Temporal change and the influence of climate and weather factors on mercury concentrations in Hudson Bay polar bears, caribou, and seabird eggs.

Temporal trends of mercury in Arctic wildlife are inconsistent within and between species and are often insignificant, which limits data interpretation. Recent multivariate analyses have shown that weather and climate factors (e.g. temperatures, sea ice conditions) are related to total Hg (THg) concentrations in wildlife tissues, though relatively few studies have explored these relationships. The present study compared time series of THg concentrations in liver of polar bear (Ursus maritimus, 2007/08-2015/16), eggs of thick-billed murres (Uria lomvia, 1993-2015) and kidney of caribou (Rangifer tarandus groenlandicus, 2006-2015) from the Hudson Bay region of Canada and statistically modelled THg over time with available climate and weather data. Significant temporal trends of THg concentrations were not detected in any species. However, in multivariate models that included time-lagged sea ice freeze up dates, THg concentrations increased 4.4% yr-1 in Qamanirjuaq caribou. Sea ice conditions were also related to THg levels in polar bear liver but not those in eggs of murres, though year was not a signifcant factor. Greater precipitation levels one to two years prior to sampling were associated with greater THg concentrations in polar bears and caribou, likely due to greater deposition, flooding and discharge from nearby wetlands and rivers. Time-lagged Arctic and/or North Atlantic Oscillation (AO/NAO) indices also generated significant, inverse models for all three species, agreeing with relationships in other time series of similar length. The magnitude and direction of many relationships were affected by season, duration of time-lags, and the length of the time series. Our findings support recent observations suggesting that temporal studies monitoring Hg in Arctic wildlife should consider including key climatic or weather factors to help identify consistent variables of influence and to improve temporal analyses of THg time series.

Special issue on mercury in Canada's North: summary and recommendations for future research.

Important scientific advances have been made over the last decade in identifying the environmental fate of mercury and the processes that control its cycling in the Canadian Arctic. This special issue includes a series of six detailed reviews that summarize the main findings of a scientific assessment undertaken by the Government of Canada's Northern Contaminants Program. It was the first assessment to focus exclusively on mercury pollution in the Canadian Arctic. Key findings, as detailed in the reviews, relate to sources and long-range transport of mercury to the Canadian Arctic, its cycling within marine, freshwater, and terrestrial environments, and its bioaccumulation in, and effects on, the biota that live there. While these accomplishments are significant, the complex nature of the mercury cycle continues to provide challenges in characterizing and quantifying the relationships of mercury sources and transport processes with mercury levels in biota and biological effects of mercury exposure. Of particular concern are large uncertainties in our understanding of the processes that are contributing to increasing mercury concentrations in some Arctic fish and wildlife. Specific recommendations are provided for future research and monitoring of the environmental impacts of anthropogenic mercury emissions, influences of climate change, and the effectiveness of mitigation strategies for mercury in the Canadian Arctic.

Effects-based marine ecological risk assessment at a polychlorinated biphenyl-contaminated site in Saglek, Labrador, Canada.

Although the presence and distribution of polychlorinated biphenyls (PCBs) in Arctic marine environments has been well documented, the implications for the health of biota are poorly understood. In the present study, multiple lines of evidence, including site-specific effects data, were used to assess PCB-related risks to marine biota at a contaminated military site in Saglek Bay, Labrador, Canada, from 1997 to 1999. Risks were evaluated for three components of the ecosystem: benthic invertebrates, a bottom-feeding fish (shorthorn sculpin, Myoxocephalus scorpius), and a diving seabird (black guillemot, Cepphus grylle). Average sediment PCB concentrations exceeded the Canadian interim sediment quality guideline level by 41-fold. However, sediment toxicity testing and a benthic community survey showed no evidence of adverse effects. In contrast, shorthorn sculpin and black guillemot PCB exposures (measured as sum of 55 congeners) were elevated enough to pose risks to survival or reproduction. Based on the collective evidence, the authors estimated that risks were posed by sediment PCB concentrations greater than 77 ng/g dry weight for black guillemots and 750 ng/g dry weight for shorthorn sculpins. The present study, along with two parallel studies, provided information to support the management decisions concerning potential remedial action on the contaminated sediments. This ecological risk assessment describes the steps and rationale taken to evaluate the risk posed by an area of PCB-contaminated marine sediments in an otherwise relatively pristine northern coastal environment.

Temporal trends of legacy POPs in Arctic biota, an update.

A statistically robust method was applied to 316 time-series of 'legacy' persistent organic pollutants (POPs) in Arctic biota from marine, freshwater and terrestrial ecosystems with the purpose of generating a 'meta-analysis' of temporal trend data collected over the past two to three decades for locations from Alaska in the west to northern Scandinavian in the east. Information from recently published temporal trend studies was tabulated and comparisons were also drawn with trends in arctic air. Most of the analysed time-series of legacy POP compounds showed decreasing trends, with only a few time-series showing significantly increasing trends. Compounds such as alpha-HCH, gamma-HCH and SigmaDDT had a relatively high proportion of time-series showing significantly decreasing trends; SigmaCHL had the lowest proportion. beta-HCH was an exception, where long-range transport through the ocean, and not the atmosphere, may explain several increasing trends that were detected in the Canadian Arctic. Moving east from the Canadian Arctic there was a trend towards a greater proportion of significantly decreasing trends. Several time-series for DDE and SigmaDDT showed significantly non-exponential trends, most often with a period of relative stability followed by a decrease. The median 'minimum detectable annual change within a 10-year period' for all of the time-series considered was 12% which did not meet the desirable level of statistical power capable of detecting a 5% annual change with a significance level of 5% within a 10-year period. The trends observed in the biota were consistent with decreasing trends of legacy POPs reported for Arctic air which appear to follow historic decreases in emissions. However, recent decreases in air are also starting to show signs of levelling off which may be an indication that atmospheric concentrations and, consequently those in the biota, are being less driven by primary sources and more by environmental processes and degradation.

Biological effects of marine PCB contamination on black guillemot nestlings at Saglek, Labrador: liver biomarkers.

Black guillemots (Cepphus grylle) in Saglek Bay, Labrador have elevated polychlorinated biphenyl (PCB) concentrations due to marine sediment contamination around a former military site. We measured liver biomarkers and sigmaPCB concentrations in 31 nestlings from three PCB-exposure groups: Reference group (range: 15-46 ng/g liver, wet wt.), moderately exposed Islands group (24-150 ng/g), and highly exposed Beach group (170-6200 ng/g). Biomarker responses were dose-dependent and in some cases sex-dependent. Livers of female Beach nestlings were enlarged 36% relative to Reference females. In both sexes, Beach nestlings had liver ethoxyresorufin-O-deethylase (EROD) activities elevated 79% and liver retinol concentrations reduced 47%. Retinyl palmitate concentrations were reduced 50% but only among female nestlings. Island nestlings also exhibited EROD induction (57%) and reductions in retinol and retinyl palmitate concentrations (28 and 58%, respectively). Liver lipid content increased with sigmaPCBs in both sexes, and correlated with liver mass in males. Malic enzyme activity and porphyrin concentrations showed little association with sigmaPCBs. Although similar associations between liver biomarkers and organochlorine exposure in fish-eating birds are well documented, typically exposures involve multiple contaminants and there is uncertainty about specific PCB effects. Our findings indicate that liver biomarkers respond to relatively low PCB exposures (approximately 73 ng/g liver) in guillemots.