Associations between complex OHC mixtures and thyroid and cortisol hormone levels in East Greenland polar bears.

The multivariate relationship between hair cortisol, whole blood thyroid hormones, and the complex mixtures of organohalogen contaminant (OHC) levels measured in subcutaneous adipose of 23 East Greenland polar bears (eight males and 15 females, all sampled between the years 1999 and 2001) was analyzed using projection to latent structure (PLS) regression modeling. In the resulting PLS model, most important variables with a negative influence on cortisol levels were particularly BDE-99, but also CB-180, -201, BDE-153, and CB-170/190. The most important variables with a positive influence on cortisol were CB-66/95, α-HCH, TT3, as well as heptachlor epoxide, dieldrin, BDE-47, p,p'-DDD. Although statistical modeling does not necessarily fully explain biological cause-effect relationships, relationships indicate that (1) the hypothalamic-pituitary-adrenal (HPA) axis in East Greenland polar bears is likely to be affected by OHC-contaminants and (2) the association between OHCs and cortisol may be linked with the hypothalamus-pituitary-thyroid (HPT) axis.

Temporal trends and future predictions of mercury concentrations in Northwest Greenland polar bear (Ursus maritimus) hair.

Hair samples from 117 Northwest Greenland polar bears (Ursus maritimus) were taken during 1892-2008 and analyzed for total mercury (hereafter Hg). The sample represented 28 independent years and the aim of the study was to analyze for temporal Hg trends. Mercury concentrations showed yearly significant increases of 1.6-1.7% (p < 0.0001) from 1892 to 2008 and the two most recent median concentrations from 2006 and 2008 were 23- to 27-fold higher respectively than baseline level from 1300 A.D. in the same region (Nuullit). This indicates that the present (2006-2008) Northwest Greenland polar bear Hg exposure is 95.6-96.2% anthropogenic in its origin. Assuming a continued anthropogenic increase, this model estimated concentrations in 2050 and 2100 will be 40- and 92-fold the baseline concentration, respectively, which is equivalent to a 97.5 and 98.9% man-made contribution. None of the 2001-2008 concentrations of Hg in Northwest Greenland polar bear hair exceeded the general guideline values of 20-30 µg/g dry weight for terrestrial wildlife, whereas the neurochemical effect level of 5.4 µg Hg/g dry weight proposed for East Greenland polar bears was exceeded in 93.5% of the cases. These results call for detailed effect studies in main target organs such as brain, liver, kidney, and sexual organs in the Northwest Greenland polar bears.

Cortisol levels in hair of East Greenland polar bears.

To demonstrate the ability to assess long-term hypothalamic-pituitary-adrenocortical (HPA) axis activity in polar bears (Ursus maritimus), a pilot study was conducted in which cortisol concentrations was analyzed in hair from 7 female (3-19 years) and 10 male (6-19 years) East Greenland polar bears sampled in 1994-2006. The hair was chosen as matrix as it is non-invasive, seasonally harmonized, and has been validated as an index of long-term changes in cortisol levels. The samples were categorized according to contamination: eight were clean (2 females, 6 males), 5 had been contaminated with bear blood (2 F, 3 M), and 4 with bear fat (3 F, 1 M). There was no significant difference in cortisol concentration between the three categories after external contamination was removed. However, contaminated hair samples should be cleaned before cortisol determination. Average hair cortisol concentration was 8.90 pg/mg (range: 5.5 to 16.4 pg/mg). There was no significant correlation between cortisol concentration and age (p=0.81) or sampling year (p=0.11). However, females had higher mean cortisol concentration than males (females mean: 11.0 pg/mg, males: 7.3 pg/mg; p=0.01). The study showed that polar bear hair contains measurable amounts of cortisol and that cortisol in hair may be used in studies of long-term stress in polar bears.

Prevalence of antibodies against Toxoplasma gondii in polar bears (Ursus maritimus) from Svalbard and East Greenland.

Serum samples from 419 polar bears (Ursus maritimus) from Svalbard and the Barents Sea (collected 1990-2000) and 108 polar bears from East Greenland (collected 1999-2004) were assayed for antibodies against Toxoplasma gondii using the modified agglutination test. Antibody prevalences were 3.6% among cubs dependent on their mothers and 21.4% among subadults and adults. Among subadults and adults there was an interaction between population and sex, with similar prevalences among females (Svalbard = 19.5%, Greenland = 18.0%), but a high frequency among Svalbard males (28.7%) as compared to Greenland males (5.8%). The pattern was also significant after correcting for differences in age distribution. The sex-population interaction term is believed to be connected to area- and sex-specific feeding ecology. The prevalences of antibodies against T. gondii in Svalbard and Greenland were high compared to previously reported findings in polar bears from Russian and Alaskan areas.

Increasing perfluoroalkyl contaminants in east greenland polar bears (Ursus maritimus): a new toxic threat to the Arctic bears.

A well-defined subsample of 128 subadult (3-5 years) polar bears (Ursus maritimus) from 19 sampling years within the period 1984-2006 was investigated for perfluoroalkyl contaminants (PFCs). Linear regression analysis of logarithmic-transformed median concentrations showed significant annual increases for PFOS (4.7%), PFNA (6.1%), PFUnA (5.9%), PFDA (4.3%), PFTrA (8.5%), PFOA (2.3%), and PFDoA (5.2%). For four of the PFCs, a LOESS smoother model provided significantly better descriptions, revealing steeper linear annual increases for PFOSA of 9.2% after 1990 and between 18.6 and 27.4% for PFOS, PFDA, and PFTrA after 2000. Concentrations of SigmaPFCs, by 2006, exceeded the concentrations of all conventional OHCs (organohalogen compounds), of which several have been documented to correlate with a number of negative health effects. If the PFC concentrations in polar bears continue to increase with the steepest observed trends, then the lowest no-adverse-effect level (NOAEL) and lowest-adverse-effect level (LOAEL) detected for rats and monkeys will be exceeded in 2014-2024. In addition, the rapidly increasing concentrations of PFCs are likely to cause cumulative and combined effects on the polar bear, compounding the already detected threats from OHCs.

In search of virus carriers of the 1988 and 2002 phocine distemper virus outbreaks in European harbour seals.

European harbour seal (Phoca vitulina) populations decreased substantially during the phocine distemper virus (PDV) outbreaks of 1988 and 2002. Different hypotheses have stated that various seals and terrestrial carnivore species might be the source of infection. To further analyse these hypotheses, grey (Halichoerus grypus) and ringed (Phoca hispida) seals, polar bears (Ursus maritimus) and minks (Mustela lutreola) were sampled from the North Sea and East Greenland coasts between 1988 and 2004 and investigated by RT-PCR using a panmorbillivirus primer pair. However, all samples were negative for morbillivirus nucleic acid.

Toxaphene in minke whales (Balaenoptera acutorostrata) from the North Atlantic.

Toxaphene contamination of minke whales (Balaenoptera acutorostrata) from North Atlantic waters was examined for the first time. Total toxaphene and SigmaCHB (sum of 11 chlorobornanes) concentrations in blubber samples ranged from 170+/-110 and 41+/-39 ng/g lipid weight (l.w.) for female minke whales from southeastern Greenland to 5800+/-4100 and 1100+/-780 ng/g l.w. for males from the North Sea, respectively. Very large variations in toxaphene concentrations among sampling areas were observed suggesting a spatial segregation of minke whales. However, much of the apparent geographical discrimination was explained by the seasonal fluctuation of animal fat mass. Patterns of CHBs in males revealed that recalcitrant CHBs were in higher proportions in animals from the more easterly areas than in animals from the more westerly areas. This trend may be influenced by the predominance of the US, over the European, input of toxaphene to North Atlantic waters.

Trends in mercury in hair of Greenlandic polar bears (Ursus maritimus) during 1892-2001.

Mercury concentrations in hair from 397 Greenland polar bears (Ursusmaritimus) sampled between 1892 and 2001 were analyzed for temporal trends. In East Greenland the concentrations showed a significant (p < 0.0001, n = 27) increase of 3.1%/year in the period 1892-1973. In Northwest Greenland, a similar (p < 0.0001, n = 69) increase of 2.1%/year was found, which continued until 1991, when the most recent samples were obtained. In East Greenland, a significant (p = 0.009, n = 322) decrease of 0.8%/year was observed after 1973. Two Northwest Greenland samples from 1300 A.D. had a mean value of 0.52 mg/kg of dry weight, which can be considered as a baseline level. The Hg concentration during 1985-1991 from Northwest Greenland (mean value of 7.45 mg/kg of dry weight) was more than 14-fold higher than the assumed baseline level from 1300 A.D. from the same region (i.e., about 93% anthropogenic). Although a decrease was found in East Greenland after 1973, the concentration is still ca. 11-fold higher than the baseline level (i.e., about 90% anthropogenic).

Trends in fluctuating asymmetry in East Greenland polar bears (Ursus maritimus) from 1892 to 2002 in relation to organohalogen pollution.

Fluctuating asymmetry (FA) was studied in skulls of 283 polar bears (Ursus maritimus) sampled in East Greenland from 1892 to 2002. Fourteen metric bilateral traits in skull and lower jaw were measured and compared between polar bears born until 1960 (n = 94) and from 1961 (n = 189). The period 1892-1960 was chosen to represent a period prior to appearance of organohalogens (polychlorinatedbiphenyls [PCBs], dichlorodiphenyltrichloroethanes [DDTs], hexacyclohexanes [HCHs], chlordanes [CHLs], hexachlorobenzene [HCB], polybrominateddiphenylethers [PBDEs] and dieldrin) originating from long-range transport to East Greenland from southern latitudes. The period 1961-2002 represents the period when polar bears have been exposed to organohalogens. During this latter period, the level of organochlorines is believed to have increased from 1960 to the late 1980s followed by a likely decrease from 1990 to 2002. Within this later period, other compounds such as, e.g., polybrominated flame retardants are believed to have increased throughout the period. Two different analysis showed, that the degree of fluctuating asymmetry did not differ statistically between the two periods in ten of thirteen traits (one trait excluded due to high measurement error). In fact, when significant differences were found in four of the traits, the fluctuating asymmetry was lower in skulls sampled after 1960. The degree of fluctuating asymmetry was higher in adults than in subadults for 6 of the 14 traits, whereas a higher degree of fluctuating asymmetry was found for only one trait in one of the analyses for subadults relative to adults. Females had a higher degree of fluctuating asymmetry than males in one trait. A time trend analysis did find fluctuations over time for five traits but the relationship was weak as the trend appeared to occur by chance due to the high number of regressions analysed (n = 42). A correlation analysis of FA versus the sum concentrations of various classes of organohalogens in adipose tissue from a subsample of 94 recently collected polar bears (1999-2002) did not show a trend either. Hence, the present study could not document a relationship between skull asymmetry in polar bears and periods with different exposure to organohalogens. These findings are possibly influenced by nutritional status, genetic factors, a subeffect exposure of organohalogens or confounded by other environmental factors (e.g. temperature) within the two investigated periods.

Histology of selected immunological organs in polar bear (Ursus maritimus) from East Greenland in relation to concentrations of organohalogen contaminants.

Samples of lymph nodes (axillary, n = 54 and inguinal, n = 45), spleen (n = 60), thymus (n = 11) and thyroid tissue (n = 5) from a total of 82 polar bears (Ursus maritimus) collected in East Greenland 1999-2002 were examined histologically. The purpose was to relate histology to concentrations of organohalogen contaminants (OHCs) [i.e., sum (Sigma)PCBs, SigmaDDTs, SigmaHCHs, SigmaCHLs, HCB, Dieldrin and SigmaPBDEs] determined in adipose tissue, as studies on polar bears have indicated that some OHCs act as immunosuppressive agents. Secondary follicle counts were evaluated in spleen and lymph nodes, and semiquantitively divided into four groups (0: few/absent to 3: high). In the spleen, a high secondary follicle count was found in 21% of the cases (12/60), and this was significantly higher in subadults (p < 0.01) compared to adults of both sexes. Also in the lymph nodes a high secondary follicle count was found in 20% of the cases (20/99), and in the axillary lymph nodes changes were significantly higher in subadults (p < 0.05) compared to adults of both sexes. Significantly weak correlations between concentrations of OHCs and the amount of secondary follicles in lymph nodes was found, but probably occurred as a consequence of other multiple stress factor(s) (all: p < 0.05) and also one significant, but modest positive correlation was found between SigmaPBDE concentrations and secondary follicle counts (p < 0.01; r = 0.41). In spleen, a significant relation between low concentrations of OHCs in adipose tissue and few/absent secondary follicles was found with respect to SigmaCHLs, SigmaHCHs, HCB and Dieldrin. No histopathological observations (e.g., neoplasia) were found in spleen or lymph nodes, nor in thymus or thyroid. In conclusion, the present data suggest that the exposure concentrations of OHCs to polar bears are unlikely to have resulted in adverse effects on the tissues in question, although SigmaCHLs, SigmaHCHs, HCB and Dieldrin were related to increased secondary follicle counts in the spleen.

Enlarged clitoris in wild polar bears (Ursus maritimus) can be misdiagnosed as pseudohermaphroditism.

A 23-year-old female polar bear (Ursus maritimus) killed in an Inuit hunt in East Greenland on July 9, 1999 had a significantly enlarged clitoris resembling, in size, form and colour, those of previously reported 'pseudohermaphroditic' polar bears from Svalbard. It has been suggested that an enzyme defect (21-hydroxylase deficiency), androgen producing tumour or high exposure to organochlorines during the foetal stage or early development could be the reason for the supposed pseudohermaphroditism observed for Svalbard bears. Except for the enlarged clitoris, all dimensions of the external and internal reproductive organs of the present were similar to a reference group of 23 normal adult female polar bears from East Greenland collected in 1999-2002. The aberrant bear was a female genotype, and macroscopic examination of her internal reproductive organs indicated that she was reproductively functional. A histological examination of the clitoral enlargement in the present East Greenland specimen allows a first-time histological evaluation of the earlier macroscopic field diagnosis from Svalbard. This examination revealed intense chronic ulcerative and perivascular clitoriditis similar to "acral lick dermatitis" frequently seen in domestic dogs (i.e., we did not find any signs of pseudohermaphroditic hyperplasia of clitoral tissue due to androgenic or antiestrogenic endocrine disruption). The levels of organohalogens and TEQ values were lower than concentration thresholds of toxicological risk. It is hence possible that the previously reported adult female polar bear pseudohermaphrodites from Svalbard are in fact misdiagnoses. Therefore, future studies examining pseudohermaphroditism in wildlife should consider that certain occurrences are natural events, e.g., enlarged clitoris in the present East Greenland polar bear. Furthermore, caution should be exercised in suggesting linkages of such inflammatory abnormalities with correlations to anthropogenic pollutant exposures.

Seasonal and temporal trends in polychlorinated biphenyls and organochlorine pesticides in East Greenland polar bears (Ursus maritimus), 1990-2001.

Persistent organochlorine (OC) contaminants (PCBs, DDTs, chlordanes (CHLs), dieldrin, hexachlorocyclohexanes (HCHs), chlorobenzenes (CBzs)) were determined in adipose tissue of 92 polar bears (Ursus maritimus) sampled between 1999 and 2001 in central East Greenland (69 degrees 00'N to 74 degrees 00'N). OC data were presented from subadults (S: females: x 5 years and males: x 6 years), adult females (F: x 5 years) and adult males (M: x 6 years). Summed chlorobiphenyl (SigmaCBs) concentrations (41 congeners including co-eluters), SigmaCHLs and SigmaDDTs were the dominant classes of OCs. SigmaCBs concentrations were found to be 6470, 8240 and 9100 ng/g lipid weight (lw) i subadults, adult females and adult males, respectively. The corresponding figures were: 2010 (S), 2220 (F) and 1710 (M) ng/g lw for SigmaCHLs and 462 (S), 462 (F) and 559 (M) ng/g lw for SigmaDDTs. The dominant CB congeners were CB153 (32.3%), CB180 (21.4%), CB170 (12.2%) and CB138 (11.0%). The metabolite p,p'-DDE (88.2%) dominated the SigmaDDTs, while oxychlordane was the dominant (57.1%) CHL-related compound. Concentrations of SigmaCBs, SigmaCBzs, SigmaDDTs, mirex and dieldrin were highest in adult males, whereas concentrations of SigmaHCHs were lower than in adult females but not than those in subadults. Adult females had the lowest concentrations of SigmaCBzs, mirex and dieldrin. Concentrations of SigmaCHLs were lowest in adult males, intermediate in subadults and highest in adult females. SigmaCB, SigmaHCH and SigmaCHL concentrations showed high seasonal variability in adult females but remained relatively constant in adult males and subadults. In general, the OC levels in females appeared to be highest in March and lowest in January or September. Concentrations of SigmaCBzs and dieldrin showed seasonal variability in all three groups, with a maximum in March in adult females. SigmaCBz concentrations in adult males and subadults of both sexes peaked in April-July, and dieldrin concentrations peaked in April-July in subadults, but not until August in adult males. SigmaDDT concentrations increased from January to a maximum in April-July for subadults and in August for adults. Temporal trends within the last decade were examined by comparing the present data to the concentrations reported in samples from 1990 from the same region. SigmaCB, p,p'-DDE and SigmaHCH concentrations in 1999-2001 were 22.1%, 66.3% and 39.3% lower than the 1990 concentrations, respectively. in contrast, SigmaCHL and dieldrin concentrations showed differences amongst sex and age groups in the temporal trends, where present concentrations are between 24.4% to 69.3% and 27.0% to 69.0% lower, respectively, relative to the 1990 levels. However, power analysis suggested that firm conclusions could not be drawn regarding the general time trend based on these two sampling periods. The range of half-lives of the various OC classes were estimated to lie between 4.5 and 20.6 years depending on the age and sex groups considered.

Hydroxylated and methyl sulfone PCB metabolites in adipose and whole blood of polar bear (Ursus maritimus) from East Greenland.

Persistent methyl sulfone (MeSO2-) and hydroxylated (HO-) polychlorinated biphenyl (PCB) metabolites have emerged as important classes of environmental contaminants in vertebrate, aquatic biota and humans. In the present study, PCB, MeSO2-PCB and HO-PCB concentrations and congener patterns were determined in the whole blood and adipose tissue of male (n = 7) and female (n = 12) polar bears (Ursus maritimus) of random age (3-25 years of age), and collected in 1999-2001 from the Ittoqqortoormiit/Scoresby Sound area in central East Greenland. There was no significant difference (P < 0.05) between males and females with respect to PCB or PCB metabolite concentrations in either tissue. The mean sum (Sigma) PCB concentrations were 7020+/-3366 ng/g lipid weight (lw) (range 2708-18148 ng/g lw) and 46.1+/-44.6 ng/g wet weight (ww) (range 12.6-204.2 ng/g ww) in adipose and blood, respectively. The mean Sigma-HO-PCB concentration in whole blood was 182.3+/-72.1 ng/g ww (range 93.8-382.1 ng/g ww). The mean Sigma-HO-PCB to Sigma-PCB concentration ratios in whole blood were 4.59+/-3.58 (range 1.03-11.88) and 8.30+/-5.56 (range 2.16-19.47) in females and males, respectively, which are the highest ratios reported so far for polar bears from any population, or for any free-ranging animal. Sigma-HO-PCB concentrations were greater than all other major classes of organochlorines (i.e. Sigma-PCBs, Sigma-MeSO2-PCBs, Sigma-chlordanes (CHLs), Sigma-hexachlorocyclohexanes (HCHs) and Sigma-chlorobenzenes (CBzs). The mean Sigma-MeSO2-PCB concentrations were 699+/-836 ng/g lw (range 127-3920 ng/g lw) and 10.9+/-9.6 ng/g ww (range 4.3-52.1 ng/g ww) in the adipose and blood, respectively. Regardless of age and sex, in both adipose and whole blood the MeSO2-PCB congener pattern was dominated by 3'- and 4'-MeSO2-CB101 and -CB87, and 4-MeSO2-CB149 (approx. 70% of the Sigma-MeSO2-PCBs). Minor differences in the MeSO2-PCB congener pattern were observed between blood and adipose, which suggests the possible influence of metabolite structure on mobilization and/or deposition to the adipose tissue. Sixteen HO-PCB congeners and one di-HO-PCB congener were identified, and five HO-PCB isomers and one di-HO-PCB isomer were detected. However, congener patterns were dominated by 4'-OH-CB120, 4-HO-CB146/3-HO-CB153, 4-OH-CB187, 4'-HO-CB172, 4-HO-CB193 and 4,4'-di-HO-CB202 (> 10 ng/g ww). HO-PCB congener patterns in whole blood were not significantly different (P < 0.05) between males and females. Other chlorinated phenolic contaminants, pentachlorophenol (0.3+/-0.3 ng/g ww) and 4-HO-heptachlorostyrene (7.5+/-2.9 ng/g ww) were also detected in blood. To our knowledge, this is to first report comparing PCBs, MeSO2-PCBs and HO-PCBs in whole blood and adipose tissue in a free-ranging wildlife species. HO-PCBs and MeSO2-PCBs are both important circulating contaminants in polar bears from this eastern Greenland population. Given the known toxicities of PCB metabolites, this population of polar bear may be experiencing health risks due to exposure to a complex loading of organohalogen contaminants that include HO-PCB and MeSO2-PCB metabolites.

Levels and patterns of persistent organochlorines in minke whale (Balaenoptera acutorostrata) stocks from the North Atlantic and European Arctic.

Regional variation in PCBs and organochlorine (OC) pesticide concentrations was examined using the blubber of 155 minke whales (Balaenoptera acutorostrata) sampled in seven regions in the North Atlantic and European Arctic, including western and southeastern Greenland, the Norwegian Sea, the North Sea and the Barents Sea. The levels and relative proportions of OCs were also used to examine the boundaries for North Atlantic minke whale stocks previously defined by the International Whaling Commission (IWC). Concentrations of major OC groups (sigmaPCB, 89.1-22 800 ng/g lipid; sigmaDDT, 65.3-6280 ng/g lipid; sigmaCHL, 33.3-2110 ng/g lipid) generally increased from west to east, while HCH concentrations (sigmaHCH, < 1-497 ng/g lipid) showed the opposite trend. Statistical comparison between six regions using sex-adjusted least squared mean concentrations showed that minke whales from the Barents Sea had significantly higher concentrations of EPCBs than those from the Vestfjorden/Lofoten, the North Sea, and west Svalbard, as well as significantly higher sigmaDDT concentrations compared to west Greenland animals. The differences in concentrations suggest that west and southeast Greenland minkes may represent one group of whales, which are distinct from both the Jan Mayen minkes and those from other IWC defined stocks in northern European waters. Principal components analysis using proportions of 71 PCB congeners and 20 OC pesticides (of total OCs) did not reveal any major differences among groups although minkes from the North Sea were distinguished from those from Greenland waters by higher loadings of more highly chlorinated PCBs and recalcitrant OC pesticides. The general similarity in mean levels of sigmaPCBs, sigmaDDT and sigmaCHL, as well as mean principal components analysis scores, among minkes sampled at Jan Mayen, Svalbard, Vestfjorden/Lofoten, the North Sea and the Barents Sea suggests that the whales are quite mobile and may feed in multiple areas within the northeastern Atlantic.

An assessment of selenium to mercury in Greenland marine animals.

Information on mercury and selenium molar relation in muscle, liver and kidney tissue of Greenland marine animals is presented. In the majority of the samples selenium was present in a molar surplus to mercury. This was most clear in molluscs, crustaceans, fish and seabirds. A 1:1 molar ratio was found in tissues of marine mammals with high mercury concentrations (above approx. 10 nmol/g). This was most clearly demonstrated for liver and kidney tissue of polar bear and for ringed seal with high mercury concentration in the liver. These findings support previous results found in liver tissue of marine mammals, suggesting that methyl mercury is detoxified by a chemical mechanism involving selenium. If the anthropogenic release of mercury to the environment increases in the future due to increasing energy demands, species such as polar bears and seals with high tissue mercury concentrations should be monitored to elucidate whether this protective mechanism can be maintained in target organs.

Geographical differences of zinc, cadmium, mercury and selenium in polar bears (Ursus maritimus) from Greenland.

Muscle, liver, and kidney tissues from 100 polar bears (Ursus maritimus), caught in the Avanersuaq area, north-west Greenland, and Ittoqqortoormiit area, central-east Greenland, were analysed for zinc, cadmium, mercury and selenium. The zinc concentrations in muscle and liver were higher than in kidney. Mean zinc concentrations ranged from 19.7 to 76.0 micrograms/g (all data are presented as geometric means on a wet wt. basis). The presented cadmium concentrations by area and age groups were all low in muscle and in many cases below the detection limit (range: < 0.015-0.048 microgram/g). Cadmium concentrations were intermediate in liver (range: 0.120-1.98 micrograms/g) and highest in kidney tissue (range: 2.16-28.9 micrograms/g). Mercury was likewise lowest in muscle tissue (range: 0.034-0.191 microgram/g). Mercury concentration ranged quite similarly in liver and kidney tissue (liver range: 2.13-22.0 micrograms/g; kidney range: 2.87-32.0 micrograms/g). The selenium concentration increased from muscle (range: < 0.2-0.452 microgram/g) over liver (range: 1.20-9.80 micrograms/g) to kidney (range: 2.34-13.9 micrograms/g). No age accumulation was found for zinc. A weak increase was found for selenium, whereas cadmium and mercury clearly accumulated with age. An exception was mercury concentrations in muscle tissue, where no clear pattern was observed. Polar bears had significantly lower cadmium concentrations than ringed seals from the same area in all three tissues. Likewise mercury was significantly lower in the muscle tissue of polar bears than in ringed seals, whereas liver and kidney concentrations were higher. Biomagnification factors are provided for different tissues and age groups. Tissue ratios are given for different age groups and metals to enable a rough extrapolation from one tissue to another. Tissue ratios for cadmium, selenium and for mercury vary up to a factor of 6 with age. No significant differences could be detected between the elements analysed in bears from two management zones in north-west Greenland. This finding is in agreement with the genetic pattern in the two areas. In central-east Greenland, however, cadmium, selenium, and some of the mercury concentrations in polar bears from the southern area were higher than from the northern area, indicating that the east Greenland area represents two different ecological regions with different polar bear populations. Geographical differences between polar bears from north-west and east Greenland were only found for mercury and cadmium in liver tissue, where the concentrations were highest in bears from north-west Greenland. The geographical trend of increasing cadmium concentrations in polar bear liver tissue from west to east, which has been found previously in Canada, could be extended to cover north-west Greenland as well. East of this region a decrease was found. Mercury concentrations in polar bear liver tissue showed an increase from Svalbard over east and north-west Greenland, peaking in bears from south-west Melville Island. A marked decrease was found west of Melville Island, and the lowest concentrations were found in the Chukchi Sea.

Temporal and spatial trends of persistent organochlorines in Greenland walrus (Odobenus rosmarus rosmarus).

Persistent organochlorines [PCBs, DDT and chlordane related compounds, dieldrin, toxaphene, hexachlorocyclohexane (HCH), chlorobenzenes] were determined in blubber of Atlantic walrus (Odobenus rosmarus rosmarus) in 1978 and 1988 from the Avanersuaq (Thule) region of north-west Greenland and in 1989 from Ittoqqortoormiit (Scoresbysund) in east Greenland. Lowest concentrations of organochlorines (OCs) were found in the samples from the Avanersuaq region while much higher levels of all compounds, except HCH isomers and mono/dichlorobiphenyls (CB5/8), were observed in samples (all males) from Ittoqqortoormiit. Total PCBs (sigma PCB) averaged 246 ng/g (wet wt.) male walrus from Avanersuaq and 2860 ng/g in samples from Ittoqqortoormiit. DDT isomers showed the greatest difference between the two locations, 50 x for p,p'-DDE and 69 x higher for p,p'-DDT. Ittoqqortoormiit walrus showed the pattern of OCs characteristic of seal-eating animals although the consumption of other organisms cannot be ruled out. The higher levels of OCs in east Greenland compared to north-west Greenland animals were consistent with results for polar bears, seals and gulls from the same regions. Principal components analysis showed that the pattern of OCs in Ittoqqortoormiit walrus was very similar to that in walrus from Inukjuaq in east Hudson Bay, which have previously been reported to be seal eaters, and quite distinct from the Avanersuaq walrus. No significant differences in mean concentrations of any OCs were found between male walrus from 1978 and 1988. For females, there were significantly higher levels of CB5/8, trichlorobiphenyls, dieldrin, toxaphene and alpha HCH as well as sigma HCH but not for sigma PCBs or DDT compounds. The data for Greenland walrus from the 1970s and late 1980s provide a baseline for future trend monitoring in walrus.

Genetic structure of the world's polar bear populations.

We studied genetic structure in polar bear (Ursus maritimus) populations by typing a sample of 473 individuals spanning the species distribution at 16 highly variable microsatellite loci. No genetic discontinuities were found that would be consistent with evolutionarily significant periods of isolation between groups. Direct comparison of movement data and genetic data from the Canadian Arctic revealed a highly significant correlation. Genetic data generally supported existing population (management unit) designations, although there were two cases where genetic data failed to differentiate between pairs of populations previously resolved by movement data. A sharp contrast was found between the minimal genetic structure observed among populations surrounding the polar basin and the presence of several marked genetic discontinuities in the Canadian Arctic. The discontinuities in the Canadian Arctic caused the appearance of four genetic clusters of polar bear populations. These clusters vary in total estimated population size from 100 to over 10 000, and the smallest may merit a relatively conservative management strategy in consideration of its apparent isolation. We suggest that the observed pattern of genetic discontinuities has developed in response to differences in the seasonal distribution and pattern of sea ice habitat and the effects of these differences on the distribution and abundance of seals.

Determinants of Home Range Size for Polar Bears (Ursus maritimus).

The mean home range size of female polar bears (Ursus maritimus; 125 100 km2 ± 11 800; n = 93) is substantially larger than the predicted value (514 km2 ) for a terrestrial carnivore of similar weight. To understand this difference, we correlated home range size and sea ice characteristics. Home range size was related to (i) the ratio of land vs. sea within a given home range (42% of explained variance), and (ii) seasonal variation in ice cover (24%). Thus, bears using land during the ice-free season had larger home ranges and bears living in areas of great seasonal variation in ice cover also had larger home ranges. In another analysis we investigated how variation in a bear's environment in space and time affects its choice of home range. We found that polar bears adjusted the size of their home range according to the amount of annual and seasonal variation within the centre of their home range. For example, polar bears experiencing unpredictable seasonal and annual ice tended to increase their home range size if increasing home range size resulted in reducing variation in seasonal and annual ice. Polar bears make trade-offs between alternate space-use strategies. Large home ranges occur when variable ice cover is associated with more seals but also a more unpredictable distribution of those seals.

Population structure and gene flow of the Atlantic walrus (Odobenus rosmarus rosmarus) in the eastern Atlantic Arctic based on mitochondrial DNA and microsatellite variation.

The population structure of the Atlantic walrus, Odobenus rosmarus rosmarus, was studied using 11 polymorphic microsatellites and restriction fragment length polymorphism detected in the NADH-dehydrogenase ND1, ND2 and ND3/4 segments in mtDNA. A total of 105 walrus samples were analysed from northwest (NW) Greenland, east (E) Greenland, Svalbard and Franz Joseph Land. Two of the 10 haplotypes detected in the four samples were diagnostic for the NW Greenland sample, which implied that the group of walruses in this area is evolutionary distinct from walruses in the other three areas. One individual sampled in E Greenland exhibited a Pacific haplotype, which proved a connection between the Pacific walrus and walruses in eastern Greenland. The Franz Joseph Land, Svalbard and E Greenland samples shared the most common haplotype, indicating very little differentiation at the mtDNA level. Gene flow (Nm) estimates among the four areas indicated a very restricted exchange of female genes between NW Greenland and the more eastern Atlantic Arctic samples, and a closer relationship between the three samples composing the eastern Atlantic Arctic. The genetic variation at 11 polymorphic microsatellite loci grouped individuals into three populations, NW Greenland, E Greenland and a common Franz Joseph Land-Svalbard population, which were connected by moderate gene flow.