Anthropogenic and Climatic Drivers of Long-Term Changes of Mercury and Feeding Ecology in Arctic Beluga (Delphinapterus leucas) Populations.

We assessed long-term changes in the feeding ecology and mercury (Hg) accumulation in Eastern High Arctic-Baffin Bay beluga (Delphinapterus leucas) using total Hg and stable isotope (δ13C, δ15N) assays in teeth samples from historical (1854-1905) and modern (1985-2000) populations. Mean δ13C values in teeth declined significantly over time, from -13.01 ± 0.55‰ historically to -14.41 ± 0.28‰ in 2000, while no consistent pattern was evident for δ15N due to high individual variability within each period. The temporal shift in isotopic niche is consistent with beluga feeding ecology changing in recent decades to a more pelagic and less isotopically diverse diet or an ecosystem wide change in isotope profiles. Mercury concentrations in modern beluga teeth were 3-5 times higher on average than those in historical beluga. These results are similar to the long-term trends of Hg and feeding ecology reported in other beluga populations and in other Arctic marine predators. Similar feeding ecology shifts across regions and species indicate a consistent increased pelagic diet response to climate change as the Arctic Ocean progressively warmed and lost sea ice. Previously, significant temporal Hg increase in beluga and other Arctic animals was attributed solely to direct inputs of anthropogenic Hg from long-range sources. Recent advances in understanding the Arctic marine Hg cycle suggest an additional, complementary possibility─increased inputs of terrestrial Hg of mixed anthropogenic-natural origin, mobilized from permafrost and other Arctic soils by climate warming. At present, it is not possible to assign relative importance to the two processes in explaining the rise of Hg concentrations in modern Arctic marine predators.

Specialized sledge dogs accompanied Inuit dispersal across the North American Arctic.

Domestic dogs have been central to life in the North American Arctic for millennia. The ancestors of the Inuit were the first to introduce the widespread usage of dog sledge transportation technology to the Americas, but whether the Inuit adopted local Palaeo-Inuit dogs or introduced a new dog population to the region remains unknown. To test these hypotheses, we generated mitochondrial DNA and geometric morphometric data of skull and dental elements from a total of 922 North American Arctic dogs and wolves spanning over 4500 years. Our analyses revealed that dogs from Inuit sites dating from 2000 BP possess morphological and genetic signatures that distinguish them from earlier Palaeo-Inuit dogs, and identified a novel mitochondrial clade in eastern Siberia and Alaska. The genetic legacy of these Inuit dogs survives today in modern Arctic sledge dogs despite phenotypic differences between archaeological and modern Arctic dogs. Together, our data reveal that Inuit dogs derive from a secondary pre-contact migration of dogs distinct from Palaeo-Inuit dogs, and probably aided the Inuit expansion across the North American Arctic beginning around 1000 BP.

High rates of vessel noise disrupt foraging in wild harbour porpoises (Phocoena phocoena).

Shipping is the dominant marine anthropogenic noise source in the world's oceans, yet we know little about vessel encounter rates, exposure levels and behavioural reactions for cetaceans in the wild, many of which rely on sound for foraging, communication and social interactions. Here, we used animal-borne acoustic tags to measure vessel noise exposure and foraging efforts in seven harbour porpoises in highly trafficked coastal waters. Tagged porpoises encountered vessel noise 17-89% of the time and occasional high-noise levels coincided with vigorous fluking, bottom diving, interrupted foraging and even cessation of echolocation, leading to significantly fewer prey capture attempts at received levels greater than 96 dB re 1 µPa (16 kHz third-octave). If such exposures occur frequently, porpoises, which have high metabolic requirements, may be unable to compensate energetically with negative long-term fitness consequences. That shipping noise disrupts foraging in the high-frequency-hearing porpoise raises concerns that other toothed whale species may also be affected.

Nontarget and suspect screening reveals the presence of multiple plastic-related compounds in polar bear, killer whale, narwhal and long-finned pilot whale blubber from East Greenland.

The monitoring of legacy contaminants in sentinel northern marine mammals has revealed some of the highest concentrations globally. However, investigations into the presence of chemicals of emerging Arctic concern (CEACs) and other lesser-known chemicals are rarely conducted, if at all. Here, we used a nontarget/suspect approach to screen for thousands of different chemicals, including many CEACs and plastic-related compounds (PRCs) in blubber/adipose from killer whales (Orcinus orca), narwhals (Monodon monoceros), long-finned pilot whales (Globicephala melas), and polar bears (Ursus maritimus) in East Greenland. 138 compounds were tentatively identified mostly as PRCs, and four were confirmed using authentic standards: di(2-ethylhexyl) phthalate (DEHP), diethyl phthalate (DEP), di(2-propylheptyl) phthalate (DPHP), and one antioxidant (Irganox 1010). Three other PRCs, a nonylphenol isomer, 2,6-di-tert-butylphenol, and dioctyl sebacate, exhibited fragmentation patterns matching those in library databases. While phthalates were only above detection limits in some polar bear and narwhal, Irganox 1010, nonylphenol, and 2,6-di-tert-butylphenol were detected in >50% of all samples. This study represents the first application of a nontarget/suspect screening approach in Arctic cetaceans, leading to the identification of multiple PRCs in their blubber. Further nontarget analyses are warranted to comprehensively characterize the extent of CEAC and PRC contamination within Arctic marine food webs.

Temporal trend of mercury in polar bears (Ursus maritimus) from Svalbard using teeth as a biomonitoring tissue.

We examined the use of mercury (Hg) and nitrogen and carbon stable isotopes in teeth of polar bear (Ursus maritimus) from Svalbard as biotracers of temporal changes in Hg pollution exposure between 1964 and 2003. Teeth were regarded as a good matrix of the Hg exposure, and in total 87 teeth of polar bears were analysed. Dental Hg levels ranged from 0.6 to 72.3 ng g(-1) dry weight and increased with age during the first 10 years of life. A decreasing time trend in Hg concentrations was observed over the recent four decades while no temporal changes were found in the stable isotope ratios of nitrogen (δ(15)N) and carbon (δ(13)C). This suggests that the decrease of Hg concentrations over time was more likely due to a lower environmental Hg exposure in this region rather than a shift in the feeding habits of Svalbard polar bears.

Validation of quantitative fatty acid signature analysis for estimating the diet composition of free-ranging killer whales.

Accurate diet estimates are necessary to assess trophic interactions and food web dynamics in ecosystems, particularly for apex predators like cetaceans, which can regulate entire food webs. Quantitative fatty acid analysis (QFASA) has been used to estimate the diets of marine predators in the last decade but has yet to be implemented on free-ranging cetaceans, from which typically only biopsy samples containing outer blubber are available, due to a lack of empirically determined calibration coefficients (CCs) that account for fatty acid (FA) metabolism. Here, we develop and validate QFASA for killer whales using full blubber from managed-care and free-ranging individuals. First, we compute full, inner, and outer blubber CCs from the FA signatures across the blubber layers of managed-care killer whales and their long-term diet items. We then run cross-validating simulations on the managed-care individuals to evaluate the accuracy of diet estimates by comparing full-depth and depth-specific estimates to true diets. Finally, we apply these approaches to subsistence-harvested killer whales from Greenland to test the utility of the method for free-ranging killer whales, particularly for the outer blubber. Accurate diet estimates for the managed-care killer whales were only achieved using killer whale-specific and blubber-layer-specific CCs. Modeled diets for the Greenlandic killer whales largely consisted of seals (75.9 ± 4.7%) and/or fish (20.4 ± 2.4%), mainly mackerel, which was consistent with stomach content data and limited literature on this population. Given the remote habitats and below surface feeding of most cetaceans, this newly developed cetacean-specific QFASA method, which can be applied to outer-layer biopsies, offers promise to provide a significant new understanding of diet dynamics of free-ranging odontocetes and perhaps other cetacean species throughout the world's oceans.

Analysis of narwhal tusks reveals lifelong feeding ecology and mercury exposure.

The ability of animals to respond to changes in their environment is critical to their persistence. In the Arctic, climate change and mercury exposure are two of the most important environmental threats for top predators.1-3 Rapid warming is causing precipitous sea-ice loss, with consequences on the distribution, composition, and dietary ecology of species4-7 and, thus, exposure to food-borne mercury.8 Current understanding of global change and pollution impacts on Arctic wildlife relies on single-time-point individual data representing a snapshot in time. These data often lack comprehensive temporal resolution and overlook the cumulative lifelong nature of stressors as well as individual variation. To overcome these challenges, we explore the unique capacity of narwhal tusks to characterize chronological lifetime biogeochemical profiles, allowing for investigations of climate-induced dietary changes and contaminant trends. Using temporal patterns of stable isotopes (δ13C and δ15N) and mercury concentrations in annually deposited dentine growth layer groups in 10 tusks from Northwest Greenland (1962-2010), we show surprising plasticity in narwhal feeding ecology likely resulting from climate-induced changes in sea-ice cover, biological communities, and narwhal migration. Dietary changes consequently impacted mercury exposure primarily through trophic magnification effects. Mercury increased log-linearly over the study period, albeit with an unexpected rise in recent years, likely caused by increased emissions and/or greater bioavailability in a warmer, ice-free Arctic. Our findings are consistent with an emerging pattern in the Arctic of reduced sea-ice leading to changes in the migration, habitat use, food web, and contaminant exposure in Arctic top predators.

Japans commercial whaling is a threat to public health.

Japans' decision to withdraw from the International Whaling Commission and reinstate commercial hunting on minke, sei and Bryde's whales has recently been discussed in several journals. Here we discuss mercury exposure to the public eating baleen whales, toothed whales and tuna in relation to the European Food Safety Authority (EFSA) tolerable weekly intake (TWI).

Skull pathology in East Greenland and Svalbard polar bears (Ursus maritimus) during 1892 to 2002 in relation to organochlorine pollution.

East Greenland and Svalbard polar bears (Ursus maritimus) are heavily polluted with long-range transported organochlorines such as PCBs (polychlorinated biphenyls). To investigate the negative health impacts, a time-trend study of skull pathology was conducted on 269 East Greenland and 241 Svalbard polar bears. The skulls were sampled during 1892-2002 and 1964-1992, respectively. Seven different pathological changes were found: adonti, displacement of teeth, caries, osseous proliferations, exostosis, tooth wear and periodontitis. Only tooth wear and periodontitis was in a prevalence that allowed statistical treatment. The most severe cases of tooth wear and periodontitis were accompanied by a substantial loss of alveolar bone structure. The prevalence of tooth wear and periodontitis increased significantly with age (p<0.001) with incisor wear being more severe than in canines, premolars and molars (p<0.001). No sex difference was found for tooth wear (p=0.22) while a significant difference between sexes was found for periodontitis (p=0.01) with males having higher prevalence than females (odds ratio of 2.5 for males:females). In East Greenland, the prevalence of tooth wear was significantly higher in polar bears collected in the pre pollution period (<1960) than in bears sampled during polluted periods (1960-1980 and 1981-2002) (p<0.001). Regarding periodontitis, the prevalence was not significantly different between pre-pollution and pollution periods (p=0.309). Polar bears from Svalbard had significantly higher prevalence of tooth wear (p<0.001) and periodontitis (p=0.02) than polar bears from East Greenland. The tooth wear and periodontitis odds ratios for Svalbard:East Greenland were 135 and 2.6, respectively. Hence, we found a clear age/sex link and geographical difference but no evidence for an association between skull pathology and exposure to organochlorines in East Greenland and Svalbard polar bears.

Sensory ability in the narwhal tooth organ system.

The erupted tusk of the narwhal exhibits sensory ability. The hypothesized sensory pathway begins with ocean water entering through cementum channels to a network of patent dentinal tubules extending from the dentinocementum junction to the inner pulpal wall. Circumpulpal sensory structures then signal pulpal nerves terminating near the base of the tusk. The maxillary division of the fifth cranial nerve then transmits this sensory information to the brain. This sensory pathway was first described in published results of patent dentinal tubules, and evidence from dissection of tusk nerve connection via the maxillary division of the fifth cranial nerve to the brain. New evidence presented here indicates that the patent dentinal tubules communicate with open channels through a porous cementum from the ocean environment. The ability of pulpal tissue to react to external stimuli is supported by immunohistochemical detection of neuronal markers in the pulp and gene expression of pulpal sensory nerve tissue. Final confirmation of sensory ability is demonstrated by significant changes in heart rate when alternating solutions of high-salt and fresh water are exposed to the external tusk surface. Additional supporting information for function includes new observations of dentinal tubule networks evident in unerupted tusks, female erupted tusks, and vestigial teeth. New findings of sexual foraging divergence documented by stable isotope and fatty acid results add to the discussion of the functional significance of the narwhal tusk. The combined evidence suggests multiple tusk functions may have driven the tooth organ system's evolutionary development and persistence.

What are the toxicological effects of mercury in Arctic biota?

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.

An evaluation of teeth of ringed seals (Phoca hispida) from Greenland as a matrix to monitor spatial and temporal trends of mercury and stable isotopes.

Total mercury (Hg) concentrations were measured in teeth of ringed seals from Qeqertarsuaq, central West Greenland (1982 to 2006) and Ittoqqortoormiit, central East Greenland (1986 to 2006). Stable isotopic ratios of carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) were determined as well to provide insights into diet variations between regions or through time. Mercury concentrations decreased the first years of life of the animals suggesting that Hg had been transferred from the mother to the foetus and newborn. The Hg concentrations in teeth were significantly lesser in ringed seals from central West Greenland compared to those from central East Greenland. Carbon and nitrogen stable isotopic values measured in the animals differed also significantly between the two regions. Increasing temporal trends of dental Hg concentrations between 1994 and 2006 were observed in ringed seals from both central West Greenland and central East Greenland. These increases were attributed to global changes in environmental Hg levels since no temporal trends in delta(15)N values were found to support the hypothesis of a diet shift over time. Furthermore, a decreasing temporal trend in delta(13)C values was observed in the teeth of seals from central East Greenland, and explained by a likely change over time towards more pelagic feeding habits; alternatively, the so-known Seuss effect was thought to be responsible for this decrease. Finally, it was concluded that the tooth of ringed seal was a good monitoring tissue to assess Hg trends.

Anthropogenic contributions to mercury levels in present-day Arctic animals--a review.

BACKGROUND: Because of concern about the recently increasing levels of biological Hg in some areas of the Arctic, we examined the literature concerning the long-term changes of Hg in humans and selected Arctic marine mammals and birds of prey since pre-industrial times (i.e. before 1800A.D.), to determine the anthropogenic contribution to present-day Hg concentrations and the historical timing of any changes. METHODS: Mercury data from published articles were extracted on historical and pre-industrial concentrations as percentages of the recent maximum, as well as the man-made contribution was calculated and depicted in a uniform manner to provide an overview of the development over time. RESULTS AND DISCUSSION: Trends of [Hg] in hard tissues such as teeth, hair and feathers consistently showed that there had been an order-of-magnitude increase of [Hg] in Arctic marine foodweb-based animals that began in the mid- to late-19th Century and accelerated in the 20th Century. The median man-made contribution to present-day Hg concentrations was 92.4% ranging from 74.2 to 94.4%. Confidence in our data was increased by accompanying data in some studies on stable isotopes (delta(13)C, delta(15)N), which allowed us to normalize where necessary for changes in animal trophic position and feeding location over time, and by careful attention to the possibility of sample chemical diagenesis (Hg contamination or loss) which can alter the Hg content of ancient hard tissues. CONCLUSIONS: Wildlife hard tissue matrices provide consistent information with respect to the steep onset of Hg exposure of Arctic wildlife beginning in the latter half of the 19th Century. Today the man-made contribution was found to be above 92%. Stable isotope analyses provide important information to normalize for possible changes in diet over time, and are highly relevant to include when interpreting temporal trends, baseline concentrations as well as man-made anthropogenic contribution of Hg.