Diet-driven mercury contamination is associated with polar bear gut microbiota

AbstractThe gut microbiota may modulate the disposition and toxicity of environmental contaminants within a host but, conversely, contaminants may also impact gut bacteria. Such contaminant-gut microbial connections, which could lead to alteration of host health, remain poorly known and are rarely studied in free-ranging wildlife. The polar bear (Ursus maritimus) is a long-lived, wide-ranging apex predator that feeds on a variety of high trophic position seal and cetacean species and, as such, is exposed to among the highest levels of biomagnifying contaminants of all Arctic species. Here, we investigate associations between mercury (THg; a key Arctic contaminant), diet, and the diversity and composition of the gut microbiota of polar bears inhabiting the southern Beaufort Sea, while accounting for host sex, age class and body condition. Bacterial diversity was negatively associated with seal consumption and mercury, a pattern seen for both Shannon and Inverse Simpson alpha diversity indices (adjusted R2 = 0.35, F1,18 = 8.00, P = 0.013 and adjusted R2 = 0.26, F1,18 = 6.04, P = 0.027, respectively). No association was found with sex, age class or body condition of polar bears. Bacteria known to either be involved in THg methylation or considered to be highly contaminant resistant, including Lactobacillales, Bacillales and Aeromonadales, were significantly more abundant in individuals that had higher THg concentrations. Conversely, individuals with higher THg concentrations showed a significantly lower abundance of Bacteroidales, a bacterial order that typically plays an important role in supporting host immune function by stimulating intraepithelial lymphocytes within the epithelial barrier. These associations between diet-acquired mercury and microbiota illustrate a potentially overlooked outcome of mercury accumulation in polar bears.

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Effects of capturing and collaring on polar bears: findings from long-term research on the southern Beaufort Sea population

Wildlife Research ◽

10.1071/wr13225 ◽

2014 ◽

Vol 41 (4) ◽

pp. 311 ◽

Cited By ~ 23

Author(s):

Karyn D. Rode ◽

Anthony M. Pagano ◽

Jeffrey F. Bromaghin ◽

Todd C. Atwood ◽

George M. Durner ◽

...

Keyword(s):

Research Methods ◽

Body Mass ◽

Body Condition ◽

Polar Bear ◽

Beaufort Sea ◽

Polar Bears ◽

Long Term Effects ◽

Movement Rates ◽

Related Mortality

Context The potential for research methods to affect wildlife is an increasing concern among both scientists and the public. This topic has a particular urgency for polar bears because additional research is needed to monitor and understand population responses to rapid loss of sea ice habitat. Aims This study used data collected from polar bears sampled in the Alaska portion of the southern Beaufort Sea to investigate the potential for capture to adversely affect behaviour and vital rates. We evaluated the extent to which capture, collaring and handling may influence activity and movement days to weeks post-capture, and body mass, body condition, reproduction and survival over 6 months or more. Methods We compared post-capture activity and movement rates, and relationships between prior capture history and body mass, body condition and reproductive success. We also summarised data on capture-related mortality. Key results Individual-based estimates of activity and movement rates reached near-normal levels within 2–3 days and fully normal levels within 5 days post-capture. Models of activity and movement rates among all bears had poor fit, but suggested potential for prolonged, lower-level rate reductions. Repeated captures was not related to negative effects on body condition, reproduction or cub growth or survival. Capture-related mortality was substantially reduced after 1986, when immobilisation drugs were changed, with only 3 mortalities in 2517 captures from 1987–2013. Conclusions Polar bears in the southern Beaufort Sea exhibited the greatest reductions in activity and movement rates 3.5 days post-capture. These shorter-term, post-capture effects do not appear to have translated into any long-term effects on body condition, reproduction, or cub survival. Additionally, collaring had no effect on polar bear recovery rates, body condition, reproduction or cub survival. Implications This study provides empirical evidence that current capture-based research methods do not have long-term implications, and are not contributing to observed changes in body condition, reproduction or survival in the southern Beaufort Sea. Continued refinement of capture protocols, such as the use of low-impact dart rifles and reversible drug combinations, might improve polar bear response to capture and abate short-term reductions in activity and movement post-capture.

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Reference intervals for blood-based biochemical analytes of southern Beaufort Sea polar bears

Conservation Physiology ◽

10.1093/conphys/coz040 ◽

2019 ◽

Vol 7 (1) ◽

Author(s):

Tricia L Fry ◽

Kristen R Friedrichs ◽

Todd C Atwood ◽

Colleen Duncan ◽

Kristin Simac ◽

...

Keyword(s):

Polar Bear ◽

Prey Availability ◽

Beaufort Sea ◽

Reference Population ◽

Reference Intervals ◽

Electrolyte Balance ◽

Polar Bears ◽

Serum Samples ◽

Age Class ◽

Baseline Values

Abstract Accurate reference intervals (RIs) for commonly measured blood-based analytes are essential for health monitoring programmes. Baseline values for a panel of analytes can be used to monitor physiologic and pathophysiologic processes such as organ function, electrolyte balance and protein catabolism. Our reference population includes 651 serum samples from polar bears (Ursus maritimus) from the southern Beaufort Sea (SB) subpopulation sampled in Alaska, USA, between 1983 and 2016. To establish RI for 13 biochemical analytes, we defined specific criteria for characterizing the reference population and relevant subgroups. To account for differences in seasonal life history characteristics, we determined separate RI for the spring and fall seasons, when prey availability and energetic requirements of bears differ. We established RI for five subgroups in spring based on sex, age class and denning status, and three subgroups in fall based on sex and age class in females only. Alkaline phosphatase activities were twice as high in subadult as in adult polar bears in spring (zmales = 4.08, Pmales < 0.001, zfemales = 3.90, Pfemales < 0.001) and did not differ between seasons. Denning females had significantly higher glucose concentrations than non-denning females (z = 4.94, P < 0.001), possibly reflecting differences in energy expenditure during lactation. A total of 10 of the 13 analytes differed significantly between seasons in either males or females; however, the physiologic importance of these differences may be minimal. Establishing these RIs allows for temporal monitoring of polar bear health in the SB and may prove useful for assessing and monitoring additional polar bear subpopulations in a changing Arctic environment.

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Concentrations of mercury and polychlorinated biphenyls in blood of Southern Beaufort Sea polar bears (Ursus maritimus) during spring: variations with lipids and stable isotope (δ15N, δ13C) values

Canadian Journal of Zoology ◽

10.1139/z11-071 ◽

2011 ◽

Vol 89 (11) ◽

pp. 999-1012 ◽

Cited By ~ 13

Author(s):

Katrina K. Knott ◽

Daryle Boyd ◽

Gina M. Ylitalo ◽

Todd M. O’Hara

Keyword(s):

Polychlorinated Biphenyls ◽

Body Condition ◽

Neutral Lipids ◽

Trophic Position ◽

Beaufort Sea ◽

Ursus Maritimus ◽

Polar Bears ◽

Adult Males ◽

Blood Concentrations ◽

Condition Indices

Polar bears ( Ursus maritimus Phipps, 1774) are exposed to heavy metal and lipophilic contaminants that are known to bioaccumulate and biomagnify. Few studies concurrently report both chemical classes in the same individuals and are thus unable to assess drivers of observed tissue concentrations, and the potential adverse biological responses to combined exposures. We examined blood concentrations of mercury (Hg) and the sum of seven polychlorinated biphenyls (Σ7PCB) from free-ranging Southern Beaufort Sea polar bears to assess which factors contributed to variations among cohorts (adult males, adult females, young) during spring. Concentrations of Hg ranged from 10.3 to 228.0 ng/g wet mass, but mean concentrations were similar between males and females independent of age. Concentrations of Σ7PCB (range 2.0–132.8 ng/g wet mass) were greater among females and young than among males. Toxicant concentrations were related to packed cell δ15N, an estimate of trophic position, after the inclusion of packed cell δ13C. Concentrations of Σ7PCB were also positively correlated with concentrations of neutral lipids (triglycerides and free fatty acids) and inversely correlated to body condition indices. Elevated concentrations of toxicants and lower body condition indices in females and young compared with males may be a sentinel to a changing arctic environment. Further assessment of the potential adverse health impacts of contaminants and nutritional stress in these cohorts is warranted.

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The Life and Status of the Polar Bear

Oryx ◽

10.1017/s0030605300004518 ◽

1965 ◽

Vol 8 (3) ◽

pp. 169-176 ◽

Cited By ~ 6

Author(s):

C. R. Harrington

Keyword(s):

Life History ◽

Endangered Species ◽

Polar Bear ◽

Polar Bears ◽

Valuable Resource ◽

Kind Permission ◽

Complete Protection ◽

Aesthetic Value ◽

Arctic Species ◽

Canadian Wildlife

Polar bears are on the IUCN list of endangered species. In 1961, when there were signs of serious depletions, the Canadian Wildlife Service started a five-year research project on the polar bear's biology and ecology, and the author is engaged on this work. He points out that polar bears are a most valuable resource, especially to the Canadian Eskimos, and if their numbers are allowed to dwindle to the point at which they have to be given complete protection they will have little more than aesthetic value, which in the case of an Arctic species is limited. These extracts from a comprehensive paper on the polar bear's life history and status are reproduced from “Canadian Audubon” by kind permission of the author and editor.

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‘Verscheurende Beyren’

Netherlands Yearbook for History of Art / Nederlands Kunsthistorisch Jaarboek ◽

10.1163/22145966-07101005 ◽

2022 ◽

Vol 71 (1) ◽

pp. 92-115

Author(s):

Robert Bauernfeind

Keyword(s):

Polar Bear ◽

The Arctic ◽

Polar Bears

This article examines the depiction of polar bears in Dutch painting and graphics from the late 16th to the early 18th centuries. Reports of the first encounters between Dutch humans and polar bears established the idea of these animals as aggressive predators. This idea dominated the image of the bear in illustrated travelogues as well as in allegorical depictions of the Arctic and whaling pictures. The polar bear thus became a symbol for the dangers of the region and appears as an obstacle to the human exploitation of the Arctic. However, depictions of the bloody hunt for polar bears indicate the economically motivated triumph of Europeans in this inhospitable area.

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An analysis of heat conduction in polar bear hairs using one-dimensional fractional model

Thermal Science ◽

10.2298/tsci1603785z ◽

2016 ◽

Vol 20 (3) ◽

pp. 785-788 ◽

Cited By ~ 5

Author(s):

Wei-Hong Zhu ◽

Shao-Tang Zhang ◽

Zheng-Biao Li

Keyword(s):

Heat Conduction ◽

Heat Conduction Equation ◽

Polar Bear ◽

Thermal Protection ◽

Polar Bears ◽

Cold Environment ◽

Membrane Pore ◽

One Dimensional ◽

Fractional Heat Conduction ◽

Maintain Body Temperature

Hairs of a polar bear are of superior properties such as the excellent thermal protection. The polar bears can perennially live in an extremely cold environment and can maintain body temperature at around 37 ?C. Why do polar bears can resist such cold environment? Its membrane-pore structure plays an important role. In the previous work, we established a 1-D fractional heat conduction equation to reveal the hidden mechanism for the hairs. In this paper, we further discuss solutions and parameters of the equation established and analyze heat conduction in polar bear hairs.

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Conservation status of polar bears ( Ursus maritimus ) in relation to projected sea-ice declines

Biology Letters ◽

10.1098/rsbl.2016.0556 ◽

2016 ◽

Vol 12 (12) ◽

pp. 20160556 ◽

Cited By ~ 31

Author(s):

Eric V. Regehr ◽

Kristin L. Laidre ◽

H. Resit Akçakaya ◽

Steven C. Amstrup ◽

Todd C. Atwood ◽

...

Keyword(s):

Sea Ice ◽

Polar Bear ◽

Extinction Risk ◽

Conservation Status ◽

Iucn Red List ◽

Arctic Sea Ice ◽

Polar Bears ◽

Near Term ◽

Conservation Assessments ◽

Global Population

Loss of Arctic sea ice owing to climate change is the primary threat to polar bears throughout their range. We evaluated the potential response of polar bears to sea-ice declines by (i) calculating generation length (GL) for the species, which determines the timeframe for conservation assessments; (ii) developing a standardized sea-ice metric representing important habitat; and (iii) using statistical models and computer simulation to project changes in the global population under three approaches relating polar bear abundance to sea ice. Mean GL was 11.5 years. Ice-covered days declined in all subpopulation areas during 1979–2014 (median −1.26 days year −1 ). The estimated probabilities that reductions in the mean global population size of polar bears will be greater than 30%, 50% and 80% over three generations (35–41 years) were 0.71 (range 0.20–0.95), 0.07 (range 0–0.35) and less than 0.01 (range 0–0.02), respectively. According to IUCN Red List reduction thresholds, which provide a common measure of extinction risk across taxa, these results are consistent with listing the species as vulnerable. Our findings support the potential for large declines in polar bear numbers owing to sea-ice loss, and highlight near-term uncertainty in statistical projections as well as the sensitivity of projections to different plausible assumptions.

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Research and management of polar bears Ursus maritimus

Polar Record ◽

10.1017/s0032247400028357 ◽

1986 ◽

Vol 23 (143) ◽

pp. 167-176 ◽

Cited By ~ 2

Author(s):

Ian Stirling

Keyword(s):

Natural Resources ◽

Polar Bear ◽

World Wide ◽

Ursus Maritimus ◽

Polar Bears ◽

International Agreement ◽

International Union ◽

International Coordination ◽

The 1950S ◽

Circumpolar Arctic

AbstractThrough the 1950s and 1960s there was a marked increase in recorded numbers of polar bears being killed for their hides, giving rise to world-wide concern that the species might be endangered. At a meeting in Fairbanks, Alaska 1965, representatives of circumpolar arctic nations discussed conservation of polar bears and concluded that international coordination of research and management efforts was essential. Subsequent meetings of scientists engaged in polar bear research were organized every two years by the International Union for the Conservation of Nature and Natural Resources, facilitating exchanges of views and cooperation; as a result, in 1973 the International Agreement on the Conservation of Polar Bears and their Habitats was signed in Oslo, Norway. This paper describes some of the research and management undertaken in the years leading up to the agreement, and initiatives that are continuing because of it.

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Allee effect in polar bears: a potential consequence of polychlorinated biphenyl contamination

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2016.1883 ◽

2016 ◽

Vol 283 (1843) ◽

pp. 20161883 ◽

Cited By ~ 8

Author(s):

Viola Pavlova ◽

Jacob Nabe-Nielsen ◽

Rune Dietz ◽

Christian Sonne ◽

Volker Grimm

Keyword(s):

Reproductive Success ◽

Population Growth ◽

Polar Bear ◽

Allee Effect ◽

Polychlorinated Biphenyl ◽

Sperm Quality ◽

Male Competition ◽

Male Reproductive Success ◽

Male Mating ◽

Polar Bears

Polar bears ( Ursus maritimus ) from East Greenland and Svalbard exhibited very high concentrations of polychlorinated biphenyls (PCBs) in the 1980s and 1990s. In Svalbard, slow population growth during that period was suspected to be linked to PCB contamination. In this case study, we explored how PCBs could have impacted polar bear population growth and/or male reproductive success in Svalbard during the mid-1990s by reducing the fertility of contaminated males. A dose–response relationship linking the effects of PCBs to male polar bear fertility was extrapolated from studies of the effects of PCBs on sperm quality in rodents. Based on this relationship, an individual-based model of bear interactions during the breeding season predicted fertilization success under alternative assumptions regarding male–male competition for females. Contamination reduced pregnancy rates by decreasing the availability of fertile males, thus triggering a mate-finding Allee effect, particularly when male–male competition for females was limited or when infertile males were able to compete with fertile males for females. Comparisons of our model predictions on age-dependent reproductive success of males with published empirical observations revealed that the low representation of 10–14-year-old males among breeding males documented in Svalbard in mid-1990s could have resulted from PCB contamination. We conclude that contamination-related male infertility may lead to a reduction in population growth via an Allee effect. The magnitude of the effect is largely dependent on the population-specific mating system. In eco-toxicological risk assessments, appropriate consideration should therefore be given to negative effects of contaminants on male fertility and male mating behaviour.

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Unusual Predation Attempts of Polar Bears on Ringed Seals in the Southern Beaufort Sea: Possible Significance of Changing Spring Ice Conditions

ARCTIC ◽

10.14430/arctic3 ◽

2009 ◽

Vol 61 (1) ◽

pp. 14 ◽

Cited By ~ 33

Author(s):

Ian Stirling ◽

Evan Richardson ◽

Gregory W. Thiemann ◽

Andrew E. Derocher

Keyword(s):

Sea Ice ◽

Polar Bear ◽

Foraging Behaviour ◽

Open Water ◽

Beaufort Sea ◽

Polar Bears ◽

Ringed Seals ◽

Decadal Scale ◽

Underlying Causes ◽

Ice Conditions

In April and May 2003 through 2006, unusually rough and rafted sea ice extended for several tens of kilometres offshore in the southeastern Beaufort Sea from about Atkinson Point to the Alaska border. Hunting success of polar bears (Ursus maritimus) seeking seals was low despite extensive searching for prey. It is unknown whether seals were less abundant in comparison to other years or less accessible because they maintained breathing holes below rafted ice rather than snowdrifts, or whether some other factor was involved. However, we found 13 sites where polar bears had clawed holes through rafted ice in attempts to capture ringed seals (Phoca hispida) in 2005 through 2006 and another site during an additional research project in 2007. Ice thickness at the 12 sites that we measured averaged 41 cm. These observations, along with cannibalized and starved polar bears found on the sea ice in the same general area in the springs of 2004 through 2006, suggest that during those years, polar bears in the southern Beaufort Sea were nutritionally stressed. Searches made farther north during the same period and using the same methods produced no similar observations near Banks Island or in Amundsen Gulf. A possible underlying ecological explanation is a decadal-scale downturn in seal populations. But a more likely explanation is major changes in the sea-ice and marine environment resulting from record amounts and duration of open water in the Beaufort and Chukchi seas, possibly influenced by climate warming. Because the underlying causes of observed changes in polar bear body condition and foraging behaviour are unknown, further study is warranted.

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