Toxicodistribution of mercury and selenium in pinnipeds of Alaska

Abstract

This study is divided into two major parts (chapters) in order to better understand mercury (Hg) and selenium (Se) tissue distribution in pinnipeds. The first part of the study focuses on determining total mercury ([THg]) and selenium ([TSe]) concentrations (mass and molar based) among cardiac and renal tissues of ice seals (focus on bearded seals, Erignathus barbatus) as compared to the more traditionally analyzed tissues (e.g. liver, skeletal muscle). Determining Hg distribution within these tissues is essential in establishing sampling methods for biomonitoring, histopathology and biochemistry of Hg. Age was determined to be an important driver of [THg] and Se:Hg molar ratios in heart and kidney. In bearded seals [THg] varied by heart region and therefore future studies should use consistent sampling methods in order to determine and compare [THg]. Despite the differences in seal kidney structure when compared to many terrestrial mammals, the kidney cortex was the main accumulation site for Hg within the kidney of bearded seals and requires consideration in sampling designs. Se:Hg molar ratios greater than 1 in all tissues can be considered a baseline for normal Se concentrations under relatively low [THg]. The second part of the study focuses on THg and TSe distribution in Steller sea lion (Eumetopias jubatus) pup tissues in addition to THg tissular and body burdens. Hair had the highest [THg] in all 5 Steller sea lion pups as compared to other tissue compartments. Since these pups were 1-2 months of age, the hair (lanugo) sampled was a good indicator of Hg exposure via maternal placental transfer (in utero) and potentially a good indicator of individual THg tissue burdens. The percent of total Hg body burden for many organs in Steller sea lion pups was similar to that found in Pacific harbor seals. The Se:Hg molar ratios were between 1 and 50 in all tissues of 4 of the 5 pups while the pup with the highest [THg] in all tissues, had Se: Hg molar ratios of 0.7 or less in 9 of 14 tissues indicating that this animal may have limited Se-dependent protection related to Hg toxicosis.