Publications by authors named "Jon Aars"

44 Publications

Sea ice reduction drives genetic differentiation among Barents Sea polar bears.

Proc Biol Sci 2021 09 8;288(1958):20211741. Epub 2021 Sep 8.

Norwegian Institute of Bioeconomy Research, Division of Environment and Natural Resources, Svanhovd, N-9925 Svanvik, Norway.

Loss of Arctic sea ice owing to climate change is predicted to reduce both genetic diversity and gene flow in ice-dependent species, with potentially negative consequences for their long-term viability. Here, we tested for the population-genetic impacts of reduced sea ice cover on the polar bear () sampled across two decades (1995-2016) from the Svalbard Archipelago, Norway, an area that is affected by rapid sea ice loss in the Arctic Barents Sea. We analysed genetic variation at 22 microsatellite loci for 626 polar bears from four sampling areas within the archipelago. Our results revealed a 3-10% loss of genetic diversity across the study period, accompanied by a near 200% increase in genetic differentiation across regions. These effects may best be explained by a decrease in gene flow caused by habitat fragmentation owing to the loss of sea ice coverage, resulting in increased inbreeding of local polar bears within the focal sampling areas in the Svalbard Archipelago. This study illustrates the importance of genetic monitoring for developing adaptive management strategies for polar bears and other ice-dependent species.
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http://dx.doi.org/10.1098/rspb.2021.1741DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8424353PMC
September 2021

Modeling the demography of species providing extended parental care: A capture-recapture multievent model with a case study on polar bears ().

Ecol Evol 2021 Apr 10;11(7):3380-3392. Epub 2021 Mar 10.

CEFE Univ Montpellier CNRS EPHE-PSL University IRD Univ Paul Valéry Montpellier 3 Montpellier France.

In species providing extended parental care, one or both parents care for altricial young over a period including more than one breeding season. We expect large parental investment and long-term dependency within family units to cause high variability in life trajectories among individuals with complex consequences at the population level. So far, models for estimating demographic parameters in free-ranging animal populations mostly ignore extended parental care, thereby limiting our understanding of its consequences on parents and offspring life histories.We designed a capture-recapture multievent model for studying the demography of species providing extended parental care. It handles statistical multiple-year dependency among individual demographic parameters grouped within family units, variable litter size, and uncertainty on the timing at offspring independence. It allows for the evaluation of trade-offs among demographic parameters, the influence of past reproductive history on the caring parent's survival status, breeding probability, and litter size probability, while accounting for imperfect detection of family units. We assess the model performance using simulated data and illustrate its use with a long-term dataset collected on the Svalbard polar bears ().Our model performed well in terms of bias and mean square error and in estimating demographic parameters in all simulated scenarios, both when offspring departure probability from the family unit occurred at a constant rate or varied during the field season depending on the date of capture. For the polar bear case study, we provide estimates of adult and dependent offspring survival rates, breeding probability, and litter size probability. Results showed that the outcome of the previous reproduction influenced breeding probability.Overall, our results show the importance of accounting for i) the multiple-year statistical dependency within family units, ii) uncertainty on the timing at offspring independence, and iii) past reproductive history of the caring parent. If ignored, estimates obtained for breeding probability, litter size, and survival can be biased. This is of interest in terms of conservation because species providing extended parental care are often long-living mammals vulnerable or threatened with extinction.
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http://dx.doi.org/10.1002/ece3.7296DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8019049PMC
April 2021

Concentrations and endocrine disruptive potential of phthalates in marine mammals from the Norwegian Arctic.

Environ Int 2021 07 4;152:106458. Epub 2021 Mar 4.

Norwegian Polar Institute, Fram Centre, N-9296 Tromsø, Norway.

This study investigated concentrations of phthalates (diesters of phthalic acids) in blubber/adipose tissue of blue whales (Balaenoptera musculus), fin whales (Balaenoptera physalus), bowhead whales (Balaena mysticetus) and polar bears (Ursus maritimus) sampled in the Svalbard Archipelago (extending westward in the case of bowhead whales). Additionally, total concentrations (free and conjugated forms) of eight phthalate monoester metabolites were analysed in plasma of polar bears. Bis(2-ethylhexyl) phthalate (DEHP) was the only phthalate quantified among the 12 phthalates investigated. This compound was present in 6/7 fin whale samples, 4/7 blue whale samples, 2/5 bowhead whale samples and 1/12 polar bear samples. DEHP concentrations ranged from <20-398 ng/g wet weight. Phthalate metabolites, mono-n-butyl phthalate and monoisobutyl phthalate, were found in low concentrations (<1.2 ng/mL) in some of the polar bear samples. In vitro reporter gene assays were used to assess transcriptional activity of fin whale peroxisome proliferator-activated receptor gamma (PPARG), glucocorticoid receptor (GR) and the thyroid hormone receptor beta (THRB) by DEHP and diisononyl phthalate (DiNP). Due to the high degree of similarity of the ligand binding domain in the THRB and PPARG among whales, polar bears and humans, the transactivation results also apply for these species. DEHP showed both agonistic and antagonistic effects towards whale THRB at considerably higher concentrations than measured in the study animals; DiNP was a weak agonist of whale THRB. No significant agonistic or antagonistic effects were detected for DEHP or DiNP for whale PPARG, whereas DEHP and DiNP decreased basal luciferase activity mediated by whale GR at several test concentrations. In conclusion, DEHP was detected in the blubber of marine mammals from the Norwegian Arctic and it appears to have potential to modulate the transcriptional activity of whale THRB, but current DEHP concentrations do not modulate the function of the studied nuclear receptors in adipose tissue of blue whales, fin whales, bowhead whales or polar bears sampled from the Norwegian Arctic.
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http://dx.doi.org/10.1016/j.envint.2021.106458DOI Listing
July 2021

Adipose Tissue Transcriptome Is Related to Pollutant Exposure in Polar Bear Mother-Cub Pairs from Svalbard, Norway.

Environ Sci Technol 2020 09 30;54(18):11365-11375. Epub 2020 Aug 30.

Norwegian Polar Institute, Fram Centre, NO-9296 Tromsø, Norway.

Being at the food chain apex, polar bears () are highly contaminated with persistent organic pollutants (POPs). Females transfer POPs to their offspring through gestation and lactation; therefore, young cubs present higher POPs concentrations than their mothers. Recent studies suggest that POPs affect the lipid metabolism in female polar bears; however, the mechanisms and impact on their offspring remain unknown. Here, we hypothesized that exposure to POPs differentially alters genome-wide gene transcription in the adipose tissue from mother polar bears and their cubs, highlighting molecular differences in response between adults and young. Adipose tissue biopsies were collected from 13 adult female polar bears and their twin cubs in Svalbard, Norway, in April 2011, 2012, and 2013. Total RNA extracted from biopsies was subjected to next-generation RNA sequencing. Plasma concentrations of summed polychlorinated biphenyls, organochlorine pesticides, and polybrominated diphenyl ethers in mothers ranged from 897 to 13620 ng/g wet weight and were associated with altered adipose tissue gene expression in both mothers and cubs. In mothers, 2502 and 2586 genes in total were positively and negatively, respectively, correlated to POP exposure, whereas in cubs, 2585 positively and 1690 negatively genes. Between mothers and cubs, 743 positively and negatively genes overlapped between mothers and cubs suggesting partially shared molecular responses to ΣPOPs. ΣPOP-associated genes were involved in numerous metabolic pathways in mothers and cubs, indicating that POP exposure alters the energy metabolism, which, in turn, may be linked to metabolic dysfunction.
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http://dx.doi.org/10.1021/acs.est.0c01920DOI Listing
September 2020

Two Decades of Mercury Concentrations in Barents Sea Polar Bears () in Relation to Dietary Carbon, Sulfur, and Nitrogen.

Environ Sci Technol 2020 06 29;54(12):7388-7397. Epub 2020 May 29.

Fram Centre, Norwegian Polar Institute, Tromsø 9296, Norway.

Temporal trends of total mercury (THg) were examined in female polar bear () hair ( = 199) from the Barents Sea in 1995-2016. In addition, hair values of stable isotopes ( = 190-197) of carbon (δC), sulfur (δS), and nitrogen (δN) and information on breeding status, body condition, and age were obtained. Stable isotope values of carbon and sulfur reflect dietary source (e.g., marine vs terrestrial) and the nitrogen trophic level. Values for δC and δS declined by -1.62 and -1.18‰ over the time of the study period, respectively, while values for δN showed no trend. Total Hg concentrations were positively related to both δC and δS. Yearly median THg concentrations ranged from 1.61 to 2.75 μg/g and increased nonlinearly by 0.86 μg/g in total over the study. Correcting THg concentrations for stable isotope values of carbon and sulfur and additionally breeding status and age slightly accelerated the increase in THg concentrations; however, confidence intervals of the raw THg trend and the corrected THg trend had substantial overlap. The rise in THg concentrations in the polar bear food web was possibly related to climate-related re-emissions of previously stored Hg from thawing sea-ice, glaciers, and permafrost.
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http://dx.doi.org/10.1021/acs.est.0c01848DOI Listing
June 2020

Pelagic vs Coastal-Key Drivers of Pollutant Levels in Barents Sea Polar Bears with Contrasted Space-Use Strategies.

Environ Sci Technol 2020 01 11;54(2):985-995. Epub 2019 Dec 11.

Norwegian Polar Institute, Fram Centre , Tromsø 9296 , Norway.

In the Barents Sea, pelagic and coastal polar bears are facing various ecological challenges that may explain the difference in their pollutant levels. We measured polychlorinated biphenyls, organochlorine pesticides, polybrominated diphenyl ethers in fat, and perfluoroalkyl substances in plasma in pelagic and coastal adult female polar bears with similar body condition. We studied polar bear feeding habits with bulk stable isotope ratios of carbon and nitrogen. Nitrogen isotopes of amino acids were used to investigate their trophic position. We studied energy expenditure by estimating field metabolic rate using telemetry data. Annual home range size was determined, and spatial gradients in pollutants were explored using latitude and longitude centroid positions of polar bears. Pollutant levels were measured in harp seals from the Greenland Sea and White Sea-Barents Sea as a proxy for a West-East gradient of pollutants in polar bear prey. We showed that pelagic bears had higher pollutant loads than coastal bears because (1) they feed on a higher proportion of marine and higher trophic level prey, (2) they have higher energy requirements and higher prey consumption, (3) they forage in the marginal ice zones, and (4) they feed on prey located closer to pollutant emission sources/transport pathways.
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http://dx.doi.org/10.1021/acs.est.9b04626DOI Listing
January 2020

How many cubs can a mum nurse? Maternal age and size influence litter size in polar bears.

Biol Lett 2019 05;15(5):20190070

1 CEFE, CNRS, Univ Montpellier , Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier , France.

Life-history theory predicts that females' age and size affect the level of maternal investment in current reproduction, balanced against the future reproductive effort, maintenance and survival. Using long-term (30 years) individual data on 193 female polar bears ( Ursus maritimus), we assessed age- and size-specific variation on litter size. Litter size varied with maternal age, younger females had higher chances of losing a cub during their first months of life. Results suggest an improvement in reproductive abilities early in life due to experience with subsequent reproductive senescence. Litter size increased with maternal size, indicating that size may reflect individual quality. We also found an optimum in the probability of having twins, suggesting stabilizing selection on female body size. Heterogeneity was observed among the largest females, suggesting that large size comes at a cost.
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http://dx.doi.org/10.1098/rsbl.2019.0070DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6548740PMC
May 2019

Temporal Trends of Persistent Organic Pollutants in Barents Sea Polar Bears ( Ursus maritimus) in Relation to Changes in Feeding Habits and Body Condition.

Environ Sci Technol 2019 01 26;53(2):984-995. Epub 2018 Dec 26.

Norwegian Polar Institute , Tromsø 9296 , Norway.

Temporal trends of persistent organic pollutants (POPs: PCBs, OH-PCBs, p, p'-DDE, HCB, β-HCH, oxychlordane, BDE-47, and 153) in relation to changes in feeding habits and body condition in adult female polar bears ( Ursus maritimus) from the Barents Sea subpopulation were examined over 20 years (1997-2017). All 306 samples were collected in the spring (April). Both stable isotope values of nitrogen (δN) and carbon (δC) from red blood cells declined over time, with a steeper trend for δC between 2012 and 2017, indicating a decreasing intake of marine and high trophic level prey items. Body condition, based on morphometric measurements, had a nonsignificant decreasing tendency between 1997 and 2005, and increased significantly between 2005 and 2017. Plasma concentrations of BDE-153 and β-HCH did not significantly change over time, whereas concentrations of ΣPCB, ΣOH-PCB, BDE-47, and oxychlordane declined linearly. Concentrations of p, p'-DDE and HCB, however, declined until 2012 and 2009, respectively, and increased thereafter. Changes in feeding habits and body condition did not significantly affect POP trends. The study indicates that changes in diet and body condition were not the primary driver of POPs in polar bears, but were controlled in large part by primary and/or secondary emissions of POPs.
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http://dx.doi.org/10.1021/acs.est.8b05416DOI Listing
January 2019

Aquatic behaviour of polar bears (Ursus maritimus) in an increasingly ice-free Arctic.

Sci Rep 2018 06 26;8(1):9677. Epub 2018 Jun 26.

Norwegian Polar Institute, Norwegian Polar Institute, Fram Centre, 9296, Tromsø, Norway.

Polar bears are ice-associated marine mammals that are known to swim and dive, yet their aquatic behaviour is poorly documented. Reductions in Arctic sea ice are clearly a major threat to this species, but understanding polar bears' potential behavioural plasticity with respect to the ongoing changes requires knowledge of their swimming and diving skills. This study quantified time spent in water by adult female polar bears (n = 57) via deployment of various instruments bearing saltwater switches, and in some case pressure sensors (79 deployments, 64.8 bear-years of data). There were marked seasonal patterns in aquatic behaviour, with more time spent in the water during summer, when 75% of the polar bears swam daily (May-July). Females with cubs-of-the-year spent less time in the water than other females from den emergence (April) until mid-summer, consistent with small cubs being vulnerable to hypothermia and drowning. Some bears undertook notable long-distance-swims. Dive depths up to 13.9 m were recorded, with dives ≥5 m being common. The considerable swimming and diving capacities of polar bears might provide them with tools to exploit aquatic environments previously not utilized. This is likely to be increasingly important to the species' survival in an Arctic with little or no persistent sea ice.
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http://dx.doi.org/10.1038/s41598-018-27947-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6018667PMC
June 2018

Effects of biometrics, location and persistent organic pollutants on blood clinical-chemical parameters in polar bears (Ursus maritimus) from Svalbard, Norway.

Environ Res 2018 08 31;165:387-399. Epub 2018 May 31.

Department of Biology, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway; Department of Bioscience, Arctic Research Centre (ARC), Aarhus University, Faculty of Science and Technology, Frederiksborgvej 399, POBox 358, DK-4000 Roskilde, Denmark; Department of Arctic Technology, The University Centre in Svarbard, POBox 156, NO-9171 Longyearbyen, Norway. Electronic address:

In the present study, blood clinical-chemical parameters (BCCPs) were analysed in 20 female and 18 male Svalbard polar bears (Ursus maritimus) captured in spring 2007. The aim was to study how age, body condition (BC), biometrics, plasma lipid content and geographical location may confound the relationship between persistent organic pollutants (POPs) including PCBs, HCB, chlordanes, DDTs, HCHs, mirex and OH-PCBs and the concentrations of 12 specific BCCPs (hematocrit [HCT], hemoglobin [HB], aspartate aminotransferase [ASAT], alanine aminotransferase [ALAT], γ-glutamyltransferase [GGT], creatine kinase [CK], triglycerides [TG], cholesterol [CHOL], high-density lipoprotein [HDL], creatinine (CREA], urea, potassium (K]), and to investigate if any of these BCCPs may be applied as potential biomarkers for POP exposure in polar bears. Initial PCA and O-PLS modelling showed that age, lipids, BC and geographical location (longitude and latitude) were important parameters explaining BCCPs in females. Following subsequent partial correlation analyses correcting for age and lipids, multiple POPs in females were still significantly correlated with HCT and HDL (all p < 0.05). In males, age, BM, BC and longitude were important parameters explaining BCCPs. Following partial correlation analyses correcting for age, biometrics, lipids and longitude in males, multiple POPs were significantly correlated with HCT, ASAT, GGT and CHOL (all p < 0.05). In conclusion, several confounding parameters has to be taken into account when studying the relations between BCCPs and POPs in polar bears. When correcting for these, in particular HCT may be used as a simple cost-efficient biomarker of POP exposure in polar bears. Furthermore, decreasing HDL concentrations and increasing CHOL concentration with increasing POP concentrations may indicate responses related to increased risk of cardiovascular disease. We therefore suggest to further study POP exposure and lipidome response to increase knowledge of the risk of cardiometabolic syndrome in polar bears.
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http://dx.doi.org/10.1016/j.envres.2018.04.026DOI Listing
August 2018

Choose Your Poison-Space-Use Strategy Influences Pollutant Exposure in Barents Sea Polar Bears.

Environ Sci Technol 2018 03 13;52(5):3211-3221. Epub 2018 Feb 13.

Norwegian Polar Institute , Fram Centre , Tromsø NO-9296 , Norway.

Variation in space-use is common within mammal populations. In polar bears, Ursus maritimus, some individuals follow the sea ice (offshore bears) whereas others remain nearshore yearlong (coastal bears). We studied pollutant exposure in relation to space-use patterns (offshore vs coastal) in adult female polar bears from the Barents Sea equipped with satellite collars (2000-2014, n = 152). First, we examined the differences in home range (HR) size and position, body condition, and diet proxies (nitrogen and carbon stable isotopes, n = 116) between offshore and coastal space-use. Second, we investigated how HR, space-use, body condition, and diet were related to plasma concentrations of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) ( n = 113), perfluoroalkyl substances (PFASs; n = 92), and hydroxylated-PCBs ( n = 109). Offshore females were in better condition and had a more specialized diet than did coastal females. PCBs, OCPs, and hydroxylated-PCB concentrations were not related to space-use strategy, yet PCB concentrations increased with increasing latitude, and hydroxylated-PCB concentrations were positively related to HR size. PFAS concentrations were 30-35% higher in offshore bears compared to coastal bears and also increased eastward. On the basis of the results we conclude that space-use of Barents Sea female polar bears influences their pollutant exposure, in particular plasma concentrations of PFAS.
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http://dx.doi.org/10.1021/acs.est.7b06137DOI Listing
March 2018

Multiple-stressor effects in an apex predator: combined influence of pollutants and sea ice decline on lipid metabolism in polar bears.

Sci Rep 2017 11 28;7(1):16487. Epub 2017 Nov 28.

Norwegian Polar Institute, Fram Centre, NO-9296, Tromsø, Norway.

There is growing evidence from experimental and human epidemiological studies that many pollutants can disrupt lipid metabolism. In Arctic wildlife, the occurrence of such compounds could have serious consequences for seasonal feeders. We set out to study whether organohalogenated compounds (OHCs) could cause disruption of energy metabolism in female polar bears (Ursus maritimus) from Svalbard, Norway (n = 112). We analyzed biomarkers of energy metabolism including the abundance profiles of nine lipid-related genes, fatty acid (FA) synthesis and elongation indices in adipose tissue, and concentrations of lipid-related variables in plasma (cholesterol, high-density lipoprotein, triglycerides). Furthermore, the plasma metabolome and lipidome were characterized by low molecular weight metabolites and lipid fingerprinting, respectively. Polychlorinated biphenyls, chlordanes, brominated diphenyl ethers and perfluoroalkyl substances were significantly related to biomarkers involved in lipid accumulation, FA metabolism, insulin utilization, and cholesterol homeostasis. Moreover, the effects of pollutants were measurable at the metabolome and lipidome levels. Our results indicate that several OHCs affect lipid biosynthesis and catabolism in female polar bears. Furthermore, these effects were more pronounced when combined with reduced sea ice extent and thickness, suggesting that climate-driven sea ice decline and OHCs have synergistic negative effects on polar bears.
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http://dx.doi.org/10.1038/s41598-017-16820-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5705648PMC
November 2017

Emission Changes Dwarf the Influence of Feeding Habits on Temporal Trends of Per- and Polyfluoroalkyl Substances in Two Arctic Top Predators.

Environ Sci Technol 2017 Oct 29;51(20):11996-12006. Epub 2017 Sep 29.

UiT-The Arctic University of Norway , Department of Arctic and Marine Biology, Tromsø, Norway.

We monitored concentrations of per- and polyfluoroalkyl substances (PFASs) in relation to climate-associated changes in feeding habits and food availability in polar bears (Ursus maritimus) and arctic foxes (Vulpes lagopus) (192 plasma and 113 liver samples, respectively) sampled from Svalbard, Norway, during 1997-2014. PFASs concentrations became greater with increasing dietary trophic level, as bears and foxes consumed more marine as opposed to terrestrial food, and as the availability of sea ice habitat increased. Long-chained perfluoroalkyl carboxylates (PFCAs) in arctic foxes decreased with availability of reindeer carcasses. The ∼9-14% yearly decline of C perfluoroalkyl sulfonates (PFSAs) following the cease in C PFSA precursor production in 2001 indicates that the peak exposure was mainly a result of atmospheric transport of the volatile precursors. However, the stable PFSA concentrations since 2009-2010 suggest that Svalbard biota is still exposed to ocean-transported PFSAs. Long-chain ocean-transported PFCAs increased 2-4% per year and the increase in C PFCAs in polar bears tended to level off since ∼2009. Emerging short-chain PFASs showed no temporal changes. Climate-related changes in feeding habits and food availability moderately affected PFAS trends. Our results indicate that PFAS concentrations in polar bears and arctic foxes are mainly affected by emissions.
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http://dx.doi.org/10.1021/acs.est.7b03585DOI Listing
October 2017

Relationships between POPs, biometrics and circulating steroids in male polar bears (Ursus maritimus) from Svalbard.

Environ Pollut 2017 Nov 12;230:598-608. Epub 2017 Jul 12.

Toxicology Laboratory, Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark. Electronic address:

The aim of this study was to determine the effects of persistent organic pollutants (POPs) and biometric variables on circulating levels of steroid hormones (androgens, estrogens and progestagens) in male polar bears (Ursus maritimus) from Svalbard, Norway (n = 23). Levels of pregnenolone (PRE), progesterone (PRO), androstenedione (AN), dehydroepiandrosterone (DHEA), testosterone (TS), dihydrotestosterone (DHT), estrone (E1), 17α-estradiol (αE2) and 17β-estradiol (βE2) were quantified in polar bear serum by gas chromatography tandem mass spectrometry (GC-MS/MS), while POPs were measured in plasma. Subsequently, associations between hormone concentrations (9 steroids), POPs (21 polychlorinated biphenyls (PCBs), 8 OH-PCBs, 8 organochlorine pesticides (OCPs) and OCP metabolites, and 2 polybrominated diphenyl ethers (PBDEs)) and biological variables (age, head length, body mass, girth, body condition index), capture date, location (latitude and longitude), lipid content and cholesterol levels were examined using principal component analysis (PCA) and orthogonal projections to latent structures (OPLS) modelling. Average concentrations of androgens, estrogens and progestagens were in the range of 0.57-83.7 (0.57-12.4 for subadults, 1.02-83.7 for adults), 0.09-2.69 and 0.57-2.44 nmol/L, respectively. The steroid profiles suggest that sex steroids were mainly synthesized through the Δ-4 pathway in male polar bears. The ratio between androgens and estrogens significantly depended on sexual maturity with androgen/estrogen ratios being approximately 60 times higher in adult males than in subadult males. PCA plots and OPLS models indicated that TS was positively related to biometrics, such as body condition index in male polar bears. A negative relationship was also observed between POPs and DHT. Consequently, POPs and body condition may potentially affect the endocrinological function of steroids, including development of reproductive tissues and sex organs and the general condition of male polar bears.
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http://dx.doi.org/10.1016/j.envpol.2017.06.095DOI Listing
November 2017

Potentiation of ecological factors on the disruption of thyroid hormones by organo-halogenated contaminants in female polar bears (Ursus maritimus) from the Barents Sea.

Environ Res 2017 10 11;158:94-104. Epub 2017 Jun 11.

Norwegian Polar Institute, Fram Centre, Tromsø, Norway. Electronic address:

As apex predators, polar bears (Ursus maritimus) are among the most heavily polluted organisms in the Arctic. In addition to this anthropogenic stressor, climate warming has been shown to negatively affect their body condition, reproductive output and survival. Among potential underlying physiological mechanisms, thyroid hormones (THs), which control thermoregulation, metabolism and reproduction, can be affected by a variety of both natural and anthropogenic factors. While THs have been extensively used as proxies for pollution exposure in mammals, including polar bears, there is a lack of knowledge of their natural variations. In this context, we examined seasonal variations in body condition and circulating TH concentrations in free-ranging female polar bears. Females with variable reproductive status (i.e., solitary, with cubs of the year or with yearlings) were sampled from locations with contrasted sea ice conditions. Furthermore, we studied THs in relation to levels of organo-halogenated contaminants. As predicted, solitary females were in better condition than females caring for offspring, especially in spring. In addition, TH levels were lower in autumn compared to spring, although this seasonal effect was mainly observed in solitary females. Finally, the negative relationships between organochlorine and perfluoroalkyl substances and some THs suggest a possible alteration of homeostasis of THs. Since the latter relationships were only observed during spring, we emphasize the importance of considering the ecological factors when using THs as proxies for pollution exposure. Yet, the combined effects of natural and anthropogenic stressors on THs might impair the ability of polar bears to adapt to ongoing climate changes.
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http://dx.doi.org/10.1016/j.envres.2017.05.034DOI Listing
October 2017

Diet and metabolic state are the main factors determining concentrations of perfluoroalkyl substances in female polar bears from Svalbard.

Environ Pollut 2017 Oct 3;229:146-158. Epub 2017 Jun 3.

Norwegian Polar Institute, Fram Centre, Tromsø, Norway.

Perfluoroalkyl substances (PFASs) have been detected in organisms worldwide, including Polar Regions. The polar bear (Ursus maritimus), the top predator of Arctic marine ecosystems, accumulates high concentrations of PFASs, which may be harmful to their health. The aim of this study was to investigate which factors (habitat quality, season, year, diet, metabolic state [i.e. feeding/fasting], breeding status and age) predict PFAS concentrations in female polar bears captured on Svalbard (Norway). We analysed two perfluoroalkyl sulfonates (PFSAs: PFHxS and PFOS) and C-C perfluoroalkyl carboxylates (PFCAs) in 112 plasma samples obtained in April and September 2012-2013. Nitrogen and carbon stable isotope ratios (δN, δC) in red blood cells and plasma, and fatty acid profiles in adipose tissue were used as proxies for diet. We determined habitat quality based on movement patterns, capture position and resource selection functions, which are models that predict the probability of use of a resource unit. Plasma urea to creatinine ratios were used as proxies for metabolic state (i.e. feeding or fasting state). Results were obtained from a conditional model averaging of 42 general linear mixed models. Diet was the most important predictor of PFAS concentrations. PFAS concentrations were positively related to trophic level and marine diet input. High PFAS concentrations in females feeding on the eastern part of Svalbard, where the habitat quality was higher than on the western coast, were likely related to diet and possibly to abiotic factors. Concentrations of PFSAs and C-C PFCAs were higher in fasting than in feeding polar bears and PFOS was higher in females with cubs of the year than in solitary females. Our findings suggest that female polar bears that are exposed to the highest levels of PFAS are those 1) feeding on high trophic level sea ice-associated prey, 2) fasting and 3) with small cubs.
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http://dx.doi.org/10.1016/j.envpol.2017.04.100DOI Listing
October 2017

An Arctic predator-prey system in flux: climate change impacts on coastal space use by polar bears and ringed seals.

J Anim Ecol 2017 09 22;86(5):1054-1064. Epub 2017 May 22.

Norwegian Polar Institute, Fram Centre, Tromsø, Norway.

Climate change is impacting different species at different rates, leading to alterations in biological interactions with ramifications for wider ecosystem functioning. Understanding these alterations can help improve predictive capacity and inform management efforts designed to mitigate against negative impacts. We investigated how the movement and space use patterns of polar bears (Ursus maritimus) in coastal areas in Svalbard, Norway, have been altered by a sudden decline in sea ice that occurred in 2006. We also investigated whether the spatial overlap between polar bears and their traditionally most important prey, ringed seals (Pusa hispida), has been affected by the sea-ice decline, as polar bears are dependent on a sea-ice platform for hunting seals. We attached biotelemetry devices to ringed seals (n = 60, both sexes) and polar bears (n = 67, all females) before (2002-2004) and after (2010-2013) a sudden decline in sea ice in Svalbard. We used linear mixed-effects models to evaluate the association of these species to environmental features and an approach based on Time Spent in Area to investigate changes in spatial overlap between the two species. Following the sea-ice reduction, polar bears spent the same amount of time close to tidal glacier fronts in the spring but less time in these areas during the summer and autumn. However, ringed seals did not alter their association with glacier fronts during summer, leading to a major decrease in spatial overlap values between these species in Svalbard's coastal areas. Polar bears now move greater distances daily and spend more time close to ground-nesting bird colonies, where bear predation can have substantial local effects. Our results indicate that sea-ice declines have impacted the degree of spatial overlap and hence the strength of the predator-prey relationship between polar bears and ringed seals, with consequences for the wider Arctic marine and terrestrial ecosystems. Shifts in ecological interactions are likely to become more widespread in many ecosystems as both predators and prey respond to changing environmental conditions induced by global warming, highlighting the importance of multi-species studies.
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http://dx.doi.org/10.1111/1365-2656.12685DOI Listing
September 2017

Sea ice-associated decline in body condition leads to increased concentrations of lipophilic pollutants in polar bears (Ursus maritimus) from Svalbard, Norway.

Sci Total Environ 2017 Jan 26;576:409-419. Epub 2016 Oct 26.

Norwegian Polar Institute, Fram Centre, Tromsø, Norway.

Global climate changes are magnified in the Arctic and are having an especially dramatic effect on the spatial and temporal distribution and the thickness traits of sea ice. Decline of Arctic sea ice may lead to qualitative and/or quantitative changes in diet and reduced body condition (i.e. adipose tissue stores) of ice-associated apex predators such as polar bears (Ursus maritimus). This may further affect their tissue concentrations of lipophilic pollutants. We determined how variations in adipose tissue stores associated to both breeding status and spatial changes in sea ice conditions and diet influence concentrations and biotransformation of lipophilic persistent organic pollutants (POPs). We collected 112 blood and fat samples from female polar bears (Ursus maritimus) of different breeding status (alone, with cubs of the year, or with yearlings) during two seasons (April and September) in 2012 and 2013 at three locations of Svalbard, Norway, with contrasted sea ice conditions. We inferred diet from nitrogen and carbon stable isotope ratios in red blood cells and fatty acid composition in adipose tissue. Relative to diet, body condition, which was negatively related to sea ice extent at both temporal and spatial scales, was the most important predictor for concentrations of POPs in plasma and fat, whereas diet showed a minor influence. Additionally, fatter females were more efficient at biotransforming PCBs than were leaner ones. Breeding status influenced the concentrations of less lipophilic compounds such as β-hexachlorocyclohexane, which were lower in females with yearlings, probably due to excretion into milk and subsequent offloading to young. In conclusion, our results indicate that declining sea ice indirectly leads to increased concentrations of lipophilic pollutants in polar bears mediated through reduced feeding opportunities and declining body condition rather than changes in diet composition.
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http://dx.doi.org/10.1016/j.scitotenv.2016.10.132DOI Listing
January 2017

Climate change impacts on wildlife in a High Arctic archipelago - Svalbard, Norway.

Glob Chang Biol 2017 02 28;23(2):490-502. Epub 2016 Jun 28.

Norwegian Polar Institute, Fram Centre, Tromsø, 9296, Norway.

The Arctic is warming more rapidly than other region on the planet, and the northern Barents Sea, including the Svalbard Archipelago, is experiencing the fastest temperature increases within the circumpolar Arctic, along with the highest rate of sea ice loss. These physical changes are affecting a broad array of resident Arctic organisms as well as some migrants that occupy the region seasonally. Herein, evidence of climate change impacts on terrestrial and marine wildlife in Svalbard is reviewed, with a focus on bird and mammal species. In the terrestrial ecosystem, increased winter air temperatures and concomitant increases in the frequency of 'rain-on-snow' events are one of the most important facets of climate change with respect to impacts on flora and fauna. Winter rain creates ice that blocks access to food for herbivores and synchronizes the population dynamics of the herbivore-predator guild. In the marine ecosystem, increases in sea temperature and reductions in sea ice are influencing the entire food web. These changes are affecting the foraging and breeding ecology of most marine birds and mammals and are associated with an increase in abundance of several temperate fish, seabird and marine mammal species. Our review indicates that even though a few species are benefiting from a warming climate, most Arctic endemic species in Svalbard are experiencing negative consequences induced by the warming environment. Our review emphasizes the tight relationships between the marine and terrestrial ecosystems in this High Arctic archipelago. Detecting changes in trophic relationships within and between these ecosystems requires long-term (multidecadal) demographic, population- and ecosystem-based monitoring, the results of which are necessary to set appropriate conservation priorities in relation to climate warming.
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http://dx.doi.org/10.1111/gcb.13381DOI Listing
February 2017

Geographical Area and Life History Traits Influence Diet in an Arctic Marine Predator.

PLoS One 2016 19;11(5):e0155980. Epub 2016 May 19.

Norwegian Polar Institute, Fram Centre, Tromsø, Norway.

Global changes are thought to affect most Arctic species, yet some populations are more at risk. Today, the Barents Sea ecoregion is suffering the strongest sea ice retreat ever measured; and these changes are suspected to modify food access and thus diet of several species. Biochemical diet tracers enable investigation of diet in species such as polar bears (Ursus maritimus). We examined individual diet variation of female polar bears in Svalbard, Norway, and related it to year, season (spring and autumn), sampling area and breeding status (solitary, with cubs of the year or yearlings). Sampling areas were split according to their ice cover: North-West (less sea ice cover), South-East (larger amplitude in sea ice extent) and North-East/South-West (NESW) as bears from that zone are more mobile among all regions of Svalbard. We measured fatty acid (FA) composition in adipose tissue and carbon (δ13C) and nitrogen (δ15N) stable isotopes in plasma and red blood cells. Females feeding in the North-West area had lower δ15N values than those from the NESW. In South-East females, δ13C values were lower in autumn compared to spring and females seemed less selective in their diet as depicted by large variances in stable isotope values. Considering the differences in FA composition and stable isotope values, we suggest that females from the North-West and South-East could ingest a higher proportion of avian prey. With regard to breeding status, solitary females had higher δ15N values and smaller variance in their stable isotopic values than females with cubs, suggesting that solitary females were more selective and prey on higher trophic level species (i.e. seals). Overall, our results indicate that prey availability for Svalbard polar bears varies according to geographical area and prey selectivity differs according to breeding status. Our findings suggest that complex changes in sea ice and prey availability will interact to affect Svalbard polar bear feeding patterns and associated nutrition.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0155980PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4873193PMC
July 2017

Genetic diversity of historical Atlantic walruses (Odobenus rosmarus rosmarus) from Bjørnøya and Håøya (Tusenøyane), Svalbard, Norway.

BMC Res Notes 2016 Feb 18;9:112. Epub 2016 Feb 18.

Natural History Museum, University of Oslo, PO Box 1172, Blindern, 0318, Oslo, Norway.

Background: The population size of Atlantic walruses (Odobenus rosmarus rosmarus) is depleted relative to historical abundance levels. In Svalbard, centuries of over-exploitation brought the walrus herds to the verge of extinction, and such bottlenecks may have caused loss of genetic variation. To address this for Svalbard walruses, mitochondrial haplotypes of historical walruses from two major haul-out sites, Bjørnøya and Håøya, within the Archipelago were explored using bone samples from animals killed during the peak period of harvesting.

Results: Using ancient DNA methodologies, the mitochondrial NADH dehydrogenase 1 (ND1) gene, the cytochrome c oxidase 1 (COI) gene, and the control region (CR) were targeted for 15 specimens from Bjørnøya (of which five were entirely negative) and 9 specimens from Håøya (of which one was entirely negative). While ND1 and COI sequences were obtained for only a few samples, the CR delivered the most comprehensive data set, and the average genetic distance among historic Svalbard samples was 0.0028 (SD = 0.0023).

Conclusions: The CR sequences from the historical samples appear to be nested among contemporary Atlantic walruses, and no distinct mitochondrial haplogroups were identified in the historical samples that may have been lost during the periods of extensive hunting. However, given the low sample size and poor phylogenetic resolution it cannot be excluded that such haplogroups existed.
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http://dx.doi.org/10.1186/s13104-016-1907-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4757977PMC
February 2016

Organophosphorous flame retardants in biota from Svalbard, Norway.

Mar Pollut Bull 2015 Dec 6;101(1):442-447. Epub 2015 Oct 6.

Norwegian Polar Institute, Fram Centre, Postboks 6606, 9296 Tromsø, Norway. Electronic address:

Eight arctic species, including fish, birds and mammals, from diverse habitats (marine and terrestrial) within the Svalbard Archipelago, Norway, were screened for 14 organophosphorus flame retardant (PFR) compounds. Ten PFRs were detected: tris(2-chloroethyl)phosphate (TCEP), tris(2-chloroisopropyl)phosphate (TCIPP), tris(1,3-dichloro-2-propyl)phosphate (TDCIPP), triphenyl phosphate (TPHP); 2-ethylhexyl diphenyl phosphate (EHDPP); tris(2-butoxyethyl)phosphate (TBOEP); tritolyl phosphate (TCrP); triisobutyl phosphate (TIBP); tris(2-ethylhexyl)phosphate (TEHP); and butyl diphenyl phosphate (DPhBP). The greatest number of different PFR compounds, and the highest detection frequency were measured in capelin (Mallotus villotus), and the lowest in Brünnich's guillemot (Uria lomvia). The highest concentrations of ΣPFR, as well as the highest concentration of a single PFR compound, TBOEP, were measured in arctic fox (Vulpes lagopus). The presence of PFR compounds in arctic biota indicates that these compounds can undergo long-range transport and are, to some degree, persistent and bioaccumulated. The potential for biomagnification from fish to higher trophic levels seems to be limited.
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http://dx.doi.org/10.1016/j.marpolbul.2015.09.049DOI Listing
December 2015

Hydroxylated polychlorinated biphenyls decrease circulating steroids in female polar bears (Ursus maritimus).

Environ Res 2015 Apr 25;138:191-201. Epub 2015 Feb 25.

Norwegian University of Science and Technology (NTNU), Department of Biology, Høgskoleringen 5, NO-7491 Trondheim, Norway.

As a top predator in the Arctic food chain, polar bears (Ursus maritimus) are exposed to high levels of persistent organic pollutants (POPs). Because several of these compounds have been reported to alter endocrine pathways, such as the steroidogenesis, potential disruption of the sex steroid synthesis by POPs may cause implications for reproduction by interfering with ovulation, implantation and fertility. Blood samples were collected from 15 female polar bears in Svalbard (Norway) in April 2008. The concentrations of nine circulating steroid hormones; dehydroepiandrosterone (DHEA), androstenedione (AN), testosterone (TS), dihydrotestosterone (DHT), estrone (E1), 17α-estradiol (αE2), 17β-estradiol (βE2), pregnenolone (PRE) and progesterone (PRO) were determined. The aim of the study was to investigate associations among circulating levels of specific POP compounds and POP-metabolites (hydroxylated PCBs [OH-PCBs] and hydroxylated PBDEs [OH-PBDEs]), steroid hormones, biological and capture variables in female polar bears. Inverse correlations were found between circulating levels of PRE and AN, and circulating levels of OH-PCBs. There were no significant relationships between the steroid concentrations and other analyzed POPs or the variables capture date and capture location (latitude and longitude), lipid content, condition and body mass. Although statistical associations do not necessarily represent direct cause-effect relationships, the present study indicate that OH-PCBs may affect the circulating levels of AN and PRE in female polar bears and that OH-PCBs thus may interfere with the steroid homeostasis. Increase in PRO and a decrease in AN concentrations suggest that the enzyme CYP17 may be a potential target for OH-PCBs. In combination with natural stressors, ongoing climate change and contaminant exposure, it is possible that OH-PCBs may disturb the reproductive potential of polar bears.
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http://dx.doi.org/10.1016/j.envres.2015.02.011DOI Listing
April 2015

Establishing a definition of polar bear (Ursus maritimus) health: a guide to research and management activities.

Sci Total Environ 2015 May 11;514:371-8. Epub 2015 Feb 11.

U.S. Geological Survey, Alaska Science Center, USA. Electronic address:

The meaning of health for wildlife and perspectives on how to assess and measure health, are not well characterized. For wildlife at risk, such as some polar bear (Ursus maritimus) subpopulations, establishing comprehensive monitoring programs that include health status is an emerging need. Environmental changes, especially loss of sea ice habitat, have raised concern about polar bear health. Effective and consistent monitoring of polar bear health requires an unambiguous definition of health. We used the Delphi method of soliciting and interpreting expert knowledge to propose a working definition of polar bear health and to identify current concerns regarding health, challenges in measuring health, and important metrics for monitoring health. The expert opinion elicited through the exercise agreed that polar bear health is defined by characteristics and knowledge at the individual, population, and ecosystem level. The most important threats identified were in decreasing order: climate change, increased nutritional stress, chronic physiological stress, harvest management, increased exposure to contaminants, increased frequency of human interaction, diseases and parasites, and increased exposure to competitors. Fifteen metrics were identified to monitor polar bear health. Of these, indicators of body condition, disease and parasite exposure, contaminant exposure, and reproductive success were ranked as most important. We suggest that a cumulative effects approach to research and monitoring will improve the ability to assess the biological, ecological, and social determinants of polar bear health and provide measurable objectives for conservation goals and priorities and to evaluate progress.
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http://dx.doi.org/10.1016/j.scitotenv.2015.02.007DOI Listing
May 2015

Implications of the circumpolar genetic structure of polar bears for their conservation in a rapidly warming Arctic.

PLoS One 2015 6;10(1):e112021. Epub 2015 Jan 6.

Alaska Science Center, US Geological Survey, Anchorage, Alaska, United States of America.

We provide an expansive analysis of polar bear (Ursus maritimus) circumpolar genetic variation during the last two decades of decline in their sea-ice habitat. We sought to evaluate whether their genetic diversity and structure have changed over this period of habitat decline, how their current genetic patterns compare with past patterns, and how genetic demography changed with ancient fluctuations in climate. Characterizing their circumpolar genetic structure using microsatellite data, we defined four clusters that largely correspond to current ecological and oceanographic factors: Eastern Polar Basin, Western Polar Basin, Canadian Archipelago and Southern Canada. We document evidence for recent (ca. last 1-3 generations) directional gene flow from Southern Canada and the Eastern Polar Basin towards the Canadian Archipelago, an area hypothesized to be a future refugium for polar bears as climate-induced habitat decline continues. Our data provide empirical evidence in support of this hypothesis. The direction of current gene flow differs from earlier patterns of gene flow in the Holocene. From analyses of mitochondrial DNA, the Canadian Archipelago cluster and the Barents Sea subpopulation within the Eastern Polar Basin cluster did not show signals of population expansion, suggesting these areas may have served also as past interglacial refugia. Mismatch analyses of mitochondrial DNA data from polar and the paraphyletic brown bear (U. arctos) uncovered offset signals in timing of population expansion between the two species, that are attributed to differential demographic responses to past climate cycling. Mitogenomic structure of polar bears was shallow and developed recently, in contrast to the multiple clades of brown bears. We found no genetic signatures of recent hybridization between the species in our large, circumpolar sample, suggesting that recently observed hybrids represent localized events. Documenting changes in subpopulation connectivity will allow polar nations to proactively adjust conservation actions to continuing decline in sea-ice habitat.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0112021PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4285400PMC
January 2016

Effect-directed analysis to explore the polar bear exposome: identification of thyroid hormone disrupting compounds in plasma.

Environ Sci Technol 2013 Aug 9;47(15):8902-12. Epub 2013 Jul 9.

Institute for Environmental Studies (IVM), VU University Amsterdam, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands.

Compounds with transthyretin (TTR)-binding potency in the blood plasma of polar bear cubs were identified with effect-directed analysis (EDA). This approach contributes to the understanding of the thyroid disrupting exposome of polar bears. The selection of these samples for in-depth EDA was based on the difference between the observed TTR-binding potency on the one hand and the calculated potency (based on known concentrations of TTR-binding compounds and their relative potencies) on the other. A library-based identification was applied to the liquid chromatography-time-of-flight-mass spectrometry (LC-ToF-MS) data by screening for matches between compound lists and the LC-ToF-MS data regarding accurate mass and isotope pattern. Then, isotope cluster analysis (ICA) was applied to the LC-ToF-MS data allowing specific screening for halogen isotope patterns. The presence of linear and branched nonylphenol (NP) was observed for the first time in polar bears. Furthermore, the presence of one di- and two monohydroxylated octachlorinated biphenyls (octaCBs) was revealed in the extracts. Linear and branched NP, 4'-OH-CB201 and 4,4'-OH-CB202 could be successfully confirmed with respect to their retention time in the analytical system. In addition, branched NP, mono- and dihydroxylated-octaCBs showed TTR-binding potencies and could explain another 32 ± 2% of the total measured activities in the extracts.
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http://dx.doi.org/10.1021/es401696uDOI Listing
August 2013

Transthyretin-binding activity of contaminants in blood from polar bear (Ursus maritimus) cubs.

Environ Sci Technol 2013 May 3;47(9):4778-86. Epub 2013 Apr 3.

Department of Biology, Norwegian University of Science and Technology (NTNU), Høgskoleringen 5, NO-7491 Trondheim, Norway.

We determined the transthyretin (TTR)-binding activity of blood-accumulating contaminants in blood plasma samples of approximately 4-months-old polar bear (Ursus maritimus) cubs from Svalbard sampled in 1998 and 2008. The TTR-binding activity was measured as thyroxine (T4)-like equivalents (T4-EQMeas). Our findings show that the TTR-binding activity related to contaminant levels was significantly lower (45%) in 2008 than in 1998 (mean ± standard error of mean: 1998, 2265 ± 231 nM; 2008, 1258 ± 170 nM). Although we cannot exclude a potential influence of between-year differences in capture location and cub body mass, our findings most likely reflect reductions of TTR-binding contaminants or their precursors in the arctic environment (e.g., polychlorinated biphenyls [PCBs]). The measured TTR-binding activity correlated positively with the cubs' plasma levels of hydroxylated PCBs (OH-PCBs). No such association was found between TTR-binding activity and the plasma levels of perfluoroalkyl substances (PFASs). The OH-PCBs explained 60 ± 7% and 54 ± 4% of the TTR-binding activity in 1998 and 2008, respectively, and PFASs explained ≤1.2% both years. Still, almost half the TTR-binding activity could not be explained by the contaminants we examined. The considerable levels of TTR-binding contaminants warrant further effect directed analysis (EDA) to identify the contaminants responsible for the unexplained part of the observed TTR-binding activity.
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http://dx.doi.org/10.1021/es305160vDOI Listing
May 2013

What are the toxicological effects of mercury in Arctic biota?

Sci Total Environ 2013 Jan 8;443:775-90. Epub 2012 Dec 8.

Aarhus University, Department for Bioscience, Arctic Research Centre, P.O. Box 358, Roskilde, DK-4000, Denmark.

This review critically evaluates the available mercury (Hg) data in Arctic marine biota and the Inuit population against toxicity threshold values. In particular marine top predators exhibit concentrations of mercury in their tissues and organs that are believed to exceed thresholds for biological effects. Species whose concentrations exceed threshold values include the polar bears (Ursus maritimus), beluga whale (Delphinapterus leucas), pilot whale (Globicephala melas), hooded seal (Cystophora cristata), a few seabird species, and landlocked Arctic char (Salvelinus alpinus). Toothed whales appear to be one of the most vulnerable groups, with high concentrations of mercury recorded in brain tissue with associated signs of neurochemical effects. Evidence of increasing concentrations in mercury in some biota in Arctic Canada and Greenland is therefore a concern with respect to ecosystem health.
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http://dx.doi.org/10.1016/j.scitotenv.2012.11.046DOI Listing
January 2013
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