Seasonal emaciation causes tissue redistribution and an increased potential for toxicity of lipophilic pollutants in farmed arctic fox (Vulpes lagopus).

Many Arctic animals carry high body burdens of organochlorine contaminants (OCs) as a result of long-range transport of persistent pollutants. It has been shown that seasonal mobilization of body fat in these species results in increased blood concentration of OCs. The authors investigated OC assimilation, tissue distribution, and biotransformation in farmed Arctic fox (Vulpes lagopus) continuously fed a diet containing contaminated minke whale blubber or lard (control) from 8 wk of age in August 2003, until sampling when they were at their fattest (in November 2004) and leanest (in June 2005). Markedly higher tissue (liver, adrenals, brain, and blood) OC levels were found in June than in November despite low exposure to OCs during emaciation, suggesting that OCs had been redistributed from adipose tissues to vital organs. There were no differences in the activities of hepatic biotransforming enzymes between exposed fat and control fat foxes, except for 16α-hydroxylation, which was higher in exposed fat foxes. In emaciated foxes, ethoxyresorufin activity was higher in exposed than in control foxes, indicating an enhanced potential for toxicity of OCs with emaciation. Lower activities of 6ß- and 2ß-hydroxylation were found in lean than in fat foxes, irrespective of OC treatment. The results show that emaciation increase the toxic potential of accumulated OCs and emphasize that body adiposity must be considered when time-trend analyses, risk assessments, and effect studies are designed. Environ Toxicol Chem 2013;32:1784-1792. © 2013 SETAC.

Effect of reduced food intake on toxicokinetics of halogenated organic contaminants in herring gull (Larus argentatus) chicks.

The aim of the present study was to investigate how contaminant exposure and reduced food intake affect tissue distribution and biotransformation of halogenated organic contaminants (HOCs) in Arctic seabirds using herring gull (Larus argentatus) as a model species. Herring gull chicks were exposed for 44 d to cod liver oil containing a typical mixture of contaminants. Following exposure, food intake was reduced for a one-week period in a subgroup of the chicks. Polyclorinated biphenyls, organochlorine pesticides, and brominated flame retardants, as well as a wide range of hydroxy, methyl sulfone, and methoxy compounds were measured in liver, brain, and plasma samples. Additionally, phase I biotransformation enzyme activities and phase I and II messenger ribonucleic acid (mRNA) expression were investigated in the liver, brain, or both. Both contaminant exposure and reduced food intake had an increasing effect on the concentrations of HOCs and their metabolites. The HOC exposure and reduced food intake also led to increased 7-ethoxyresorufin-O-deethylation (EROD) activity, whereas mRNA expression of the biotransformation enzymes increased only following the reduced food intake. Tissue distribution of HOCs and their metabolites was not affected by either contaminant exposure or reduced food intake. In conclusion, the results indicate that biotransformation capacity and formation of HOC metabolites increase during reduced food intake. This finding supports the hypothesis that reduced food intake increases the susceptibility of Arctic animals to the effects of lipophilic HOCs.

Chronic dietary exposure to environmental organochlorine contaminants induces thyroid gland lesions in Arctic foxes (Vulpes lagopus).

The impact of dietary organochlorine (OC) exposure on thyroid gland pathology was studied in farmed male Arctic foxes (Vulpes lagopus). The exposed group (n=16) was fed a diet based on wild minke whale (Balaenoptera acutorostrata) blubber as a main fat source in order to mimic the exposure to OC cocktails in the Artic environment. This resulted in an exposure of approximately 17 microg Sigma OC/kg day and a Sigma OC residue adipose tissue and liver concentration of 1700 and 4470 ng/gl.w., respectively, after 16 months of exposure. Control foxes (n=13) were fed a diet with pork (Sus scrofa) fat as a main fat source containing significantly lower OC concentrations. The food composition fed to the control and exposed group was standardized for nutrient contents. Four OC-related histopathological changes were found: (1) flat-epithelial-cell true thyroid cysts (TC) characterized by neutral content; (2) remnants of simple squamous epithelial-cell embryonic ducts containing neutral debris (EDN); (3) remnants of stratified squamous epithelial-cell embryonic ducts containing acid mucins often accompanied with debris of leukocyte inflammatory nature (EDM) and (4) disseminated thyroid C-cell hyperplasia (HPC). Of these, the prevalence of TC, EDN and HPC was significantly highest in the exposed group (chi(2) test: all p<0.04). The study shows that the OC mixture in minke whale blubber may cause development of thyroid gland cysts, C-cell hyperplasia and increase the prevalence of cystic remnants of embryonic ducts. The mechanism causing these effects could include endocrine disruption of the hypothalamus-pituitary-thyroid (HPT) axis, a disturbance of the calcium homeostasis/metabolism or energy metabolism or immune suppression. Because concentrations of OCs are higher in wild Arctic foxes, it is likely that these animals could suffer from similar OC-induced thyroid gland pathological and functional changes.

Tissue-specific contaminant accumulation and associated effects on hepatic serum analytes and cytochrome P450 enzyme activities in hooded seals (Cystophora cristata) from the Gulf of St. Lawrence.

The current study aims to assess contaminant levels and tissue burdens in hooded seal (Cystophora cristata) blubber, liver, and blood in association with cytochrome P450 (CYP) enzymes (CYP1A and -3A) and serum analytes (hepatic enzymes like alanine aminotransferase [ALT], aspartate aminotransferase, alkaline phosphatase [AP], and gamma-glutamyltransferase [GGT], serum proteins, and creatine kinase). Contaminant accumulation levels and patterns of polychlorinated biphenyls, chlorinated pesticides, and polybrominated diphenyl ethers (PBDEs) differed between tissues and seal groups, with the highest levels in liver. Pups showed higher liver contaminant levels, especially for PBDEs, than adults. These high levels might be associated with the ingestion of large amounts of contaminated milk and subsequent accumulation in the liver. Adult males and females mainly differed in PBDE levels, which were higher in females, possibly due to a sex-specific diet. The association between blubber contaminant burdens and the diagnostic enzymes ALT, GGT, and AP, and serum albumin, was inconclusive. In contrast, several CYP isoenzymes showed a clear positive relationship with the overall blubber contaminant burden, indicating enzyme induction following exposure to polyhalogenated hydrocarbons. Therefore, liver CYP isoenzymes may serve as a sensitive biomarker for long-term exposure to polyhalogenated hydrocarbons.

Mineral density and biomechanical properties of bone tissue from male Arctic foxes (Vulpes lagopus) exposed to organochlorine contaminants and emaciation.

We investigated the impact from dietary OC (organochlorine) exposure and restricted feeding (emaciation) on bone mineral density (BMD; g hydroxy-apatite cm(-2)) in femoral, vertebrate, skull and baculum osteoid tissue from farmed Arctic blue foxes (Vulpes lagopus). For femur, also biomechanical properties during bending (displacement [mm], load [N], energy absorption [J] and stiffness [N/mm]) were measured. Sixteen foxes (EXP) were fed a wet food containing 7.7% OC-polluted minke whale (Balaenoptera acutorostrata) blubber in two periods of body fat deposition (Aug-Dec) and two periods of body fat mobilisation (Jan-July) in which the food contained less energy and only 2% blubber. SigmaOC food concentration in the food containing 7.7% whale blubber was 309 ng/g wet mass. This corresponded to a SigmaOC exposure of ca. 17 microg/kg body mass/d and a responding SigmaOC residue in subcutaneous adipose tissue of ca. 1700 ng/g live mass in the 8 EXP fat foxes euthanized after 16 months. A control group (CON) composed of 15 foxes were fed equal daily caloric amounts of clean pork (Sus scrofa) fat. After 16 months, 8 EXP and 7 CON foxes were euthanized (mean body mass=9.25 kg) while the remaining 8 EXP and 8 CON foxes were given restricted food rations for 6 months resulting in a body weight reduction (mean body mass=5.46 kg). The results showed that only BMD(skull) vs. BMD(vertebrae) were significantly correlated (R=0.68; p=0.03; n=10) probably due to a similar composition of trabecular and cortical osteoid tissue. No difference in any of the BMD measurements or femoral biomechanical properties was found between EXP and CON foxes although BMD baculum was 1.6-folds lower in the EXP group. However, lean summer foxes had significantly lower femoral biomechanical properties measured as displacement (mm), energy absorption (J) and time (s) biomechanical properties than fat winter foxes (all p<0.004). This indicates lower stiffness and softer bones from fasting which is in agreement with previous studies. Further, it should be kept in mind when studying bone tissues in Arctic mammals also in order to avoid confounding effects from body condition.

Biomarker responses and decreasing contaminant levels in ringed seals (Pusa hispida) from Svalbard, Norway.

Blubber was analyzed for a wide range of contaminants from five sub-adult and eight adult male ringed seals sampled in 2004, namely, for polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), toxaphenes, chlordanes, dichlorodiphenyldichloroethylene (DDE), and polybrominated diphenylethers (PBDEs). Contaminant levels were compared to previously sampled animals from the same area, as well as data from literature for other arctic wildlife species from a wide variety of locations. Ringed seals sampled in 2004 showed 50-90% lower levels of legacy contaminants such as PCBs and chlorinated pesticides compared to animals sampled in 1996 of similar age (14 sub-adults and 7 adult males), indicating that the decline of chlorinated contaminants observed during the 1990s in a variety of arctic wildlife species is continuing into the 21st century. The results also indicated that PBDE declined in ringed seals; levels in 2004 were about 70-80% lower than in animals sampled in 1998. This is one of the first observations of reduced exposure to these compounds and might be a first indication that restrictions of production and use of these contaminants have resulted in lower exposures in the Arctic. The PCB pattern shifted toward the less chlorinated (i.e., less persistent) PCBs, especially in adult ringed seals, possibly as a result of reduced overall contaminant exposures and a consequently lower cytochrome P-450 (CYP) induction, which results in a slower metabolism of less persistent PCBs. The overall effect would be relative increases in the lower chlorinated PCBs and a relative decreases in the higher chlorinated PCB. Possibly due to low exposure and consequent low induction levels, ethoxyresorufin O-deethylation (EROD) activity proved to be a poor biomarker for contaminant exposure in ringed seals in the present study. The close negative correlation (r(2) = 70.9%)between EROD activity and percent blubber indicates that CYP might respond to increased bioavailability of the contaminant mixtures when they are mobilized from blubber during periods of reduced food intake.

Organochlorine-induced histopathology in kidney and liver tissue from Arctic fox (Vulpes lagopus).

The effects of persistent organic pollutants on renal and liver morphology in farmed arctic fox (Vulpes lagopus) were studied under experimental conditions. Control animals received a diet containing pork (Sus scrofa) fat with low amounts of persistent organic pollutants, while the diet of the exposed animals contained whale blubber, 'naturally' contaminated with persistent organic pollutants. Polychlorinated biphenyls (PCB) and organochlorine pesticide (OCP) concentrations in the whale blubber were 488 and 395 ng/g wet weight, respectively. Animals were sacrificed and sampled when they were at their fattest (winter) as well as their lowest body weight (summer). The results show that PCB and OCP exposure causes renal (and probably also liver) lesions in arctic foxes. The prevalence of glomerular, tubular and interstitial lesions was significantly highest in the exposed group (chi-square: all p<0.05). The frequency of liver lesions (steatosis, intravascular granulocyte accumulations, interstitial cell infiltrations, lipid granulomas, portal fibrosis and bile duct hyperplasia) were also highest in the exposed group, although not significantly (chi-square: all p>0.05). The prevalence of lesions was not significantly different between lean (winter) and fat (summer) foxes for any of the lesions (chi-square: all p>0.05). We suggest that wild arctic foxes exposed to an environmental cocktail of persistent organic pollutants, such as PCBs and OCPs, in their natural diet are at risk for developing chronic kidney and liver damage. Whether such lesions may have an impact on age and health of the animals remains uncertain.

Accumulation and transfer of contaminants in killer whales (Orcinus orca) from Norway: indications for contaminant metabolism.

Blubber tissue of one subadult and eight male adult killer whales was sampled in Northern Norway in order to assess the degree and type of contaminant exposure and transfer in the herring-killer whale link of the marine food web. A comprehensive selection of contaminants was targeted, with special attention to toxaphenes and polybrominated diphenyl ethers (PBDEs). In addition to assessing exposure and food chain transfer, selective accumulation and metabolism issues also were addressed. Average total polychlorinated biphenyl (PCB) and pesticide levels were similar, approximately 25 microg/g lipid, and PBDEs were approximately 0.5 microg/g. This makes killer whales one of the most polluted arctic animals, with levels exceeding those in polar bears. Comparing the contamination of the killer whale's diet with the diet of high-arctic species such as white whales reveals six to more than 20 times higher levels in the killer whale diet. The difference in contaminant pattern between killer whales and their prey and the metabolic index calculated suggested that these cetaceans have a relatively high capacity to metabolize contaminants. Polychlorinated biphenyls, chlordanes, and dichlorodiphenyldichloro-ethylene (DDE) accumulate to some degree in killer whales, although toxaphenes and PBDEs might be partly broken down.

Congener-specific accumulation and patterns of chlorinated and brominated contaminants in adult male walruses from Svalbard, Norway: indications for individual-specific prey selection.

Blubber samples from 17 adult, male walruses were sampled in eastern Svalbard and analyzed for chlorinated and brominated contaminants. A wide range of contaminants were detected, including PCBs (mean 2000; 95% range 1165-4005 ng/g lipid), DDE (mean 100: 95% range 50-310) ng/g lipid), chlordanes (mean 2500; 95% range 1347-5009) ng/g lipid, toxaphenes (mean 80; 95% range 51-132 ng/g lipid) and polybrominated diphenyl ethers (PBDEs) (mean 15 ng/g; 95% range 9-27 ng/g lipid). PCB and DDE levels were substantially lower than those of animals sampled 10 year earlier in this area, confirming a decreasing trend for these compounds in the Arctic. However, compared to other recently sampled marine mammals from Svalbard, walruses showed relatively high PCB and chlordane levels although they had lower levels of DDE, toxaphenes, and PBDEs, possibly due to species- and location-specific differences in exposure and metabolism. The range in contaminant levels found within the sample group was vast, despite the fact that the animals investigated were all adult males from the same location. The PCB pattern in highly contaminated animals was different from that in animals with low levels of contamination, with relatively more persistent PCBs in the highly contaminated group. This suggests that the more contaminated animals were feeding at higher trophic levels; possibly targeting seals in addition to mollusks as their prey. This suggestion was reinforced by the fatty acid profiles of the inner blubber layer of walruses with low versus high contaminant levels, which suggested different diets for the two groups.

Tissue-specific accumulation and lactational transfer of polychlorinated biphenyls, chlorinated pesticides, and brominated flame retardants in hooded seals (Cistophora cristata) from the Gulf of St. Lawrence: applications for monitoring.

Accumulation and mother-pup transfer of halogenated organic contaminants was studied in hooded seal tissues from eastern Canada. Blubber polychlorinated biphenyl (PCB) and total pesticide concentrations were relatively high, possibly due to their high trophic level and demersal feeding habits. Blood plasma showed the lowest contaminant concentrations compared to blubber and liver, possibly due to a lower affinity of these compounds to lipoproteins in blood plasma. Total contaminant body burden correlated well with blubber, liver, and milk contaminants, but not with blood plasma contaminants, indicating that blood plasma might be less suitable to monitor contaminants in hooded seals. Lactational transfer favored less lipophilic contaminants and was associated with relatively high blood plasma PCB and polybrominated diphenyl ether concentrations in females. Despite lactational transfer, females did not show significantly lower blubber contaminant concentrations or burdens than males. This might be caused by their low blubber, and thus contaminant, loss during lactation compared to other species.

Bioaccumulation of PCBs in Arctic seabirds: influence of dietary exposure and congener biotransformation.

Four seabird species and their prey (zooplankton or fish) were collected in the Barents Sea to determine how dietary exposure, cytochrome P450 (CYP) enzyme activities and sex influenced their hepatic PCB concentrations and accumulation patterns. Five males and five females from each seabird species (little auk (Alle alle), Brunnich's guillemot (Uria lomvia), black guillemot (Cepphus grylle) and black-legged kittiwake (Rissa tridactyla)) were analysed. PCB concentrations could not be explained directly by carbon source (delta13C) or trophic position (delta15N), but by a combination of dietary parameters (delta13C, delta15N, migratory pattern, age) and contaminant metabolism. Contrary to previous studies, the PCB pattern differed among seabirds, with a higher proportion of persistent congeners (% of PCB-153, RPCB-153) in black-legged kittiwake than in auks. The PCB pattern also differed among auks, with little auk as the most efficient biotransformer (highest RPCB-153 values of persistent congeners). Based on high RPCB-153 values, Brunnich's guillemot poorly metabolised ortho-meta-unsubstituted congeners, whereas black guillemot poorly metabolised meta-para unsubstituted congeners. Species-specific differences in PCB biotransformation were confirmed by metabolic indices, where PCB patterns in seabirds were adjusted for PCB pattern in prey. The relative contribution of ortho-meta-unsubstituted congeners to SigmaPCBs decreased with increasing EROD activity. There were no differences in PCB concentrations, PCB patterns or cytochrome P450 enzyme activities between males and females. CYP P450 activities (CYP1A- and CYP2B/3A-like: EROD and testosterone 6beta-hydroxylation, respectively) were low and did not correlate with concentrations of non- or mono-ortho Cl-substituted PCBs (NO- and MO-PCBs), or with total toxic equivalent concentrations (TEQs) for dioxin-like effects of NO- and MO-PCBs.

Congener-specific accumulation and food chain transfer of polybrominated diphenyl ethers in two arctic food chains.

Congener-specific accumulation and prey to predator transfer of 22 polybrominated diphenyl ethers (PBDEs) were assessed in polar cod, ringed seal, polar bear, and beluga whale. Although the concentrations found were relatively low, these results show that PBDEs have reached the Arctic. PBDE congeners 47, 99, and 100 were dominant in all species studied. The pattern in ringed seal was somewhat simpler than in polar cod, with PBDE 47 accounting for more than 90% of the total PBDEs. In contrast, beluga whales, feeding on prey similar to that of ringed seals, showed higher PBDE levels and a more complex PBDE pattern than ringed seals. In contrast, polar bears contained only PBDE 47 in relatively small amounts. These differences in levels and patterns are likely due to species-specific differences in PBDE metabolism and accumulation. The metabolic index suggested that PBDEs 47 and 99 accumulate to the same magnitude as PCB 153 (PCB = polychlorinated biphenyl) in ringed seals and beluga whales. In contrast to beluga whales, ringed seals can metabolize PBDE 100 to some extent. Polar bears are seemingly capable of metabolizing virtually all PBDEs and are therefore unsuitable as indicators for PBDE contamination in the environment.

Organotins in marine mammals and seabirds from Norwegian territory.

An increasing number of studies indicate that marine mammals and some seabirds are exposed to organotins. However, results from northern and Arctic areas are few. Here results from analysis of tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPhT), diphenyltin (DPhT) and monophenyltin (MPhT) in harbour porpoise (Phocoena phocoena), common seal (Phoca vitulina), ringed seal (Phoca hispida) and glaucous gull (Larus hyperboreus) from Norwegian territory are presented. Relatively high concentrations of DBT, TBT and MBT were observed in muscle, kidney and liver from harbour porpoises caught in northern Norway in 1988, just before restrictions on the use of tributyltin (TBT)(mainly on small boats) were introduced in several European countries. The concentrations in harbour porpoise muscle tissue were reduced significantly 11 years later, possibly as a result of the introduced restrictions. Considerably lower concentrations of butyltins were observed in the seals compared to porpoises. The lowest levels of organotins were found in ringed seals from Spitsbergen, where only traces of dibutyltin (DBT) and monobutyltin (MBT) were observed. Traces of DBT and MBT were also found in some individual glaucous gulls from Bear Island. The sum of the degradation products MBT and DBT in liver samples from all analysed species were generally higher than TBT itself. Triphenyltin (TPhT) was observed in all porpoise samples and in livers of common seals. Also the sum of the degradation products MPhT and DPhT in liver samples from porpoise and common seals were higher than TPhT. No traces of phenyltins were found in ringed seals from Spitsbergen or in glaucous gulls from Bear Island. The limited data available indicate low to moderate exposure to organotins in northern areas (Spitsbergen and Bear Island). Marine mammals are however more exposed further south along the Norwegian Coast.

Accumulation and lactational transfer of PCBs and pesticides in harbor seals (Phoca vitulina) from Svalbard, Norway.

The harbor seal population on Svalbard, the northernmost breeding site for this species, appears to have a truncated age distribution with older animals being largely absent. PCBs and pesticides were measured in harbor seal males, females, milk and pups from Svalbard to explore whether contaminant exposure or accumulation is a possible cause of premature death for these animals. The levels and patterns of these contaminants were assessed. In addition, transfer of these compounds from females to their pups during lactation was assessed. Both PCB and pesticide levels were low compared to more southern harbor seal populations. Animals from Svalbard contained 5-10 times lower contaminant levels, compared to seals from the Norwegian mainland, and 30 times lower concentrations than those of harbor seals from the Gulf of St. Lawrence in eastern Canada. Ringed seals from Svalbard have contaminant levels that are comparable to the harbor seals, probably because the diet, as well as the metabolic capacity, of the two species is similar at this location. The findings of this study indicate that the early mortality observed for harbor seals on Svalbard, is not likely to be due to contaminant exposure. Female harbor seals transfer a modified contaminant mixture to their pups compared to that found within their own tissues; compounds with higher log Kow, such as some penta-chlorinated PCBs, were selectively transferred into milk. As a result, the contaminant pattern between males and females differed, with penta-chlorinated PCBs more abundant in males than in females. In addition, pups receive a relatively high amount of the less lipophylic compounds and a low amount of the more lipophylic compounds. The similar contaminant pattern in milk and pups suggested that they are probably unable to metabolize contaminants and consequently, accumulate all ingested chemicals.

Contaminants in Svalbard polar bear samples archived since 1967 and possible population level effects.

Blood plasma samples were collected in 1967 from 32 polar bears (Ursus maritimus) in eastern Svalbard. These samples were stored frozen until 2001 and then analyzed for 33 polychlorinated biphenyls (PCB), two toxaphene congeners, DDTs, chlordanes (CHL), hexachlorobenzene, hexachlorocyclohexanes (HCHs), and polybrominated flame retardants (biphenyls and diphenyl ethers). The 1967 pollutant levels were compared with values from 1993 to 1994 for adult females and adult males to obtain insights into the historical development of pollution in the Norwegian Arctic. Differences in the OC levels measured between 1967 and 1993-1994 ranged from a decrease (PCB 187 and p,p-DDE) to unchanged in both sexes (PCBs 105, 118, 209, and HCH) to an increase in females (PCBs 99, 128, and CHL), to increases in both sexes (PCBs 138, 153, 156, 157, 170, 180, 194, and 206). The maximum change was a nine-fold increase in PCB 157 in adult females. Changes from 1967 to 1993-1994 in contaminant pattern expressed relative to PCB 153 could be explained by a combination of selective metabolism and accumulation of organochlorines in polar bears and temporal changes in the contaminant mixture being transported to the Arctic. Harvest of polar bears in Svalbard ended in 1973 and it appears that most pollutant levels were increasing at the same time that the population was expected to recover from over-harvest. The mean age of adult females in the Svalbard population was similar to other populations where pollution levels are lower but harvest is intense. Females with cubs-of-the-year > or =16 years old are uncommon in the population for unknown reasons. The impacts of contaminants on the Svalbard polar bear population are inconclusive but there are suggestions of contaminant-related population level effects that could have resulted from reproductive impairment of females, lower survival rates of cubs, or increased mortality of reproductive females.

Blood is a poor substrate for monitoring pollution burdens in phocid seals.

The present study investigated how concentrations of different organochlorines (OCs) vary with nutritional condition in adult harp seal (Phoca groenlandica) females in a captive fasting experiment and in the wild. During the first part of this study seals in good condition (N= 5) were fasted for a period of 28 days and blood and blubber samples were collected at days 1, 14 and 28. Blubber OC concentrations remained unchanged throughout the experimental period, and were consistently significantly higher than concentrations in the blood. In contrast to blubber OC levels, blood OC levels showed a significant time-dependant increase. During the fasting experiment the seals lost an average of 24 kg of body mass, which is less than half the natural annual variation in this species in the wild. The second part of this study compared OC concentrations in blood and blubber from seals collected at prime condition before the breeding season (N = 10) with animals collected during molt when condition is poor (N = 7). The average mass difference between the two groups was more than 40 kg. Blood levels of most OCs were significantly higher in the thin seals compared with the levels found in the fat seals. These differences in blood OC concentrations were much greater than what was found during the fasting experiment. For example sigmaPCB levels in the blood during the fasting experiment increased by approximately 83%, while the corresponding increase in blood levels of sigmaPCB between the two other samples was 720% (from 201 to 1,447 ng/g lipid). Blubber levels of OCs from the animals in the wild were significantly higher in the thin seals compared with the fat animals. In addition, the blubber levels of OCs were significantly higher than blood levels of OCs only for the fat seals. This study demonstrates the extreme variability present in the concentrations of OCs in blood of seals in response to change in condition. Since the natural variation in condition is extreme during phocid seals' annual cycles, we recommend that blood should not be used in studies of OCs where the aim of the study is to monitor OC levels for comparative purposes or time-trend analysis.

Modeling biomagnification and metabolism of contaminants in harp seals of the Barents Sea.

A simple fugacity-based bioaccumulation model is presented for harp seals (Phoca groenlandica), which feed primarily on polar cod (Boreogadus saida) and a pelagic crustacean (Themisto libellula). Using concentration data reported for 15 polychlorinated biphenyl (PCB) congeners and 27 pesticides in the food and blubber of harp seals from the Barents Sea, the model was used to determine biomagnification factors and metabolic half-lives as well as rates of contaminant uptake and loss processes in seals, including a discussion of uncertainty in biomagnification factors and half-lives. Examination of the model output shows considerable, but highly variable, biomagnification attributable to differences in metabolic rates. It is suggested that two biomagnification factors can be defined and should be used in such assessments, one based on concentration ratios and the other on fugacity ratios or lipid-normalized concentrations. A maximum biomagnification factor specific to the seal is deduced using biomagnification data for the most persistent substances, and from this, metabolic half-lives are estimated for all substances. The approach can be applied to other biomagnification situations, thus quantifying metabolic half-lives as a function of the properties of the bioaccumulating substance and ultimately its molecular structure and the physiological characteristics of the consuming animal.

Transfer of polychlorinated biphenyls and chlorinated pesticides from mother to pup in relation to cytochrome P450 enzyme activities in harp seals (Phoca groenlandica) from the gulf of St. Lawrence, Canada.

Congener-specific transfer of polychlorinated biphenyls (PCBs) and chlorinated pesticides from female to pup was studied in harp seals from eastern Canada. Possible effects on hepatic cytochrome P450 enzymes (CYP450) due to contaminant mobilization from blubber lipids in females and ingestion of contaminated milk in pups were studied. Contaminant transfer from blubber to milk in females favored the more polar compounds (lower chlorinated PCBs, toxaphenes, hexachlorocyclohexanes, and hexachlorobenzene) relative to more lipophilic compounds (higher chlorinated PCBs, dichlorodiphenyltrichloroethane [DDT], chlordane). In spite of substantial contaminant mobilization from blubber in females and ingestion of contaminated milk by pups, CYP450 activities were low in all animals. Possibly, increased plasma estradiol concentrations, involved in breeding after lactation, suppressed CYP450 directly. Although the pups were exposed to contaminants in milk, CYP450 activities were low, resulting in low contaminant metabolism. This was confirmed by similar contaminant patterns in milk and pups. A strong positive relation between CYP1A-like activities and body weight in the pups suggested not yet fully developed CYP1A enzymes. A negative association between CYP3A and pesticides in females and pups was hypothesized to be a result of metabolic inactivation of CYP450. The CYP450 enzyme activities were considered unsuitable indicators for contaminant mobilization and transfer in harp seals.

Bioaccumulation of radiocaesium in Arctic seals.

Seals are high trophic level feeders that bioaccumulate many contaminants to a greater degree than most lower trophic level organisms. Their trophic status in the marine food web and wide-spread distribution make seals useful sentinels of arctic environmental change. The purpose of this investigation is to document the levels and bioaccumulation potential of radiocaesium in high latitude seal species for which data have not previously been available. The study was carried out on harp, ringed, and bearded seals caught north of the island archipelago of Svalbard (82 degrees N) in 1999. The results are then compared with previous studies in order to elucidate factors responsible for bioaccumulation in Arctic seals. Concentrations of 137Cs were determined in muscle, liver and kidney samples from a total of 10 juvenile and one adult seal. The mean concentration in muscle samples for all animals was 0.23 +/- 0.045 Bq/kg f.w. 137Cs concentrations in both liver and kidney samples were near detection limits (approximately 0.2 Bq/kg f.w.). The results are consistent with previous studies indicating low levels of radiocaesium in Arctic seals in response to a long term trend of decreasing levels of 137Cs in the Barents Sea region. Bioconcentration factors (BCFs) estimated for seals from NE Svalbard are low, ranging from 34 to 130. Comparing these values with reported BCFs for Greenland seals from other sectors of the European Arctic, we suggest that the combination of physiological and ecological factors on radiocaesium bioaccumulation is comparable among different Arctic seal populations. The application of this work to Arctic monitoring and assessment programs is discussed.