Methylmercury bioconcentration in muscle tissue of the European eel (Anguilla anguilla) from the Adour estuary (Bay of Biscay, France)

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BaselineEdited by Bruce J. RichardsonMethylmercury bioconcentration in muscle tissue of the Europeaneel (Anguilla anguilla) from the Adour estuary (Bay of Biscay, France)Ina Arleny a,b, Hele`ne Tabouret c, Pablo Rodriguez-Gonzalez a, Gilles Bareille a,Olivier F.X. Donard a, David Amouroux a,*a Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, IPREM CNRS UMR 5254, Universite de Pau et des Pays de lAdour,Helioparc, F-64053 Pau, Franceb Provincial Health Laboratory of Central Kalimantan, JI Let. Jend. Soeprato No1 Palangka Raya 73112, Kalimantan Tengah, Indonesiac IFREMER, Laboratoire des Ressources Halieutiques dAquitaine, Technopole Izarbel, 64210 Bidart, FranceThe life history of the European eel (Anguilla anguilla)begins in the Sargasso Sea in the Atlantic Ocean whereLeptocephalus larvae drift with the gulf stream in orderto reach European coastal waters. After their metamorpho-sis into transparent juveniles (glass eels) and an acclima-tising phase in estuaries, they migrate upstream into riversto become yellow eels (the sub-adult stage). The yellow eelsspend between 2 and 20 years of their lifetime in freshwateruntil they change into silver eels (the adult stage) andnally migrate back to the Atlantic Ocean for spawning(Gomez-Mourelo, 2005). A. anguilla is thus an organismable to tolerate a wide range of environmental conditions,including variations in oxygen availability, dierent rangesof salinities and exposure to a variety of anthropogeniccompounds. In addition, it is a migratory, benthic andbenthivorous species at the top of the food chain and ischaracterised by a high fat content (>30%). For all thesereasons A. anguilla can bioaccumulate a wide range of con-taminants and it has been widely employed as a bioindica-tor of pollution caused by metals (Batty et al., 1996; Has-Schon et al., 2006) and organic contaminants (Storelliet al., 2007; Yamaguchi et al., 2003).The environmental and toxicological impact of Hg bio-accumulation in sh is related to the methylation of inor-ganic mercury to form the more toxic methylmercury(MeHg) species. Fish tend to concentrate MeHg in theirtissues by a factor of 105107, leading to dangerous levelseven in areas with tolerable Hg concentrations (Masonet al., 1996). It has been reported that about 98% of theHg present in aquatic systems is immobilised in sediments(Stein et al., 1996) and that most of the MeHg is producedat the sediment water interface as a result of biotic orabiotic transformations caused by specic redox gradientsand bacterial activity (Gilmour and Henry, 1991). Accord-ingly, A. anguilla may be an eective biomagnicator andbioaccumulator of Hg due to its longevity during the con-tinental development phase in freshwaters (where it foragesand lives upwards of 15 years) and its position at the top ofthe food chain as a carnivorous species feeding on benthicfauna (Mancini et al., 2005).The River Adour (located at the South West of France)has a length of 335 km, enters the Atlantic Ocean at 4330 0North latitude 132 0 West longitude and drains a largeagricultural area of 17,000 km2. The Adour estuary isaected by a dynamic macrotidal range (up to 70 kmupstream) and it is under strong anthropogenic pressuredue to urban, agricultural and industrial activities includ-ing tourism, sheries or recreational boating (Brunet andAstin, 1999). In the upstream estuarine zone, the river pre-sents large, at man-made modied oodplains (knownlocally as the Barthes) that constitute an area of15 km2, lying up to 2 km on both sides of the river. TheThe objective of BASELINE is to publish short communications on different aspects of pollution of the marineenvironment. Only those papers which clearly identify the quality of the data will be considered for publication.Contributors to Baseline should refer to BaselineThe New Format and Content (Mar. Pollut. Bull. 42, 703704).* Corresponding author. Tel.: +33 559 407 756; fax: +33 509 407 781.E-mail address: david.amouroux@univ-pau.fr (D. Amouroux).www.elsevier.com/locate/marpolbulMarine Pollution Bulletin 54 (2007) 10311071Barthes are ooded twice a year and play a signicanthydraulic and hydrological role owing their high storagecapacity. Such capacity, together with the existence ofman-made dykes, aords ood protection to the regionand allows a signicant dilution of point discharges inthe area (Brunet and Astin, 2000). The Barthes is a naturalhabitat for A. Anguilla (Gomez-Mourelo, 2005) and itsexploitation constitutes the basis of the economy of thelocal professional shermen and hence plays an importanteconomic role in this region. However, A. Anguilla stockhas been reported to be in dangerous decline in all its geo-graphic life areas (Dekker, 2000; Feunteun, 2002).Mercury speciation analyses in surface sediments ofmacrotidal estuaries and coastal systems from the RiverAdour have shown a moderate contamination of MeHgand inorganic mercury (Stoichev et al., 2004). Moreover,bioaccumulation and biomagnication of MeHg in the tro-phic network of benthic macrofauna from the Adour estu-ary and its adjacent coastal zone has been recentlyobserved (Monperrus et al., 2005). Thus, speciation analy-sis of mercury in A. Anguilla from the River Adour appearsto be necessary in order to ascertain the risk of transfer(generated by mercury biomagnication) to the higher lev-els of the food web, including human beings. A. anguillahas been used as a biomarker for the study of mercury con-tamination in many aquatic ecosystems (Batty et al., 1996;Burger et al., 2001; Edwards et al., 1999; Linde et al., 1999;Maes et al., 2005; Ribeiro et al., 2005). However, there hasbeen only one study providing information about theMeHg levels in eels, particularly in long-ned eels Anguilladieenbachii from New Zealand (Redmayne et al., 2000).Therefore, this is the rst environmental study reportingHg speciation data from European eels. The aim of thepresent work was the determination of inorganic mercuryand MeHg levels in muscle tissues of A. anguilla fromtwo dierent aquatic ecosystems of the Adour estuary.This study is part of a research program, Groupementde Recherche Adour (GDR Adour), involving several lab-oratories that investigate possible eects of contaminantson dynamic eel populations. During this program, the sam-pling strategy was dened by the LRHA (Laboratoire deRessources Halieutique dAquitaine) IFREMER (Insti-tute Francais pour lExploration de la Mer) according to,rst, various phases characterizing the annual biologicalcycle of A. anguilla (colonizationsedentarisationdown-stream migration) and second, the specic period of agri-cultural practice such as maize plantation, irrigation andpesticide treatment. According to this, three periods ofsampling corresponding approximately to the months ofApril, July and October were selected.The mercury speciation data reported in the presentstudy are derived from eels caught from two sampling sites(Fig. 1): the downstream estuarine zone (Redon site) and acanal located upstream in the oodplains (Barthes) at SaintLaurent de Gosse, sampled in July and October 2005,respectively. The Redon site is located in the mixing zoneof the Adour estuary and, therefore, is under the inuenceof urban and industrial activities as well as physicochemicalprocesses caused by the mixing of river water and seawater.The sampling site located at Saint Laurent de Gosse is in thefreshwater tidal zone of the estuary and mostly subjectto agricultural activities developed within the BarthesNAtlanticOceanTarnosUrtAngletBayonneNAtlanticOcean Saline zoneNive RiverKp 135Kp 110110Kp 110120KpAdour RiverGaves RiversFluvial zoneADOUR ESTUARYAdourEstuary4332N4330N4328N130W 115W120W 110W125WDownstream estuarine samplingsite (Redon zone)Floodplain sampling site (Saint-Laurent de Gosse)Fig. 1. Location of sampling areas in the lower estuary and upper estuary oodplain (Adour River, France).1032 Baseline / Marine Pollution Bulletin 54 (2007) 10311071catchments. It is also linked to the estuary only by valves,permitting at some point the input of uvial water.A total of 22 yellow eel samples were analysed for Hgspeciation. Fifteen samples were collected from the down-stream estuarine zone (Redon site) and the rest from theupstream wetland of Barthes (Saint Laurent de Gosse).The individual length of the eels ranged from 23.9 to65 cm (mean: 43.2 12.2), and the weight ranged from22 to 607 g (mean: 180.1 163.8). The eels were trans-ported to the laboratory in cool boxes and then dissectedto remove their organs. The muscle tissues of the eels werelyophilised and homogenised before analysis. A sample of0.1 g of the lyophilised muscle tissue was digested with4 ml of 25% tetra methyl ammonium hydroxide (TMAH)by using a microwave assisted extraction at 70 C for4 min. Then, 0.4 mL of the extract was adjusted to pH 4with an acetic acid/sodium acetate buer solution. Mercuryspecies were derivatised using NaBPr4 after the addition ofethyl mercury as an internal standard and after 5 min ofmechanical shaking they were extracted into isooctane forGCICP-MS (gas chromatographyinductively coupledplasma mass spectrometry) or GCMIP-AED (gas chro-matographymicrowave induced plasma atomic-emissiondetection) analysis. The analytical methodology has beenoptimised (see previous publications; Tseng et al., 1997;Moreno et al., 2006) and was validated by the analysis ofthe certied reference material DORM 2 (dogsh muscletissue from the National Research Council of Canada).The results obtained in the validation of the methodologywere in agreement using both detection techniques andare shown in Table 1.The concentrations of the mercury species in muscle tis-sues of A. anguilla collected from the two sampling sites aresummarized in Table 2. The average concentration of totalHg was found to be 0.31 0.10 and 0.18 0.04 lg Hg g1(expressed as wet weight) for the estuary and the ood-plains, respectively. These concentrations were alwaysbelow 0.5 lg Hg g1, which is the maximum set by theEuropean Union for total Hg in foodstus (CommissionRegulation No. 78/2005) and the admitted value set bythe World Health Organisation for human consumption(International Programme on Chemical Safety, Environ-mental Health Criteria No. 1, Mercury).Higher MeHg values were encountered in the down-stream estuary (mean: 0.27 0.09 lg Hg g1 wet weight)compared to the oodplains, which averaged 0.11 0.03 lg Hg g1. As a result, most of the total mercury foundin the samples is present as MeHg (Table 2). Indeed, theaverage percentage of MeHg from the total mercury burdenwas found to be 86% in the samples from the estuary and65% in those from the oodplains. These numbers indicatethe need for applying specic speciation protocols to inves-tigate the environmental and toxicological impact of metal-lic contaminants.Table 3 compares the results obtained in this work withthose collected from previous publications reporting totalmercury and MeHg levels in eels from dierent parts ofthe world. The results obtained for total mercury in theRiver Adour are of the same order of magnitude as otherpublished studies. However, MeHg can be only comparedwith a single study reporting MeHg concentrations in eelsfrom New Zealand (A. dieenbachii). Similar values areobtained in both studies in terms of concentration and per-centage of MeHg in the samples.In contrast to the values from the estuary, MeHg con-centrations in the muscle tissues from the oodplains didnot change drastically in relation to the individual lengthsof the eels but nonetheless showed a signicant correlation(Fig. 2). Within the scatter observed for estuarine MeHgvalues, some eels showed MeHg concentrations close tothose found in the oodplains. This may be the conse-quence of eel life history, as they are able to migrate fromestuaries to either river or coastal habitats. Indeed, in arecent study in the Gironde estuary, Fablet et al. (2007)have shown, according to Sr:Ca proles in otoliths, that72% of the eels sampled changed their habitats once ormore. Thus, we cannot exclude the possibility that someof eels caught in the Adour estuary had recently come fromthe adjacent coastal or oodplain areas. Alternatively, thelarge spatial variability in the MeHg content in both sedi-ment and benthic food may also explain these results.If the percentages of methyl mercury (normalised to thetotal mercury content) are considered, there is a clear linearregression between the length of the eels and MeHg relativeconcentrations, whatever the origin of eels (p value Fig. 3). The correlation was higher in the oodplains. It isworth noticing that the lower MeHg concentrationsobtained for small eels in the oodplains indicates a lowerinitial exposure to MeHg. The higher slope indicates ahigher biomagnication rate versus the length of the shthan that obtained in the downstream estuary. Neverthe-less, both ecosystems show the same overall biomagnica-tion factor in the largest eels. These results can beexplained with regard to the dierent physical characteris-tics of both environmental compartments (i.e. salinity, foodavailability) and/or individual physiological characteristicssuch as growth rate.Although there are still no data regarding contamina-tion levels and the reactivity of Hg in the Barthes, previ-ous work in the Adour estuary has shown that mercuryspecies (particularly MeHg) were encountered in urban-related euents at signicantly higher levels compared tothe rivers draining upstream watersheds (Point, 2004).Moreover, Stoichev et al. (2006) reported that MeHg levelsin surface waters from the Adour estuary were character-ised by longitudinal variations, with highest concentrations(in both dissolved and particulate fractions) occurringwithin the downstream, urban estuarine area. This hasbeen explained not only by the high methylation potentialof the sediments, but also by direct anthropogenic inputs ofMeHg from specic discharge points. Such methylationpotential has been found to be enhanced under anaerobicconditions in sediments from the Adour River (Rodriguezy = 0.002x + 0.027R2 = 0.643FloodplainsEstuaryLength (cm)y = 0.002x + 0.027R2 = 0.64300.10.20.30.40.50.60 10 20 30 40 50 60 70FloodplainsEstuaryMeHgConcentration ( g Hg g -1 )Fig. 2. Concentration of MeHg (lg Hg g1 wet weight) according to the length of eels from the downstream urban estuary and from the oodplains of theAdour River.Table 3Comparison of total mercury and methyl mercury concentrations in eels obtained in similar studies (lg Hg g1 wet weight)Species Location Type Total Hg MeHg Sample Refs.A. Anguilla Vaccares (France) Pond 0.22 (n = 15) Liver Batty et al. (1996)A. Anguilla Berre (France) Pond 0.23 (n = 15) Liver Batty et al. (1996)A. Anguilla East Anglia (UK) River estuary 0.26 (n = 51) Muscle Edwards (1997)A. Anguilla East Anglia (UK) River broadening 0.10 (n = 51) Muscle Edwards (1997)A. dieenbachii Leith (New Zealand) River 0.12 (n = 1) 0.08 (n = 27) Muscle Redmayne et al. (2000)A. dieenbachii Flemming (New Zealand) River 0.31 (n = 1) 0.48 (n = 34) Muscle Redmayne et al. (2000)A. dieenbachii Kyeburne (New Zealand) River 0.65 (n = 1) 0.50 (n = 23) Muscle Redmayne et al. (2000)A. rostrata Savannah River (USA) River 0.15 (n = 24) Muscle Burger et al. (2001)A. Anguilla Thames River (UK) River 0.15 (n = 2) Muscle Yamaguchi et al. (2003)A. Anguilla La Capelie`re (France) Pond 0.03 (n = 9) Muscle Ribeiro et al. (2005)A. Anguilla La Capelie`re (France) Pond 0.06 (n = 10) Liver Ribeiro et al. (2005)A. Anguilla Fumemorte (France) Pond 0.09 (n = 9) Muscle Ribeiro et al. (2005)A. Anguilla Fumemorte (France) Pond 0.08 (n = 9) Liver Ribeiro et al. (2005)A. Anguilla Morne`se (France) Pond 0.12 (n = 8) Muscle Ribeiro et al. (2005)A. Anguilla Morne`se (France) Pond 0.15 (n = 8) Liver Ribeiro et al. (2005)A. Anguilla Yser (Belgium) River 0.15 (n = 8) Muscle Maes et al. (2005)A. Anguilla Meuse (Belgium) River 0.17 (n = 20) Muscle Maes et al. (2005)A. Anguilla Scheldt (Belgium) River 0.09 (n = 33) Muscle Maes et al. (2005)A. Anguilla Tiber River (Italy) River 0.23 (n = 8) Muscle Mancini et al. (2005)A. Anguilla Lesina (Italy) Lagoon 0.18 (n = 2) Muscle Storelli et al. (2007)A. Anguilla Adour River (France) River estuary 0.31 (n = 15 0.27 (n = 15) Muscle This workA. Anguilla Adour River(France) River oodplain 0.18 (n = 7) 0.11 (n = 7) Muscle This work1034 Baseline / Marine Pollution Bulletin 54 (2007) 10311071Martin-Doimeadios et al., 2004). On the other hand, mer-cury species concentrations in coastal sediments from theAdour were found to be high enough to assess the impactof estuarine inputs on the nearby coastal area (Stoichevet al., 2004). Finally, in agreement with these results, MeHganalysis in three dierent trophic groups (suspension feed-ers, predators and deposit feeders) from dierent samplingsites of the downstream Adour estuary showed that MeHgis also subject to biomagnication in the benthic foodchains (Monperrus et al., 2005).Taking into account these results, the high correlationsobtained for eels from the oodplains in (Figs. 2 and 3)can be explained by the population type and the exposuremode. Concerning the eels from the Barthes, which is arelatively closed ecosystem, it can be assumed that expo-sure is mostly based on identical trophic routes providedby specic local food chains. On the other hand, becausethe downstream estuary receives an additional MeHg con-tribution from anthropogenic sources, various mercuryaccumulation routes related to dierent trophic chainscan be assumed.Our research suggests a basis for large scale of studies inthe Adour estuary and provides, for the rst time, prelimin-ary data on MeHg burdens, variability and compositionof mercury species in muscle tissues of European eels(A. Anguilla). In addition A. anguilla appears to be an eec-tive bioaccumulator of MeHg, even in aquatic environmentsmoderately contaminated by mercury, demonstrating theusefulness of this species as a bioindicator of the impactsof mercury pollution in dierent aquatic ecosystems.AcknowledgementsThis work is a contribution to the Groupement deRecherche Adour sponsored by the IFREMER, the Uni-versity de Pau et des Pays de lAdour and the CNRS.I. Arleny acknowledges the French Ministry of ForeignAair for her fellowship, H. Tabouret acknowledgesIFREMER and the Aquitaine Region for her Ph.D. grantand P. Rodriguez-Gonzalez acknowledges the Secretariade Estado de Universidades e Investigacion of the SpanishMinistry of Education and Science for his postdoctoral re-search fellowship. The authors are also grateful to N. Caill-Milly and P. Prouzet (LHA, IFREMER), the ConseilSuperieur de la Peche and MIGRADOUR for their helpin the eld logistic and sh sampling.ReferencesBatty, J., Pain, D., Caurant, F., 1996. Metal concentrations in eelsAnguilla anguilla from the Camargue region of France. BiologicalConservation 76, 1723.Brunet, R.C., Astin, K.B., 1999. Spatio-temporal variation in somephysical and chemical parameters over a 25-year period in thecatchment of the River Adour. Journal of Hydrology 220, 209221.Brunet, R.C., Astin, K.B., 2000. A 12-month sediment and nutrientbudget in a oodplain reach of the River Adour, Southwest France.Regulated Rivers: Research & Management 16, 267277.Burger, J., Gaines, K.F., Boring, C.S., Stephens, W.L., Snodgrass, J.,Gochfeld, M., 2001. Mercury and selenium in sh from the SavannahRiver: species, trophic level, and locational dierences. EnvironmentalResearch Section A 87, 108118.Dekker, W., 2000. A procrustean assessment of the European eel stock.ICES Journal of Marine Science 57, 938947.Edwards, S.C., MacLeod, C.L., Lester, J.N., 1999. Mercury contamina-tion of the eel (Anguilla Anguilla) and roach (Rutilus Rutilos) in EastAnglia, UK. Environmental Monitoring and Assessment 55, 371387.Fablet, R., Daverat, F., De Pontual, H., 2007. Unsupervised Bayesianreconstruction of individual life histories from otolith signatures: casestudy of Sr:Ca transects of eel (Anguilla anguilla) otoliths. CanadianJournal of Fisheries and Aquatic Sciences 64, 152165.Feunteun, E., 2002. Management and restoration of European eelpopulation (Anguilla anguilla): an impossible bargain. EcologicalEngineering 18, 575591.Gilmour, C.C., Henry, E.A., 1991. Mercury methylationin Aquaticsystems aected by acid deposition. Environmental Pollution 71,131169.Gomez-Mourelo, P., 2005. A model for the upstream motion of elvers inthe Adour River. C. R. Biologies 328, 367378.Has-Schon, E., Bogut, I., Strelec, I., 2006. Heavy metal prole in vespecies included in human diet, domiciled in the end ow of Rivery = 1.82x - 7.35R2 = 0.93y = 0.65x + 56.43R2 = 0.570 10 20 30 40 50 60 70Length (cm)FloodplainsEstuarypNeretva (Croatia). Archives of Environmental Contamination andToxicology 50, 545551.Linde, A.R., Sanchez-Galan, S., Klein, D., Garcia-Vazquez, E., Summer,K.H., 1999. Metallothionein and heavy metals in Brown Trout (Salmotrutta) and European eel (Anguilla anguilla): a comparative study.Ecotoxicology and Environmental Safety 44, 168173.Maes, G.E., Raeymaekers, J.A.M., Pampoulie, C., Seynaeve, A., Goemans,G., Belpaire, C., Volckaert, F.A.M., 2005. The Catadromous Euro-pean eel Anguilla Anguilla (L.) as a model for freshwater evolutionaryecotoxicology: relationship between heavy metal bioaccumulation,condition and genetic variability. Aquatic Toxicology 73, 99114.Mancini, L., Caimi, S., Ciardullo, S., Zeiner, M., Bottoni, P., Tancioni, L.,Cautadella, S., Carola, S., 2005. A pilot study of the contents ofselected pollutants in sh from the River Tiber (Rome). MicrochemicalJournal 79, 171175.Mason, R.P., Reinfelder, J.R., Morel, F.M., 1996. Uptake, toxicity, andtrophic transfer of mercury in a coastal diatom. Environmental Scienceand Toxicology 30, 18351845.Monperrus, M., Point, D., Grall, J., Chauvaud, L., Amouroux, D.,Bareille, G., Donard, O., 2005. Determination of metal and organo-metal trophic bioaccumulation in the Benthic Macrofauna of theAdour estuary coastal zone (SW France, Bay of Biscay). Journal ofEnvironmental Monitoring 7, 693700.Moreno, M.J., Pacheco-Arjona, J., Rodriguez-Gonzalez, P., Preud-homme, H., Amouroux, D., Donard, O.F.X., 2006. Simultaneousdetermination of monomethylmercury, monobutyltin, dibutyltin andtributyltin in environmental samples by multi-elemental species-specic isotope dilution analysis using electron ionisation GCMS.Journal of Mass Spectrometry 41, 14911497.Point, D., 2004. Speciation et Biogeochimie des elements traces metall-iques dans lestuaire de lAdour. Ph.D. Thesis, Universite de Pau et desPays de lAdour, pp. 218.Redmayne, A.C., Kim, J.P., Closs, G.P., Hunter, K.A., 2000. Methylmercury bioaccumulation in long-nned eels, Anguilla dieenbachia,from the three rivers in Otago, New Zealand. The Science of the TotalEnvironment 262, 3747.Ribeiro, C.A.O., Vollaire, Y., Sanchez-Chardi, A., Roche, H., 2005.Bioaccumulation and the eects of organochlorine pesticides, PAHand heavy metals in the eels (Anguilla anguilla) at the Camargue naturereserve, France. Aquatic Toxicology 74, 569.Rodriguez Martin-Doimeadios, R.C., Tessier, E., Amouroux, D., Guyo-neaud, R., Duran, R., Caumette, P., Donard, O.F.X., 2004. Mercurymethylation/demethylation and volatilization pathways in estuarinesediment slurries using species-specic enriched stable isotopes. MarineChemistry 90, 107123.Stein, E.D., Chen, Y., Winer, A.M., 1996. Environmental distribution andtransformation of mercury compounds. Critical Review in Environ-mental Science and Technology 26, 143.Stoichev, T., Amouroux, D., Wasserman, J.C., Point, D., de Diego, A.,Bareille, G., Donard, O.F.X., 2004. Dynamics of mercury species insurface sediments of a macrotidal estuarine-coastal system (AdourRiver, Bay of Biscay). Estuarine, Coastal and Shelf Science 59, 511521.Stoichev, T., Amouroux, D., Monperrus, M., Point, D., Tessier, E.,Bareille, G., Donard, O.F.X., 2006. Mercury in surface waters of amacrotidal urban estuary (River Adour, South-West France). Chem-istry and Ecology 22, 137148.Storelli, M.M., Barone, G., Garofalo, R., Marcotrigiano, G.O., 2007.Metals and organochlorine compounds in eel (Anguilla Anguilla) fromthe Lesina lagoon, Adriatic Sea (Italy). Food Chemistry 100, 13371341.Tseng, C.M., De Diego, A., Martin, F.M., Amouroux, D., Donard,O.F.X., 1997. Rapid determination of inorganic mercury and meth-ylmercury in biological reference materials by hydride generation,cryofocusing, atomic absorption spectrometry after open focusedmicrowave-assisted alkaline digestion. Journal of Analytical AtomicSpectrometry 12, 743750.Yamaguchi, N., Gazzard, D., Scholey, G., Macdonald, D.W., 2003.Concentrations and hazard assessment of PCBs, organochlorinepesticides and mercury in sh species from the upper Thames: Riverpollution and its potential eects on top predators. Chemosphere 50,265273.0025-326X/$ - see front matter 2007 Elsevier Ltd. All rights reserved.doi:10.1016/j.marpolbul.2007.04.004Endocrine-disrupting phenols in selected riversand bays in the PhilippinesEvangeline C. Santiago *, Charita S. KwanResearch and Analytical Services Laboratory, Natural Sciences Research Institute, University of the Philippines,Diliman, 1101 Quezon City, PhilippinesEndocrine-disrupting (ED) compounds are known tointerfere with hormonal systems, aecting growth, develop-ment and reproduction in humans and animals (Colburnet al., 1993; Colon et al., 2000; Guo et al., 2001; Kogevinas,2001). Alkylphenols and bisphenols are among the waste-water pollutants that have been found to have ED proper-ties (Soto et al., 1995; Bustos-Obregon, 2001; Foster et al.,2001). Industrial euents from chemical plants and micro-bial processing of phenol derivatives can contribute to theload of alkylphenols and chlorophenols in natural waters(Junglaus et al., 1978; Lopez-Avila and Hites, 1980).The presence of ED phenols in water bodies may havean adverse impact on sh. Exposures of swordtail sh at100 ppb nonylphenol indicated reproductive damage andaected its growth (Kwak et al., 2001). Nonylphenol wasalso found to induce complete feminization of the gonadin genetically controlled all-male amago salmon (Nakam-ura et al., 2002). Many Filipinos depend on shing andaquaculture for livelihood; thus, it is important to know* Corresponding author. Tel.: +63 2920 7731; fax: +63 2928 6868.E-mail address: ecs@nsri.upd.edu.ph (E.C. Santiago).1036 Baseline / Marine Pollution Bulletin 54 (2007) 10311071Methylmercury bioconcentration in muscle tissue of the European eel (Anguilla anguilla) from the Adour estuary (Bay of Biscay, France)AcknowledgementsReferences

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