Concentrations and Interactions of Selected Essential and Non-Essential Elements in Ringed Seals and Polar Bears of Arctic Alaska

Abstract

In this study, we evaluated concentrations of twelve essential and non-essential elements (As, Cd, Co, Cu, Pb, Mg, Mn, Hg, Mo, Se, Ag, and Zn) in tissues of ringed seals (Phoca hispida) and polar bears (Ursus maritimus) of arctic Alaska (USA). All samples were collected between 1995-97 in conjunction with subsistence harvests. The essential elements are reported to help develop reference ranges for health status determination and to help assess known or suspected interactions affecting toxicoses of cadmium (Cd) and mercury (Hg). In some tissues, Cd, Hg, and selenium (Se) were present at concentrations that have been associated with toxicoses in some domestic animals. Nevertheless, tissue levels of all elements were within ranges that have been reported previously in other pinnipeds and polar bears. Significant associations included: Cd with Zn or Cu; Cu with Zn or Ag; and Hg with Se, Zn, or Cu. This study found hepatic Hg: Se molar ratios to be lower than unity and different between the two species. Based upon significant differences in mean tissue elemental concentrations for polar bear versus ringed seal, we concluded that biomagnification factors (bear/seal) were significant for: Cu in liver and muscle; Pb in kidney; Se in kidney and muscle; Zn in liver and muscle; and Hg in liver. Possible explanations for observed elemental correlations (i.e., interactions) and ancillary mechanisms of Cd and Hg detoxification are discussed.

Essential and non-essential elements in eight tissue types from subsistencehunted bowhead whale: Nutritional and toxicological assessment

“…However, Hg concentrations in bowheads are relatively miniscule compared to other marine mammals, and are below levels used by regulatory agencies for marketed animal products. Compared to other species of northern Alaska, bowhead whales of this study had similar or lower tissue concentrations of the toxic metal Hg (17,18). The Cd concentrations are similar to those previously reported for bowhead whales (18,27), which accumulate Cd with age in liver, and particularly in kidney (18), similar to other arctic mammals, including both terrestrial and marine species (17,18,32,33,34,35,36,37,38,39).…”

“…Compared to other species of northern Alaska, bowhead whales of this study had similar or lower tissue concentrations of the toxic metal Hg (17,18). The Cd concentrations are similar to those previously reported for bowhead whales (18,27), which accumulate Cd with age in liver, and particularly in kidney (18), similar to other arctic mammals, including both terrestrial and marine species (17,18,32,33,34,35,36,37,38,39). Other reports have addressed potential nutritional and toxic effects of such elemental concentrations in bowhead whales and domestic animals (32,18).…”

“…With respect to elements, this "nutritional" assessment must be balanced with an evaluation of non-essential elements that have no known physiologic function. Past studies of element interactions (17,18) were limited to classical tissues (liver, kidney, muscle, blubber), and did not consider human consumers. Hoekstra et al (7) offered a comprehensive assessment of bowhead whalebased subsistence diets with respect to organochlorines in various tissues.…”

What are the toxicological effects of mercury in Arctic biota?

“…This complex probably represents a direct covalent (or other strong) interaction of Hg and Se. In some wild aquatic predatory bird and mammal species, it has been shown that MeHg predominates in the liver at low total Hg (THg) concentrations whereas at higher concentrations an increasingly large percentage of THg is present as inorganic Hg associated with Se, and some studies have identified this complex as HgSe (tiemanite) (Koeman and van deVen, 1975;Dietz et al, 1990Dietz et al, , 1998aDietz et al, , 1998bDietz et al, , 2000aDietz et al, 2000bScheuhammer et al, 1998Scheuhammer et al, , 2008Wang et al, 2001;Woshner et al, 2001aWoshner et al, , 2001bWoshner et al, , 2008O'Hara et al, 2003;Arai et al, 2004;Ikemoto et al, 2005;Dehn et al, 2005Dehn et al, , 2006Eagles-Smith et al, 2009;Moses et al, 2009;Routti et al, 2011).…”

The Effects of Environmental Mercury Contamination on Wild and Domestic Animals

“…Among studies that do examine mercury levels in non-laboratory animals, many have examined exposures of wild and domestic animals to mercury that could serve as sentinels for human exposure [8][9][10]. Animals including wild mink [9], vampire bats [10], hares and rabbits [11], wild seals and bears [12], wild birds [13], domestic cattle and domestic fowl [14][15][16], and domestic dogs [17] are some of the animals that have been assessed for their mercury "body load" over the past 20 to 25 years.…”