Gary A Stern

University of Manitoba, Winnipeg, Manitoba, Canada

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Publications (166)480.52 Total impact

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    ABSTRACT: Sea ice facilitates delivery of organic contaminants to the Arctic marine food web. • Organic contaminants are concentrated in brine, under-ice seawater, and melt ponds. • We model contaminant concentrations in melt ponds based on air concentrations. • CUPs pose a risk of increased exposures via dry deposition to melt ponds. • Dry deposition to melt ponds is important loading route of CUPs to the Arctic Ocean. For decades sea ice has been perceived as a physical barrier for the loading of contaminants to the Arctic Ocean. We show that sea ice, in fact, facilitates the delivery of organic contaminants to the Arctic marine food web through processes that: 1) are independent of contaminant physical–chemical properties (e.g. 2–3-fold increase in exposure to brine-associated biota), and 2) depend on physical–chemical properties and, therefore, differen-tiate between contaminants (e.g. atmospheric loading of contaminants to melt ponds over the summer, and their subsequent leakage to the ocean). We estimate the concentrations of legacy organochlorine pesticides (OCPs) and current-use pesticides (CUPs) in melt pond water in the Beaufort Sea, Canadian High Arctic, in 2008, at near-gas exchange equilibrium based on Henry's law constants (HLCs), air concentrations and exchange dynamics. CUPs currently present the highest risk of increased exposures through melt pond loading and drain-age due to the high ratio of melt pond water to seawater concentration (Melt pond Enrichment Factor, MEF), which ranges from 2 for dacthal to 10 for endosulfan I. Melt pond contaminant enrichment can be perceived as a hypothetical 'pump' delivering contaminants from the atmosphere to the ocean under ice-covered condi-tions, with 2–10% of CUPs annually entering the Beaufort Sea via this input route compared to the standing stock in the Polar Mixed Layer of the ocean. The abovementioned processes are strongly favored in first-year ice compared to multi-year ice and, therefore, the dynamic balance between contaminant inventories and con-taminant deposition to the surface ocean is being widely affected by the large-scale icescape transition taking place in the Arctic.
    Science of The Total Environment 01/2015; 506-507:444. · 3.16 Impact Factor
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    ABSTRACT: Temporal trends of contaminants are monitored in Arctic higher trophic level species to inform us on the fate, transport and risk of contaminants as well as advise on global emissions. However, monitoring mercury (Hg) trends in species such as belugas challenge us, as their tissue concentrations reflect complex interactions among Hg deposition and methylation, whale physiology, dietary exposure and foraging patterns. The Beaufort Sea beluga population showed significant increases in Hg during the 1990s; since that time an additional 10years of data have been collected. During this time of data collection, changes in the Arctic have affected many processes that underlie the Hg cycle. Here, we examine Hg in beluga tissues and investigate factors that could contribute to the observed trends after removing the effect of age and size on Hg concentrations and dietary factors. Finally, we examine available indicators of climate variability (Arctic Oscillation (AO), the Pacific Decadal Oscillation (PDO) and sea-ice minimum (SIM) concentration) to evaluate their potential to explain beluga Hg trends. Results reveal a decline in Hg concentrations from 2002 to 2012 in the liver of older whales and the muscle of large whales. The temporal increases in Hg in the 1990s followed by recent declines do not follow trends in Hg emission, and are not easily explained by diet markers highlighting the complexity of feeding, food web dynamics and Hg uptake. Among the regional-scale climate variables the PDO exhibited the most significant relationship with beluga Hg at an eight year lag time. This distant signal points us to consider beluga winter feeding areas. Given that changes in climate will impact ecosystems; it is plausible that these climate variables are important in explaining beluga Hg trends. Such relationships require further investigation of the multiple connections between climate variables and beluga Hg. Copyright © 2014 Elsevier B.V. All rights reserved.
    Science of The Total Environment 11/2014; · 3.16 Impact Factor
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    ABSTRACT: With declining sea ice conditions in Arctic regions owing to changing climate, the large prospective reservoirs of oil and gas in Baffin Bay and Davis Strait are increasingly accessible, and the interest in offshore exploration and shipping through these regions has increased. Both of these activities are associated with the risk of hydrocarbon releases into the marine ecosystem. However, hydrocarbons are also present naturally in marine environments, in some cases deriving from oil seeps. We have analyzed hydrocarbon concentrations in eleven sediment cores collected from northern Baffin Bay during 2008 and 2009 Amundsen expeditions and have examined the hydrocarbon compositions in both pre- and post-industrial periods (i.e., before and after 1900) to assess the sources of hydrocarbons, and their temporal and spatial variabilities. Concentrations of ΣPAHs ranged from 341 to 2693ngg(-1) dw, with concentrations in cores from sites within the North Water (NOW) Polynya generally higher. Individual PAH concentrations did not exceed concentrations of concern for marine aquatic life, with one exception found in a core collected within the NOW (one of the seven sediment core samples). Hydrocarbon biomarkers, including alkane profiles, OEP (odd-to-even preference), and TAR (terrigenous/aquatic ratios) values indicated that organic carbon at all sites is derived from both terrigenous higher plants and marine algae, the former being of greater significance at coastal sites, and the latter at the deepest sites at the southern boundary of the NOW. Biomarker ratios and chemical profiles indicate that petrogenic sources dominate over combustion sources, and thus long-range atmospheric transport is less significant than inputs from weathering. Present-day and historic pre-1900 hydrocarbon concentrations exhibited less than an order of magnitude difference for most compounds at all sites. The dataset presented here provides a baseline record of hydrocarbon concentrations in Baffin Bay sediments in advance of offshore exploration and increased shipping activities. Copyright © 2014 Elsevier B.V. All rights reserved.
    Science of The Total Environment 11/2014; 506-507C:430-443. · 3.16 Impact Factor
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    ABSTRACT: In 2012, Arctic cod (Boreogadus saida) were collected from offshore regions of the Beaufort Sea to determine the concentrations of CYP1A1 phase I metabolites of polycyclic aromatic hydrocarbons (OH-PAHs) in liver and to correlate measured concentrations with (i) morphometric measurements that are known to be indicative of fish health and, (ii) biochemical endpoints of health including vitamin A/E and metabolites and hepatic deiodinase activity (DI). Four ring OH-PAHs were detected in 90% of our samples with a mean liver concentration of 1829.2 ± 159.2 ng/g (ww). Total (∑) concentrations of 5/6-membered ring OH-PAHs in liver were smaller [mean of 931.6 ± 104.3 ng/g, (ww)] and detected less frequently (75%) than the 4-ring OH-PAHs. Fish length and liver weight were both negatively correlated to ∑concentrations of 4-ringed OH-PAHs (p<0.001). Liver somatic index was also negatively correlated to ∑4-OH-PAHs (p<0.05) but not for ∑5/6-OH-PAHs (p>0.1). There was a significant positive relationship between DI and 4-ring OH-PAHs (p<0.05) in liver suggesting an induction of this enzyme. No such correlation was observed for the 5/6-ring OH-PAHs. Retinyl palmitate (RP) was the only vitamin that could be measured in liver ranging from 0.230 to 26.3 ug/g (ww). No associations between RP and levels of the 4- or 5/6-ringed OH-PAHs were observed. Continued baseline studies are clearly warranted to further understand effects of OH-PAHs on fish health before planned exploration activities begin in this region.
    Environmental Science and Technology 09/2014; · 5.48 Impact Factor
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    ABSTRACT: The Canadian Arctic has vast freshwater resources, and fish are important in the diet of many Northerners. Mercury is a contaminant of concern because of its potential toxicity and elevated bioaccumulation in some fish populations. Over the last decade, significant advances have been made in characterizing the cycling and fate of mercury in these freshwater environments. Large amounts of new data on concentrations, speciation and fluxes of Hg are provided and summarized for water and sediment, which were virtually absent for the Canadian Arctic a decade ago. The biogeochemical processes that control the speciation of mercury remain poorly resolved, including the sites and controls of methylmercury production. Food web studies have examined the roles of Hg uptake, trophic transfer, and diet for Hg bioaccumulation in fish, and, in particular, advances have been made in identifying determinants of mercury levels in lake-dwelling and sea-run forms of Arctic char. In a comparison of common freshwater fish species that were sampled across the Canadian Arctic between 2002 and 2009, no geographic patterns or regional hotspots were evident. Over the last two to four decades, Hg concentrations have increased in some monitored populations of fish in the Mackenzie River Basin while other populations from the Yukon and Nunavut showed no change or a slight decline. The different Hg trends indicate that the drivers of temporal change may be regional or habitat-specific. The Canadian Arctic is undergoing profound environmental change, and preliminary evidence suggests that it may be impacting the cycling and bioaccumulation of mercury. Further research is needed to investigate climate change impacts on the Hg cycle as well as biogeochemical controls of methylmercury production and the processes leading to increasing Hg levels in some fish populations in the Canadian Arctic.
    Science of The Total Environment 06/2014; · 3.16 Impact Factor
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    ABSTRACT: This review summarizes data and information which have been generated on mercury (Hg) in the marine environment of the Canadian Arctic since the previous Canadian Arctic Contaminants Assessment Report (CACAR) was released in 2003. Much new information has been collected on Hg concentrations in marine water, snow and ice in the Canadian Arctic. The first measurements of methylation rates in Arctic seawater indicate that the water column is an important site for Hg methylation. Arctic marine waters were also found to be a substantial source of gaseous Hg to the atmosphere during the ice-free season. High Hg concentrations have been found in marine snow as a result of deposition following atmospheric mercury depletion events, although much of this Hg is photoreduced and re-emitted back to the atmosphere. The most extensive sampling of marine sediments in the Canadian Arctic was carried out in Hudson Bay where sediment total Hg (THg) concentrations were low compared with other marine regions in the circumpolar Arctic. Mass balance models have been developed to provide quantitative estimates of THg fluxes into and out of the Arctic Ocean and Hudson Bay. Several recent studies on Hg biomagnification have improved our understanding of trophic transfer of Hg through marine food webs. Over the past several decades, Hg concentrations have increased in some marine biota, while other populations showed no temporal change. Marine biota also exhibited considerable geographic variation in Hg concentrations with ringed seals, beluga and polar bears from the Beaufort Sea region having higher Hg concentrations compared with other parts of the Canadian Arctic. The drivers of these variable patterns of Hg bioaccumulation, both regionally and temporally, within the Canadian Arctic remain unclear. Further research is needed to identify the underlying processes including the interplay between biogeochemical and food web processes and climate change.
    Science of The Total Environment 06/2014; · 3.16 Impact Factor
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    ABSTRACT: We show 2008 seasonal trends of total and mono-methyl mercury (THg and MeHg, respectively) in herbivorous (Calanus hyperboreus) and predatory (Chaetognaths, Paraeuchaeta glacialis and Themisto abyssorum) zooplankton species from the Canadian High Arctic (Amundsen Gulf and the Canadian Beaufort Sea) in relation to ambient seawater and diet. It has recently been postulated that the Arctic marine environment may be exceptionally vulnerable to toxic MeHg contamination through post-depositional processes leading to mercury transformation and methylation. Here, we show that C. hyperboreus plays a hitherto unrecognized central role in mercury transformation while, itself, not manifesting inordinately high levels of THg compared to its prey (pelagic particulate organic matter (POM)). Calanus hyperboreus shifts Hg from mainly inorganic forms in pelagic POM (> 99.5%) or ambient seawater (> 90%) to primarily organic forms (> 50%) in their tissue. We calculate that annual dietary intake of MeHg could supply only ~30% of the MeHg body burden in C. hyperboreus and, thus, transformation within the species, perhaps mediated by gut microbial communities, or bioconcentration from ambient seawater likely play overriding roles. Seasonal THg trends in C. hyperboreus are variable and directly controlled by species-specific physiology, e.g. egg laying and grazing. Zooplankton that prey on species such as C. hyperboreus provide a further biomagnification of MeHg and reflect seasonal trends observed in their prey.
    Environmental Science and Technology 06/2014; · 5.48 Impact Factor
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    ABSTRACT: This paper synthesizes the sediment geochemistry data for 19 sediment cores from 16 lakes from various regions of Canada to describe general relationships between mercury (Hg) and the relative amount of labile organic matter (OM) as a proportion of total organic carbon. These relationships form the basis for proposing a general classification scheme of the capacity of a lake system to bind Hg to OM, which provides a first order screening of lakes to quickly assess them before further detailed analytical methods are employed. Mercury is known to have a strong affinity to OM before entering the lakes (binding with soil OM in the watershed) and also within the lakes (scavenging by autochthonous OM). Association of Hg with particulate OM, irrespective of the source, effectively captures available Hg (II) and ultimately sequesters it in bottom sediments. Relationships between total Hg concentration and the relative amount of labile OM in the sediments of a given system reveal important geochemical information; for example, the overall capacity of the system to effectively scavenge and fix available Hg, or its vulnerability to be overwhelmed by excess inputs of Hg in organic-poor or Hg contaminated systems.
    Chemical Geology 05/2014; · 3.48 Impact Factor
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    ABSTRACT: A combination of Rock-Eval pyrolysis and isotopic analyses is used to characterize the sources and distribution of organic matter in modern marine sediments from the subarctic Hudson Bay (including Hudson Strait and Foxe Basin), Canada. This approach reveals organic matter contributions from both marine and terrigenous sources, with spatial patterns and varying degrees of degradation that are consistent with inferences from traditional geochemical tracers for modern organic matter. Rock-Eval parameters characterize Hudson Bay organic matter with low hydrogen index, high oxygen index and a high degree of residual carbon that suggests heavily reworked materials. Locations of higher primary productivity in Hudson Strait, Foxe Basin, the northeast and far west of Hudson Bay, and the concentration of watershed runoff in the southern part of Hudson Bay can be delineated using the ratios between hydrogen and oxygen indices and from the distribution of labile organic carbon. Relatively high temperatures of peak hydrocarbon yield identify an advanced state of OM degradation or humic substances as important classes of organic carbon compounds in the majority of the sediment. Such highly degraded and oxygenated organic matter is unusual compared to that typically observed in other Arctic shelf seas and is consistent with a strong role for sediment and organic matter recycling in Hudson Bay. In the offshore region, the source of highly oxidized and labile organic matter identified by Rock-Eval parameters is resolved with δ13C and biomarker information that also permit examination of the sediment biogeochemical regime. This approach suggests that a distinct association with Mn enriched sediment contributes to the oxidization signal by abiotic or biological Mn related processes. These interpretations extend the limited information available on using Rock-Eval analyses to characterize organic matter in recently deposited marine sediments and describe an important consideration to using this method in Mn enriched environments.
    Organic Geochemistry 03/2014; · 2.52 Impact Factor
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    ABSTRACT: Surface sediment samples from the Hudson Bay system were analysed in order to examine the role of key regulators of arctic marine productivity—light and nutrients as affected by freshwater stratification and sea-ice cover—on the spatial distribution and production of dinoflagellate cysts. Total cyst fluxes vary from 0.2 × 106 to 30.6 × 106 cysts m- 2 a- 1, with the highest values observed in eastern Hudson Bay. A total of 24 cyst taxa, representing 11 genera of five orders, were identified and distribution maps of the most common taxa have been produced. This is the first record of Echinidinium aculeatum, Echinidinium karaense, cf. Echinidinium delicatum, Islandinium brevispinosum, Selenopemphix quanta, cysts of Protoperidinium americanum, cysts of cf. Biecheleria sp. and Polarella glacialis in the Hudson Bay system. Dinoflagellate cyst assemblages show distinct spatial patterns revealing three compositional domains: eastern Hudson Bay, western-central Hudson Bay and Hudson Strait. The eastern domain is characterised by a dominance of autotrophic cysts of Pentapharsodinium dalei whereas the western-central domain is characterized by autotrophic Operculodinium centrocarpum with some contribution by heterotrophic Polykrikos sp. var. arctic morphotype and Polykrikos spp. Sites from Hudson Strait are distinguished by an overwhelming prevalence of heterotrophic Protoperidiniaceae cysts, mainly Islandinium minutum, and have the highest values of sedimentary biogenic silica, used as a proxy for diatom productivity. Sediment geochemical tracers are used as proxies for freshwater inputs (lignin and its biomarkers) and nitrate availability (nitrogen isotopes), and sea-ice concentrations derived from passive microwave data as a proxy for light availability. Sea-ice regulated length of the dark season has a negligible influence on the proportion and production of heterotrophic (dark-adapted) versus autotrophic (light-dependent) dinoflagellate cysts, perhaps due to the location of our study area on the southern fringe of the Arctic. Instead, cyst populations in Hudson Bay are primarily regulated by vertical stratification and nitrate availability, while in Hudson Strait the pivotal mechanism constitutes food availability.
    Marine Micropaleontology 01/2014; · 1.93 Impact Factor
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    ABSTRACT: Water column concentrations of α-HCH were measured in the southern Beaufort Sea as part of the Canadian Arctic Shelf Exchange Study (CASES; 2003–04), the Circumpolar Flaw Lead System Study (CFL; 2007–08), and in the Mackenzie River during the 2008 NAHIDIK program. Atmospheric α-HCH concentrations were measured during CASES program. Inventories of α-HCH in the Polar Mixed Layer (PML) and the Pacific Mode Layer (PL) of the Beaufort Sea were calculated between 1986 and 2007 based on the available data. Between 1986 and 1993, there was a significant loading of α-HCH to the Beaufort Sea via the ocean currents. About 12% of the loading to the PML could be explained by the combined effect of the air–water gas exchange and the river runoff. After 1993, α-HCH inventories started decreasing, and could be well predicted exclusively by degradation. Ice formation was shown to be a solvent depleting process leading to a significant increase in the α-HCH concentration in the water just beneath the ice. Associated low α-HCH concentrations in the ice and relatively low ice export from the Beaufort Sea resulted in negligible influence of this output route on the inventories in the PML. The majority of α-HCH in the Beaufort Sea could be eliminated due to degradation by 2020, with concentrations in 2040 dropping to
    Journal of Marine Systems 11/2013; · 2.48 Impact Factor
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    ABSTRACT: In this study, we examine mercury bioaccumulation by a first-year sea-ice (FYI) algal community in the western Canadian Arctic during the spring of 2008. Total mercury concentration in bottom sea-ice particulate ([PHg]T) ranged 0.004–0.022 mg/g dw and was limited by the amount of mercury available for uptake when the spring bloom commenced. Mercury in ice algae originated from a combination of brine and seawater as sources, while atmospheric mercury depletion events did not appear to significantly contribute as a source in a coupled manner. We show that the bottom sea-ice brine presents a chemically and biologically unique niche from which inorganic Hg makes its way into the food web. Once incorporated into algae, mercury can be transported spatially and trophically within the ecosystem by a range of processes including grazing, resuspension, remineralization, and sedimentation. Ice algae contribute 10–60% of the annual primary production in the Arctic and are thought to become even more productive and abundant under a mild climate change scenario. Replacement of multiyear ice with FYI in the Beaufort Sea alone could result in an additional influx of 48 kg/yr of particle bound Hg. Further studies are thus warranted to elucidate mechanisms by which mercury transformation processes and transfer into the Arctic marine food web are impacted by the interaction between sea ice, brine, and seawater.
    Journal of Geophysical Research Atmospheres 10/2013; 118:1-9. · 3.44 Impact Factor
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    ABSTRACT: Archived specimens of the scavenging amphipod Eurythenes gryllus, collected from 2075-4250 m below the surface on five expeditions to the western and central Arctic Ocean between 1983-1998, were analyzed for total mercury (sum-Hg), methyl mercury (MeHg), polychlorinated biphenyls (PCBs) and other industrial or byproduct organochlorines (chlorobenzenes, pentachloroanisole, octachlorostyrene), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs). Median sum-Hg concentrations ranged from 70 to 366 ng g-1 wet weight (ww). MeHg concentrations (3.55 to 23.5 ng g-1 ww) accounted for 1.7 to 20.1% (median 3.7%) of sum-Hg. Sum-Hg and MeHg were positively and significantly correlated with ww (sum-Hg r2 = 0.18, p = 0.0004, n=63; MeHg r2 = 0.42, p = 0.0004, n=25), but not significantly with δ13C nor δ15N. Median concentrations of total persistent organic pollutants (POPs) ranged from 9750-156000 ng g-1 lipid weight, with order of abundance: sum-TOX (chlorobornanes quantified as technical toxaphene) > sum-PCBs > sum-DDTs > sum-chlordanes > sum-mirex compounds > sum-PBDEs ~ sum-chlorobenzenes ~ octachlorostyrene > alpha-hexachlorocyclohexane ~ hexachlorobenzene ~ pentachloroanisole. Enantioselective accumulation was found for the chiral OCPs o,p'-DDT, cis- and trans-chlordane, nonachlor MC6 and oxychlordane. Lipid-normalized POPs concentrations were elevated in amphipods with lipid percentages ≤10%, suggesting that utilization of lipids resulted in concentration of POPs in the remaining lipid pool. Multidimensional Scaling (MDS) analysis using log-transformed physiological variables and lipid-normalized organochlorine concentrations distinguished amphipods from the central vs. western arctic stations. This distinction was also seen for PCB homologs, while profiles of other compound classes were more related to specific stations rather than central-west differences.
    Environmental Science & Technology 04/2013; · 5.48 Impact Factor
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    ABSTRACT: The toxicokinetics of mercury (Hg) in key species of Arctic ecosystem are poorly understood. We sampled five brain regions (frontal lobe, temporal lobe, cerebellum, brain stem and spinal cord) from beluga whales (Delphinapterus leucas) harvested in 2006, 2008, and 2010 from the eastern Beaufort Sea, Canada, and measured total Hg (HgT) and total selenium (SeT) by inductively coupled plasma mass spectrometry (ICP-MS), mercury analyzer or cold vapor atomic absorption spectrometry, and the chemical forms using a high performance liquid chromatography ICP-MS. At least 14% of the beluga whales had HgT concentrations higher than the levels of observable adverse effect (6.0mgkg(-1) wet weight (ww)) in primates. The concentrations of HgT differed between brain regions; median concentrations (mgkg(-1) ww) were 2.34 (0.06 to 22.6, 81) (range, n) in temporal lobe, 1.84 (0.12 to 21.9, 77) in frontal lobe, 1.84 (0.05 to 16.9, 83) in cerebellum, 1.25 (0.02 to 11.1, 77) in spinal cord and 1.32 (0.13 to 15.2, 39) in brain stem. Total Hg concentrations in the cerebellum increased with age (p<0.05). Between 35 and 45% of HgT was water-soluble, of which, 32 to 41% was methyl mercury (MeHg) and 59 to 68% was labile inorganic Hg. The concentration of MeHg (range: 0.03 to 1.05mgkg(-1) ww) was positively associated with HgT concentration, and the percent MeHg (4 to 109%) decreased exponentially with increasing HgT concentration in the spinal cord, cerebellum, frontal lobe and temporal lobe. There was a positive association between SeT and HgT in all brain regions (p<0.05) suggesting that Se may play a role in the detoxification of Hg in the brain. The concentration of HgT in the cerebellum was significantly associated with HgT in other organs. Therefore, HgT concentrations in organs that are frequently sampled in bio-monitoring studies could be used to estimate HgT concentrations in the cerebellum, which is the target organ of MeHg toxicity.
    Science of The Total Environment 04/2013; 456-457C:278-286. · 3.16 Impact Factor
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    ABSTRACT: Like most zooplankton, Calanus hyperboreus undergoes seasonal migration spending late spring and summer grazing at the surface and the rest of the year in diapause at depth. As a result, in the Arctic Ocean this copepod resides for part of the year in the hexachlorocyclohexane (HCH) enriched surface water and for part of the year at depth where HCH undergoes significant microbial degradation resulting in far lower concentrations (∼3 times for α-HCH). We collected C. hyperboreus from summer and winter from the Amundsen Gulf and measured their α-HCH concentrations, enantiomeric compositions, and bioaccumulation factors (BAFs) to investigate how this copepod responds to the change in exposure to α-HCH. C. hyperboreus collected in winter were also cultured for 5 weeks under surface water conditions without feeding to investigate bioconcentration dynamics following spring ascent. Concentration of α-HCH was 2-3 times higher in individuals from the summer than those from the winter. Log BAF from the summer (feeding period) does not exceed log BCF (bioconcentration factor) from the culturing experiment (no feeding) suggesting that α-HCH concentration in C. hyperboreus is maintained through equilibration rather than feeding. After the spring ascent from deep waters, C. hyperboreus approach equilibrium partitioning with the higher surface water concentrations of α-HCH within 3-4 weeks with about 60% of bioconcentration taking place in the first week. The C. hyperboreus α-HCH chiral signature also reflects ambient seawater and can therefore be used as a determinant of residence depth. Even though a single cycle of seasonal migration does not result in a significant redistribution of α-HCH in the water column, this process could have a significant cumulative effect over longer time scales with particular local importance where the zooplankton biomass is high and the ocean depth is great enough to provide substantial vertical concentration gradients.
    Environmental Science & Technology 04/2013; · 5.48 Impact Factor
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    ABSTRACT: Elimination of persistent organic pollutants (POPs) under national and international regulations reduces "primary" emissions, but "secondary" emissions continue from residues deposited in soil, water, ice and vegetation during former years of usage. In a future, secondary source controlled world, POPs will follow the carbon cycle and biogeochemical processes will determine their transport, accumulation and fate. Climate change is likely to affect mobilisation of POPs through e.g., increased temperature, altered precipitation and wind patterns, flooding, loss of ice cover in polar regions, melting glaciers, and changes in soil and water microbiology which affect degradation and transformation. Chiral compounds offer advantages for following transport and fate pathways because of their ability to distinguish racemic (newly released or protected from microbial attack) and nonracemic (microbially degraded) sources. This paper discusses the rationale for this approach and suggests applications where chiral POPs could aid investigation of climate-mediated exchange and degradation processes. Multiyear measurements of two chiral POPs, trans-chlordane and α-HCH, at a Canadian Arctic air monitoring station show enantiomer compositions which cycle seasonally, suggesting varying source contributions which may be under climatic control. Large-scale shifts in the enantioselective metabolism of chiral POPs in soil and water might influence the enantiomer composition of atmospheric residues, and it would be advantageous to include enantiospecific analysis in POPs monitoring programs.
    Mass spectrometry (Tokyo, Japan). 01/2013; 2(Spec Iss):S0019.
  • Canadian Arctic Contaminants Assessment Report On Persistent Organic Pollutants – 2013, Edited by D.C.G. Muir, P. Kurt-Karakus, J. Stow, 01/2013: chapter 4: pages pp. 273-422; Aboriginal Affairs and Northern Development Canada.
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    ABSTRACT: 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.
    Science of The Total Environment 12/2012; 443C:775-790. · 3.16 Impact Factor

Publication Stats

3k Citations
480.52 Total Impact Points

Institutions

  • 2003–2014
    • University of Manitoba
      • • Centre for Earth Observation Science
      • • Department of Environment and Geography
      Winnipeg, Manitoba, Canada
  • 1993–2013
    • Fisheries and Oceans Canada
      • Institute of Ocean Sciences
      Ottawa, Ontario, Canada
    • University of South Carolina
      • Marine Science
      Columbia, SC, United States
  • 1993–2012
    • The University of Winnipeg
      Winnipeg, Manitoba, Canada
  • 2003–2005
    • Lancaster University
      • Lancaster Environment Centre
      Lancaster, ENG, United Kingdom
  • 2004
    • University of Toronto
      • Department of Geography
      Toronto, Ontario, Canada
  • 2001–2004
    • Environment Canada
      • Science and Technology Branch
      Gatineau, Quebec, Canada
  • 2000
    • National Water Research Institute
      Fountain Valley, California, United States