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Abstract

American (Anguilla rostrata) and European (Anguilla anguilla) eel populations are declining since the 1980s, and contamination is thought to play a role. To determine the influence of organic (organochlorinated pesticides (OCPs), polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs)) and inorganic (Zn, As, Cd, Cu, Pb, Cr, Ni, Ag, Se, Hg) contaminants on wild yellow eels liver and muscle metabolic capacities, enzymatic assays were performed. In A. rostrata liver, G6PDH moderate negative correlations with Ag, Pb, and As suggest impacts on lipid metabolism, and correlations between Cd and age (positive) and between Cd and relative condition factor (Kn; negative) indicate impacts on older eels health. Anguilla anguilla liver proteins, pyruvate kinase (PK), and lactate dehydrogenase (LDH) were positively linked to Zn, Pb, and Cu, suggesting effects on glycolytic and anaerobic capacities. In A. anguilla muscle, absence of correlation between age and lipids plus strong positive correlations between age and OCPs, PBDEs, PCBs, and Hg suggest lipid storage impairment in older contaminated eels. Overall, our study indicates contamination impacts on both species’ metabolic capacities, but the broader range of contaminants found in A. anguilla brings greater impacts compared with A. rostrata.

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... In a series of related studies performed by our team along the St. Lawrence and Gironde hydrosystems (Eastern Canada and Southwest France, respectively), we have identified that certain metals and organic contaminants could disturb physiological functions in yellow Atlantic eels (Baillon et al., 2015a(Baillon et al., , 2015b(Baillon et al., , 2016Caron et al., 2016;Pannetier et al., 2016). In Baillon et al. (2015aBaillon et al. ( , 2015bBaillon et al. ( , 2016, we conducted a large scale and without a priori transcriptomic based approach. ...
... Metal analyses (Ag, As, Cd, Cr, Cu, Ni, Pb, Se, Zn, Hg) were carried out in liver and muscle samples as previously described by Pannetier et al. (2016). The concentrations of seven indicators of PCBs (CB50þ28, CB 52, CB 101, CB 118, CB 138, CB 153 and CB 180), eight OCPs (2,4 0 -DDE, 4,4 0 -DDE, 2,4 0 -DDD, 4,4 0 -DDD, 2,4 0 -DDT and 4,4 0 -DDT, hexachlorobenzene (HCB) and lindane) and eight PBDEs (BDE 28,47,49,99,100,153,154,183,209), were performed on muscle samples following the procedures described by Caron et al. (2016). ...
... Since contamination and biological characteristics of eels from this study have been reported in companion studies (Baillon et al., 2015b(Baillon et al., , 2016Caron et al., 2016;Laporte et al., 2016;Pannetier et al., 2016), they will only be briefly summarized here. ...
Article
Since the early 1980s, populations of American (Anguilla rostrata) and European eels (Anguilla anguilla) have suffered a sharp decline. The causes of their decline are likely multifactorial and include chemical pollution. A field study was conducted in eight sites varying in organic and metal contamination along the St. Lawrence (Eastern Canada) and Gironde (France) systems to investigate the relationships among contaminants, biological characteristics and biotransformation, antioxidant and histopathological biomarkers in eels from both species. For A. rostrata, no major influences of persistent organic contaminants on biomarkers were identified. For A. anguilla, eels from the most contaminated site expressed higher surface of MelanoMacrophage Centers (MMCs) and eels from another contaminated site expressed higher amount of spleen lipofuscin pigment. These two histopathological biomarkers were also associated with aging. Compared to eels from the cleanest French site, higher hepatic catalase activity and density of MMC in eels from contaminated sites was related to higher concentration of organic (DDT and metabolites, sum of PCBs, sum of PBDEs) and inorganic (Hg and Cd) contaminants. In both species, a higher deposition of spleen hemosiderin pigment was measured in eels from the most brackish sites compared to eels living in freshwater environments. Our results suggest an association between higher hemosiderin pigment and metal contamination (As for A. anguilla and Pb for A. rostrata). Parasitism by A. crassus was observed in European eels from freshwater sites but not in eels from brackish habitats. Overall, contamination may pose a greater risk for the health of European compared to American eels.
... Elevated liver Cu concentrations were also associated with a disturbance of aerobic and anaerobic capacities, as indicated by key enzyme indicators. Indeed, another study of the IMMORTEEL project (Caron et al., 2016) confirms an association between elevated liver Cu concentrations and effects on tissue protein content and metabolic capacities. Hence, our data suggest that especially for the larger eels from LSF and LSP, accumulation of Cu in their liver may pose a risk to their health. ...
... Hence, environmental Cd contamination may affect reproductive capacities and could contribute to the decline of Atlantic eels, especially larger eels, which are also the most contaminated. More recently, Caron et al. (2016) suggested that Cd accumulation in the muscle of the same individuals as those used in the present study may interfere with energy accumulation in A. rostrata. In addition, we have also reported that Cd was, along with other contaminants (including the metals described in the present study but also some organic pollutants), a major factor affecting the eels' hepatic transcriptome. ...
... Our study raises the possibility that, at least in the most contaminated eels, Hg may pose a risk to their health. Indeed, the study by Caron et al. (2016) suggested that elevated tissue Hg concentrations could affect lipid storage in older eels. ...
... In a series of related studies performed by our team along the St. Lawrence and Gironde hydrosystems (Eastern Canada and South- west France, respectively), we have identified that certain metals and organic contaminants could disturb physiological functions in yellow Atlantic eels ( Baillon et al., 2015aBaillon et al., , 2015bBaillon et al., , 2016Caron et al., 2016;Pannetier et al., 2016). In Baillon et al. (2015aBaillon et al. ( , 2015bBaillon et al. ( , 2016, we conducted a large scale and without a priori transcriptomic based approach. ...
... Metal analyses (Ag, As, Cd, Cr, Cu, Ni, Pb, Se, Zn, Hg) were carried out in liver and muscle samples as previously described by Pannetier et al. (2016). The concentrations of seven indicators of PCBs (CB50þ28, CB 52, CB 101, CB 118, CB 138, CB 153 and CB 180), eight OCPs (2,4 0 -DDE, 4,4 0 -DDE, 2,4 0 -DDD, 4,4 0 -DDD, 2,4 0 -DDT and 4,4 0 -DDT, hexachlorobenzene (HCB) and lindane) and eight PBDEs (BDE 28, 47, 49, 99, 100, 153, 154, 183, 209), were performed on muscle samples following the procedures described by Caron et al. (2016). ...
... Since contamination and biological characteristics of eels from this study have been reported in companion studies ( Baillon et al., 2015bBaillon et al., , 2016Caron et al., 2016;Laporte et al., 2016;Pannetier et al., 2016), they will only be briefly summarized here. ...
Conference Paper
This study is part of an international program ‘IMMORTEEL’ investigating the possible contribution of habitat contamination in the decline of Atlantic eels. Biomarker responses and muscle concentrations of persistent organic contaminants (POPs) were examined in European eels (Anguilla anguilla) and American eels (Anguilla rostrata) in the Gironde and St. Lawrence Rivers basins. In 2011 and 2012, yellow eels were collected at two reference sites (Certes and Dordogne in France and Rivière Sud-Ouest and Rivière Saint-Jean in Quebec, Canada) and two contaminated sites (Garonne and Gironde in France and Lake Saint-Pierre and Lake Saint François in Quebec). Principal component analysis was useful to discriminate effects of natural ecological gradients and anthropogenic contaminant gradients on biological responses, over a large geographic scale. Patterns of contamination differed markedly between France and Quebec, with higher PCB concentrations relative to other POPs from France. In 2012 but not in 2011, hepatic ethoxyresorufin O-deethylase induction and increased density of splenic melanomacrophage centers were detected in eels from Garonne and Gironde compared to reference sites. In Quebec, morphometric characteristics were the major discriminant factors between upstream contaminated and downstream reference sites. Links between biomarker responses, exposure to other groups of contaminants and health impacts will be discussed.
... The activities of all four enzymes in this study are commonly considered environmental biomarkers that are responsive to a large number of environmental contaminants in field and laboratory studies [23][24][25][26]. Environmental pollutants have been reported to induce and inhibit the activities of these biomarkers [27,28]. ...
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Endocrine disrupting compounds (EDCs) are commonly detected in aquatic environments and can endanger aquatic life. The responses of enzymatic biomarkers in asexual freshwater planarians (lactate dehydrogenase, glutathione S-transferase, glucose-6-phosphate dehydrogenase, and isocitric dehydro-genase) were evaluated after 7-day exposure to en-docrine disruptors (bisphenol A [BPA], diethylstil-bestrol [DES], 17α-ethinylestradiol [EE2], and 17β-estradiol [E2]). These biomarkers are ubiquitous enzymes and play crucial physiological roles in living organisms. In this study, EDCs influenced the non-specific enzyme activities of asexual planarians. However, the effects of EDCs on enzymatic bi-omarkers did not correspond with the order of their estrogenic potencies. Furthermore, exposure to EDCs for 7 days mostly slightly or significantly reduced the enzyme activities of planarians compared with those of their respective controls. Alterations in enzyme activities can affect the energy metabolism and health status of organisms. The environmental levels of E2, EE2, and DES can range from lower than their detectable limits to tens of ng L-1 , and BPA levels in river water can be several μg L −1. These findings suggest that some aquatic animals might be affected by the current levels of BPA in hotspot pollution scenarios.
... Enzymatic validation results are shown in Figs. S1-S2 and complete protocol is described in SM. 1. Enzymatic activities were measured according to Caron et al. (2016). We provide what we consider to be an optimized customized protocol for subcellular fractionation of liver and gonads of Yellow Perch, as current protocols for Yellow Perch liver are not enzyme-validated (Campbell et al., 2005;Giguère et al., 2006;Kraemer et al., 2006). ...
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Mercury (Hg) is a trace element of particular concern since it is ubiquitous in the environment and because its methylated form (MeHg) readily bioaccumulates and biomagnifies in food webs. This latter process leads to elevated Hg concentrations in fish and may thus induce toxicity. Maternal transfer of bioaccumulated contaminants to offspring is a suggested mechanism of impaired reproductive success in fish. The purpose of this study was to assess the toxicity potential of Hg during maternal transfer in Yellow Perch from Lake Saint-Pierre (Quebec, Canada) using a subcellular partitioning approach. We also evaluated potential protective effects of selenium, as this element has been shown to alleviate Hg toxicity through sequestration. A customized subcellular partitioning protocol was used to separate liver and gonad of Yellow Perch into various subcellular fractions. Results show that, in the liver, MeHg was primarily (51%) associated to the subcellular fraction containing cytosolic enzymes. Furthermore, 23% and 15% of MeHg was found in hepatic and gonadal mitochondria, respectively, suggesting that Yellow Perch is not effectively detoxifying this metal. There was also a strong relationship (R2 = 0.73) between MeHg bioaccumulation in the liver and MeHg concentrations in gonadal mitochondria, which corroborates the potential risk linked to MeHg maternal transfer. On the other hand, we also found that selenium might have a protective effect on Hg toxicity at a subcellular level. In fact, Se:Hg molar ratios in subcellular fractions were systematically above 1 in all tissues and fractions examined, which corresponds to the suggested protective threshold. This study provides the first assessment of subcellular Se:Hg molar ratios in fish. Since early developmental stages in aquatic biota are particularly sensitive to Hg, this study represents a step forward in understanding the likelihood for toxic effects in wild fish through maternal transfer.
... Citrate synthase (CS) is a mitochondrial biomarker located in the mitochondrial matrix. Its activity was measured according to Caron et al. (2016). In each well, 10 μL of each subcellular fraction was mixed with 170 μL of a reaction solution composed of phosphate buffer (1 mM, pH 8), Tris (100 mM; Merck), acetyl coenzyme A (0.2 mM; Sigma Aldrich), and 2-nitro-benzoic acid (0.1 mM; DTNB; Sigma Aldrich). ...
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The European eel (Anguilla anguilla Linnaeus 1758) is a species typical for waters of Western Europe. Thanks to early expeditions on the Atlantic Ocean by the Danish biologist Johannes Schmidt who found small (<10mm) leptocephali larvae in the Sargasso Sea about 100 years ago, we have now a strong indication where the spawning site for this species is located. The American eel (Anguilla rostrata, LeSueur) also spawns in the Sargasso Sea. The spawning time and location of both species have been supported and refined in recent analyses of the available historical data. Subsequent ichthyoplankton surveys conducted by McCleave (USA) and Tesch (Germany) in the 1980s indicated an increase in the number of leptocephali <10 mm , confirming and refining the Sargasso Sea theory of Johannes Schmidt. Distinctions between the European and American eel are based on morphological characteristics (number of vertebrae) as well as molecular markers (allozymes, mitochondrial DNA and anonymous genomic-DNA. Although recognised as two distinct species, it remains unclear which mechanisms play a role in species separation during larval drift, and what orientation mechanism eels use during migration in the open sea. The current status of knowledge on these issues will be presented. The hypothesis that all European eel migrate to the Sargasso Sea for reproduction and comprise a single randomly mating population, the so called panmixia theory, was until recently broadly accepted. However, based on field observations, morphological parameters and molecular studies there are some indications that Schmidt’s claim of complete homogeneity of the European eel population and a unique spawning location may be an overstatement. Recent molecular work on European eel indicated a genetic mosaic consisting of several isolated groups, leading to a rejection of the panmixia theory. Nevertheless, the latest extensive genetic survey indicated that the geographical component of genetic structure lacked temporal stability, emphasising the need for temporal replication in the study of highly vagile marine species. Induced spawning of hormone treated eels in the aquarium was collective and simultaneous. In this work for the first time group spawning behaviour has ever been observed and recorded in eels. Studies in swim-tunnels indicate that eels can swim four to six times more efficiently than non-anguilliform fish such as trout. After a laboratory swim trial of eels over 5,500 km, the body composition did not change and fat, protein and carbohydrate were used in the same proportion. This study demonstrated for the first time that European eel are physiologically able of reaching the Sargasso Sea without feeding. Based on catches of newly hatched larvae, temperature preference tests and telemetry tracking of mature hormone treated animals, it can be hypothesised that spawning in the Sargasso Sea is collective and simultaneous, while presumably taking place in the upper 200 m of the ocean. Successful satellite tracking of longfin female eels in New Zealand has been performed to monitor migration pathways. Implementation of this new technology is possible in this species because it is three times larger than the European eel. In the future, miniaturisation of tagging technology may allow European eels to be tracked in time by satellite. The most interesting potential contribution of telemetry tracking of silver eels is additional knowledge about migration routes, rates, and depths. In combination with catches of larvae in the Sargasso Sea, it may elucidate the precise spawning locations of different eel species or groups. Only then, we will be able to define sustainable management issues by integrating this novel knowledge into spawners escapement and juvenile fishing quota.
Article
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Since the 1980s, the eel population has been decreasing dangerously. Persistent Organic Pollutants (POPs) such as Polychlorinated Biphenyls (PCBs) are one of the suspected causes of this decline. A preliminary study of PCB contamination carried out on different fish from the Gironde estuary (southwest of France, Europe) has shown a relatively high level of contamination of eel muscles. In order to characterize the contamination level of PCBs and PBDEs (PolyBrominated Diphenyl-Ethers) in eels from this estuary more than 240 eels were collected during the years 2004-2005 in the Gironde estuarine system, from glass eels to silver eels. Individual European eels were grouped according to length and localization sites. The results have shown a low contamination level of glass eels: respectively 28±11 ng g(-1)dw for PCBs and 5±3 ng g(-1)dw for PBDEs. The contamination level in eels (expressed in ng g(-1)dw) increases from glass eels to silver eels up to 3399 ng g(-1)dw of PCBs for the most contaminated silver eel. Such levels of PCBs similar to those observed in Northern Europe, could raise sanitary problems connected with the World Health Organization (WHO) recommendations. These results are worrying for the local people who regularly eat eels caught in the Gironde estuary.
Article
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European eel (Anguilla anguilla (L.)) stocks are in decline in most of their geographical distribution and their status is considered below safe biological limits. Recently, there is an increasing awareness that spawner quality might be an essential element in the decline of the species since pollution by bioaccumulating chemical substances may have a large impact on the reproduction success of the eel. This review gives an overview of the literature on the effects of contaminants on the European eel and on the consequences on the biology and fitness of the eel in order to document the role of pollution in its decline. A variety of contaminants have been found to affect the eel. These contaminants may cause disturbance of the immune system, the reproduction system, the nervous system and the endocrine system and effects were reported on several levels of biological organization, from subcellular, organ, individual up to even population level. More extensive research is needed in order to evaluate how pollutants are detrimental to eel populations. Getting a comprehensive overview of the quality (including contamination levels, biomarker responses, lipid content and condition) of the silver eel population all over Europe seems to be an essential and urgent objective for the European eel management.
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To investigate the mechanisms involved in metal stress in wild fish, yellow perch (Perca flavescens) were collected in eight lakes of the Rouyn-Noranda and Sudbury regions (Canada). Due to mining and smelting activities, these two regions indeed present a broad contamination gradient in metal concentrations (Cd, Cu, Zn and Ni; water, sediment and prey) and offer a unique research opportunity to investigate relationships between metal bioaccumulation and resulting deleterious effects in indigenous biota chronically exposed to metal mixtures. The expression level of genes encoding for proteins involved in metal detoxification (metallothioneins, mts), protein protection (heat shock protein-70, hsp-70), growth (insulin-like growth factor-1, igf-1), aerobic energy metabolism (cytochrome c oxydase, cco-1) and protection against oxidative stress (Cu/Zn superoxide dismutase, sod-1) were assessed in fish liver and muscle in association with protein and enzymatic assays for cytochrome c oxidase (CCO). Bioaccumulation of both Cd and Cu increased in response to higher ambient metal concentrations, but the two metals clearly have different modes of action. For Cd, changes in gene expression levels were more marked in the liver than in the dorsal muscle, whereas for Cu the opposite trend was observed. Hepatic Cd accumulation was linked to decreased cco-1 and sod-1 gene expression, whereas Cu accumulation was associated with a decrease in CCO enzymatic activity and an increase in total protein concentration and in cco-1, mts and hsp-70 gene expression levels. For Ni, no significant correlations were observed at the transcriptional level, but increasing hepatic Ni concentrations were significantly and positively correlated with protein concentrations and CCO activity. By coupling gene expression to biochemical and physiological endpoints, this work provides new insights into the mechanisms involved in metal stress and the adaptive response of fish chronically exposed to metal mixtures.
Book
A strong demand for an English version of the third German Edition of this extremely important book paved the way for this excellent new translation, which contains much new information from over 500 publications, not covered by the previous English language edition. The Eel is the standard work on the species with chapters in the book covering body structure and functions, developmental stages and distribution of the eel species, post-larval ecology and behaviour, harvest and environmental relationships, fishing methods, eel culture, diseases, parasites and bodily damage, the world trade in eels and eel processing. Contributions are included from several world authorities including new information concerning genetic diversity in eel populations and the consequences for their management. Written by Friedrich-Wilhelm Tesch, one of the foremost world authorities on eels and carefully edited by Professor Thorpe, well known for his work in fish biology, writing and editing, The Eel is an essential purchase for all those working with the species, including fish biologists, physiologists and ecologists, aquatic and environmental scientists, fisheries managers and fish farm personnel. Copies of this landmark publication should be available in the libraries of all research establishments and universities where these subjects are studied or taught. The Fisheries Society of the British Isles provided generous financial support enabling the translation and publication of this book.
Article
A protein determination method which involves the binding of Coomassie Brilliant Blue G-250 to protein is described. The binding of the dye to protein causes a shift in the absorption maximum of the dye from 465 to 595 nm, and it is the increase in absorption at 595 nm which is monitored. This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr. There is little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose. A small amount of color is developed in the presence of strongly alkaline buffering agents, but the assay may be run accurately by the use of proper buffer controls. The only components found to give excessive interfering color in the assay are relatively large amounts of detergents such as sodium dodecyl sulfate, Triton X-100, and commercial glassware detergents. Interference by small amounts of detergent may be eliminated by the use of proper controls.
Article
The main energetic stores at the silver eel stage were studied by analysing muscle fat concentrations and hepatosomatic indices in female silver eels from various habitats in Sweden. Muscle fat concentrations varied both within and between localities and lean eels with muscle fat concentrations <20% occurred at all study sites. Furthermore, no correlation could be found between muscle fat content and internal or external maturation indices, neither was the relative liver size related to the maturation process, as the correlation between the hepatosomatic and gonadosomatic indices was very weak. Consequently, it was concluded that silvering and the spawning migration may begin also at low muscle fat concentrations. However, most of the energy reserve is stored as muscle fat in eel, and it is highly unlikely that female silver eels with such low fat contents, as were observed occasionally in this study, will ever recruit to the next generation. Therefore, it is suggested that the maturation process in eel is more flexible than previously recognized, and that this process might be temporarily arrested and feeding resumed during the first part of the migratory phase.
Article
Estimated fecundity of matured eels ranged from 0.7-2.6 million eggs. An estimate of an energy budget for migration and spawning was established.-from Sport Fishery Abstracts
Article
This study is based on elementary chemical analyses made on whole eels. It is shown that eels during development from elver to silver eel accumulate lipid from about 20 to about 80% calculated as the lipid part of the eel's total energy. Silver eels can endure long-term starvation. Our record is 1594 days at 14 ± 2C. Logarithms of body weights decrease linearly against days of starvation. Samples of male silver eels taken at intervals from a starving batch were analysed for water, lipid (L) and protein (P). During starvation the lipid reserve (gL/eel) is decomposed at a lower rate than that of the protein reserve (gPIeel). HaIf-lives are 667 and 416 days respectively. Calculations of energy loss (Cal/kg L or P/day) during starvation showed that the two energy reserves are mobilized in such a way that they (per kg reserve) contribute almost equally to the total metabolism. When the eel's body weight is used as reference (Cal/kg eel/day) an increasing rate of decomposition is typical of L while the rate of P is decreasing. During the entire period of starvation the energy released from L surpasses that of P. The sum of L-and P-energies remains consrant. Determinations of oxygen consumption were made no starving male silver eels kept individually in respiromerric bottles over about four years. Their merabolic rate increased by a factor 3. This is in conflict with the above results. The discrepancy is discussed.
Article
To ascertain whether growth rate modifies the oxidative capacity of fish white muscle, we examined the effects of individual growth rate on the activities of four mitochondrial enzymes in white muscle of the fast growing Atlantic cod,Gadus morhua. Growth rates were individually monitored in cod held at three acclimation temperatures during experiments repeated in four seasons. The size dependence of citrate synthase (CS), cytochrome C oxidase (CCO) and β-hydroxyacyl CoA dehydrogenase (HOAD) activities was established using wild cod ranging from 115 to 17,350 g. Given their negative allometry, CS and CCO activities in the experimental cod were corrected to those expected for a 1.2 kg animal. HOAD activities did not change with size. The specific activities of CCO and CS were positively correlated with growth rate. However, for both enzymes, season explained more of the variability than growth rate or temperature. Season was the only factor to significantly affect the activity of HOAD, while temperature and season interacted to determine glutamate dehydrogenase activity. CS activity was positively correlated with the initial condition of the cod, which differed among the seasons. The other enzymes did not show this relationship. The independent changes of these enzymes suggest that mitochondria undergo qualitative modifications with changes in growth rate, season and size. Although growth rate and the activities of CCO and CS are positively correlated, the activity of the mitochondrial enzymes is more affected by size, physical condition and season.
Article
Mirex concentrations were measured in eels (Anguilla rostrata) from eastern Canada to determine the contribution of Lake Ontario eels to the Saint Lawrence commercial fishery. Mirex could be detected in all eels (50 specimens) collected in Lake Ontario (0.18 ± 0.11 μg∙g−1). Most sedentary eels collected from the Saint Lawrence commercial fishery and both the migratory and sedentary eels collected from the Saint Lawrence tributaries and the Maritimes had no mirex. Of the migrating eels collected in the Saint Lawrence 74% contained mirex (0.17 ± 0.19 μg∙g−1). These results show that stocks can be discriminated on the basis of the presence of synthetic chemical products such as pesticides and other contaminants that are distributed heterogeneously in the environment. Based on a presence–absence criterion, this method for stock discrimination has the distinct advantage that it is more accurate and less time consuming than similar methods based on the presence of natural chemical products.
Article
This study examined seasonal variations in tissue metal contamination and physiological condition of yellow perch (Perca flavescens) from a clean lake (Halfway Lake) and a metal-contaminated environment (Whitson Lake) in spring, summer, and fall of 1999. Dietary metal content influenced liver metal concentrations, especially for cadmium. Fulton's condition factor (FCF), an indicator of recent feeding activity, was lower in Whitson fish except in summer, when higher FCF values corresponded with higher liver copper concentrations, presumably because of higher feeding rate. Tissue protein concentrations and indicators of biosynthetic capacities (nucleoside diphosphate kinase and RNA/DNA ratios) suggested lower biosynthesis in Whitson fish. Muscle aerobic and anaerobic capacities (using citrate synthase and lactate dehydrogenase as indicators, respectively) were consistently lower in Whitson fish, with maximal differences in summer. In contrast, although liver aerobic capacities were generally comparable among populations, anaerobic capacities were much higher in Whitson fish. Finally, gill sodium/potassium adenosinetriphosphatase (Na+/K+ ATPase) activity peaked in the spring in fish from both lakes, and higher activities were correlated with elevated gill copper concentrations. This study highlights the importance of seasonal variations in tissue metal concentrations and fish condition. This information is essential to evaluate the extent of impairment in condition faced by metal-contaminated wild fish.
Article
Understanding the effects of chronic exposure to pollutants on the genome and transcriptome of diadromous fish populations is crucial for their resilience under combined anthropogenic and environmental selective pressures. The catadromous European eel (Anguilla anguilla L.) has suffered a dramatic decline in recruitment for three decades, necessitating a thorough assessment of the transcriptional effects of environmental pollutants on resident and migrating eels in natural systems. We investigated the relationship between muscular bioaccumulation levels of metals (Hg, Cd, Pb, Cu, Zn, Ni, Cr, As and Se), PCBs and organochlorine pesticides (DDTs), the health status (condition factor and lipid reserves) and the associated transcriptional response in liver and gill tissues for genes involved in metal detoxification (metallothionein, MT) and oxidative metabolism (cytochrome P4501A, CYP1A) of xenobiotic compounds. In total 84 resident eels originating from three Belgian river basins (Scheldt, Meuse and Yzer) were analyzed along with five unpolluted aquaculture samples as control group. There was a large spatial variation in individual contaminant intensity and profile, while tissue pollution levels were strongly and negatively associated with condition indices, suggesting an important impact of pollution on the health of sub-adult resident eels. Gene transcription patterns revealed a complex response mechanism to a cocktail of pollutants, with a high variation at low pollution levels, but strongly down-regulated hepatic and gill gene transcription in highly polluted eels. Resident eels clearly experience a high pollution burden and seem to show a dysfunctional gene transcription regulation of detoxification genes at higher pollutant levels, correlated with low energy reserves and condition. To fully understand the evolutionary implications of pollutants on eel reproductive fitness, analyses of mature migrating eels and the characterization of their transcriptome-wide gene transcription response would be appropriate to unveil the complex responses associated with multiple interacting stressors and the long-term consequences at the entire species level. In the meanwhile, jointly monitoring environmental and tissue pollution levels at a European scale should be initiated, while preserving high quality habitats to increase the recovery chance of European eel in the future.
Article
Understanding the effects of chronic exposure to pollutants on the genome and transcriptome of diadromous fish populations is crucial for their resilience under combined anthropogenic and environmental selective pressures. The catadromous European eel (Anguilla anguilla L.) has suffered a dramatic decline in recruitment for three decades, necessitating a thorough assessment of the transcriptional effects of environmental pollutants on resident and migrating eels in natural systems. We investigated the relationship between muscular bioaccumulation levels of metals (Hg, Cd, Pb, Cu, Zn, Ni, Cr, As and Se), PCBs and organochlorine pesticides (DDTs), the health status (condition factor and lipid reserves) and the associated transcriptional response in liver and gill tissues for genes involved in metal detoxification (metallothionein, MT) and oxidative metabolism (cytochrome P4501A, CYP1A) of xenobiotic compounds. In total 84 resident eels originating from three Belgian river basins (Scheldt, Meuse and Yzer) were analyzed along with five unpolluted aquaculture samples as control group. There was a large spatial variation in individual contaminant intensity and profile, while tissue pollution levels were strongly and negatively associated with condition indices, suggesting an important impact of pollution on the health of sub-adult resident eels. Gene transcription patterns revealed a complex response mechanism to a cocktail of pollutants, with a high variation at low pollution levels, but strongly down-regulated hepatic and gill gene transcription in highly polluted eels. Resident eels clearly experience a high pollution burden and seem to show a dysfunctional gene transcription regulation of detoxification genes at higher pollutant levels, correlated with low energy reserves and condition. To fully understand the evolutionary implications of pollutants on eel reproductive fitness, analyses of mature migrating eels and the characterization of their transcriptome-wide gene transcription response would be appropriate to unveil the complex responses associated with multiple interacting stressors and the long-term consequences at the entire species level. In the meanwhile, jointly monitoring environmental and tissue pollution levels at a European scale should be initiated, while preserving high quality habitats to increase the recovery chance of European eel in the future.
Article
Concepts of correlation and regression may be applied not only to ordinary one-dimensional variates but also to variates of two or more dimensions. Marksmen side by side firing simultaneous shots at targets, so that the deviations are in part due to independent individual errors and in part to common causes such as wind, provide a familiar introduction to the theory of correlation; but only the correlation of the horizontal components is ordinarily discussed, whereas the complex consisting of horizontal and vertical deviations may be even more interesting. The wind at two places may be compared, using both components of the velocity in each place. A fluctuating vector is thus matched at each moment with another fluctuating vector. The study of individual differences in mental and physical traits calls for a detailed study of the relations between sets of correlated variates. For example the scores on a number of mental tests may be compared with physical measurements on the same persons. The questions then arise of determining the number and nature of the independent relations of mind and body shown by these data to exist, and of extracting from the multiplicity of correlations in the system suitable characterizations of these independent relations. As another example, the inheritance of intelligence in rats might be studied by applying not one but s different mental tests to N mothers and to a daughter of each
Article
American eel (Anguilla rostrata) recruitment has declined dramatically, in parallel with that of European eel (Anguilla anguilla). Since both species spawn in the Sargasso Sea and migrate as larvae to continental waters, the coincidence in recruitment failure implies an Atlantic-wide cause, due perhaps to ocean climate. There is indirect evidence that the Gulf Stream has weakened in the 1980s. A slower Gulf Stream could interfere with larval transport and generate observed patterns of declining abundance of American eel only in northern North America and relatively uniform declines of European eel throughout Europe. While specific causes are still unclear, these data indicate a threat to both species and to their commercial fisheries.
Article
Abstract –  Since the 1980s, the European eel Anguilla anguilla stock is in steep decline. Lipid reserves are essential to cover energetic requirements for silver eel migration and reproduction. Two large and independent data sets from Belgium and The Netherlands show an average one-third decrease in fat contents of yellow eels over the past 15 years. Also Le Cren’s relative condition factor decreased. On the basis of the somatic energy reserves, reproductive potential of eels from various latitudes over Europe was estimated, assuming fat levels in yellow eel are indicative of those in silver eels. Only large individuals, females as well as males, with high lipid content seem to be able to contribute to the spawning stock. The decrease in fat content in yellow eels may be a key element in the stock decline and raises serious concerns about the chances of the stock to recover.
Article
The main energetic stores at the silver eel stage were studied by analysing muscle fat concentrations and hepatosomatic indices in female silver eels from various habitats in Sweden. Muscle fat concentrations varied both within and between localities and lean eels with muscle fat concentrations <20% occurred at all study sites. Furthermore, no correlation could be found between muscle fat content and internal or external maturation indices, neither was the relative liver size related to the maturation process, as the correlation between the hepatosomatic and gonadosomatic indices was very weak. Consequently, it was concluded that silvering and the spawning migration may begin also at low muscle fat concentrations. However, most of the energy reserve is stored as muscle fat in eel, and it is highly unlikely that female silver eels with such low fat contents, as were observed occasionally in this study, will ever recruit to the next generation. Therefore, it is suggested that the maturation process in eel is more flexible than previously recognized, and that this process might be temporarily arrested and feeding resumed during the first part of the migratory phase.
Article
Glucose-6-phosphate dehydrogenase (G6PDH), lactate dehydrogenase (LDH) and pyruvate kinase (PK) are key metabolic enzymes. G6PDH has been used as a biomarker of pollution-induced carcinogenesis in fish. LDH has been used as marker of lesions in toxicology and clinical chemistry, and PK catalyses the conversion of phosphoenol pyruvate to pyruvate, with regeneration of ATP. The effect of different concentrations of lead nitrate on the activity of these enzymes in two different early ontogenetic stages (embryonic and free embryonic stage) of the African catfish Clarias gariepinus was investigated. Embryo homogenates were used for measurements of G6PDH, LDH and PK activity spectrophotometrically at 340nm and 25°C. The ontogenetic variations of the three enzymes during early ontogeny, from the 30h to the 168h post-fertilisation stage (PFS) (beginning of exogenous feeding), were studied. There was a significant decrease in activities of all three enzymes from 30h-PFS to 96h-PFS, followed by a significant increase in G6PDH and LDH. PK showed insignificant fluctuations in activity. Different patterns of enzyme activities were recorded due to exposure to different lead nitrate concentrations (100μg/l, 300μg/l and 500μg/l). In the pre-hatching stage (30h-PFS) the activity of the three enzymes increased at exposure to 100μg/l lead nitrate and then decreased with increasing dose. In the post-hatching stages (48h-PFS–168h-PFS) G6PDH activity increased and LDH activity decreased with increasing lead concentrations. Unlike G6PDH and LDH, the PK enzyme fluctuated during the post-hatching stages and did not reveal a specific trend of response (increase or decrease) with increasing lead concentrations. Therefore, the measurement of G6PDH and LDH activities, but not PK activity, could be useful biomarkers of intoxication to reveal the embryotoxic potential of lead nitrate in fish embryos. The post-hatching stages of the African catfish are more sensitive than the pre-hatching stage (30h-PFS) is, probably due to the protective capacity provided by the hardened chorion. The interaction and the main effects of age and lead doses were found to be highly significant, referring to the great impact of lead on these enzyme systems with increasing early development.
Article
The Gironde estuary, one of the largest in Europe, is considerated as a reference ecological system, with all the western European diadromous fish species present. The national biomonitoring program on the coastal marine environment has revealed since 1979 severe metal pollution (mostly cadmium [Cd]) in oysters collected from the estuary. No data are available on metal contamination levels in fish, despite their ecological and economic importance. We present the results from a detailed study based on 4 metals (Cd, zinc [Zn], copper [Cu], and mercury [Hg]) measured in 4 organs (gills, dorsal skeletal muscle, liver, and kidneys) from 8 fish species illustrating several ecological combinations: European eel (Anguilla anguilla), twaite shad (Alosa fallax), bass (Dicentrarchus labrax), meagre (Argyrosomus regius), flounder (Platichthys flesus),, thin-lippid grey mullet (Liza ramada), sole (Solea vulgaris), and Canary drum (Umbrina canariensis). The results show very marked differences between species and organs, as well as very significant variations between the 4 metals. Although metal concentrations measured in fish muscle are low, except in the case of Hg for theA. fallax, high levels of Cu and Cd were observed in the kidneys and livers ofL. ramada andA. anguilla. A multifactorial analysis based on rank ordered metal concentrations for the 8 fish species clearly shows 4 clusters of species assigned to the different degrees of metal contamination, from the lowest contaminated (A. regius, D. labrax, S. vulgaris, andU. canariensis), to the most contaminated group (L. ramada). The most contaminated species (L. ramada, A. angailla, andP. flesus) are characterized by long residence times in the estuary, between 3.5 and 14 yr. ForL. ramada, biofilms with high metal storage capacities would be the principal uptake route; the two other species are benthic with a carnivorous regime. Comparisons between our data and four estuaries (Seine, France; Mersey, U.K.; La Plata, Argentina; Guadalquivir, Spain), on a limited number of common species, metals and fish organs, clearly reveal higher Cd bioaccumulation levels in the Gironde estuary.
Article
Despite its role as an essential micronutrient, copper (Cu) can be present in aquatic ecosystems at concentrations able to cause adverse health effects on aquatic organisms. Although Cu is acquired by fish by either water or diet, studies that have investigated Cu impacts in fish have mainly focused on the toxicity of waterborne Cu. Moreover, as the majority of experiments were carried out under simplified conditions, little is known about the effects of natural factors other than competitive ions on Cu toxicity in fish. As temperature is a primary factor that affects the physiological state of poikilotherm organisms, we investigated the individual and combined effects of temperature and waterborne or dietary Cu on fathead minnows (Pimephales promelas). Fish were exposed to environmentally realistic concentrations of waterborne or dietary Cu at 20 °C and 32 °C. Transcriptional and enzymatic responses of various indicators of metabolic capacities as well as indicators of heat, oxidative and metal stresses were measured in fish muscle. Under our experimental conditions, temperature was the most important factor affecting the general condition of fish. Although no significant Cu accumulation was observed in the muscle of Cu-exposed fish, at 20 °C, waterborne and dietary Cu triggered significant changes in the transcription level of genes encoding for proteins involved in energy metabolism, metal detoxification and protein protection. Moreover, the response was quantitatively more important for dietary Cu than for waterborne Cu. Combined exposure to heat and Cu triggered the most significant changes in gene transcription levels and enzyme activities. During combined exposure to heat and Cu, in addition to synergistic effects of the two factors, both waterborne and dietary Cu impaired the adaptive response developed by fish to curb heat stress. Reciprocally, temperature impaired the adaptive response developed by fish to combat Cu toxicity. These results suggest that wild fish populations subjected to elevated temperatures due to seasonal warming or global climate change may become more susceptible to Cu pollution, and vice versa.
Article
This paper describes the development and validation of an analytical methodology to determine 28 polybrominated diphenyl ethers (PBDEs) in European eel (Anguilla anguilla) tissues using matrix solid-phase dispersion (MSPD) and gas chromatography coupled to triple quadrupole mass spectrometry (GC-QQQ-MS/MS). A total of 28 PBDEs were targeted, including tri- to deca-brominated congeners. The robustness and effectiveness of the proposed sample preparation procedure was demonstrated in lipid-rich eel tissues. The use of batch MSPD with activated silica gel and H(2)SO(4)-impregnated silica gel, followed by H(2)SO(4) digestion and multilayer cartridge clean-up allowed for complete lipid removal and eliminated matrix effects during GC-QQQ-MS/MS analysis. The average PBDE recoveries from eel muscle samples spiked with PBDEs at two levels were in the range 56.2-119.0%. Precision was satisfactory since relative standard deviations were lower than 19.6%, regardless of spike level, and method quantification limits ranged between 1 and 170 pg g(-1) (wet weight). The method demonstrated its successful application for the analysis of eel samples from two coastal lagoons located on the western French Mediterranean coast. All samples tested positive, but for tri- to hexa-brominated congeners only and total PBDE levels observed in this study were in the range 0.08-1.80 ng g(-1) wet weight.
Article
The aim of this study was to assess the physiological response of Anguilla anguilla to propanil and the degree of recovery after being moved to clean water. Preliminary acute toxicity test was carried out in the laboratory and the median lethal concentration (LC50) at 96 h was calculated as 31.33 mg/L (29.60-33.59 mg/L). NOEC and LOEC values (at 96 h) were also calculated as 20 and 25mg/L, respectively. The fish were exposed to 0.63 and 3.16 mg/L of propanil for 72 h and allowed to recover for 144 h. Total proteins (TPs), gamma-glutamil transpeptidase (gamma-GT), alanin aminotransferase (AlAT), alkaline phosphatase (AP), lactate dehydrogenase (LDH) and water content (WC) were assayed in muscle and liver tissues, liver somatic index (LSI) was also determined. Liver TPs and gamma-GT activity decreased after propanil exposure while AlAT and LDH increased. Muscular AP, AlAT and proteins decreased in intoxicated eels while LDH and gamma-GT activities increased. WC increased in both tissues after herbicide exposure as well as LSI. These results revealed that propanil affects the intermediary metabolism of A. anguilla and that the assayed enzymes can be used as good biomarkers of herbicide contamination. However a longer recovery period should be necessary to re-establish eel physiology. The parameters measured in the present study can be used as herbicide toxicity indicators and are recommended for environmental monitoring assessments.
Article
This study on yellow perch (Perca flavescens) examines a series of enzymatic markers and the relative weights of pyloric caeca and visceral lipids, their response to changes in feeding regime and their potential use to infer recent changes in growth rate and fish condition. Fish were exposed to four different feeding regimes for 12 weeks resulting in specific growth rates ranging from 0.3% to 3.5% (%/day). Growth and condition responded rapidly to changes in ration and the weight of pyloric caeca and visceral lipids reflected increased feed intake. Growth rate was correlated with muscle citrate synthase and caecal nucleoside-diphosphate kinase activities, whereas condition was correlated with muscle citrate synthase and lactate dehydrogenase activities and with caecal glucose-6-phosphate dehydrogenase activity. Results showed that enzyme activities and biometric parameters responded rapidly to increased feed intake, but the response was slower when food intake decreased. Plateaus were attained for both condition and visceral lipid index, but the relative weight of pyloric caeca continued to increase throughout the experimental period. Results from this study could, in principle, be used to infer recent growth and energy status in wild yellow perch and thus provide an indicator of food availability in their environment.
Article
A protein determination method which involves the binding of Coomassie Brilliant Blue G-250 to protein is described. The binding of the dye to protein causes a shift in the absorption maximum of the dye from 465 to 595 nm, and it is the increase in absorption at 595 nm which is monitored. This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr. There is little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose. A small amount of color is developed in the presence of strongly alkaline buffering agents, but the assay may be run accurately by the use of proper buffer controls. The only components found to give excessive interfering color in the assay are relatively large amounts of detergents such as sodium dodecyl sulfate, Triton X-100, and commercial glassware detergents. Interference by small amounts of detergent may be eliminated by the use of proper controls.
Article
The effects of heavy metals on growth, intermediary metabolism and enzyme activities were investigated in yellow perch (Perca flavescens), sampled in summer and fall from lakes situated along a contamination gradient of Cd, Zn and Cu in the mining region of Rouyn-Noranda, Québec. An exposure-dependent decrease in condition factor was observed in both seasons. Liver glycogen and triglyceride reserves were higher in summer than in fall in fish from the reference lake, while the seasonal pattern was different in fish from the contaminated lakes. Plasma free fatty acids (FFA) levels were also influenced by season and contamination. Activities of malic enzyme (ME) and glucose 6-phosphate dehydrogenase (G6PDH) in the liver were higher in the summer than in the fall in reference lakes whereas no seasonal variations were detected in fish from contaminated lakes. Activities of pyruvate kinase (PyK), aspartate transaminase (AST), phosphoenolpyruvate carboxykinase (PEPCK) and malate dehydrogenase (MDH), were higher in fish from contaminated lakes in fall but not in summer. Chronic exposure of yellow perch to sublethal levels of heavy metals impairs growth and alters the seasonal cycling of liver glycogen and triglycerides as well as the activities of metabolic enzymes.
Article
This study examined variations in resting oxygen consumption rate (ROCR), post-exercise oxygen consumption rate, relative scope for activity (RSA), liver and muscle aerobic and anaerobic capacities (using citrate synthase (CS) and lactate dehydrogenase, respectively, as indicators), and tissue biosynthetic capacities (using nucleoside diphosphate kinase (NDPK) as an indicator), in wild yellow perch from four lakes varying in copper (Cu) and cadmium (Cd) contamination. Liver Cu and Cd concentrations largely reflected environmental contamination and were positively correlated with liver protein concentrations and NDPK activities. Our results suggest that metal contamination leads to an upregulation of liver protein metabolism, presumably at least in part for the purpose of metal detoxification. In contrast, muscle NDPK activities decreased with increasing liver Cd concentrations and NDPK activities. There was a 25% decrease in ROCR for a doubling of liver Cu concentrations and a 42% decrease in RSA for a doubling of liver Cd concentrations in the range studied. Cu contamination was also associated with lower muscle CS activities. Our results support previous findings of impaired aerobic capacities in the muscle of metal-contaminated fish, and demonstrate that this impairment is also reflected in aerobic capacities of whole fish. The evidence presented suggests that mitochondria may be primary targets for inhibition by Cu, and that Cd may reduce gill respiratory capacity. Muscle aerobic and anaerobic capacities were inversely related. This work indicates that metal exposure of wild yellow perch leads to a wide range of disturbances in metabolic capacities.
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Eel populations worldwide are dangerously close to collapsing. Our study is the first to show that current levels of dioxin-like contaminants are strong candidates because of their devastating effects on development and survival of eel embryos. Female and male silver eels were artificially stimulated to maturation and reproduction by treatment with carp pituitary extracts and hCG, respectively. During maturation of female European silver eels, about 60 g fat per kg eel is incorporated in the oocytes. Together with the fat, however, persistent organic pollutants such as dioxin-like polychlorinated biphenyls (PCBs) are incorporated too. The total dioxin-like toxic potency of the individual gonad batches was determined as 2,3,7,8-tetrachlorodibenzo-p-dioxine equivalents (TEQs), using an in vitro reporter gene assay. The observed differences in development and survival showed a significant negative correlation with the TEQ levels in the gonads, already at levels far below the maximal allowable level for fish consumption, i.e., 4 ng TEQ/kg fish. The clear inverse relationship between the TEQ level and the survival period of the fertilised eggs strongly suggests that the current levels of dioxin-like compounds seriously impair the reproduction of the European eel. The peak of the environmental levels of dioxin-like PCBs and the decline of eel coincide worldwide, further suggesting that, in addition to other threats, these contaminants contributed significantly to the current collapse in eel populations.
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Because European silver eels (Anguilla anguilla) fast during their reproductive migration to the Sargasso Sea, the successful completion of their unusual life cycle depends on quantity of lipids stored beforehand. These lipids are mainly accumulated during the growth phase stage of the animals, called yellow eel, as triglycerides in muscle. They are then catabolized to provide sufficient energy to enable migration, gonad maturation and spawning. In the laboratory, we investigated the possible impact of cadmium on the lipid storage efficiency of yellow eels in order to evaluate the possible contribution of this pollutant to the reported decline of European eel populations. Eels were exposed to dissolved cadmium at nominal concentrations of 0 and 5 microgL(-1) for 1 month. Cd toxicity was then examined by studying the activity and expression level of several enzymes involved in liver lipolysis and lipogenesis and by determining lipid content in muscle. Contaminated eels showed a lower body weight growth with a lower efficiency of lipid storage compared to controls. Using two complementary approaches, genetic and enzymatic, it was possible to conclude that this impairment is mainly explained by an increased utilisation of triglycerides since cadmium contamination did not trigger a reduced fatty acid synthesis. These observations suggest an increased fat consumption in presence of cadmium, which could compromise successful reproduction.
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European eel (Anguilla anguilla) populations are in decline. Glass eel recruitment has fallen 10-fold since the early 1980s. Estuaries play a fundamental role in the life history of eels because glass eels must pass through them to reach freshwater ecosystems. Unfortunately, because of their geographical position at the upstream basin slopes, estuaries accumulate metals like cadmium and are important sites of hypoxia events. In this context, we studied the effect of the oxygen level on the ventilation of the glass eel. In parallel, glass eels were submitted to different dissolved cadmium concentrations (0, 2, and 10 microg L(-1)) under two oxygen levels (normoxia PO2 = 21 kPa and Hypoxia PO2 = 6 kPa). The expression level of various genes involved in the mitochondrial respiratory chain, in the cellular response to metal and oxidative stresses, was investigated. Our results showed that hypoxia enhances (1) ventilation of the postlarval stage and (2) Cd accumulation in gills only at the lowest metal water concentration tested (2 microg Cd L(-1)). At the gene level, Cd exposure mimics the effect of hypoxia since we observed a decrease in expression of genes involved in the respiratory chain and in the defense against oxidative stress.
Article
The availability and bioaccumulation of metals and metalloids, and the geochemical interactions among them, are essential to developing an ecological risk assessment (ERA) framework and determining threshold concentrations for these elements. The purpose of this study was to explore the relationships among total recoverable and reactive metals and metalloid in sediment and their bioaccumulation by chironomids. In the fall of 2004 and 2005, 58 stations located in the three fluvial lakes of the St. Lawrence River and its largest harbour area in Montreal, Canada, were sampled. Nine total recoverable and reactive metals (Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) and one metalloid (As) were measured in whole sediment using two extraction methods: HCl/HNO(3) and HCl 1N, respectively. The bioaccumulation of six metals (Cd, Cr, Cu, Ni, Pb and Zn) and As by chironomids was evaluated in a subset of 22 stations. Strong collinearities were observed between some total recoverable or reactive metal concentrations in sediment; two principal clusters, including collinear metals, were obtained. The first one included metals of mainly geological origin (Al, Cr, Fe, Mn, Ni), while the second one included As, Cd, Cu, Pb and Zn, which likely derive mainly from point sources of anthropogenic contamination. Each element also showed strong collinearity between their total recoverable and reactive forms (0.65< or =r < or =0.97). We can conclude that both chemical forms are equivalent for use in statistical models needed to explain biological responses and also in screening risk assessment. However, these relationships are not always proportional. Lower availability percentages were observed for Cd, Cu and Zn in the highly mixed-contaminated area of the Montreal Harbour, even though concentrations in sediment were higher. We observed a significant correlation (0.50< or =r < or =0.56) between concentrations in chironomids and concentrations of both total recoverable and reactive Cr and Pb in sediment. Arsenic was an exception, with accumulation by chironomids being highly related to reactive sediment concentrations. Finally, we observed variable influences of explanatory factors (e.g. sediment grain size, Al, Fe, Mn, S, TOC), depending on which metal or metalloid was being predicted in chironomids. In this context, it is difficult to choose a universal predictive method to explain the bioaccumulation of specific metals, and more research is still needed into normalization procedures that consider a combination of explanatory factors.
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This paper describes fast and simple extraction methods for the determination of polychlorinated biphenyls and polybrominated diphenyl ethers in biological matrices. Four extraction protocols were tested. The first protocol used microwave-assisted extraction combined with two purification steps. The second one was similar, except that microwave-assisted extraction was replaced by accelerated solvent extraction. The third one combined extraction/purification by accelerated solvent extraction with final purification on a silica gel column. The last one combined microwave-assisted extraction with purification on an acidic silica gel column. The protocols were tested on various matrices: a spiked matrix, two certified matrices (SRM 2977, WMF 01), and natural matrices (mysids and fish). All of the protocols produced good performance in terms of recovery and reproducibility. The two last protocols showed promising results in terms of applicability to natural matrices, as they required a minimum of sample handling and minimal amounts of solvent and time. These methods allowed at least 24 samples to be handled per day, and could easily be used for routine analysis.