher than our findings. This is perhaps due to the trace elements levels in different species depend on feeding habits, age, size and length of fish and their habitats (Canli and Atli, 2003). On the other hand, in the present study the concentrations of Cr and Cu in muscle fishes were within the range of values reported for fishes by Tamira et al. (2001), while Pb and Zn were within the range of values reported by Türkman et al. (2005) and Topcuoğlu et al. (2002). 4. Final consideration All of the studied elements, with exception of Zn and Cu, showed values exceeding MPC in at least one fish species examined. Chromium was the element that most exceeded the permissible levels in muscle, followed by cadmium. No evident pattern of elemental incorporation was shown for certain species with regard to their position in the trophic levels. In coastal semi-enclosed bays like Eastern Harbour and El-Mex Bay, with low depth, even piscivorous fish feed on sediments when searching for invertebrates. Species feeding on plankton by filtering water also use the sediment for detritus and algae, which complement their diet (De Souza Lima Jr., et al., 2002). Therefore, in most cases both piscivorous and planktivorous species have a close relation to the substrata, the system component most likely to be contaminated by trace elements via sedimentation.
Table 4 Comparison of trace element concentrations in El-Mex Bay and E.H fishes (mg/kg dry wt) with those in other regions Sample area
Cd
Pb
Cu
Cr
Zn
References
El-Mex Bay Eastern Harbour California Lagoons Caspian Sea Southern Aegean Sea Iskenderun Bay Black Sea Coast Mediterranean Sea Masan Bay, Korea
b0.02–3.76 b0.02–2.65 0.10–0.30 0.001–0.35 b0.01–0.04 0.02–4.16 b0.02–0.24 0.37–0.79 0.01
0.94–6.49 b0.02–3.27 0.8–4.1 0.001–0.19 b0.02–0.4 0.19–6.95 b0.05–0.06 2.98–6.12 0.04–0.14
b0.02–8.25 b0.02–9.69 1.9–7.5 0.75–5.02 b0.10 0.04–5.43 1.01–4.4 2.19–4.4 0.18–0.25
b0.02–14.4 b0.02–30.6 1.9–24 0.08–1.4 – 0.07–6.46 b0.06–0.84 1.24–2.42 0.02–0.05
4.4–57.2 3.9–29.5 36–150 12–201 b0.5–7.2 0.6–11.57 25.7–44.2 16.5–37.4 6.33–12.9
Present study Present study Tamira et al. (2001) Anan et al. (2005) Dalman et al. (2006) Türkman et al. (2005) Topcuoğlu et al. (2002) Canli and Atli (2003) Kwon and Lee (2001)
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Overall, most of the study fish from El-Mex Bay presented higher trace elements than fishes from E.H. as expected. On the other hand, fish from the E.H., unexpectedly, presented high concentrations of Cd and Cr. The industrial effluents that continuously come to El-Mex Bay, additionally over fishing using bottom trawling stirs the top layers of the substrata, contributing to increased pollution in the two Bays. This is in addition to the contribution of atmospheric pollution. The results show an evident increase in contamination of El-Mex Bay by trace elements, especially toxic elements (Cd, Cr and Pb), with a risk to human population through consumption of fish. Eastern Harbour seems to be suffering the same environmental disturbances that are occurring in El-Mex Bay. Acknowledgments The author thanks Prof. Dr. Mohamed El Komi the head of Hydrobiology Division in the National Institute of Oceanography and Fisheries for his support in classification and ecological characteristics of fishes and Dr. Alla El-Haweet, Division of Fisheries for his support in the classification and identification the fishes. References Abdallah, M.A., 2007. Speciation of trace metals in coastal sediments of El-Mex Bay South Mediterranean Sea-west of Alexandria (Egypt). Environmental Monitoring and Assessment 132 (1–3), 111–123 (September 2007). Abdallah, A.M., Abdallah, M.A., 2007. Biomonitoring study of heavy metals in biota and sediments from the southern coast of the Mediterranean Sea, Egypt. Egyptian Journal of Aquatic Biology and Fisheries 11 (3), 1110–6131 (June 2007). Abdel-Moati, M.A.R., 2001. Long term impact of land-based activities on the coastal waters of Alexandria, Egypt. In: Ozhan, E. (Ed.), Proceeding of the Fifth International Conference on the Mediterranean Coastal Environment. MEDCOAST 01. Tunisia, vol. (23–27), pp. 463–474. Abouldahab, O., Khalil, A.N., Halim, Y., 1990. Chromium fluxes through Mex Bay inshore waters. Marine pollution Bulletin 21, 68–73. Alquezar, R., Markich, S.J., Booth, D.J., 2006. Metal accumulation in the smooth toadfish, Tetractenos glaber, in estuaries around Sydney. Australian Environmental Pollution 142, 123–131. Anan, Y., Kunito, T., Watanabe, I., Sakai, H., Tanabe, S., 2001. Trace element accumulation in hawksbill turtles (Eretmochelys imbricata) and green turtles (Chelonia mydas) from Yaeyama Islands, Japan. Environmental Toxicology and Chemistry 20, 2802–2814. Anan, Y., Kunito, T., Tanabe, S., Mitrofanov, I., Aubrey, G.D., 2005. Trace element accumulation in fishes collected from coastal waters of the Caspian Sea. Marine Pollution Bulletin 51, 882–888. Andres, S., Ribeyre, F., Toureneq, J.-N., Boudou, A., 2000. Interspecific comparison of cadmium and Zinc contamination in the organs of four fish species along a polymetallic pollution gradient (Lot River, France). The Science of the Total Environment 248, 11–25.
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Canli, M., Atli, G., 2003. The relationships between heavy metal (Cd, Cr, Cu, Fe, Pb, Zn) levels and the size of six Mediterranean fish species. Environmental Pollution 121, 129–136. CETESB, 1982. Bioacumulaçao de metais pesados em peixes da Baia de Santos e São Vicente, São Paulo, Brasil, Relatorio tecnico. CETESB, 1984. Niveis de contaminacao por metais pesados e pesticidas na ăgua sedimento e peixes da represa de Barra Bonita, Săo paulo, Brasil. Relatório técnico. Chan, H.M., Scheuhammer, A.M., Ferran, A., Loupelle, C., Holloway, J., Weech, S., 2003. Impacts of mercury on freshwater fish-eating wildlife and humans. Human and Ecology Risk Assessment 9, 867–883. Dalman, Ö., Demirak, A., Balci, A., 2006. Determination of heavy metals (Cd, Pb) and trace elements (Cu, Zn) in sediments and fish of the Southeastern Aegean Sea (Turkey) by atomic absorption spectrometry. Food Chemistry 95, 157–162. De Souza Lima, G.R., Araújo, G.F., Maia, F.M., de Silveira Braz Pinto, S.A., 2002. Evaluation of heavy metals in fish of the Sepetiba and Iiha Grande Bays, Rio de Janeiro, Brazil. Environ. Research. Section A 89, 171–179. El-Rayis, O.A., Abdallah, M.A., 2006. Contribution of some trace elements from an Egyptian huge drain to the Mediterranean Sea, West of Alexandria. Egypt. Mediterranean Marine Science 7 (1), 79–86. El-Rayis, O.A., Abouldahab, O., Halim, Y., Riley, J.P., 1997. Levels of trace metals in some food chain organisms from El-Mex Bay, west of Alexandria, Egypt. Proc. 7th Int. Conf. On: “Environment protection is a must” Alex. Univ. & USPD, Alexandria, 20–22 May, pp. 26–35. El-Sabarouti, M.A., Bader El-din, A.M., El-Sammak, A.A., 1997. Textural and chemical characteristics of the surface sediment in two coastal bays of Alexandria, Egypt. Proc. 6th int. Conf. Environmental Protection Is a Must. Alex. Univ & ISA, Alexandria 20–22 May 1997, pp. 118–130. EPA, 1972. Water quality criteria. Environmental Protection Agency, Washington, DC. Evangelista, S., 1984. Altmentos, um estudo abrangente. Ed. Atheneu Sao paulo Rio de janero Belo Horizonte. FAO (Food and Agricultural Organization), 1983. Compilation of legal limits for hazardous substances in fish and fishery products, FAO fishery circular, vol. 464, pp. 5–100. Honda, K., Sahrul, M., Hidaka, H., Tatsukawa, R., 1983. Organ and tissue distribution of heavy metals, and their growth-related changes in Antarctic fish, Pagothenia borchgrevinki. Agricultural and Biological Chemistry 47, 2521–2532. Kirby, J., Maher, W., Harasti, D., 2001a. Changes in selenium, copper, cadmium and zinc concentrations in mullet (Mugil cephalus) from the southern basin of Lake Macquarie, Australia, in response to alterations of coal-fired power station fly ash handling procedures. Archives of Environmental Contamination and Toxicology 41, 171–181. Kirby, J., Maher, W., Krikowa, F., 2001b. Selenium, cadmium, copper and zinc concentrations in sediments and mullet (Mugil cephalus) from the southern basin of Lake Macquarie, NSW, Australia. Archives of Environmental Contamination and Toxicology 40, 246–256. Kwon, T.T., Lee, C.W., 2001. Ecological risk assessment of sediments in wastewater discharging area by means of metal speciation. Microchemical Journal 70, 255–264. Langston, W.J., Spencer, S.K., 1995. Biological factors involved in metal concentrations observed in aquatic organisms. In: Tissier, A., Turner, D.R. (Eds.), Metal Speciation and Bioavailability in Aquatic System. John Wiley, Chichester, pp. 407–478.
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Rosenthal, H., Alderdice, D.F., 1976. Sublethal effects of environmental stressors, natural and pollutional on marine fish eggs and larvae. Journal of the Fisheries Board of Canada 33, 2047–2055. Saward, D., Stirling, A., Topping, G., 1975. Experimental studies on the effects of copper on a marine food chain. Marine Biology 29, 351–361. SEMA, 1998. Macroplano de gestao e saneamento ambientl da bacia da Baia de Sapetiba, Vol I, Secretaria de Estado de Meio ambiente de Rio de Janeiro, Rio de Janeiro. Tamira, C., Shane, S.Q.H., Ambrose, R.F., 2001. Trace metals in fish and invertebrates of three California Coastal Wetlands. Marine Pollution Bulletin 42 (3), 224–232.
Topcuoğlu, S., Kirbasoglu, Ç., Güngör, N., 2002. Heavy metals in organisms and sediments from Turkish coast of the Black Sea, 1997–1998. Environment International 27, 521–526. Türkman, A., Türkman, M., Tepe, Y., Akyurt, I., 2005. Heavy metals in three commercially valuable fish species from Iskenderun Bay, Northern East Mediterranean Sea, Turkey. Food Chemistry 91, 167–172.
Journal of Marine Systems 73 (2008) 114 – 122 www.elsevier.com/locate/jmarsys
Trace element levels in some commercially valuable fish species from coastal waters of Mediterranean Sea, Egypt Maha Ahmed Mohamed Abdallah National Institute of Oceanography and Fisheries, Kayet Bey, Alexandria, Egypt Received 18 December 2006; received in revised form 9 September 2007; accepted 12 September 2007 Available online 12 October 2007
Abstract Concentrations of 5 trace elements (Cd, Pb, Cu, Cr, Zn) were determined in muscle of fishes collected from two coastal areas of the Egyptian coast of the Mediterranean Sea west of Alexandria (El-Mex Bay and Eastern Harbour). Sardinella aurita, Alepes djedaba, Siganus luridus, Siganus rivulatus, Sphyraena chrysotoenia, and Scomberomorus commerson were collected from ElMex Bay. While Boops boops, Lithognathus mormyrus, Sparisoma cretense, Serranus cabrilla and Synodus saurus were collected from the E.H. In all fishes zinc was highest (up to 57 mg/kg) followed by Cr, Cu, Pb and Cd. The concentrations of several metals in fishes were significantly different among the species in each area. For all trace element examined, the concentrations decreased significantly with body weight of some fishes. In contrast, a positive correlation with body weight was found especially for Zn and Cu concentrations in 5 fish species and for Pb in 4 fish species. The concentrations of Cd, Pb and Zn were higher in fishes from El-Mex Bay (3.76, 6.49 and 57.21 mg/kg) than those from Eastern Harbour, whereas the opposite trend was observed for Cu and Cr, revealing the direct sources of trace metal pollution present in El-Mex coastal area. Levels of Cr surpassed the Maximum Permissible Concentration in most fish tissues, followed by Pb and Cd in some species. Cu and Zn presented concentrations below the maximum permissible levels in fish tissues. © 2007 Elsevier B.V. All rights reserved. Keywords: Trace elements; Fish; Growth-variation; MPC; El-Mex Bay; Eastern Harbour
1. Introduction Accumulation of trace elements in aquatic organisms is one of the most striking effects of pollution in aquatic system. Some trace metals are necessary in small amounts for individual metabolic processes, being assimilated by marine organisms. However, their capacity to form complexes with organic substances can result in concentrations up to 1000 times higher than their assimilation and fixation in tissues, becoming toxic to organisms (CETESB, 1982). The northwest coast of Egypt has been subjected to high inputs of anthropogenic E-mail address: [email protected]. 0924-7963/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jmarsys.2007.09.006
contamination over the past decades, mainly contributed by Alexandria City. El-Mex Bay and the Eastern Harbour (E.H.) are two parts of Alexandria coast on the Mediterranean Sea, they consider as the two main fishing sources in the City and its adjacent areas. As a semi-enclosed environment (E.H.), various pollutants have accumulated in the E.H due to effluents from coastal catchment's areas and several land-based sources. Levels of trace elements in water of huge drain (6 × 106 m3/day) called Omoum Drain (El-Rayis and Abdallah, 2006), have increased over the past 15 years (El-Rayis et al., 1997; Abouldahab et al., 1990). Furthermore, elevated concentrations of some trace elements have been reported in sediments (El-Sabarouti
M.A.M. Abdallah / Journal of Marine Systems 73 (2008) 114–122
et al., 1997; Abdel-Moati, 2001). Since sediments act as sinks for contaminants, which can persist in the aquatic environment for decades, changes in sediment in fauna activity and water chemistry allow these persistent contaminants to enter food chain, and thus into fish tissues (Kirby et al., 2001a,b). Many studies have been conducted on the human health effects of metals due to consumption of contaminated fish flesh (Chan et al., 2003; Alquezar et al., 2006). However only a few studies have been conducted to reveal the status of trace element contamination in bony fishes from El-Mex Bay and Eastern Harbour (El-Rayis et al., 1997). The two sample sites chosen for this study, El-Mex Bay and the Eastern Harbour (E.H.), all fishing areas in Alexandria City, are shown in Fig. 1. They were selected on the basis of potentially different pollution input levels. El-Mex Bay is considered to be a site of high industrial point source pollution associated with the activities of a chloroalkali plant, tanneries, petroleum refining and also an iron and steel factory. In addition, this Bay is an estuarine zone, it receives primary agricultural runoff by rate of 2547.7 × 106 m3/year from huge drain called Omoum Drain (El-Rayis and Abdallah, 2006). The downstream part of this drain receives considerable amounts of Alexandria domestic and industrial wastes prior to discharging to the Bay. The E.H. is a relatively shallow semi-enclosed basin, sheltered from the Mediterranean Sea by an artificial breakwater leaving two openings. The Harbour has been
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subject to high levels of pollution due to municipal waste disposal in addition, it is also affected by the waste products and (fuel) spills resulted from the ships anchored at its western side. El-Mex Bay and E.H. represent an area with complex urban, agricultural and industrial influences including industrial and urban storm water runoffs, treated sewage effluents associated with shipping, docking and manufacturing. The present study seeks to evaluate the present levels of 5 trace elements (Cd, Pb, Cu, Cr, Zn) in the edible parts (muscles and fillet) of 11 commercially used fish species from two polluted Bays, which is situated on the southeast Mediterranean Sea coast of Egypt, discusses the species and growth related variation of trace element levels and also establish comparisons with the Maximum Permissible Concentration standard. 2. Materials and methods 2.1. Samples Fish samples were collected along two coastal areas of El-Mex Bay and E.H. in 2005 and 2006 (Fig. 1). Round Sardinella (Sardinella aurita, n = 22), Shrimp Scad (Alepes djedaba, n = 10), Dusky Spinefoot (Siganus luridus, n = 9), Marbled Spinefoot (Siganus rivulatus, n = 10), Obtuse Barracuda (Sphyraena chrysotoenia, n = 10) and Spanish Mackerel (Scomberomorus
Fig. 1. The study area of El-Mex Bay and Eastern Harbour.
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variance (ANOVA) and Duncan's test (p = 0.05) were used to access whether trace elements concentrations varied significantly. All statistical calculations were performed with SPSS 9.0 for windows. Dependence of trace elements concentration on body weight was examined using Spearman rank correlation test. A p value of less than 0.05 was considered to indicate statistical significance.
commerson, n = 8) were caught from El-Mex Bay. Bogue (Boops boops, n = 13), Striped Seabream (Lithognathus mormyrus, n = 10), European Parrotfish (Sparisoma cretense, n = 8), Comber (Serranus cabrilla, n = 15) and Atlantic Lizardfish (Synodus saurus, n = 10) were caught from the E.H. Body weight and length of fishes were measured prior to dissection (Table 1). Muscle samples taken and stored at − 20 °C until chemical analysis.
3. Results and discussion 2.2. Chemical analysis 3.1. Species dependent variations of trace elements levels in fishes from Alexandria coastal areas
The procedure used for measuring concentrations of trace elements has been described previously (Anan et al., 2001). Tissue samples were dried for 12 h at 80 °C and then weighed and digested in a microwave oven using nitric acid in a Teflon PTFE tube. Concentrations of five trace elements (Cd, Pb, Cu, Cr and Zn) were measured using AAS (Varian Spectra 220 Fast Spectrometry). Results were expressed as milligram of element per dry weight kilogram of fish. The Maximum Permissible Concentrations (MPC) were established by FAO (1983). Accuracy of this analysis was examined using standard reference materials SRM Dorm-2 (National Research Council Canada). Recoveries of all the elements ranged from 93% to 109%. In the present study, concentrations are expressed on a dry weight basis. Moisture content of the muscle samples was 71.5 ± 2.3%. In order to compare our data to published values reported on a wet weight basis, we have converted the latter to dry weight basis using a conversion factor 3.51 (including FAO and MPCs).
Concentrations of five elements in the muscle of fishes from El-Mex Bay and Eastern Harbour (E.H) are shown in (Table 2). Zinc was highest in muscle of all species analyzed in this study, followed by Cr, Cu, Pb and Cd. The concentrations of several metals in fishes were significantly different among the species in each area. Concentrations of Cd, Pb and Zn were higher in muscle of S. rivulatus and S. aurita than in the rest species from El-Mex Bay (p b 0.01). In contrast, concentrations of Cr and Cu (p b 0.01) were higher in muscle of S. luridus than in the other species from the same Bay. Among the five species collected from the E.H, the levels were different between species for all the elements. The highest concentration of Cd, Pb and Cu were found in S. saurus and S. cabrilla (p b 0.05), while the highest concentrations of Cr and Zn were found in B. boops species. In contrast, Cr was below the detection limit in three species (L. mormyrus, S. cretense and S. saurus). Trace element levels are known to vary in fishes depending on various factors such as its habitat, feeding behavior and migration even in the same area (Andres et al., 2000; Canli and Atli, 2003). The ecological
2.3. Statistical analysis Non-parametric tests were used for statistical analysis to improve normality (because some of the variables were not normally distributed). One way analysis of
Table 1 Biometric data (mean ± S.D. and range) of fishes from El-Mex Bay and Eastern Harbour Location
Species
n
Body weight (g)
Body length (cm)
El-Mex Bay
Sardinella aurita Alepes djedaba Siganus rivulatus Siganus luridus Sphyraena chrysotoenia Scomberomorus commerson Boops boops Lithognathus mormyrus Sparisoma cretense Serranus cabrilla Synodus saurus
22 10 10 9 10 8 13 10 14 15 10
15.3 ± 1.7 (12.7–17.9) 34.7 ± 1.2 (33.5–36.8) 44.6 ± 9.9 (30.6–53.7) 40.7 ± 0.99 (39.2–41.2) 41.1 ± 4.9 (36.1–47.3) 106.9 ± 11.8 (93.6–115.9) 32.3 ± 1.2 (31.2–34.1) 57.7 ± 1.4 (57.8–60.5) 73.7 ± 14.7 (54.4–85.8) 50.8 ± 10.6 (35.1–66.3) 84.4 ± 16.6 (64.2–114.5)
9.1 ± 1.4 14.9 ± 1.7 13.5 ± 3.1 11.3 ± 1.3 13.6 ± 1.0 28.2 ± 5.8 15.2 ± 1.8 14.8 ± 1.4 21.4 ± 4.6 15.9 ± 3.4 20.8 ± 6.6
Eastern Harbour
(7.2–11.5) (13–16.2) (9.5–12.5) (12–14.5) (12–15.2) (25.3–30.8) (13.4–17.0) (13.0–16.4) (18.5–24.4) (14.1–17.4) (18.4–22)
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Table 2 Concentrations (range and average ± S.D. on mg/kg dry weight) of trace elements in muscle of fishes from coastal waters of El-Mex Bay and Eastern Harbour Area
Species
n
Cd
Pb
Cu
Cr
Zn
El-Mex
Sardinella aurita
22 10
2.46–4.93 4.0 ± 1.4 b0.003
Siganus luridus
9
Siganus rivulatus
10
Sphyraena chrysotoenia
10
Scomberomorus commerson
8
Boops boops
13
2.72–6.49 4.7 ± 1.9 1.4–3.2 2.1 ± 0.9 1.09–1.69 1.33 ± 0.32 0.96–1.30 1.2 ± 0.2 0.94–2.04 1.5 ± 0.6 0.98–2.52 1.9 ± 0.8 b0.02
b0.005
Alepes djedaba
0.16–1.49 1.2 ± 0.8 b0.0006
Lithognathus mormyrus
10
Sparisoma cretense
8
Serranus cabrilla
15
Synodus saurus
10
28.1–54.4 42.0 ± 10.9 13.3–31.1 20.4 ± 9.4 4.4–15.2 10.4 ± 5.5 30.0–57.2 43.9 ± 13.6 19.7–28.3 22.9 ± 4.7 17.7–31.0 22.4 ± 7.5 12.6–29.5 19.3 ± 8.9 15.9–19.9 17.8 ± 2.0 3.9–14.1 7.4 ± 4.7 8.6–17.1 14.1 ± 4.8 9.9–22.2 16.7 ± 6.2
E.H.
b0.002–0.42 0.3 ± 0.2 2.23–3.76 2.8 ± 0.8 1.87–2.93 2.34 ± 0.54 b0.0006–0.19 0.14 ± 0.1 b0.0006 1.37–1.57 1.50 ± 0.11 0.09–0.93 0.6 ± 0.4 b0.0006 0.44–2.65 1.9 ± 0.3
characteristics of eleven fish species analyzed in the two studied areas, El-Mex Bay and E.H are shown in (Table 3). The studied fishes could be grouped, according to their feeding habits, into three groups. The first one is filter feeders on phytoplankton (including S. aurita and B. boops) the second group is carnivores on macrofauna (including A. djedaba, S. chrysotoenia, S. commerson and L. mormyrus), while S. cabrilla and S. saurus are classified as carnivores on fish and crustacea. The third group is deposit feeders on detritus and organic materials (including S. luridus, S. rivulatus and S. cretense). These species-specific characteristics
1.66–1.78 1.72 ± 0.06 0.88–1.76 1.2 ± 0.5 0.92–3.27 2.1 ± 1.2 0.90–2.53 1.4 ± 0.9
4.12–8.25 5.9 ± 2.1 1.35–4.56 2.7 ± 1.7 1.98–3.24 2.8 ± 0.7 b0.003 3.36–7.87 5.2 ± 2.4 1.63–3.08 2.28 ± 0.74 b0.003–0.48 0.4 ± 0.1 7.49–9.69 8.3 ± 1.2 2.49–5.73 4.0 ± 1.6
3.6–8.4 4.5 ± 2.6 3.7–14.4 8.4 ± 5.5 b0.005 b0.005 5.9–6.9 6.4 ± 0.5 13.1–30.6 20.1 ± 9.3 b0.005 b0.005 7.1–20.4 12.2 ± 7.2 b0.005
may result in the variation of trace element accumulation between the species from the two areas. Growth-dependent variations were found in concentrations of several trace elements in muscle of fishes from El-Mex Bay and E.H. Since significant correlations between body weight and length were found in most fish species (p b 0.01), only relationships between body weight and trace element concentrations are reported here. Representative relationships are shown in Fig. 2. Significant negative correlations with body weight were found for Zn (0.01) concentrations in A. djedaba and S. rivulatus, and for Cu (0.05) in S. aurita, S. chrysotoenia
Table 3 Fish species examined and their ecological characteristics English name
Scientific name
Feeding habits
Biotope complex
Round Sardinella Shrimp Scad
Sardinella aurita Alepes djedaba
Filter feeders on phytoplankton and zooplankton Carnivores on macrofauna and zooplankton
Dusky Spinefoot Marbled Spinefoot Obtuse Barracuda Spanish Mackerel Bogue Striped Seabream European Parrotfish Comber Atlantic lizardfish
Siganus luridus Siganus rivulatus Sphyraena chrysotoenia Scomberomorus commerson Boops boops Lithognathus mormyrus Sparisoma cretense Serranus cabrilla Synodus saurus
Deposit feeders on detritus and organic materials Deposit feeders on detritus and organic materials Carnivores on macrofauna Carnivores on macrofauna Filter feeder on selective plankton Carnivores on macrofauna and zoobenthose Deposit feeders on detritus and organic materials Carnivores on macrofauna, zoobenthose, cephalopods and fish Carnivores on fish and crustacean
Pelagic (water column) Rock associate (schools near shore, reef) Rock associate (reef) Rock associate (reef) Pelagic (water column) Pelagic and rock associate Demersal and pelagic Seagrass bed Rock associate (reef) Pelagic (water column) Demersal and pelagic
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Fig. 2. Growth-dependent variation of trace element concentrations in the muscle of fishes from El-Mex Bay and E.H.
and L. mormyrus, for Cd (0.01) in S. luridus, S. rivulatus, S. chrysotoenia and S. commerson, for Pb (0.01) in A. djedaba and S. commerson and for Cr (0.05) in A. djedaba and S. luridus. Until now, growth (body weight, length and age) dependent decrease in trace elements level has been reported for many fish species (Anan et al., 2005). Honda et al. (1983) found that the concentrations of Cu, Cd and Pb in muscle decreased with an increase in body weight in Antarctic fish Pagothenia borchgrevinki. Generally, the growth-dependent variations of trace element levels are known to be influenced by various factors such as metabolic rate, and growth dilution of elements (Langston and Spencer 1995). In contrast, positive significant correlations with body weight were found in El-Mex Bay for Zn (0.05) in S. chrysotoenia, Cu (0.05) in S. luridus and S. rivulatus, Pb (0.05) in S. aurita and S. chrysotoenia, for Cr (0.05) in S. commerson.
Similarly in E.H. area, positive correlation with body weight were found for Zn (0.05) L. mormyrus, S. saurus and S. cretense, Cu (0.05) in S. saurus, Cd (0.05) in S. cretense and S. saurus, Pb (0.05) in L. mormyrus and S. cabrilla and Cr (0.05) in S. cabrilla. 3.2. Accumulated trace elements and Maximum Permissible Concentration (MPC) 3.2.1. Cadmium Cadmium concentrations (Fig. 3) were below MPC, except for muscles of S. rivulatus and S. chrysotoenia in El-Mex Bay and S. saurus in the E.H. As humans commonly consume muscles (edible parts) Cd toxicity via fish ingestion is unlikely. However, Cd is not an essential element, it is difficult to excrete once ingested, it presents high toxicity, and in both El-Mex Bay and E.H it is very widespread (concentration in sediments
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119
Fig. 3. Concentrations of Cd, Pb, Cu, Cr and Zn in fish muscles from El-Mex Bay and Eastern Harbour, MPC, Maximum Permissible Concentration.
were 8.09 and 3.8 μg/g respectively, Abdallah (2007) and Abdallah and Abdallah, 2007). 3.2.2. Lead Concentrations of Pb (Fig. 3) exceeding MPC were found in S. aurita, A. djedaba and S. commerson from El-Mex Bay, and S. cabrilla from E.H. The other species had concentrations below MPC, Pb does not present beneficial or nutritional effects to organisms and is extremely toxic (CETESB, 1982). Overall it occurs in very low concentrations in the biota, even when there are high concentrations in the abiotic environment (De
Souza Lima Jr. et al., 2002). This metal is used in several industrial processes and is a common residue from gasoline combustion (Evangelista, 1984). It ranks as the metal of largest diffusion through the atmosphere (SEMA, 1998). 3.2.3. Copper Overall Cu levels (Fig. 3) were below the MPC for human consumption in all studied fish tissues. This metal accumulates by several means, depending on environmental conditions and habits of species (Saward et al., 1975; Rosenthal and Alderdice, 1976).
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Copper is essential for animals and plants, as it takes part in enzyme formation and participates in respiratory processes, with accumulation levels varying widely among aquatic organisms. Variations in Cu concentration are related to levels of tolerance and toxicity symptom outbreaks, depending on species and period of passive accumulation (CETESB, 1984). 3.2.4. Chromium Concentrations of Cr (Fig. 3) exceeded MPC in most fish species tissues studied, for both bays. This metal is used in the leather industry, in inks and in processing of steel, among other uses (Evangelista, 1994). In El-Mex Bay there are several of those types of industries (Abdallah, 2007). 3.2.5. Zinc Concentrations of Zn (Fig. 3) were below the MPC for human consumption in all studied fish muscles. Most of the samples with slightly high Zn concentrations were from El-Mex Bay. The present work agrees with CETESB (1982), that the highest Zn concentrations occurred in S. rivulatus, which associated with substrate. While S. aurita, species less related to substrate than the others, had also high Zn concentrations, it could be due to the filter feeder habits of this fish (feeds upon plankton organisms, mainly diatoms and copepods). Phytoplankton is the most likely biota compartment for Zn and Cu concentration (EPA, 1972), along with sediments, due to great capacity of Zn and Cu for precipitation. Therefore, this may interpret the high concentrations of Zn being found in S. aurita. 3.3. Comparison of trace element levels in El-Mex Bay and Eastern Harbour fishes with those in other regions Levels of trace elements in muscle of fishes from ElMex Bay and E.H were compared with those reported
for fishes in other regions (Table 4). In general, the concentrations of all trace elements in muscle of El-Mex Bay and E.H fishes were higher than the values reported for fishes around the world (Tamira et al., 2001; Anan et al., 2005; Dalman et al., 2006; Türkman et al., 2005; Topcuoğlu et al., 2002; Canli and Atli, 2003; Kwon and Lee, 2001). Except for Cd, Pb and Zn levels that were reported by Türkman et al. (2005), Tamira et al. (2001) and Anan et al. (2005), Table 4 were higher than our findings. This is perhaps due to the trace elements levels in different species depend on feeding habits, age, size and length of fish and their habitats (Canli and Atli, 2003). On the other hand, in the present study the concentrations of Cr and Cu in muscle fishes were within the range of values reported for fishes by Tamira et al. (2001), while Pb and Zn were within the range of values reported by Türkman et al. (2005) and Topcuoğlu et al. (2002). 4. Final consideration All of the studied elements, with exception of Zn and Cu, showed values exceeding MPC in at least one fish species examined. Chromium was the element that most exceeded the permissible levels in muscle, followed by cadmium. No evident pattern of elemental incorporation was shown for certain species with regard to their position in the trophic levels. In coastal semi-enclosed bays like Eastern Harbour and El-Mex Bay, with low depth, even piscivorous fish feed on sediments when searching for invertebrates. Species feeding on plankton by filtering water also use the sediment for detritus and algae, which complement their diet (De Souza Lima Jr., et al., 2002). Therefore, in most cases both piscivorous and planktivorous species have a close relation to the substrata, the system component most likely to be contaminated by trace elements via sedimentation.
Table 4 Comparison of trace element concentrations in El-Mex Bay and E.H fishes (mg/kg dry wt) with those in other regions Sample area
Cd
Pb
Cu
Cr
Zn
References
El-Mex Bay Eastern Harbour California Lagoons Caspian Sea Southern Aegean Sea Iskenderun Bay Black Sea Coast Mediterranean Sea Masan Bay, Korea
b0.02–3.76 b0.02–2.65 0.10–0.30 0.001–0.35 b0.01–0.04 0.02–4.16 b0.02–0.24 0.37–0.79 0.01
0.94–6.49 b0.02–3.27 0.8–4.1 0.001–0.19 b0.02–0.4 0.19–6.95 b0.05–0.06 2.98–6.12 0.04–0.14
b0.02–8.25 b0.02–9.69 1.9–7.5 0.75–5.02 b0.10 0.04–5.43 1.01–4.4 2.19–4.4 0.18–0.25
b0.02–14.4 b0.02–30.6 1.9–24 0.08–1.4 – 0.07–6.46 b0.06–0.84 1.24–2.42 0.02–0.05
4.4–57.2 3.9–29.5 36–150 12–201 b0.5–7.2 0.6–11.57 25.7–44.2 16.5–37.4 6.33–12.9
Present study Present study Tamira et al. (2001) Anan et al. (2005) Dalman et al. (2006) Türkman et al. (2005) Topcuoğlu et al. (2002) Canli and Atli (2003) Kwon and Lee (2001)
M.A.M. Abdallah / Journal of Marine Systems 73 (2008) 114–122
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