Dietary biomagnification of organochlorine contaminants in Alaskan polar bears

Concentrations of organochlorine contaminants in the adipose tissue of polar bears ( Ursus maritimus Phipps, 1774) vary throughout the Arctic. The range in concentrations has not been explained fully by bear age, sex, condition, location, or reproductive status. Dietary pathways expose polar bears to a variety of contaminant profiles and concentrations. Prey range from lower trophic level bowhead whales ( Balaena mysticetus L., 1758), one of the least contaminated marine mammals, to highly contaminated upper trophic level ringed seals ( Phoca hispida (Schreber, 1775)). We used δ15N and δ13C signatures to estimate the trophic status of 42 polar bears sampled along Alaska’s Beaufort Sea coast to determine the relationship between organochlorine concentration and trophic level. The δ15N values in the cellular portions of blood ranged from 18.2‰ to 20.7‰. We found strong positive relationships between concentrations of the most recalcitrant polychlorinated biphenyls (PCBs) and δ15N values in models incorporating age, lipid content, and δ13C value. Specifically these models accounted for 67% and 76% of the variation in PCB153 and oxychlordane concentration in male polar bears and 85% and 93% in females, respectively. These results are strong indicators of variation in diet and biomagnification of organochlorines among polar bears related to their sex, age, and trophic position.

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Using art to explore children’s perceptions of their Arctic community in a changing climate

10.5194/egusphere-egu21-16449 ◽

2021 ◽

Author(s):

David Lipson ◽

Kim Reasor ◽

Kååre Sikuaq Erickson

Keyword(s):

Climate Change ◽

Sea Ice ◽

Marine Mammals ◽

School Curriculum ◽

Arctic Sea Ice ◽

The Arctic ◽

Polar Bears ◽

Way Of Life ◽

Subsistence Hunting ◽

Sea Ice Decline

In this project we analyze artwork and recorded statements of 5th grade students from the community of Utqia&#289;vik, Alaska, who participated in a science-art outreach activity. The team consisted of a scientist (Lipson), an artist (Reasor) and an outreach specialist (Erickson) of Inupiat heritage from a village in Alaska. We worked with four 5th grade classes of about 25 students each at Fred Ipalook Elementary. The predominantly Inupiat people of Utqia&#289;vik are among those who will be most impacted by climate change and the loss of Arctic sea ice in the near future. Subsistence hunting of marine mammals associated with sea ice is central to the Inupiat way of life. Furthermore, their coastal homes and infrastructure are increasingly subject to damage from increased wave action on ice-free Beaufort and Chukchi Seas. While the people of this region are among the most directly vulnerable to climate change, the teachers reported that the subject is not generally covered in the elementary school curriculum.The scientist and the local outreach specialist gave a short presentation about sea ice and climate change in the Arctic, with emphasis on local impacts to hunting and infrastructure. We then showed the students a large poster of historical and projected sea ice decline, and asked the students to help us fill in the white space beneath the lines. The artist led the children in making small paintings that represent things that are important to their lives in Utqia&#289;vik (they were encouraged to paint animals, but they were free to do whatever they wanted). We returned to the class later that week and had each student briefly introduce themselves and their painting, and place it on the large graph of sea ice decline, which included the dire predictions of the RCP8.5 scenario. Then we added the more hopeful RCP2.6 scenario to end on a positive note.Common themes expressed in the students&#8217; artwork included subsistence hunting, other aspects of traditional Inupiat culture, nature and family. Modern themes such as sports and Pok&#233;mon were also common. The students reacted to the topic of climate change with pictures of whales, polar bears and other animals, and captions such as &#8220;Save the world/ice/animals.&#8221; There were several paintings showing unsuccessful hunts for whales or seals. Some students displayed an understanding of ecosystem science in their recorded statements. For example, a student who painted the sun and another who painted a krill both succinctly described energy flow in food webs that support the production of whales (for example, &#8220;I drew krill because without krill there wouldn&#8217;t be whales&#8221;). Some of the students described the consequences of sea ice loss to local wildlife with devastating succinctness (sea ice is disappearing and polar bears will go extinct). The overall sense was that the children had a strong grasp of the potential consequences of climate change to their region and way of life.

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Examining predator–prey body size, trophic level and body mass across marine and terrestrial mammals

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2014.2103 ◽

2014 ◽

Vol 281 (1797) ◽

pp. 20142103 ◽

Cited By ~ 29

Author(s):

Marlee A. Tucker ◽

Tracey L. Rogers

Keyword(s):

Community Structure ◽

Body Size ◽

Body Mass ◽

Marine Environment ◽

Trophic Level ◽

Marine Mammals ◽

Trophic Position ◽

Trophic Levels ◽

Predator Prey ◽

Terrestrial Mammals

Predator–prey relationships and trophic levels are indicators of community structure, and are important for monitoring ecosystem changes. Mammals colonized the marine environment on seven separate occasions, which resulted in differences in species' physiology, morphology and behaviour. It is likely that these changes have had a major effect upon predator–prey relationships and trophic position; however, the effect of environment is yet to be clarified. We compiled a dataset, based on the literature, to explore the relationship between body mass, trophic level and predator–prey ratio across terrestrial ( n = 51) and marine ( n = 56) mammals. We did not find the expected positive relationship between trophic level and body mass, but we did find that marine carnivores sit 1.3 trophic levels higher than terrestrial carnivores. Also, marine mammals are largely carnivorous and have significantly larger predator–prey ratios compared with their terrestrial counterparts. We propose that primary productivity, and its availability, is important for mammalian trophic structure and body size. Also, energy flow and community structure in the marine environment are influenced by differences in energy efficiency and increased food web stability. Enhancing our knowledge of feeding ecology in mammals has the potential to provide insights into the structure and functioning of marine and terrestrial communities.

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Variation in winter diet of southern Beaufort Sea polar bears inferred from stable isotope analysis

Canadian Journal of Zoology ◽

10.1139/z07-036 ◽

2007 ◽

Vol 85 (5) ◽

pp. 596-608 ◽

Cited By ~ 54

Author(s):

T.W. Bentzen ◽

E.H. Follmann ◽

S.C. Amstrup ◽

G.S. York ◽

M.J. Wooller ◽

...

Keyword(s):

Stable Isotope ◽

Sea Ice ◽

Trophic Level ◽

Polar Bear ◽

Isotope Analysis ◽

Beaufort Sea ◽

Polar Bears ◽

Bowhead Whales ◽

Lower Trophic Level ◽

Winter Diet

Ringed seals ( Phoca hispida Schreber, 1775 = Pusa hispida (Schreber, 1775)) and bearded seals ( Erignathus barbatus (Erxleben, 1777)) represent the majority of the polar bear ( Ursus maritimus Phipps, 1774) annual diet. However, remains of lower trophic level bowhead whales ( Balaena mysticetus L., 1758) are available in the southern Beaufort Sea and their dietary contribution to polar bears has been unknown. We used stable isotope (13C/12C, δ13C, 15N/14N, and δ15N) analysis to determine the diet composition of polar bears sampled along Alaska’s Beaufort Sea coast in March and April 2003 and 2004. The mean δ15N values of polar bear blood cells were 19.5‰ (SD = 0.7‰) in 2003 and 19.9‰ (SD = 0.7‰) in 2004. Mixing models indicated bowhead whales composed 11%–26% (95% CI) of the diets of sampled polar bears in 2003, and 0%–14% (95% CI) in 2004. This suggests significant variability in the proportion of lower trophic level prey in polar bear diets among individuals and between years. Polar bears depend on sea ice for hunting seals, and the temporal and spatial availabilities of sea ice are projected to decline. Consumption of low trophic level foods documented here suggests bears may increasingly scavenge such foods in the future.

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Spatial segregation and similar trophic-level diet among eastern Canadian Arctic/north-west Atlantic killer whales inferred from bulk and compound specific isotopic analysis

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315413001379 ◽

2013 ◽

Vol 94 (6) ◽

pp. 1343-1355 ◽

Cited By ~ 22

Author(s):

Cory J.D. Matthews ◽

Steven H. Ferguson

Keyword(s):

Trophic Level ◽

Marine Mammals ◽

Trophic Position ◽

Canadian Arctic ◽

Isotopic Analysis ◽

Killer Whales ◽

Dietary Specialization ◽

North West ◽

Isotopic Variation ◽

Eastern Canadian Arctic

Killer whales in the Eastern Canadian Arctic (ECA) prey on narwhal, beluga, bowhead whales and seals, while further south in the north-west Atlantic (NWA), killer whales off the coast of Newfoundland and Labrador prey on both marine mammals and fish. Bulk and amino acid (AA) specific isotopic composition of dentinal collagen in teeth of 13 ECA/NWA killer whales were analysed to assess the degree, if any, of dietary specialization of killer whales across the region. Dentine was sampled from within annual growth layer groups (GLGs) to construct chronological profiles of stable nitrogen (δ15N) and carbon (δ13C) isotopic compositions for individual whales spanning 3–25 years. Interannual isotopic variation across GLGs was less than that among individuals, and median bulk δ15N values differed by up to 5‰ among individuals. Significant correlation between bulk δ15N values and baseline (source AA) δ15N values indicates much of the observed isotopic variation among individuals reflects foraging within isotopically distinct food webs, rather than diet differences. This interpretation is supported by consistent differences in bulk δ13C values between the two individuals with lowest source AA δ15N values and the remaining whales. After accounting for baseline isotopic variation, comparable δ15N values among individuals indicates similar trophic-level diet, although uncertainties in relative trophic 15N enrichment of individual AAs currently limits trophic position estimates for top consumers. Further research is required to clarify seasonal movement patterns and possible diet shifts of ECA/NWA killer whales to better define their role in marine ecosystems across the region.

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Bowhead Whales and Alaskan Eskimos: a problem of survival

Polar Record ◽

10.1017/s0032247400021665 ◽

1983 ◽

Vol 21 (134) ◽

pp. 467-473 ◽

Cited By ~ 5

Author(s):

Ray Gambell

Keyword(s):

Endangered Species ◽

Marine Mammals ◽

The Arctic ◽

Bering Strait ◽

Bowhead Whales ◽

Domestic Legislation ◽

The Arctic Ocean ◽

Native Alaskans ◽

The Right ◽

Commercial Hunting

The hunt for Bowhead Whales Balaena mysticetus has for centuries been a tradition in the culture of coastal Alaskan Eskimos. Commercial hunting began in 1848, when the first American whaling vessel, under Captain Thomas Roys, worked northward through the Bering Strait and started pelagic whaling in the Arctic Ocean. This fishery ended about 1914, because of severe depletion of the stock. However, Eskimos continued to hunt the remaining whales, using traditional boats and skills augmented by methods and equipment acquired from Yankee whalers. They still carry on the hunt today, using essentially the same methods; the right of native Alaskans to hunt in this way is permitted by US domestic legislation relating to marine mammals and endangered species (Mitchell and Reeves 1980).

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Evironmental threats to marine mammals in the Canadian Arctic

Polar Record ◽

10.1017/s003224740002163x ◽

1983 ◽

Vol 21 (134) ◽

pp. 433-449 ◽

Cited By ~ 12

Author(s):

Ian Stirling ◽

Wendy Calvert

Keyword(s):

Sea Ice ◽

Arctic Ocean ◽

Marine Mammals ◽

Canadian Arctic ◽

Ursus Maritimus ◽

The Arctic ◽

Polar Bears ◽

Alopex Lagopus ◽

Arctic Foxes ◽

The Arctic Ocean

The Arctic Ocean is the home of three major groups of mammals that depend on the sea for survival and show varying degrees of adaptation for maritime life. Most fully adapted are the whales (Cetacea), which never leave the water, and the seals and walruses (Pinnipedia) that feed entirely at sea but emerge onto land or ice for pupping and basking. Less exclusively marine are two species of the order Carnivora—Polar Bears (Ursus maritimus), that seldom live far from the sea because they feed almost entirely upon seals, and Arctic Foxes (Alopex lagopus), some of which move out onto the sea ice during the winter, mainly to scavenge on the remains of seals killed by Polar Bears.

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Biomagnification and bioaccumulation of mercury in an arctic marine food web: insights from stable nitrogen isotope analysis

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f98-001 ◽

1998 ◽

Vol 55 (5) ◽

pp. 1114-1121 ◽

Cited By ~ 263

Author(s):

Lisa Atwell ◽

Keith A Hobson ◽

Harold E Welch

Keyword(s):

Food Web ◽

Muscle Tissue ◽

Mercury Concentration ◽

Total Mercury ◽

Trophic Position ◽

The Arctic ◽

Polar Bears ◽

Marine Food Web ◽

Ringed Seals ◽

Marine Food

Several recent studies have shown that the use of delta 15N analysis to characterize trophic relationships can be useful for tracing biocontaminants in food webs. In this study, concentration of total mercury was measured in tissues from 112 individuals representing 27 species from the arctic marine food web of Lancaster Sound, Northwest Territories. Samples ranged from particulate organic matter through polar bears (Ursus maritimus). Using delta 15N values to identify trophic position, we found that total mercury in muscle tissue biomagnified in this food web. Polar bears were a notable exception, having a lower mean mercury concentration than their main prey, ringed seals (Phoca hispida). Most vertebrates showed greater variance in mercury concentration than invertebrates, and there was a trend in seabirds toward increased variability in mercury concentration with trophic position. Within species, we found no evidence of bioaccumulation of mercury with age in the muscle tissue of clams (Mya truncata) or ringed seals. Because stable nitrogen isotopes illustrated the relationship in this biome between trophic position and mercury level on a continuous, quantitative scale, we were able to determine that log10[Hg] ( µg/g dry weight) = 0.2( delta 15N) - 3.3. The measurement of delta 15N values and mercury concentration allowed us to quantitatively assess mercury biomagnification within this extensive arctic marine food web.

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Unusual fatty acid biomarkers reveal age- and sex-specific foraging in polar bears (Ursus maritimus)

Canadian Journal of Zoology ◽

10.1139/z07-028 ◽

2007 ◽

Vol 85 (4) ◽

pp. 505-517 ◽

Cited By ~ 23

Author(s):

G.W. Thiemann ◽

S.M. Budge ◽

S.J. Iverson ◽

I. Stirling

Keyword(s):

Fatty Acid ◽

Marine Mammals ◽

Ursus Maritimus ◽

The Arctic ◽

Specific Information ◽

Polar Bears ◽

Arctic Ecosystems ◽

Novel Approach ◽

Fatty Acid Biomarkers ◽

Bearded Seals

We used fatty acid (FA) biomarkers in a novel approach to study the foraging habits of a top predator. We tested the hypothesis that non-methylene-interrupted FA (NMI FA), synthesized by benthic molluscs, are transferred via pinnipeds to polar bears ( Ursus maritimus Phipps, 1774) at the top of the arctic marine food web. Among eight species of marine mammals preyed upon by polar bears, NMI FA were prevalent only in benthic-feeding bearded seals ( Erignathus barbatus (Erxleben, 1777)) and Atlantic walruses ( Odobenus rosmarus rosmarus (L., 1758)). These two prey species differed in their relative proportions of NMI FA — 22:2Δ7,15 was almost exclusive to bearded seals, whereas 20:2Δ5,11 was most abundant in Atlantic walruses. Six different NMI FA were identified in polar bears. Trends in individual NMI FA showed that large, adult male polar bears were the primary predators of bearded seals and Atlantic walruses. These findings were confirmed through quantitative FA signature analysis (QFASA) using an entirely different set of FA. In addition to corroborating the accuracy of QFASA diet estimates, these results indicate that individual NMI FA can provide specific information on polar bear foraging and therefore provide insights into the bottom–up effects of environmental change in arctic ecosystems.

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The isotopic niche of Atlantic, biting marine mammals and its relationship to skull morphology and body size

Scientific Reports ◽

10.1038/s41598-021-94610-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Massimiliano Drago ◽

Marco Signaroli ◽

Meica Valdivia ◽

Enrique M. González ◽

Asunción Borrell ◽

...

Keyword(s):

Body Size ◽

Atlantic Ocean ◽

Fisheries Management ◽

Marine Mammals ◽

Trophic Position ◽

Sympatric Species ◽

Isotopic Niche ◽

Apex Predators ◽

Skull Morphology ◽

Ecosystem Based Fisheries Management

AbstractUnderstanding the trophic niches of marine apex predators is necessary to understand interactions between species and to achieve sustainable, ecosystem-based fisheries management. Here, we review the stable carbon and nitrogen isotope ratios for biting marine mammals inhabiting the Atlantic Ocean to test the hypothesis that the relative position of each species within the isospace is rather invariant and that common and predictable patterns of resource partitioning exists because of constrains imposed by body size and skull morphology. Furthermore, we analyze in detail two species-rich communities to test the hypotheses that marine mammals are gape limited and that trophic position increases with gape size. The isotopic niches of species were highly consistent across regions and the topology of the community within the isospace was well conserved across the Atlantic Ocean. Furthermore, pinnipeds exhibited a much lower diversity of isotopic niches than odontocetes. Results also revealed body size as a poor predictor of the isotopic niche, a modest role of skull morphology in determining it, no evidence of gape limitation and little overlap in the isotopic niche of sympatric species. The overall evidence suggests limited trophic flexibility for most species and low ecological redundancy, which should be considered for ecosystem-based fisheries management.

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