Article pubs.acs.org/est
Western Canadian Arctic Ringed Seal Organic Contaminant Trends in Relation to Sea Ice Break-Up A. Gaden,† Steve H. Ferguson,†,‡ L. Harwood,§ H. Melling,∥ J. Alikamik,⊥ and G. A. Stern*,†,‡ †
Department of Environment and Geography, University of Manitoba, 500 University Crescent, Winnipeg MB, R3T 2N2, Canada Fisheries and Oceans Canada, 501 University Crescent, Winnipeg MB, R3T 2N6, Canada § Fisheries and Oceans Canada, Yellowknife, Northwest Territories, X1A 1E2, Canada ∥ Fisheries and Oceans Canada, Sidney, British Columbia, V8K 4B2, Canada ⊥ Olokhatomiut Hunters and Trappers Committee, Ulukhaktok, Northwest Territories, X0E 0S0, Canada ‡
S Supporting Information *
ABSTRACT: The association between changing sea ice conditions and contaminant exposure to Arctic animals interests Inuvialuit harvesters, communities, and researchers. We examined organochlorine contaminant (OC) concentrations in the blubber of 90 male adult ringed seals (Phoca hispida) sampled from the subsistence harvest in Ulukhaktok (formerly Holman), NT, Canada, just prior to break-up of the sea ice (1993−2008). OC blubber concentrations were assessed with respect to year and sea ice break-up date. HCB and age- and blubber-adjusted concentrations of p,p′-DDT and ΣCHB (chlorobornane) significantly decreased over the study period. With respect to the timing of the spring break-up, highly lipophlic OCs, such as p,p′DDE and PCB 153, were higher during years of early ice clearing (at least 12 days earlier than the mean annual break-up date), whereas no trends were observed for α, β, and γ isomers of HCH, trans- and cis-chlordane, oxychlordane, or ΣCHB. The higher contaminant concentrations found in earlier break-up years is likely due to earlier and/or increased foraging opportunities. This situation also has potential for enhancing bioaccumulation and biomagnification of contaminants over the long-term if projected changes continue to result in lighter and earlier ice conditions.
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INTRODUCTION The harvest and subsistence use of country foods are an integral part of Inuvialuit livelihood in northern Canada. Not only do the practices of harvesting, preparing, and consuming game animals from the land and sea provide a means of socialization, exercise, and a feeling of fulfillment,1 but also the traditional diet offers a suite of nutritional benefits.2,3 Climate change impacts to food quality and quantity could, however, have serious implications to Inuit well-being, including aspects of dietary contaminant exposure. Due to the stability and bioavailability of organochlorine contaminants (OCs), polar-bound chemicals originating in pesticides and industrial byproducts in southern latitudes,4 long-lived marine predators such as ringed seals (Phoca hispida) accumulate relatively large quantities of OCs through the food web.5−7 Although the industrial production and use of OCs has declined in the last few decades8 and these reductions have been largely paralleled in Arctic wildlife OC concentrations,9,10 including ringed seals from Ulukhaktok (formerly Holman) of the Northwest Territories, Canada, since the 1970s,11,12 climate-change related shifts in prey type or abundance could affect seal contaminant exposure. One mechanism lies with foraging times and success, and is dependent upon environ© 2012 American Chemical Society
mental conditions. For example, earlier break-up of the sea ice in spring may enable some marine animals to forage (1) earlier, (2) for longer periods, and/or (3) allow access to foraging areas not accessible under previous break-up regimes (e.g., ref 13). Other ways in which the timing of break-up could affect seals are linked to food web changes. Although ringed seals in the western Canadian Arctic prefer energy-rich prey, particularly Arctic cod (Boreogadus saida), they are also opportunistic foragers, consuming crustaceous zooplankton and a variety of marine invertebrates.14 Environmental and oceanographic conditions have a strong influence on the flow of carbon through the food web (i.e., toward pelagic vs benthic ecosystems), which can then, through bottom-up processes, impact higher trophic levels via prey species.7 Furthermore, the availability of prey species may shift in light of climate change (e.g., ref 15). The Eastern Amundsen Gulf (Figure 1), somewhat protected from offshore storm influences, and with many large, sheltered Received: Revised: Accepted: Published: 4427
November 18, 2011 March 9, 2012 March 19, 2012 March 19, 2012 dx.doi.org/10.1021/es204127j | Environ. Sci. Technol. 2012, 46, 4427−4433
Environmental Science & Technology
Article
Figure 1. Ringed seals were sampled at Masoyak near Ulukhaktok (Holman) in the western Canadian Arctic.
to earlier break up.18 This is in stark contrast to the pan-Arctic perspective, where observations reveal statistical trends to thinner ice, earlier break-up, and longer ice-free seasons.19 These trends are in large part linked to the decreasing presence of thick multiyear sea ice in the Arctic as a whole. They do not appear in our ice data and region of study because multiyear ice has never been common here. We analyzed OC concentrations in Ulukhaktok ringed seal blubber samples from 1993 to 2008. Contaminants were assessed with respect to biological variables, such as age and blubber thickness of the seals, and in association to year and date of the spring sea ice break-up to determine and evaluate possible trends.
bays and sounds with persistent fast ice during winter and spring, provides prime ringed seal breeding habitat in Canada’s western Arctic. The large bays have stable fast ice for many months, critical to mating and nursing by adult ringed seals that remain all winter. The large amount of landfast ice offers a stable platform that allows for mating territories and sufficient snow catchment for snow dens used during lactation.16 Equally important as the availability of sea ice is the availability of sufficient prey to sustain the seals throughout the winter when they are restricted in movement. East Amundsen Gulf provides habitat for pupping, lactation, moulting/basking, and protection from ambient weather and from predators.14 Thus the ice conditions in East Amundsen Gulf are particularly relevant to adult ringed seals during winter and spring, and the timing of break-up represents a suite of variables (wind, currents, water, and air temperatures) which collectively influence the productivity of the ecosystem in spring. The local ice conditions are also particularly important for ringed seal foraging during the open water period,17 which is our rationale for assessing variation in ringed seal OC concentrations in relation to the local ice-climate indicator of break-up date. When exploring the association between OC concentrations and climate change, we must bear in mind that variations and trends in the climatic indicator we are using (e.g., timing of the sea ice break-up) depend upon the geographic scale and region. In the southeast Beaufort region, for example, sustained observations over the past 40 years have revealed appreciable variation on annual and decadal scales in ice presence and thickness, but no net trend to thinner ice and only weak trends
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METHODS Field Analysis. Members of the Hunters and Trappers Committee in Ulukhaktok, NT harvested ringed seals from the Masoyak hunting camp near Ulukhaktok, located along the NW shore of Prince Albert Sound on Victoria Island (Figure 1). The annual sample size for contaminant analyses in this study was 9−15 adult (≥7 yrs) male seal samples in 1993, 2002−2005, 2007, and 2008, and seven samples in 1995 (total n = 90). On account of the small female seal representation in the sample size (average five per year) and potential for insufficient statistical power, we chose to focus research on males for the analysis. These samples, harvested in June, approximated 20% of the ringed seals sampled annually in the harvest-based sampling program which has been underway at this location since the 1970s.14,20 4428
dx.doi.org/10.1021/es204127j | Environ. Sci. Technol. 2012, 46, 4427−4433
Environmental Science & Technology
Article
Table 1. Summary of the GLM Results for Each OCa break-up
age
blubber thickness
model
OC
r
p
r
p
r
p
F
p
HCB γ-HCH t-chlor c-chlor CB 28 α-HCH CB 105 CB 156 β-HCH Dieldrin Mirex CB 31 p,p′-DDT ΣCHB CB 118 oxychlor p,p′-DDE CB 52 CB 101 CB 138 CB 153 CB 180
−0.16 −0.01 0.08 0.10 −0.23 −0.09 −0.11 −0.21 −0.04 0.02 0.04 -0.32 0.31 0.39 -0.43 -0.21 -0.21 -0.32 -0.32 -0.31 -0.30 -0.29
0.14 0.93 0.51 0.35 0.08 0.42 0.31 0.10 0.69 0.81 0.70 0.03 0.002
