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Marine Environmental Research 72 (2011) 258e264

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Marine Environmental Research

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Polybrominated diphenyl ethers and their methoxylated analogs in mullet(Mugil cephalus) and sea bass (Dicentrarchus labrax) from Bizerte Lagoon, Tunisia

Walid Ben Ameur a, Sihem Ben Hassine a, Ethel Eljarrat b,*, Yassine El Megdiche a, Souad Trabelsi a,Bèchir Hammami a, Damià Barceló b, Mohamed Ridha Driss a

a Laboratory of Environmental Analytical Chemistry (05/UR/12-03), University of Carthage, Faculty of Sciences, Bizerte, 7021 Zarzouna, TunisiabDepartment of Environmental Chemistry, IDAEA-CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain

a r t i c l e i n f o

Article history:Received 7 July 2011Received in revised form12 September 2011Accepted 15 September 2011

Keywords:PBDEsMeO-PBDEsMulletSea bassBizerte Lagoon

* Corresponding author. CSIC e Institute of EnvironmResearch, Department of Environmental Chemistry, B400 6100; fax: þ34 93 204 5904.

E-mail address: eeeqam@cid.csic.es (E. Eljarrat).

0141-1136/$ e see front matter � 2011 Elsevier Ltd. Adoi:10.1016/j.marenvres.2011.09.009

a b s t r a c t

Concentrations of ten polybrominated diphenyl ethers (PBDEs) and eight methoxylated polybrominateddiphenyl ethers (MeO-PBDEs) in mullet (Mugil cephalus) and sea bass (Dicentrarchus labrax) collectedfrom the Bizerte Lagoon and the Mediterranean Sea were investigated. To the best of our knowledge, thisis the first report of these compounds in marine fishes from Tunisia. The PBDE mean concentrations infish from Bizerte Lagoon were 45.3 and 96.2 ng g�1 lw respectively in mullet and sea bass, while theconcentrations of these compounds in mullet and sea bass from Mediterranean Sea were 7.80 and27.9 ng g�1 lw respectively. MeO-PBDE concentrations in mullet and sea bass from Bizerte Lagoon rangedfrom 6.46 to 286 ng g�1 lw and from 49.4 to 798 ng g�1 lw respectively, while the concentrations of thesecompounds in mullet and sea bass from Mediterranean Sea ranged from 190 to 401 ng g�1 lw and from353 to 578 ng g�1 lw respectively.

The total PBDEs and total MeO-PBDEs concentration in fish from Bizerte Lagoon were similar orslightly lower than those reported for other species from other locations around the world.

� 2011 Elsevier Ltd. All rights reserved.

1. Introduction

Polybrominated diphenyl ethers (PBDEs) are brominatedorganic compounds used as additive flame retardants in plastics,paints, textiles, and building materials. PBDEs have a structure inwhich 1e10 bromines are substituted on two benzene rings con-nected by an ether bond. According to the numbers of brominesand their substitution positions, theoretically there are 209congeners. Among these man-made chemicals, approximately 30are normally found in environmental samples. There are threemajor commercial mixtures of these compounds: the Penta-, Octa-and Deca-mixtures. Penta-BDE, marketed under the trade namesBromkal-70 and DE-71, contains predominately the congenersBDE-47, 99, 100, 153, and 154. It is used mainly in polyurethanefoams and textiles (Department of Health and Human Services,2004). The Octa-mixture, which is principally composed of BDE-183 and 153, is used in styrenes, polycarbonates and thermosets(Department of Health and Human Services, 2004). Deca-mixturesare used in most types of synthetic materials including textiles and

ental Assessment andWaterarcelona, Spain. Tel.: þ34 93

ll rights reserved.

electronics (Birnbaum and Staskal, 2004). The annual worldwideproduction of the three technical PBDE products in 2001 was67,000 metric tons (de Wit, 2002). Contamination by PBDEs is ofenvironmental concern due to their persistence, potential forendocrine disruption and bioaccumulation, and long-range trans-port. As a result, they have been widely found in air, soil, water,sediment, freshwater fish and marine organisms, and in humantissues from around the world.

In in vivo and in vitro studies using experimental mammals andhuman cell lines, it has been reported that PBDEs cause adverseeffects, such as clinical, morphological, immunological, andbehavioral changes, disturbance of thyroid hormone homeostasis,and enzyme induction (Darnerud, 2003; Gill et al., 2004; Legler andBrouwer, 2003).

Several structural PBDE analogs, such as the methoxylatedPBDEs (MeO-PBDEs), have recently been evidenced in fish andmarine mammals and measured at high concentrations in marineorganisms, including top-predators (Weijs et al., 2009). There areno known anthropogenic sources of these compounds. MeO-PBDEsare known to occur as natural products from marine environments(Gribble, 2000) andmetabolites (Feng et al., 2010) of anthropogenicpolybrominated diphenyl ethers (PBDEs). The possibility of MeO-PBDEs formation via methylation of either PBDEs or their hydrox-ylated homologs has also been reported (Teuten et al., 2005). It has

W. Ben Ameur et al. / Marine Environmental Research 72 (2011) 258e264 259

been shown that MeO-PBDEs can also be demethoxylated to OH-PBDEs in vitro, at a faster rate than that of PBDE transformationto OH-PBDEs (Wan et al., 2010).

MeO-PBDEs are naturally-produced in the marine environmentby sponges or algae (Vetter et al., 2002; Malmvärn et al., 2005).There is at present exceedingly little information about the bio-logical effects and thus the toxicological potential of environmen-tally relevant MeO-PBDEs in laboratory animals and wildlife. Aprevious study showed the cytotoxic effect of 6-MeO-BDE-47 inhuman hepatoma cell line HepG2 (An et al., 2010). Biologicalactivity has been investigated for 20-MeO-BDE-68, where anti-bacterial and anti-inflammatory activity was observed in bacteria(Kuniyoshi et al., 1985).

The aims of this study were to measure PBDE and MeO-PBDEconcentration in muscle samples of two fish specie (Mugil cepha-lus and Dicentrarchus labrax) from the Bizerte Lagoon and theMediterranean Sea and to identify the potential sources of thesetwo kinds of brominated organic pollutants. Both species have higheconomic importance and gastronomic value and have demon-strated to be suitable for aquatic ecosystems biomonitoring.

2. Materials and methods

2.1. Sample collection

Populated cities and/or industrial zones in northern Tunisiahave been mostly developed along Mediterranean coastal lagoons,e.g. Tunis and Bizerte. Bizerte Lagoon located in northern Tunisia, is

Fig. 1. Map showing

one such lagoon near the industrial and urban zones. It extends forabout 150 km2, between latitude 37�08 and 37�14N and longitude9�48 and 9�56E and is connected to the Mediterranean Sea andLake Ichkeul by straight channels.

Fifteen fish samples from the Bizerte Lagoon (BL) and five fishsamples from the Mediterranean Sea (MS) 8 km northwards fromthe lagoon (reference site) for each specie were sampled usinga net, in November 2009 (Fig. 1). The low analyzed number of fishcollected from theMS is due to difficulty of their fishing in this area.The fish were immediately sacrificed, weighed, measured,dissected and kept frozen (�20 �C) until required for chemicalanalyses. The biota species collected in the present study includedMullet (M. cephalus), and sea Bass (D. labrax). Table 1 shows theinformation on the fish samples used in the present study.

2.2. Chemicals

The solvents used in this study (n-hexane, acetone anddichloromethane) were pesticide quality and were obtained fromFluka (Buchs, Switzerland). Sulfuric acid was obtained from Bio-technica. Florisil (60e100mesh) was obtained from Fluka, activatedat 650 �C for 8 h and re-heated at 130 �C for 5 h before use.Anhydrous sodium sulfate suitable for use in pesticide analysis waspurchased from Fluka, heated at 300 �C and stored in a 130 �C oven.

Individual standard solutions of PBDEs (BDE-28, BDE-47, BDE-66, BDE-85, BDE-99, BDE-119, BDE-138, BDE-153, BDE-154, andBDE-183) at 50 mg mL�1 in isooctane were purchased from Supelco(CIL, USA). TheMeO-PBDE analytical mixture standard solutionwas

sampling areas.

Table 1Details of samples from the Bizerte Lagoon (BL) and the Mediterranean Sea (MS).

Common name Scientific name Number of samples Weight g (�SD) Length cm (�SD) Lipid % (�SD)

BL MS BL MS BL MS BL MS

Mullet Mugil cephalus 15 5 265.8 (83.4) 185 (15.0) 30.5 (3.5) 26.7 (1.7) 6.30(5.4) 5.70 (1.6)Sea bass Dicentrarchus labrax 15 5 265.3 (52.6) 290 (10.0) 29.4 (1.3) 30.7 (1.0) 4.60 (3.1) 6.10 (4.4)

SD: standard deviation.

W. Ben Ameur et al. / Marine Environmental Research 72 (2011) 258e264260

purchased from Wellington Laboratories (Guelph, ON, Canada)containing 6-MeO-BDE-47, 20-MeO-BDE-68, 5-MeO-BDE-47, 4-MeO-BDE-49, 5-MeO-BDE-100, 4-MeO-BDE-103, 5-MeO-BDE-99,and 4-MeO-BDE-101 at 5 mg mL�1 in nonane. These standardsolutions were further diluted by n-hexane to obtain mixed for-tifying and GC calibration standard solutions for all compounds.

2.3. Sample preparation

PBDEs and MeO-PBDEs were analyzed following the methoddescribed by Guo et al. (2008) with slight modifications. Samples offreeze dried muscle tissues (10 g) was Soxhlet extracted with n-hexane:acetone (4:1; v/v) for 16 h at a rate of five cycles per hour.The extract was concentrated with a rotary evaporator. An aliquotof 1 mL was used for gravimetric determination of the extractablelipid content. The remaining lipids, after adding BDE-77 as internalstandard were removed by treatment with concentrated sulfuricacid (4 � 10 mL). Further, cleanup was done on a column(40 cm� 0.5 cm ID) packedwith 5 g of activated Florisil and toppedwith 1 g of anhydrous sodium sulfate. The extract was eluted with50 mL of dichloromethane and n-hexane (1:9; v/v). The eluate wasfinally concentrated to incipient dryness and re-dissolved with50 mL of hexane prior to the analysis by gas chromatographycoupled with electron capture negative ionization mass spec-trometry (GCeECNI-MS).

2.4. Instrumental analysis

GCeECNI-MS analyses were performed on a gas chromatographAgilent 6890 connected to a mass spectrometer Agilent 5973Network (Agilent Technologies Espa�na, Madrid, Spain). An HP-5ms(30 m 0.25 mm i.d., 0.25 mm film thickness) containing 5% phenylmethyl siloxane (model HP 19091S-433) capillary columnwas usedfor the determination of the PBDEs and MeO-PBDEs. The temper-ature program was from 110 �C (held for 1 min) to 180 �C (held for1 min) at 8� C/min, then from 180 �C to 240 �C (held for 5 min) at2 �C/min, and then from 240 �C to 265 �C (held for 6 min) at 2 �C/min, using the splitless injection mode during 1 min, and injectionvolume of 2 mL. The operating conditions were as follows: ionsource temperature ¼ 250 �C, ammonia as chemical ionizationmoderating gas at an ion source pressure of 1.9 � 10�4 torr.Experiments were carried out monitoring the two most abundantisotope peaks from themass spectra corresponding tom/z¼ 79 and81 ([Br]�) (Eljarrat et al., 2002).

2.5. Quality assurance and quality control

Confirmation criteria for the detection and quantification ofPBDEs and MeO-PBDEs should include the following: (1) theretention time should match that of the standard compoundwithin�1 s, (2) the signal-to-noise ratio (S/N) should be �3, and (3) thedeviation of the two monitored ions intensities ratio should bewithin 15% of that of the standard compound. Quantification of thetarget compounds was carried out by internal standard procedurewith the BDE-77 as internal standard. Using the described

methodology, recoveries ranged from 46 to 72% for PBDEs and from53 to 90% for MeO-PBDEs. All samples were recovery corrected. Thelimit of detection (LOD) calculated as three times the signal-to-noise ratio, ranged from 57 to 695 pg g�1 lipid weight (lw) forPBDEs and from 35 to 645 pg g�1 lw for MeO-PBDEs. Relativestandard deviations of the method (n ¼ 3) were in the range of1e13%. Moreover, procedural blanks were carried out and no ana-lytes of interest were detected. Multi-level calibration curves in thelinear response interval of the detector were created for thequantification and good correlation (r2 > 0.999) was achieved.

2.6. Statistical analysis

Statistical treatment of the obtained results was performedwithSPSS software (SPSS 10.0 forWindows, SPSS Inc.). Our datawere notnormally distributed. In the first step we tried to log-transform thedata, but even then most of them were still not normally distrib-uted. Therefore we further used non-parametric tests for thesedata. For general comparisons, we used k-independent sample andif difference was significant (p < 0.05), subsequent multiplecomparisons between fish groups and sites were tested usingManneWhitney U-test. Spearman rank correlation was used toexamine the strength of associations between parameters. Statis-tical significance was accepted at p < 0.05.

3. Results

3.1. Polybrominated diphenyl ethers

Of the 10 PBDE congeners measured, seven compounds (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, and BDE-183)were frequently detected in the fish samples. Therefore, only datafor these seven PBDE congeners are reported herein. The concen-trations of PBDEs expressed in nanograms per gram lipid weight(ng g�1 lw) in the muscle of the analyzed species are presented inTable 2. PBDEs were detected in all samples, indicating ubiquitouscontamination by these compounds in aquatic biota from the BL.

At both sampling areas, theP

PBDE concentrations in sea bassare higher than those of mullet, with values ranging from 37.3 to218 ng g�1 lw for sea bass, and 8.01e98.8 ng g�1 lw for mullet in BL,and from 20.8 to 36.6 ng g�1 lw for sea bass, and5.52e10.4 ng g�1 lw for mullet in the MS. However no statisticallysignificant differences in concentration existed betweenmullet andsea bass (p ¼ 0.28). On the other hand and comparing the twosampling sites,

PPBDEs in the two studied species were higher in

BL than in the MS. However, although the concentrations werefound to be different between the two areas, no statisticallysignificant differences in concentration were observed betweensites (p ¼ 1.000 mullet; p ¼ 0.99 sea bass).

The compounds analyzed in the current work were constituentsof the PBDE Penta-mixture (BDE-28, BDE-47, BDE-66, BDE-99, BDE-100, BDE-138, BDE-153 and BDE-154) and Octa-mixture (BDE-153,BDE-154 and BDE-183). The PBDE profiles measured in BL fish andin MS fish are presented in Fig. 2. As is shown, very similar patternswere obtained formullet and sea bass samples in both studied sites.

Table 2PBDE and MeO-PBDE concentrations (ng g�1 lw) in fishes from Bizerte Lagoon (BL) and the Mediterranean Sea (MS).

Compound Mugil cephalus Dicentrarchus labrax

BL MS BL MS

Mean Range Mean Range Mean Range Mean Range

BDE-28 3.01 (3.20) nde8.80 0.57 (0.51) nde1.00 9.40 (16.0) nde39.3 2.92 (2.79) nde5.57BDE-47 26.8 (20.9) 4.66e68.8 4.83 (1.44) 3.74e6.46 49.4 (26.1) 20.3e98.7 14.6 (4.48) 9.45e17.8BDE-99 0.48 (1.05) nde3.07 0.12 (0.20) nde0.35 2.59 (4.61) nde14.0 0.44 (0.77) nde1.33BDE-100 0.31 (1.07) nde3.70 0.17 (0.29) nde0.50 1.74 (8.71) nde15.5 0.92 (1.59) nde2.75BDE-153 3.47 (3.45) nde10.2 0.44 (0.47) nde0.93 9.57 (8.71) nde26.8 1.28 (0.91) 0.42e2.23BDE-154 3.41 (4.81) nde14.1 0.38 (0.93) nde0.90 11.4 (18.4) nde63.9 1.79 (0.81) 1.30e2.73BDE-183 7.86 (8.14) nde21.6 1.25 (0.41) 0.95e1.27 12.1 (4.41) 1.63e16.1 5.90 (3.20) 2.26e8.26P

PBDEs 45.3 (31.12) 8.01e98.8 7.80(2.44) 5.52e10.4 96.2 (48.1) 37.3e218 27.9 (8.03) 20.8e36.6

6-MeO-BDE-47 72.5 (97.3) nde220 211 (70.9) 130e253 223 (152) 45.9e530 242 (54.1) 180e28120-MeO-BDE-68 28.2 (40.1) nde96.3 82.1 (109) 60.3e109 34.3 (47.7) nde115 189 (252) 100e2525-MeO-BDE-47 4.56 (4.33) nde32.1 23.7 (41.0) nde71.1 43.1 (77.4) nde267 51.4 (44.8) nde81.7SMeO-PBDEs 105 (114) 6.46e286 317 (112) 190e401 300 (218) 49.4e798 482 (117) 353e578

nd ¼ not detected, and assumed as 0 for the calculation of total PBDE and total MeO-PBDE values. Values in parentheses represent the standard deviation.

W. Ben Ameur et al. / Marine Environmental Research 72 (2011) 258e264 261

In all the samples, BDE-47 was the predominant among the sevendetected congeners. For instance, its contribution to

PPBDEs

ranged from 24.2% to 82.7% inmullet and from 25.3% to 92.6% in seabass from BL.

3.2. Methoxylated polybrominated diphenyl ethers

Only three out of the 8 targeted MeO-PBDE congeners werefound at measurable levels in the studied fish samples (Table 2).The MeO-PBDEs detected in fish samples were 20-MeO-BDE-68, 6-MeO-BDE-47 and 5-MeO-BDE-47. Concentrations of MeO-PBDEs inmullet and sea bass from BL ranged from 6.46 to 286 ng g�1 lw andfrom 49.4 to 798 ng g�1 lw respectively, while the concentrations ofthese compounds in mullet and sea bass from MS ranged from 190to 401 ng g�1 lw and from 353 to 578 ng g�1 lw respectively. TheP

MeO-PBDEs were shown to be significantly higher for sea basscomparedwithmullet for both studied areas (p¼ 0.03 BL; p¼ 0.001MS). Moreover, concentrations of MeO-PBDEs in the two specieswere significantly higher in the MS than in BL (p ¼ 0.02).

20-MeO-BDE-68, 6-MeO-BDE-47 and 5-MeO-BDE-47 accountedfor 68.9%, 26.8% and 4.33% of the

PMeO-PBDE concentration in

mullet from BL and 74.4%, 11.3% and 14.4% of theP

MeO-PBDEconcentration in sea bass from BL respectively. MeO-PBDE profileswere similar in the two investigated groups for the two studiedareas, with 20-MeO-BDE-68, 6-MeO-BDE-47 and 5-MeO-BDE-47contributing with almost 90.7% and 91.0% of the

PMeO-PBDEs in

fish from BL and MS respectively. 5-MeO-BDE-47 contribution tothe

PMeO-PBDEs in fish from BL and MS was 9.30% and 9.00%

respectively.

Fig. 2. PBDE congener profiles in mullet (Mugil cephalus) and sea bass (Dicentrarchuslabrax) from the Bizerte Lagoon (BL) and the Mediterranean Sea (MS).

In our study there was no significant correlation between thelevels of BDE-47 and 6-MeO-BDE-47 in mullet (rs ¼ 0.23, p ¼ 0.48),and in sea bass (rs ¼ �0.37, p ¼ 0.22) from BL. The levels of 6-MeO-BDE-47 were highly correlated with the levels of 20-MeO-BDE-68 inmullet and sea bass from BL (rs ¼ 0.93, p ¼ 0.03) and (rs ¼ 0.99,p ¼ 0.01).

3.3. Correlation ofP

PBDEs andP

MeO-PBDEs with fishcharacteristics

Levels of PBDEs in mullet and sea bass from BL were notcorrelated with weight (rs ¼ 0.38, p ¼ 0.21 and rs ¼ 0.5, p ¼ 0.89respectively) or length (rs ¼ 1.55, p ¼ 0.63 and rs ¼ �0.32, p ¼ 0.31respectively) or with lipid percentage (rs ¼ 0.41, p ¼ 0.18 andrs ¼ �0.38, p ¼ 0.22 respectively). Moreover, levels of MeO-PBDEsin biota from BL were not correlated with weight (rs ¼ 0.89,p ¼ 0.79 and rs ¼ 0.50, p ¼ 0.45 respectively) or length (rs ¼ 0.35,p ¼ 0.91 and rs ¼ 1.55, p ¼ 0.78 respectively) or with lipidpercentage (rs¼ 0.47, p¼ 0. 85 and rs¼ 0.50, p¼ 0.76 respectively).

4. Discussion

4.1. Polybrominated diphenyl ethers

The interspecies differences in PBDE levels are possibly relatedto their feeding habits, their trophic position in the food chain andto the difference in the metabolic capacity of both species (Johnsonand Olson, 2001;Wan et al., 2010). The lowconcentrations of PBDEsin mullet may be attributed to its feeding habits being omnivorousand consuming mostly phytoplankton, and to its low trophicposition in the food chain (Nyunja et al., 2009). In contrast, the seabass is a top predator (carnivorous fish) and has a high trophicposition in the food chain (Pasquaud et al., 2008).

The lack of inter-site variability in PBDE levels may partly bedue to large variations in concentrations between individual fishspecimens. This high variability in concentrations of persistentchemicals has been reported in a similar study (Gevao et al.,2010), even when samples were collected within a smallgeographical region, as was the case in this study. Also, it is maybe due to the low number of samples and the relatively highstandard deviation of weight values. The relatively high PBDElevels in BL may be caused by the industrial development andpopulation growth. The most obvious sources are effluents fromfactories producing textile and plastic products and from localwastewater discharges.

W. Ben Ameur et al. / Marine Environmental Research 72 (2011) 258e264262

The similarity of PBDE abundances across the two fish speciesindicates that the seven congeners are accumulated in the fish tothe same extent.

The dominance of BDE-47 in the present study was consistentwith the general pattern found in fish samples collected from Anoiaand Cardener River, Spain (Labandeira et al., 2007).

In this study, the aquatic biota from the BL seemed to accumu-late higher proportion of tri-BDEs (BDE-28) than penta-BDEs (BDE-100, BDE-99). This result was in line with results in the YangtzeRiver Delta (Xian et al., 2008) and Pearl River Delta (Guo et al.,2008).

The congener pattern observed in this studywas similar to thosedescribed in previous studies conducted for fish samples (Xianet al., 2008; Gao et al., 2009). These profiles do not reflect thecomposition of Penta-mixture or Octa-mixture formulations, butthis might be explained, for example, by the differences in theuptake and clearance efficiency of particular congeners.

Table 3 shows a global view of the PBDE levels in fish samplesfrom other studies located in different geographical areas.

PPBDE

concentrations and concentrations of an individual congener (BDE-47, commonly the most abundant congener in biological samples)are shown. Concentrations observed in BL samples were compa-rable to those obtained in fish from Georgia coast, USA (Sajwanet al., 2008), from Gironde Estuary, France (Tapie et al., 2011) andfrom Sydney Harbor, Australia (Losada et al., 2009). However,concentrations in the present study were relatively lower to thosefrom Anoia and Cardener River, Spain (Labandeira et al., 2007) andfrom Tokyo Bay, Japan (Mizukawa et al., 2009), while theseconcentrations were much lower to those found in fishes fromHardley Lake, USA (Dodder et al., 2002) and from Virginia water-sheds, USA (Hale et al., 2001). The concentrations observed in BLwere relatively higher to those from Northwestern Arabian Gulf(Gevao et al., 2010) and much higher to those from Eastern Chinacoastline (Xia et al., 2011) and from Storfjorden, Svalbard Islands,Norway (Wolkers et al., 2004). Mean BDE-47 concentration in fishfrom BL was lower than that found in fish collected from North-western Arabian Gulf (Gevao et al., 2010), Eastern China coastline(Xia et al., 2011) and from Storfjorden, eastern Svalbard (Wolkerset al., 2004). Moreover this concentration was lower to that foundin fish sampled from Yakima River, USA (Johnson and Olson, 2001)and from Hardley Lake, USA (Dodder et al., 2002). However thismean concentration was similar to that found in fish caught from

Table 3Global PBDE levels in fish muscles (ng g�1 lw).

Location SpeciesP

PBDE(min-m

Georgia coast, USA Anchovy, Flounder, Rock sea bass,Silver Perch, Spot and Spade fish

77.5 (9.

Gironde Estuary, France Eel (24e23Sydney Harbour, Australia Flounder, tailor, yellowfin bream,

luderick, fanbelly leatherjacketand sea mullet

(24e11

Anoia and Cardener River, Spain Carp 160 (29Tokyo Bay, Japan Japanese sea bass Ureogenic goby 130 (ndYakima River, USA Carp 960Hardley Lake, USA Carp 1600 (7Virginia watersheds, USA Carp 7200 (5Northwestern Arabian Gulf Mullet, tonguesole and

yellowfin seabream19.5 (2,

Eastern China coastline Yellow croaker and silver pomfret 3.04 (1.Storfjorden, eastern Svalbard Polar cod 3.55 (2.Yangtze River, China Carp 140 (17Bizerte Lagoon, Tunisia Mullet and sea bass 70.8 (8.

nr ¼ not reported.

Georgia coast, USA (Sajwan et al., 2008) and from Sydney Harbour,Australia (Losada et al., 2009).

4.2. Methoxylated polybrominated diphenyl ethers

The MeO-PBDEs found in fish muscle from this study have beenalso detected in previous studies (Pena-Abaurrea et al., 2009; Suet al., 2010).

As in the case of PBDEs, the interspecies differences in MeO-PBDE levels are possibly related to their feeding habits, theirtrophic position in the food chain and to the difference in themetabolic capacity of both species (Johnson and Olson, 2001; Wanet al., 2010). The existence of a difference in MeO-PBDE levelsbetween the two investigated locations is in accordance witha result obtained in a work conducted in Brazil that showed thatconcentration levels of MeO-PBDEs are higher in samples collectedfrom oceanic waters than those collected from coastal waters(Dorneles et al., 2010).

The MeO-PBDE profiles in fish from the investigated areas agreewith published literature for marine species (Pena-Abaurrea et al.,2009). The lower level of 5-MeO-BDE-47 in fish simple compared tothat of 6-MeO-BDE-47 and 20-MeO-BDE-68 is in accordance withresults obtained by Pena-Abaurrea et al. (2009) and by Wan et al.(2010).

TheP

MeO-PBDEs concentrations in the two fish species arehigher than the

PPBDEs in both areas. These results are similar to

those reported by Strid et al. (2010) and by Su et al. (2010) and mayindicate the natural origin of the MeO-PBDEs. According toMalmvärn et al. (2005), the fact thatMeO-BDEs are present at muchhigher concentrations than the PBDEs in both the alga and musselsamples may also provide further evidence supporting a naturalorigin for these compounds. Our result showed a difference inMeO-PBDE concentrations for both species between the BL and theMS. Because there is no anthropogenic source of these MeO-PBDEs,the difference in the concentrations may possibly be due to thedifference in the distribution of marine sponge, algae, and otheraquatic organisms that are known to synthesize these compounds.

The absence of significant correlation between the levels of BDE-47 and 6-MeO-BDE-47 in the two fish species suggests that 6-MeO-BDE-47 is not only a possiblemetabolic product of BDE-47 infish butcould also come from other marine sources. This fact is also sup-ported byVetter et al. (2001)whodid not detect significant amounts

Meanax)

BDE-47 Mean(min-max)

Number ofmeasuredPBDEcongeners

References

9e337) 27.4 (10e241) 6 Sajwan et al. (2008)

7) (97e121) 12 Tapie et al. (2011)5) (13.2e78.2) 9 Losada et al. (2009)

e744) 105 (20e565) 40 Labandeira et al. (2007)e177) 66.5 21 Mizukawa et al. (2009)

910 nr Johnson and Olson (2001)60e2500) 400e1200 nr Dodder et al. (2002)e47900) 74 nr Hale et al. (2001)80e190) 12.5 (1,8e130) 4 Gevao et al. (2010)

11e5.28) 1.79 (0.47e4.29) 9 Xia et al. (2011)53e4.98) 2.09 (1.33e3.28) 6 Wolkers et al. (2004)e1100) 8.3e160 nr Xian et al. (2008)01e218) 38.1 (4.66e98.7) 10 This study

W. Ben Ameur et al. / Marine Environmental Research 72 (2011) 258e264 263

of parent compounds (PBDEs) in marine mammals from north-eastern Australia despite the high levels found of 60-MeO-BDE-47.

Since the levels of 6-MeO-BDE-47 were highly correlated withthe levels of 20-MeO-BDE-68, it is highly plausible that thesecompounds have both accumulated from similar sources.

The literature on MeO-PBDEs in fish from different locations israther scarce and only a few reports of these compounds in otheraquatic organisms are available. The mean MeO-PBDEs concen-tration found in our study, 203 ng g�1 lw, is similar to that found inwild bluefin tuna (Thunnus thynnus) from the Mediterranean Sea,150 ng g�1 lw (Pena-Abaurrea et al., 2009) and it was higher thanthat found in anchovy (coila sp.) from the Yangtze River Delta,9.10 ng g�1 lw (Su et al., 2010) and to that found in marine speciesfrom the Sydney Harbor, 26.7 ng g�1 lw (Losada et al., 2009).However, and compared with those obtained in Brazilian waters,the mean MeO-PBDEs concentrations in the present study werelower than those found in dolphin (Pseudorca crassidens), mean148 700 ng g�1 lw (Dorneles et al., 2010).

4.3. Correlation ofP

PBDEs andP

MeO-PBDEs with fishcharacteristics

The PBDE levels in BL fish were not significantly correlatedeither with fish size, or with fish weight and or with lipidpercentage. These results were similar to those found by Mariottiniet al. (2008); Borghesi et al. (2009); by Gao et al. (2009) and by Stridet al. (2010). The absence of significant correlation between MeO-PBDE concentrations and lipid percentage, between MeO-PBDEconcentration and fish length was in accordance with the resultsobtained by Valters et al. (2005) and by Strid et al. (2010). Thissuggests that these characteristics were not large determinants ofcontaminant burdens.

5. Conclusions

PBDEs andMeO-PBDEswere detected inmullet and sea bass fromthe Bizerte Lagoon. This is the first report of these compounds inmarinefishes of Tunisia.

PPBDEs and

PMeO-PBDEs in sea basswere

higher thanthose inmullet inboth investigatedareas, apatternwhichmay be related to the different feeding habits and trophic position inthe food chain of the two species. Similar profiles of anthropogenicand naturally-produced organobrominated compounds wereobserved in the two studied species from the both areas.

The PBDE and MeO-PBDE concentrations in biota from theBizerte Lagoonwere similar to or slightly lower than those reportedfor other species from other locations around the world. The resultsof this study as well as those of other studies suggest that PBDEs inboth fish species are primarily of synthetic origin and released byhuman activities around Bizerte Lagoon, while MeO-PBDEs in thetwo studied species are primarily from nature as natural productsfrom the sea instead of metabolism of PBDEs in these fishes.

Acknowledgments

The authors are grateful to R. Chaler, D. Fangul andM. Comesañafor their assistance with the gas chromatographyemass spec-trometry (GCeMS) analyses.We thank also the anonymous refereesfor their helpful comments, which will improve the paper.

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