Killer whales (Orcinus orca) are major predators that may reshape marine ecosystems via top-down forcing. Climate change models predict major reductions in sea ice with the subsequent expectation for ...readjustments of species' distribution and abundance. Here, we measure changes in killer whale distribution in the Hudson Bay region with decreasing sea ice as an example of global readjustments occurring with climate change. We summarize records of killer whales in Hudson Bay, Hudson Strait, and Foxe Basin in the eastern Canadian Arctic and relate them to an historical sea ice data set while accounting for spatial and temporal autocorrelation in the data. We find evidence for "choke points," where sea ice inhibits killer whale movement, thereby creating restrictions to their Arctic distribution. We hypothesize that a threshold exists in seasonal sea ice concentration within these choke points that results in pulses in advancements in distribution of an ice-avoiding predator. Hudson Strait appears to have been a significant sea ice choke point that opened up approximately 50 years ago allowing for an initial punctuated appearance of killer whales followed by a gradual advancing distribution within the entire Hudson Bay region. Killer whale sightings have increased exponentially and are now reported in the Hudson Bay region every summer. We predict that other choke points will soon open up with continued sea ice melt producing punctuated predator-prey trophic cascades across the Arctic.
We investigated the role of sea ice-derived carbon in the food web of Eclipse Sound, Canadian Arctic during the spring ice-covered season to understand the potential ecological impact of changes to ...the sea-ice habitat. Chlorophyll a (chl a) concentrations in the bottom of sea ice (438.2 ± 154.2 μg l−1, 19.8 ± 6.6 mg m−2) were more than 2 orders of magnitude higher than in surface waters (0.9 ± 0.7 μg l−1). Fatty acid (FA) composition showed that algal communities in the bottom sea ice comprised higher abundances of diatoms compared to surface waters. Benthic invertebrates (ophiuroids, polychaetes) and sediments had high proportions of diatom-associated FAs in their lipid composition. H-Print estimates of the proportional contributions of sea icederived carbon to the carbon pool of the benthic community were substantial, ranging on average between 77 and 85%. High carbon stable isotope values (δ13C) in benthic invertebrates and sediments (δ13C: −19.6 to −11.6‰) further suggests that a large portion of the benthic carbon pool was of sea-ice origin, while surface waters were significantly lower (δ13C: −22.32 ± 2.17‰). In this ecosystem where landfast ice is present for most of the year, strong sea ice−benthic coupling emphasizes the dependency of the food web on ice productivity. As timing and magnitude of sea icederived carbon will change under alterations of climatic conditions and possibly with increased shipping activities in the study region, the adaptive capacity of sea ice-dependent species is anticipated to play a key role in determining future food webs.
Determination of trace element concentrations in continuously growing biological structures such as otoliths, whiskers, and teeth can provide important insight into physiological and ontogenetic ...processes. We examined concentrations of 11 trace elements (Li, Mg, Mn, Cu, Zn, Se, Rb, Sr, Cs, Ba, Pb) in the annual dentine growth layer groups (GLGs) of teeth of 66 Eastern Canadian Arctic belugas (Delphinapterus leucas). Several of these trace elements displayed clear and consistent patterns in early life, though few longer term trends or signals were present in trace element data for either females or males. Large changes in Sr and Ba concentrations in fetal dentine reflected in utero shifts in element deposition in the teeth of developing belugas. Marked changes in these elements during the first years after birth were likely associated with the onset of nursing and subsequent weaning. Mg, Mn, and Zn also displayed clear and consistent patterns in early life that correlated strongly with dentine stable nitrogen isotope (δ15N) data, suggesting these elements merit further study as potential tools for studying nursing and weaning. Depositional patterns of Zn and Pb, which have been linked to sexual maturation in female Pacific walruses (Odobenus rosmarus divergens), were inconsistent in beluga teeth. Some individuals (including males) displayed patterns strongly resembling those observed in female walruses, whereas many animals did not, perhaps because they had not yet reached sexual maturity. The lack of clear patterns in trace element deposition after the first few years of life may have resulted from pooling samples from multiple populations/regions collected across more than two decades, but may also indicate that elemental concentrations are primarily driven by other, extrinsic processes later in life, and might be useful as biomonitors of environmental element concentrations or tools for delineating population structure.
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•Tooth growth layers contain a time series of trace element deposition•Provide information about physiology, life history, and contaminant exposure•Clearest trace element deposition patterns in beluga teeth occurred in early life•Sr and Ba driven by maternal transfer differences in utero and during nursing•Mg, Mn, and Zn correlate with tooth stable isotopes, likely reflect nursing/weaning•Understanding physiological patterns critical to interpret environmental influence
Classification of animal vocalizations is often done by a human observer using aural and visual analysis but more efficient, automated methods have also been utilized to reduce bias and increase ...reproducibility. Beluga whale, Delphinapterus leucas, calls were described from recordings collected in the summers of 2006-2008, in the Churchill River, Manitoba. Calls (n=706) were classified based on aural and visual analysis, and call characteristics were measured; calls were separated into 453 whistles (64.2%; 22 types), 183 pulsed∕noisy calls (25.9%; 15 types), and 70 combined calls (9.9%; seven types). Measured parameters varied within each call type but less variation existed in pulsed and noisy call types and some combined call types than in whistles. A more efficient and repeatable hierarchical clustering method was applied to 200 randomly chosen whistles using six call characteristics as variables; twelve groups were identified. Call characteristics varied less in cluster analysis groups than in whistle types described by visual and aural analysis and results were similar to the whistle contours described. This study provided the first description of beluga calls in Hudson Bay and using two methods provides more robust interpretations and an assessment of appropriate methods for future studies.
To provide insight into how climate-driven diet shifts may impact contaminant exposures of Arctic species, we compared feeding ecology and contaminant concentrations in ringed seals (Pusa hispida) ...from two Canadian sub-Arctic (Nain at 56.5°N, Arviat at 61.1°N) and two Arctic sites (Sachs Harbour at 72.0 °N, Resolute Bay at 74.7 °N). In the sub-Arctic, empirical evidence of changing prey fish communities has been documented, while less community change has been reported in the Arctic to date, suggesting current sub-Arctic conditions may be a harbinger of future Arctic conditions. Here, Indigenous partners collected tissues from subsistence-harvested ringed seals in 2018. Blubber fatty acids (FAs) and muscle stable isotopes (δ15N, δ13C) indicated dietary patterns, while measured contaminants included heavy metals (e.g., total mercury (THg)), legacy persistent organic pollutants (e.g., dichlorodiphenyltrichloroethanes (DDTs)), polybrominated diphenyl ethers (PBDEs), and per-/polyfluoroalkyl substances (PFASs). FA signatures are distinct between sub-Arctic and Resolute Bay seals, likely related to higher consumption of southern prey species including capelin (Mallotus villosus) in the sub-Arctic but on-going feeding on Arctic species in Resolute Bay. Sachs Harbour ringed seals show FA overlap with all locations, possibly consuming both southern and endemic Arctic species. Negative δ13C estimates for PFAS models suggest that more pelagic, sub-Arctic type prey (e.g., capelin) increases PFAS concentrations, whereas the reverse occurs for, e.g., THg, ΣPBDE, and ΣDDT. Inconsistent directionality of δ15N estimates in the models likely reflects baseline isotopic variation not trophic position differences. Adjusting for the influence of diet suggests that if Arctic ringed seal diets become more like sub-Arctic seals due to climate change, diet-driven increases may occur for newer contaminants like PFASs, but not for more legacy contaminants. Nonetheless, temporal trends studies are still needed, as are investigations into the potential confounding influence of baseline isotope variation in spatial studies of contaminants in Arctic biota.
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•Fatty acids and stable isotopes used as diet tracers for ringed seals at four sites.•Diet tracers differ between ringed seals of the sub-Arctic and Arctic.•Stable isotopes best explain contaminant variation among ringed seals.•Diet differences linked to higher levels of PFASs in sub-Arctic seals.•Future climate-driven diet shifts in Arctic seals may increase levels of new POPs.
Climate change is altering the biogeochemical and physical characteristics of the Arctic marine environment, which impacts sea ice algal and phytoplankton bloom dynamics and the vertical transport of ...these carbon sources to benthic communities. Little is known about whether the contribution of sea ice-derived carbon to benthic fauna and nitrogen cycling has changed over multiple decades in concert with receding sea ice. We combined compound-specific stable isotope analysis of amino acids with highly branched isoprenoid diatom lipid biomarkers using archived (1982-2016) tissue of benthivorous Atlantic walrus to examine temporal trends of sea ice-derived carbon, nitrogen isotope baseline and trophic position of Atlantic walrus at high- and mid-latitudes in the Canadian Arctic. Associated with an 18% sea ice decline in the mid-Arctic, sea ice-derived carbon contribution to Atlantic walrus decreased by 75% suggesting a strong decoupling of sea ice-benthic habitats. By contrast, a nearly exclusive amount of sea ice-derived carbon was maintained in high-Arctic Atlantic walrus (98% in 1996 and 89% in 2006) despite a similar percentage in sea ice reduction. Nitrogen isotope baseline or the trophic position of Atlantic walrus did not change over time at either location. These findings indicate latitudinal differences in the restructuring of carbon energy sources used by Atlantic walrus and their benthic prey, and in turn a change in Arctic marine ecosystem functioning between sea ice-pelagic-benthic habitats.
Interspecific interactions may be altered as a result of poleward species range shifts caused by climate change. In recent decades, Cumberland Sound, Nunavut, in the Canadian Arctic, has undergone ...concurrent increases in the availability of the forage fish capelin (
Mallotus villosus
) and the number of migratory harp seals (
Pagophilus groenlandicus
) during the open-water period; however, the impacts of these changes on endemic Arctic species, such as ringed seals (
Pusa hispida
), have received little attention. We coupled stomach contents with stable isotope analysis (
δ
13
C and
δ
15
N) of muscle and liver to determine the extent of potential competition between ringed seals (
n
= 91) and harp seals (
n
= 39) in Cumberland Sound. Isotopic niche breadth was greater for ringed seals (95% ellipse: 10.08‰
2
) than for harp seals (95% ellipse: 8.00‰
2
), and harp seal isotopic niche overlapped more with ringed seal isotopic niche than vice versa, suggesting asymmetrical competition potential. Although there was high overlap in isotopic niche breadth (range 50.3–91.0%) and prey species consumed (Schoener’s Index 0.60), stomach content analysis revealed differences in prey species proportions and size composition, thereby reducing the degree of realized niche overlap. Harp seals consumed a higher biomass of fish (66.7%) than did ringed seals (31.9%), and harp seals also consumed larger capelin (64–200 mm), polar cod (
Boreogadus saida
; 28–194 mm), and Liparidae (55–115 mm) than ringed seals (63–154 mm, 20–189 mm, and 16–128 mm, respectively). With climate change and range shifts predicted to continue into the future, our results provide an important baseline for future studies examining interspecific interactions.
Arctic sea ice loss has direct consequences for predators. Climate‐driven distribution shifts of native and invasive prey species may exacerbate these consequences. We assessed potential changes by ...modelling the prey base of a widely distributed Arctic predator (ringed seal; Pusa hispida) in a sentinel area for change (Hudson Bay) under high‐ and low‐greenhouse gas emission scenarios from 1950 to 2100. All changes were relatively negligible under the low‐emission scenario, but under the high‐emission scenario, we projected a 50% decline in the abundance of the well‐distributed, ice‐adapted and energy‐rich Arctic cod (Boreogadus saida) and an increase in the abundance of smaller temperate‐associated fish in southern and coastal areas. Furthermore, our model predicted that all fish species declined in mean body size, but a 29% increase in total prey biomass. Declines in energy‐rich prey and restrictions in their spatial range are likely to have cascading effects on Arctic predators.
Although research on the effects of climate change on Arctic marine ecosystems has focused on the direct impacts of sea ice decline and increased anthropogenic activity on apex species, little attention has been given to the other compounding effects of environmental change (e.g. warming waters, ocean acidification) on the prey base of predators. We modelled the indirect effects of climate change on Arctic predators and highlight how the business‐as‐usual climate change scenario drives a borealisation of the Arctic marine prey base biomass, distribution and species composition through year 2100. Declines in energy‐rich prey and restrictions in their spatial range are likely to have cascading effects on predators.
We review seven Arctic and four subarctic marine mammal species, their habitat requirements, and evidence for biological and demographic responses to climate change. We then describe a pan-Arctic ...quantitative index of species sensitivity to climate change based on population size, geographic range, habitat specificity, diet diversity, migration, site fidelity, sensitivity to changes in sea ice, sensitivity to changes in the trophic web, and maximum population growth potential ($R_{\max }$). The index suggests three types of sensitivity based on: (1) narrowness of distribution and specialization in feeding, (2) seasonal dependence on ice, and (3) reliance on sea ice as a structure for access to prey and predator avoidance. Based on the index, the hooded seal, the polar bear, and the narwhal appear to be the three most sensitive Arctic marine mammal species, primarily due to reliance on sea ice and specialized feeding. The least sensitive species were the ringed seal and bearded seal, primarily due to large circumpolar distributions, large population sizes, and flexible habitat requirements. The index provides an objective framework for ranking species and focusing future research on the effects of climate change on Arctic marine mammals. Finally, we distinguish between highly sensitive species and good indicator species and discuss regional variation and species-specific ecology that confounds Arctic-wide generalization regarding the effects of climate change.
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.
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•Marine mammal blubber was nontarget/suspect screened for environmental contaminants.•Suspect screening revealed 138 compounds, mostly plastic-related compounds (PRCs).•Phthalates were only detected in a few individuals, but concentrations ranged up to ∼7 mg/kg.•Irganox 1010, an antioxidant, and alkylphenols were detected in >50% of all samples.•Biomagnification of these PRCs is likely limited relative to legacy persistent organic pollutants.
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