Lipid reserve dynamics and magnification of persistent organic pollutants in spawning sockeye salmon (Oncorhynchus nerka) from the Fraser River, British Columbia

Persistent contaminants in adipose fins of returning adult salmonids to the river Tees (UK)

We report on concentrations of polybrominated diphenylethers (PBDEs), polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p'-DDE) and hexachlorobenzene (HCB) measured in the adipose fins of returning adult Atlantic salmon (Salmo salar) and sea trout (Salmo trutta) to the river Tees in the Northeast of England. Overall, higher concentrations of these contaminants were found in sea trout samples, where detected congeners reflected the more widely used commercial formulations, in particular for the PBDEs. Our results suggest that these fish could be bioaccumulating persistent organic pollutants via diet during their migratory routes (North Sea and the Norwegian Sea) and, in addition, some level of re-mobilisation of these compounds could still be occurring in the UK eastern coastal areas. The use of adipose fin of returning salmonids could be further developed as a non-lethal approach to assess whether persistent contaminants are being accumulated during the juvenile to adult phase of salmonids originating from UK rivers.

Tissue-specific distribution and maternal transfer of polybrominated diphenyl ethers (PBDEs) and their metabolites in adult common sole (Solea solea L.) over an entire reproduction cycle

Tissue-specific accumulation and distribution of polybrominated diphenyl ethers (PBDEs) and their debrominated metabolites were studied in common sole (Solea solea) over an entire reproduction cycle. The fish were dietary-exposed to selected PBDEs in laboratory-controlled conditions for one year. Fish of both sexes were sampled throughout the reproduction cycle and their muscle, liver, viscera, carcass, skin and gonads (female) were analysed for total lipid content, PBDEs and their debrominated metabolites. On a wet weight basis, the concentrations of most spiked congeners showed an increase at the end of the exposure time in the whole body of fish of both sexes. Conversely, BDE-99 and BDE-209 - the two most highly metabolized congeners - did not show a similar increase, while their debrominated metabolites exhibited a linear increase over time. Biomagnification factors (BMFs) calculated in whole body were > 1 for all PBDEs except BDE-99 (0.89 ± 0.22) and BDE-209 (0.013 ± 0.006). BMFs were strongly correlated to apparent assimilation efficiencies, which ranged from 1.6% ± 0.7% (BDE-209) to 88% ± 11% (BDE-100). Fish carcass was the most predominant storage compartment for all PBDEs except BDE-209 in both male and female fish, followed by skin, muscle, female gonads, liver and visceral tissue. BDE-209 showed a different distribution and was stored more predominantly in the liver, viscera and female gonads than other congeners, probably due to its transport with lipoproteins. All PBDEs except BDE-209 showed equilibrium partitioning between the liver and other studied compartments, while BDE-209 showed a higher affinity with blood-enriched tissues, leading to higher liver / carcass, skin and muscle concentration ratios. Visceral tissue and liver exhibited the most pronounced differences in terms of concentration variations between sexes and over time. In females, both tissues showed a significant decrease in most PBDE concentrations (ww) and TLC in March during the spawning season, with low inter-individual variability, reflecting the striking utilisation of lipids by females for reproduction at this time. In males, no differences were found in concentrations in these compartments over time and a high inter-individual variability was observed. Maternal transfer of PBDEs from gonad to eggs was constant, regardless of spawn rank in the spawning season. Egg / gonad PBDE concentration ratios (in lw) were 1.3 ± 0.7 for all congeners and 2.6 ± 0.3 for BDE-209, suggesting a higher transfer of this congener from gonads to eggs.

Persistent Organohalogens in Paired Fish Fillet and Eggs: Implications for Fish Consumption Advisories

Fish consumption is associated with both health benefits from high-quality proteins, minerals, vitamins, and fatty acids and risks from contaminants in fish. Fish consumption advisories are issued by many government agencies to keep exposure to contaminants at a safe level. Such advisories are typically based on fillets and neglect consumption of other fish parts such as eggs by certain subpopulations. To evaluate potential for dietary exposure to toxic organic chemicals via fish eggs, we analyzed polybrominated diphenyl ethers (PBDEs), polychlorinated naphthalenes (PCNs), dioxin-like polychlorinated biphenyls (dlPCBs), and polychlorinated dibenzodioxins/furans (PCDD/Fs) in paired fillet and eggs of fish from a tributary to Lake Ontario, one of the North American Great Lakes. All wet weight based concentrations in fish eggs were statistically higher than in the paired fillet samples. In fish eggs, concentrations of Σ14PBDEs, Σ14PCNs, and Σ12dlPCBs were 41-118, 0.3-1.7, and 30-128 ng/g wet weight (ww), respectively; Σ3PCDD/Fs and total (dlPCB+ PCDD/Fs) toxic equivalents (TEQs) were 4-22 and 9-54 pg/g ww, respectively. In fillet samples, Σ14PBDEs, Σ14PCNs, and Σ12dlPCBs were 4-116, 0.05-0.66, and 6-85 ng/g, respectively; Σ3PCDD/Fs and TEQs were 2-10 and 3.4-31 pg/g ww, respectively. In contrast, the fillets had higher lipid normalized concentrations than the paired egg samples, suggesting that these chemicals did not reach equilibrium between the fillets and eggs. Accordingly, measured concentrations in eggs or empirical relationship with fillet rather than prediction from equilibrium partitioning model should be used to evaluate contaminant exposure via consumption of fish eggs. For fatty fish from the lower Great Lakes area, we suggest one fillet meal be reduced from the advised fish consumption frequency for consumptions of 207 ± 37, 39 ± 2, 105 ± 51, and 119 ± 9 g fish eggs of brown trout, Chinook salmon, Coho salmon, and rainbow trout, respectively.

Distinctive metabolite profiles in in-migrating Sockeye salmon suggest sex-linked endocrine perturbation

The health of Skeena River Sockeye salmon (Onchorhychus nerka) has been of increasing concern due to declining stock returns over the past decade. In the present work, in-migrating Sockeye from the 2008 run were evaluated using a mass spectrometry-based, targeted metabolomics platform. Our objectives were to (a) investigate natural changes in a subset of the hepatic metabolome arising from migration-associated changes in osmoregulation, locomotion, and gametogenesis, and (b) compare the resultant profiles with animals displaying altered hepatic vitellogenin A (vtg) expression at the spawning grounds, which was previously hypothesized as a marker of xenobiotic exposure. Of 203 metabolites monitored, 95 were consistently observed in Sockeye salmon livers and over half of these changed significantly during in-migration. Among the most dramatic changes in both sexes were a decrease in concentrations of taurine (a major organic osmolyte), carnitine (involved in fatty acid transport), and two major polyunsaturated fatty acids (eicosapentaenoic acid and docosahexaenoic acid). In females, an increase in amino acids was attributed to protein catabolism associated with vitellogenesis. Animals with atypical vtg mRNA expression demonstrated unusual hepatic amino acid, fatty acid, taurine, and carnitine profiles. The cause of these molecular perturbations remains unclear, but may include xenobiotic exposure, natural senescence, and/or interindividual variability. These data provide a benchmark for further investigation into the long-term health of migrating Skeena Sockeye.

Organohalogen concentrations and feeding status in Atlantic salmon (Salmo salar L.) of the Baltic Sea during the spawning run

Changes in the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in Baltic salmon muscle were studied during the spawning migration from the southern Baltic Sea to rivers flowing into the northern Gulf of Bothnia and during the spawning period. The aim was to obtain information to facilitate the arrangement of salmon fisheries such that the human dioxin intake is taken into account. The EC maximum allowable total toxic equivalent concentration (WHO-TEQPCDD/F+PCB) was exceeded in the muscle of the majority of the migrating salmon, except in the Baltic Proper. The fresh-weight-based concentrations of all toxicant groups in salmon tended to be the lowest in the Baltic Proper and the Northern Quark, and all toxicant concentrations, except PCDDs and PCDFs, were significantly higher in the spawning salmon than in the salmon caught during the spawning run. The fat content of the salmon muscle decreased by 60% during the spawning run, and the lipid-based total toxicant concentrations were consequently 4.2-6.2 times higher during the spawning period than during the spawning migration. However, the toxicants were concentrated just before spawning, and thus there is no essential difference related to whether the salmon are caught in the sea or the recreational river fishery.

Bioamplification as a bioaccumulation mechanism for persistent organic pollutants (POPs) in wildlife

Persistent organic pollutant bioaccumulation models have generally been formulated to predict bioconcentration and biomagnification. A third bioaccumulation process that can mediate chemical fugacity in an organism is bioamplification.Bioamplification occurs when an organism loses body weight and the chemical partitioning capacity occurs at a rate that is faster than the chemical can be eliminated.Although bioamplification has not been widely recognized as a bioaccumulation process, the potential consequences of this process are significant. Bioamplification causes an increase in chemical fugacity in the animal's tissues and results in there distribution of contaminants from inert storage sites to more toxicologically sensitive tissues. By reviewing laboratory and field studies, we have shown in this paper that bioamplification occurs across taxonomic groups that include, invertebrates,amphibians, fishes, birds, and mammals. Two case studies are presented, and constitute multi-life stage non-steady state bioaccumulation models calibrated for yellow perch and herring gulls. These case studies were used to demonstrate that bioamplification is predicted to occur under realistic scenarios of animal growth and seasonal weight loss. Bioamplification greatly enhances POP concentrations and chemical fugacities during critical physiological and behavioral events in an animal's life history, e.g., embryo development, juvenile stages, metamorphosis, reproduction, migration, overwintering, hibernation, and disease. Consequently,understanding the dynamics of bioamplification, and how different life history scenario scan alter tissue residues, may be helpful and important in assessing wildlife hazards and risks.

Metabolic concentration of lipid soluble organochlorine burdens in the blubber of southern hemisphere humpback whales through migration and fasting

Southern hemisphere humpback whales undertake the longest migrations and associated periods of fasting of any mammal. Fluctuations in lipid energy stores are known to profoundly affect the toxicokinetics of lipophilic organochlorine compound (OC) burdens. Results from blubber biopsy sampling of adult, male humpback whales at two time points of the annual migration journey revealed dramatic concentration effects for the majority of OC compounds. The observed concentration effect was, however, not linear with measured average blubber lipid loss indicating significant redistribution of OCs and hence the importance of alternate lipid depots for meeting the energetic demands of the migration journey. Applying lipophilic OC burdens as novel tracers of whole-body lipid dynamics, the observed average concentration index suggests an average individual weight loss of 13% over 4 months of the migration journey. This value is based upon lipid derived energy and is in good agreement with previous weight prediction formulas. Notably, however, these estimates may greatly underestimate individual weight loss if significant protein catabolism occurs. Biomagnification factors between migrating southern hemisphere humpback whales and their principal prey item, Antarctic krill, closely resembled those of baleen whales feeding on herbivorous zooplankton in the Arctic. This study emphasizes the importance of considering prolonged periods of food deprivation when assessing chemical risks posed to wildlife. This is of particular importance for Polar biota adapted to extremes in ecosystem productivity.

PCBs contamination does not alter aerobic metabolism and tolerance to hypoxia of juvenile sole (Solea solea L. 1758)

Coastal habitats play a major role as nurseries for many fish species; however, they are also submitted to pollutants and oxygen fluctuations. Fry's concept of metabolic scope for activity was used to evaluate the effect of polychlorinated biphenyls (PCBs) on the aerobic metabolism in juvenile common sole (0-1 year old). Aerobic metabolic scope (AMS) in control and PCB-contaminated fish via food pathway was determined using respirometry techniques. Furthermore, the hypoxia tolerance in control and PCB-contaminated fish was evaluated by assessing their critical oxygen concentration (O(2crit)). Our results showed that while PCB-contaminated fish were able to maintain a constant AMS and O(2crit), PCBs tend to affect their aerobic metabolism by acting on maximal oxygen consumption (MO(2max)) in hypoxia and standard metabolic rate, but only at the highest PCB concentration between 30 and 60 days of exposure. In conclusion, we can hypothetise that the tested PCB-exposures may not impair the tolerance to hypoxia and the survival of common sole in their natural environment.

Evaluation of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in Mullus barbatus from Sicily Channel and risk-based consumption limits

Our study is a preliminary step to evaluate water contamination of the Mediterranean Sea surrounding Lampedusa island and health risks for fish consumers. We analyzed muscle tissue of Mullus barbatus specimens to detect metals and polycyclic aromatic hydrocarbons (PAHs). Results show the following average concentrations of heavy metals: Pb 0.035, Cd 0.001, Hg 0.027, Cr 0.524, As 27.01, Cu 0.433, Co 0.013, Ni 0.042, Se 0.487, V 0.072, U 0.055 and Zn 3.360 ppm. PAHs ranged from 0.250 to 13.16 ppb. A possible risk to human health was determined based on consumption limits data and the content of total PAHs in fillets of this species.

The predictive power of the elimination of dioxin-like pollutants from pigs: an in vivo study

Pigs accidentally given feed contaminated by dioxin-like pollutants are a serious public health issue. We have examined whether pigs with limited exposure during early periods of fattening would be categorized as non-compliant with the EU limit at slaughtering when growth-dilution, excretion and metabolism effects are considered. Sixteen female and sixteen castrated male weaned pigs were divided into four groups (e.g. DG0, DG1, DG2 and DG3) in week 2 after birth. From weeks 3 to 13, groups DG1, DG2, and DG3 pigs were fed with a polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/F) and polychlorinated biphenyl (PCB) mixture at dosages of 1, 10 and 100ng-toxic equivalent (TEQ) per kg dry mass feed in capsules, respectively. From weeks 13 to 23, the animals were nourished with clear feed. Control group DG0 was always fed with clear feed. Subcutaneous fat samples were collected at weeks 13, 18 and 23 by biopsies. The pollutant residues were analyzed by high resolution gas chromatography-high resolution mass spectrometry and quantified by a (13)C-isotope dilution method. The results showed the following: (1) when slaughtered at week 23, the TEQ for DG1 pigs (0.66±0.21pg/g fat) was under the EU limit of 1pg PCDD/F-TEQ/g fat; (2) PCDD/F congener-specific first-order elimination rates were linearly correlated with their toxicity equivalency factors (TEFs), and the rates were significantly dose-dependent for the more toxic congeners (TEF≥0.1). Therefore, the pigs' exposure above the EU limit during the early fattening stage did not necessarily lead to their categorization as non-compliant pork; and the residual TEQ for pork can be predicted from early exposure concentrations based on the models established here.

Development and validation of protocols to differentiate PCB patterns between farmed and wild salmon

Polychlorinated biphenyl (PCB) congener patterns based on full congener PCB analyses of three farmed and five wild species of salmon from coastal British Columbia, Canada are compared using principal components analysis (PCA) and the best fit linear decomposition of the observed PCB composition in terms of Aroclor 1242, 1254, and 1260 end-members. The two complementary analysis methods are used to investigate congener composition pattern differences between species, trophic levels, feeding preferences, and farmed or wild feeding regimes, with the intent of better understanding PCB processes in both salmon and salmon consumers. PCA supports classification of PCB congeners into nine groups based on a) structure activity groups (SAG) related to the bioaccumulation potential in fish-eating mammals, b) Cl number, and c) the numbers of vicinal meta- and para-H. All three factors are needed to interpret congener distributions since SAGs by themselves do not fully explain PCB distributions. Farmed salmon exhibit very similar congener patterns that overlap the PCA and Aroclor composition of their food, while wild salmon separate into two distinct groups, with chinook and "coastal" coho having higher proportions of the higher chlorinated, Aroclor 1260 type, nonmetabolizable congeners, and chum, pink, sockeye, and "remote" coho having higher proportions of the lower chlorinated, more volatile and metabolizable Aroclor 1242 type, congeners. Wild chinook have the highest PCB and toxic equivalent (TEQ) concentrations, and the highest proportions of A1254 A1260, and PCB congeners in the most refractory SAG. Because both "coastal" and "remote" coho groups are likely to be consuming prey of similar size and trophic level, the PCB delivery mechanism (e.g., atmosphere vs runoff) apparently has more influence on the salmon PCB profile than biotransformation, suggesting that the wild chinook PCB profile is determined by feeding preference. Overall, wild salmon distributions primarily relate to trophic level, feeding preferences, and longevity, while metabolism appears at most a minor factor. The new classification protocol takes better advantage of individual congener PCB analyses and provides a better framework for understanding the PCB distributions in salmon and, potentially, the movement of individual PCB congeners through marine food chains than previous classification schemes.

Tissue residue concentrations of organohalogens and trace elements in adult Pacific salmon returning to the Fraser River, British Columbia, Canada

We report measured concentrations of organohalogens and trace elements in muscle and eggs of returning wild Pacific sockeye and chinook salmon during their 2007 migration through the Fraser River watershed in Canada. Chemical analyses revealed the presence of ppb to ppm levels of a wide variety of contaminants in these fish, including polychlorinated biphenyls (PCBs); polychlorinated dibenzo-p-dioxins (PCDDs); polychlorinated dibenzofurans (PCDFs); polybrominated diphenyl ethers (PBDEs); organochlorine pesticides (OCPs) such as DDTs, hexachlorocyclohexanes (HCHs), octachlorostyrene, and cyclodienes; and Hg, As, Cd, Pb, and several other trace elements. Body weights and flesh lipid contents declined during upstream migration, resulting in significantly higher (p < 0.05) lipid-normalized concentrations of lipophilic organohalogens (PCBs, PCDD/Fs, pesticides) in those spawning salmon. Postmigration magnification factors (MFs) of organohalogens (0.1-10) were comparable to previous observations and model predictions. MFs generally increased with increasing hydrophobicity (K(OW)). For example, MFs of tetra- and pentachlorobenzenes and HCH isomers (log K(OW) range: 3.8-5) were relatively low (between 0.1 and 1.7) compared with those of more lipophilic compounds (log K(OW) > 6) such as PCBs, DDTs, and mirex (MFs between 5 and 10). Lipid-normalized muscle:egg ratios in female salmon, which varied between 0.1 and 8, also exhibited a positive relationship with chemical K(OW). The results indicate that lipophilic compounds (K(OW) > 10(6)) can be magnified in flesh lipids of Pacific salmon during spawning migration, but maternal transfer kinetics (deposition to eggs) of those chemicals are relatively slow compared with less hydrophobic compounds. 2,3,7,8-TCDD toxic equivalents (ΣTEQs) in eggs of these spawning salmon, calculated using WHO toxic equivalency factors (WHO-TEFs) for fish health, in some cases exceeded the 0.3 pg·g(-1) threshold level associated with 30% salmonid egg mortality, indicating the potential for reproductive impacts in Fraser River salmon populations.

Gene expression profiling and environmental contaminant assessment of migrating Pacific salmon in the Fraser River watershed of British Columbia

The health and physiological condition of anadromous salmon is of concern as their upriver migration requires navigation of human-impacted waterways and metabolism of stored energy reserves containing anthropogenic contaminants. Such factors may affect reproductive success of fish stocks. This study investigates chemical contaminant burdens and select gene expression profiles in Pacific Sockeye (Oncorhynchus nerka) and Chinook (Oncorhynchus tshawytscha) salmon which traverse the Fraser River watershed during their spawning migration. Chemical analyses of muscle tissue and eggs of salmon collected from the lower Fraser River (pre-migration) and from upstream spawning grounds (post-migration) during the 2007 migration revealed the presence of numerous chemical contaminants, including PCBs, dioxins/furans, pesticides, and heavy metals. However, muscle tissue residue concentrations were well below human health consumption guidelines and 2,3,7,8 TCDD toxic equivalents (SigmaTEQs) in salmon eggs, calculated using WHO toxic equivalency factors (WHO-TEFs) for fish health, did not exceed the 0.3pgg(-1) wet weight toxicological threshold level previously associated with 30% egg mortality in salmon populations. Quantitative real-time PCR probes were generated and used to assess differences in abundance of key mRNA transcripts encoding nine gene products associated with reproduction, stress, metal toxicity, and exposure to environmental contaminants. Gene expression profiles were characterized in liver and muscle tissue of pre- and post-migration Sockeye and Chinook salmon. The results of stock-matched animals indicate that dynamic changes in mRNA levels occur for a number of genes in both species during migration and suggest that Sockeye salmon exhibit a greater level of biological stress compared to the Chinook salmon population. Using a male-specific genotypic marker, we found that out of the 154 animals examined, one Sockeye was genotypically male but phenotypically female. This individual's gene expression profile in liver and muscle was reminiscent of, but not identical to, the female expression profile. These studies provide the first glimpse of the dynamic yet common nature of changes in the transcriptome that are shared between species during in-migration and highlight differences that may relate to population success. Continued longitudinal assessment will further define the association between contaminant burden, physiological stress, and modulation of gene expression in migrating Pacific salmon.

Polychlorinated biphenyl (PCB) load, lipid reserves and biotransformation activity in migrating Atlantic salmon from River Mörrum, Sweden

Atlantic salmon accumulate high levels of contaminants such as polychlorinated biphenyls (PCBs) in their lipids during the adult growth phase spent at sea. The lipids are later utilized during migration for swimming and biological adaptations. We hypothesize that migrating salmons' biotransformation processes are affected by the high levels of built-up PCBs compared to salmon that in a pre-migrational stage. For these analyses we sampled adult Atlantic salmon during migration in the Swedish River Mörrum and measured the 21 most common PCB congeners ( summation operatorPCB) and lipid levels in muscle tissue, aryl hydrocarbon receptor (AHR2) and cytochrome P4501A1 (CYP1A1) transcript levels as well as ethoxyresorufin-O-deethylase activity (EROD) in liver. We also determined which AHR2 genotypes the salmon carried. We show that EROD activity is correlated to CYP1A1 level but not to summation operatorPCB concentration. summation operatorPCB concentration does not predict levels of neither the AHR2 nor CYP1A1 genes. We find no associations between specific AHR2 transcription levels and AHR2 genotypes or a correlation between AHR2 and CYP1A1 transcription levels, which is in direct contrast to pre-migrational adult salmon from the Baltic Sea. When we compare River Mörrum to salmon we have previously sampled in the Baltic Sea we show that migrating salmon have significantly lower lipid levels in their muscles; higher muscle concentrations of summation operatorPCB on a lipid basis; and significantly lower CYP1A1 and EROD levels compared to salmon from the Baltic Sea. Also, transcript levels of three out of four AHR2 genes are significantly different. In conclusion, migrating Swedish Atlantic salmon carry higher concentrations of PCBs in their lipids compared to salmon in the Baltic Sea, but have lower activation of biotransformation genes and enzymes. Our results indicate that accumulated pollutants from the Baltic Sea are deactivated inside the migrating salmon's lipid tissues and increase in concentration when migration is initiated thereby limiting their impact on biotransformation processes.

Transcripts level responses in a marine medaka (Oryzias javanicus) exposed to organophosphorus pesticide

The differential expression of a set of genes encoding antioxidant enzymes and stress-responsive proteins was investigated by real-time quantitative PCR in intestine, liver, and muscle tissues extracted from Oryzias javanicus after exposure to the organophosphorus pesticide, Iprobenfos (IBP). After IBP exposure, transcriptional changes in all the tested genes were prominent in the liver and moderate in the intestine, but unpredictable in the muscle. In the liver, CAT transcription increased after exposure to IBP at all concentrations (P<0.05). CYP1A mRNA was induced in the intestine and liver at the two higher concentrations. G6PD transcription was induced in the liver at the three higher IBP concentrations, but was suppressed in muscle at the same concentrations. GPx expression in the liver increased at three higher concentrations of IBP. In the intestine and liver, GR expression was induced at two higher and three higher concentrations, respectively. However, no significant changes were observed in the muscle. GST and SOD transcription was induced in the liver at all IBP concentrations. IBP exposure induced UB expression in the intestine and liver in a concentration-dependent manner. The transcriptional changes in these genes in the liver could be good biomarkers for stress levels in O.javanicus, and be used as critical biomarkers for environmental quality assessment.