Mercury in Ringed Seals (Pusa hispida) from the Canadian Arctic in Relation to Time and Climate Parameters

Abstract

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.

Trace elements in grey seals from the Gulf of St. Lawrence

“…In the present study, THg concentration ranges in adult grey seal muscle (0.086 - 1.90 µg/g) were lower than ranges for grey seals from the Faroe Islands sampled in 1993 - 1995 (0.13 4.61 µg/g, in Bustamante et al, 2004) and similar to ranges from Sable Island sampled in 1996 - 1998 (0.4 - 1.6 µg/g in Nyman et al, 2002). The mean calculated for adult seals in the present study was 0.34 µg THg/g muscle tissue, which is in the same range as means for ringed seals from across the Canadian Arctic (0.10 - 0.69 µg THg/g muscle tissue in Houde et al (2020)) and on the low end of averages reported in other studies of Arctic ringed seals (Brown et al, 2016; Gaden et al, 2009). THg concentrations in grey seal liver are discussed in the next paragraph.…”

“…Hepatic Se ranges in the present study (2.2 - 110 µg/g for adult seals) were similar to those reported for grey seals from the Faroe Island (1.2 - 99 µg/g) and Sable Island (9.3 - 83 µg/g). Average hepatic Se concentrations in the present study (13.87 µg/g) were also very close to average concentrations from populations of ringed seals in the Canadian Arctic, which ranged from 3.49 to 14.7 µg/g in Houde et al (2020).…”

“…These Hg concentrations in grey seal livers are higher than those for ringed seals from Svalbard and the eastern Canadian Arctic, but similar to hepatic Hg levels for ringed seals in the western Arctic (Fant et al, 2001; Wagemann et al, 1996). Although these studies in the Canadian Arctic are from 20 years ago, a recent study shows only very limited declines in Hg concentrations in Arctic ringed seals over the last five decades, despite declines in atmospheric mercury concentrations (Houde et al, 2020). Recent studies in the Canadian Arctic report average hepatic THg concentrations of 6.1 to 70.4 µg/g (Brown et al, 2016) and 1.8 to 27.8 µg/g (Houde et al, 2020) which overlap with averages calculated for juvenile and adult seals in the present study (13.8 and 31.5 µg THg/g of liver tissue, respectively).…”

An ecosystem-scale litter and microplastics monitoring plan under the Arctic Monitoring and Assessment Programme (AMAP)

“…This will allow for future spatial trend monitoring across large scale areas that experience similar oceanographic conditions. (Braune et al 2014;Houde et al 2020), and since 2007 stomach samples from the same individuals collected for contaminants research have also been examined for microplastics (Baak et al 2020;Bourdages et al 2020).…”

Investigating the dynamics of methylmercury bioaccumulation in the Beaufort Sea shelf food web: a modeling perspective

“…21 A number of studies have linked the temporal trends of Hg in some Arctic species (e.g., polar bears, ringed seals, beluga, and seabirds) to rapid sea-ice reduction, which has altered the timing, intensity, and composition of plankton production and induced ecosystem shi from an iceassociated food web to a pelagic one. [22][23][24][25][26][27] Measured concentrations of MeHg in Arctic species over time represent the net effect of environmental factors governing Hg loading, methylation and demethylation rates, and ecological characteristics such as trophic interactions and bioenergetics; [28][29][30] thus, it is oen challenging to use these empirical data alone to identify the driving factors of changes in Hg levels in biota. To elucidate the pathways of global environmental change on MeHg bioaccumulation in Arctic ecosystems, an effective tool that connects environmental factors (e.g., sea ice, temperature, and contaminant loading) with food-web dynamics is urgently needed.…”