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Mercury in the marine environment of the Canadian Arctic: Review of recent findings
Abstract and Figures
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.
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... These elements naturally exist in the aquatic ecosystem mainly because of volcanic reactions, however, the last decades their levels in the environment have increased due to anthropogenic processes, e.g. industrial, agricultural and mining activities (Braune et al., 2015). Shrimps are nowadays also being used as a bioindicator organism for the monitoring of pollutants in seawater and seafood (Dokmeci et al., 2014). ...
The aim of this study was to determine lead, mercury, cadmium, arsenic and selenium in muscle and cephalothorax of giant red Mediterranean shrimp (Aristaeomorpha foliacea). Arsenic was also determined in the lipid fraction of the shrimp to provide an estimate of the arsenolipids. The results indicated that Pb and Cd were higher in cephalothorax than in muscle (p < 0.05), while Hg was doubled in muscle. The concentrations of Cd, Pb and Hg in the edible tissue of shrimp were under the European Union maximum levels for contaminants in foodstuffs. The molar ratio of Se:Hg was calculated to 2.4:1 and 20:1 in muscle and cephalothorax, respectively, results higher than the recommended (1:1). Arsenic concentration was one order of magnitude higher than the rest of the elements. The arsenolipids comprised 0.4 and 1.9 % of the total As in muscle and cephalothorax, respectively, whereas the rest was comprised by water soluble compounds. Analysis of the lipid extracts with High Performance Liquid Chromatography coupled to Inductively Coupled Plasma Mass Spectrometry showed the existence of several arsenolipids, with a dominant peak eluting at 2-4 min, in both muscle and cephalothorax. The Estimated Weekly Intake per meal size in both tissues for adults was calculated.
... Prior studies concerning MeHg metabolism have focused on human populations (Rand et al., 2016;Rothenberg et al., 2016Rothenberg et al., , 2019Caito et al., 2018) or experimental animal models (Bridges et al., 2018;Zhang et al., 2019;Lin et al., 2020), while few, if any, studies have focused on fish-consuming wildlife in natural settings. As a large carnivorous marine mammal, the Pacific walrus (Odobenus rosmarus divergens) is a reservoir for global contaminants, including MeHg (Arctic Monitoring and Assessment Program (AMAP), Braune et al., 2015;Dietz et al., 2013;Quakenbush et al., 2016). In this study, associations between MeHg and gut microbiota were investigated in wild Pacific walruses. ...
Objectives
Methylmercury metabolism was investigated in Pacific walruses ( Odobenus rosmarus divergens ) from St. Lawrence Island, Alaska, United States.
Methods
Total mercury and methylmercury concentrations were measured in fecal samples and paired colon samples ( n = 16 walruses). Gut microbiota composition and diversity were determined using 16S rRNA gene sequencing. Associations between fecal and colon mercury and the 24 most prevalent gut microbiota taxa were investigated using linear models.
Results
In fecal samples, the median values for total mercury, methylmercury, and %methylmercury (of total mercury) were 200 ng/g, 4.7 ng/g, and 2.5%, respectively, while in colon samples, the median values for the same parameters were 28 ng/g, 7.8 ng/g, and 26%, respectively. In fecal samples, methylmercury was negatively correlated with one Bacteroides genus, while members of the Oscillospirales order were positively correlated with both methylmercury and %methylmercury (of total mercury). In colon samples, %methylmercury (of total mercury) was negatively correlated with members of two genera, Romboutsia and Paeniclostridium .
Conclusions
Median %methylmercury (of total mercury) was 10 times higher in the colon compared to the fecal samples, suggesting that methylmercury was able to pass through the colon into systemic circulation. Fecal total mercury and/or methylmercury concentrations in walruses were comparable to some human studies despite differences in seafood consumption rates, suggesting that walruses excreted less mercury. There are no members (at this time) of the Oscillospirales order which are known to contain the genes to methylate mercury, suggesting the source of methylmercury in the gut was from diet and not in vivo methylation.
Although mercury (Hg) in polar ecosystems has been well-studied, there is little information on Hg in the Arctic during low-productivity seasons like the polar night. We quantified Hg concentrations, carbon, and nitrogen stable isotope ratios (δ13C and δ15N) in the muscle of polar cod (Boreogadus saida), Atlantic cod (Gadus morhua), and capelin (Mallotus villosus) sampled from the North-West and North-East Barents Sea during November-December 2019. Hg concentrations varied between species (14-175 ng/g dw), dependent on region, but were well below the toxicity threshold for fish health and the EU-accepted threshold for human consumption. Interspecific differences were observed only in the North-East region, with Atlantic cod having the highest Hg concentrations, explained by its larger size, higher trophic position and benthopelagic feeding. Spatial differences in polar cod with higher Hg concentrations in the North-East than the North-West were likely due to a combination of differences in food web structure and Hg exposure.
Mercury (Hg) levels in the environment have substantially increased over the past century leading to increased concentrations in many high trophic level predators, including Arctic seabirds. From the Canadian high Arctic, research on seabird eggs has documented some of the greatest concentrations of egg Hg anywhere in the Arctic. Farther east, in high Arctic Greenland, no similar data on Hg concentrations in eggs exist, making spatial comparisons unfeasible. To address this paucity of data, we collected whole eggs from Thick-billed Murre Uria lomvia (n = 11), Black-legged Kittiwake Rissa tridactyla (n = 9), and Common Eider Somateria mollissima (n = 12) in the high Arctic of northwest Greenland in the summer of 2014 and assessed their concentration of total Hg. Thick-billed Murre eggs had the highest mean total Hg concentrations (1.32 ± 0.42 mg g−1 dw) followed by kittiwakes (0.64 ± 0.19) and eiders (0.23 ± 0.10). When compared with murre and kittiwake egg samples collected in high Arctic Canada during the same time period, total Hg concentrations from northwest Greenland were higher, but not significantly. Based on what is known about lethal Hg concentrations in murre eggs, these results indicate that some murre eggs may be at risk for increased embryonic mortality and further monitoring is suggested to determine long-term trends in egg Hg concentrations.
Clarifying the sources and fates of atmospheric mercury (Hg) in the Antarctic is crucial to understand the global Hg circulation and its impacts on the fragile ecosystem of the Antarctic. Herein, the annual variations in the isotopic compositions of total gaseous Hg (TGM), with 5-22 days of sampling duration for each sample, were presented for the first time to provide isotopic evidence of the sources and environmental processes of gaseous Hg around the Chinese Great Wall Station (GWS) in the western Antarctic. Different from the Arctic tundra and lower latitude areas in the northern hemisphere, positive δ202Hg (0.58 ± 0.21‰, mean ± 1SD) and negative Δ199Hg (-0.30 ± 0.10‰, mean ± 1SD) in TGM at the GWS indicated little impact from the vegetation-air exchange in the Antarctic. Correlations among TGM Δ199Hg, air temperature, and ozone concentrations suggested that enhanced katabatic wind that transported inland air masses to the continental margin elevated TGM Δ199Hg in the austral winter, while the surrounding marine surface emissions controlled by sea-ice dynamics lowered TGM Δ199Hg in the austral summer. The oxidation of Hg(0) might elevate Δ199Hg in TGM during atmospheric Hg depletion events but have little impact on the seasonal variations of atmospheric Hg isotopes. The presented atmospheric Hg isotopes were essential to identify the transport and transformation of atmospheric Hg and further understand Hg cycling in the Antarctic.
It is widely accepted that nanotechnology attracted more interest because of various values that nanomaterial applications offers in different fields. Recently, researchers have proposed nanomaterials based electrochemical sensors and biosensors as one of the potent alternatives or supplementary analytical tools to the conventional detection procedures that consumes a lot of time. Among different nanomaterials, researchers largely considered magnetic nanomaterials (MNMs) for developing and fabricating the electrochemical (bio)sensors for numerous utilizations. Among several factors, healthier and higher quality foods are the most important preferences of consumers and manufacturers. For this reason, developing new techniques for rapid, precise as well as sensitive determination of components or contaminants of foods is very important. Therefore, developing the new electrochemical (bio)sensors in food analysis is one of the key and effervescent research fields. In this review, firstly, we presented the properties and synthesis strategies of MNMs. Then, we summarized some of the recently developed MNMs-based electrochemical (bio)sensors for food analysis including detecting the antioxidants, synthetic food colorants, pesticides, heavy metal ions, antibiotics and other analytes (bisphenol A, nitrite and aflatoxins) from 2010 to 2020. Finally, the present review described advantages, challenges as well as future directions in this field.
With increasing input of neurotoxic mercury to environments as a result of anthropogenic activity, it has become imperative to examine how mercury may enter biotic systems through its methylation to bioavailable forms in aquatic environments. Recent development of stable isotope-based methods in methylation studies has enabled a better understanding of the factors controlling methylation in aquatic systems. In addition, the identification and tracking of the hgcAB gene cluster, which is necessary for methylation, has broadened the range of known methylators and methylation-conducive environments. Study of abiotic factors in methylation with new molecular methods (the use of stable isotopes and genomic methods) has helped elucidate the confounding influences of many environmental factors, as these methods enable the examination of their direct effects instead of merely correlative observations. Such developments will be helpful in the finer characterization of mercury biogeochemical cycles, which will enable better predictions of the potential effects of climate change on mercury methylation in aquatic systems and, by extension, the threat this may pose to biota.
Mercury is found in Arctic marine mammals that are important in the diet of northern Indigenous peoples. The objectives of the present long-term study, spanning a 45-yr period, were to 1) investigate the temporal trends of total mercury (THg; muscle and liver) and selenium (Se; liver) in ringed seals (Pusa hispida) from different regions of the Canadian Arctic; and 2) examine possible relationships with age, diet, and climate parameters such as air temperature, precipitation, climatic indices, and ice-coverage. Ringed seals were collected by hunters in northern communities in the Beaufort Sea, Central Arctic, Eastern Baffin Island, Hudson Bay, and Ungava/Nunatsiavut regions (Canada) between 1972 and 2017. Mercury levels did not change through time in seal liver, but THg levels in muscle decreased in seals from Hudson Bay (-0.91%/yr) and Ungava/Nunatsiavut (-1.30%/yr). Carbon stable isotope values in seal muscle decreased significantly through time in 4 regions. Selenium-to-THg ratios were found to be >1 for all years and regions. Variation partitioning analyses across regions indicated that THg trends in seals were mostly explained by age (7.3-21.7%), climate parameters (3.5-12.5%), and diet (up to 9%); climate indices (i.e., Arctic and North Atlantic Oscillations, Pacific/North American pattern) explained the majority of the climate portion. The THg levels had a positive relationship with Arctic Oscillation for multiple regions. Associations of THg with air temperature, total precipitation, and sea-ice coverage, as well as with North Atlantic Oscillation and Pacific/North American pattern were found to vary with tissue type and geographical area. Environ Toxicol Chem 2020;00:1-13. © 2020 Her Majesty the Queen in Right of Canada. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Fisheries and Oceans Canada.
The Inuit of Nunavik (Northern Quebec, Canada) are exposed to polychlorinated biphenyls (PCBs) and mercury (Hg) through their consumption of marine country foods. A temporal trend study was initiated in 1992 to monitor circulating levels of PCBs and Hg in pregnant Inuit women, since the fetus is most at risk of adverse health effects. We set out (1) to describe temporal trends of PCBs and Hg levels in pregnant Nunavik women between 1992 and 2017; (2) to determine the prevalence of participants exceeding the guidance values in 2017; (3) to investigate relations between marine country food intake and contaminant levels over the study period. A total of 559 pregnant women provided a blood sample for contaminant analysis from 1992 to 2017. PCB congeners were quantified in plasma (serum) by gas chromatography (GC) coupled to electron capture detection or mass spectrometry (MS). We determined whole blood mercury concentration by cold vapor atomic absorption or inductively-coupled plasma MS. We performed multilevel modeling to assess temporal trends in contaminant levels and relations with marine country food consumption. Concentrations of total PCBs and Hg decreased by 84% and 65% between 1992 and 2017, respectively. Nevertheless, 10% and 22% of women in 2017 exceeded guidance values for PCBs and Hg, respectively. While the decline in marine country food intake is the only factor associated with decreasing Hg levels, other factors may explain the decline in PCB levels. Despite the significant decline in PCBs and Hg levels from 1992 to 2017, exposure to these contaminants is still quite prevalent among pregnant Nunavik women. Most of the decline in Hg exposure is likely due to a shift away from marine country foods to store-bought foods, which is a concern given the cultural and nutritional importance of country foods and the high food insecurity that prevails in Nunavik.
Mercury is a persistent, toxic and bio-accumulative pollutant of global interest. Its main mass in the troposphere is in the form of elemental gas-phase mercury. Rapid, near-complete depletion of mercury has been observed during spring in the atmospheric boundary layer of frozen marine areas in Arctic, sub-Arctic and Antarctic locations. It is strongly correlated with ozone depletion. To date, evidence has indicated strongly that chemistry involving halogen gases from surface sea-salt is the mechanism of this destruction. Precisely which halogen gases are the main players has remained unresolved. Our novel kinetic data and multiscale modelling show that Br atoms and BrO radicals are the most effective halogens driving mercury oxidation. The reduction of oxidized mercury deposited in the snow pack back to Hg 0 and subsequent diffusion to the atmosphere is observed. However, it cannot compensate for the total deposition, and a net accumulation occurs. We use a unique global atmospheric mercury model to estimate that halogen-driven mercury depletion events result in a 44% increase in the net deposition of mercury to the Arctic. Over a 1-yr cycle, we estimate an accumulation of 325 tons of mercury in the Arctic. DOI: 10.1111/j.1600-0889.2004.00118.x
Using the Swedish icebreaker Oden as a platform, continuous measurements of airborne mercury (gaseous elemental mercury (Hg0), divalent mercury HgII(g) (acronym RGM) and mercury attached to particles (PHg)) and some long-lived trace gases (carbon monoxide CO and ozone O3) were performed over the North Atlantic and the Arctic Ocean. The measurements were performed for nearly three months (July–September, 2005) during the Beringia 2005 expedition (from Göteborg, Sweden via the proper Northwest Passage to the Beringia region Alaska – Chukchi Penninsula – Wrangel Island and in-turn via a north-polar transect to Longyearbyen, Spitsbergen). The Beringia 2005 expedition was the first time that these species have been measured during summer over the Arctic Ocean going from 60° to 90° N. During the North Atlantic transect, concentration levels of Hg0, CO and O3 were measured comparable to typical levels for the ambient mid-hemispheric average. However, a rapid increase of Hg0 in air and surface water was observed when entering the ice-covered waters of the Canadian Arctic archipelago. Large parts of the measured waters were supersaturated with respect to Hg0, reflecting a strong disequilibrium. Heading through the sea ice of the Arctic Ocean, a fraction of the strong Hg0} pulse in the water was spilled with some time-delay into the air samples collected ~20 m a.s.l. Several episodes of elevated Hg0(g) were encountered along the sea ice route with higher mean concentration (1.81±0.43 ng m−3) compared to the marine boundary layer over ice-free oceanic waters (1.55±0.21 ng m−3). In addition, an overall majority of the variance in the temporal series of Hg0 concentrations was observed during July. Atmospheric boundary layer {O3} mixing ratios decreased when initially sailing northward. In the Arctic, an O3 minimum around 15–20 ppbv was observed during summer (July–August). Alongside the polar transect during the beginning of autumn, a steady trend of increasing O3 mixing ratios was measured returning to initial levels of the expedition (>30 ppbv). Ambient CO was fairly stable (84±12 ppbv) during the expedition. However, from the Beaufort Sea and moving onwards steadily increasing CO mixing ratios were observed (0.3 ppbv day−1). On a comparison with coeval archived CO and O3 data from the Arctic coastal strip monitoring sites Barrow and Alert, the observations from Oden indicate these species to be homogeneously distributed over the Arctic Ocean. Neither correlated low ozone and GEM events nor elevated concentrations of RGM and PHg were at any extent sampled, suggesting that atmospheric mercury deposition to the Arctic basin is low during the Polar summer and autumn. Elevated levels of Hg0 and CO were episodically observed in air along the Chukchi Peninsula indicating transport of regional pollution.
In Arctic Canada, Hudson Bay is a site of great exploration history, aboriginal culture, and a vast marine wilderness supporting large populations of marine mammals and birds. These include some of the most iconic Arctic animals like beluga, narwhal, bowhead whales, and polar bears. Due to the challenges of conducting field research in this region, some of the mysteries of where these animals move, and how they are able to survive in such seemingly inhospitable, ice-choked habitats are just now being unlocked. For example, are polar bears being replaced by killer whales? This new information could not be more salient, as the Hudson Bay Region is undergoing rapid environmental change due to global warming, as well as increased pressures from industrial development interests. A Little Less Arctic brings together some of the world's leading Arctic scientists to present the current state of knowledge on the physical and biological characteristics of Hudson Bay and in particular the ecology of marine wildlife to highlight what information is required to better understand and adapt to the changes underway, and to forecast what will happen to marine wildlife of this vast inland sea in the future.
