Distribution of mercury and selenium in blood compartments of bottlenose dolphins (Tursiops truncatus) from Sarasota Bay, Florida

Abstract

Total mercury and selenium concentrations ([THg], [Se]) in serum, plasma, whole blood, and packed cells were examined in a resident population of free-ranging bottlenose dolphins (Tursiops truncatus) from Sarasota Bay, Florida, USA. The authors determined how these elements partition in blood and assess compartment-specific associations. Determining the distribution of Se and THg can provide physiologic insight into potential association of Hg with selenol-containing biomolecules (e.g., antioxidants) in blood compartments. Concentrations of THg were ranked serum < plasma < whole blood < packed cells; whereas for Se concentrations, plasma < serum < whole blood < packed cells. The Se:THg molar ratio was greater than 1 in all compartments, with the higher ratios found in serum and plasma (plasma < serum) and the lower in whole blood and packed cells (packed cells < whole blood). Age was positively correlated with [THg] in all blood compartments and with [Se] in serum, plasma, and whole blood. Age was negatively correlated with Se:THg molar ratios in all blood compartments, driven by low [THg] in young animals. Although [THg] was highly correlated among all blood compartments, this was not the case for [Se]. The feasibility of calculating packed cell [THg], [Se], and Se:THg molar ratios using hematocrit measurements in combination with whole blood and plasma [THg] and [Se] was validated, allowing routine assessment of compartmentalization within erythrocytes using standard clinical measurements.

Assessment of mercury and selenium tissular concentrations and total mercury body burden in 6 Steller sea lion pups from the Aleutian Islands

“…Approximately 0.030-0.050g of each homogenized powdered tissue was digested by microwave using nitric acid (HNO 3 ) and hydrogen peroxide (H 2 O 2 ) and analyzed for total selenium concentration ([TSe]) following previous methods [37-39] . For each set of digestions, quality control samples included a blank spike (Perkin Elmer, Waltham, Massachusetts), duplicate, sample spike, internal standard (DORM 3) and certified reference material (DOLT 4 = 8.30μg/g; National Research Council Canada, Institute for National Measurement Standards, Ottawa, Canada).…”

Mercury in the brain of polar bears (Ursus maritimus ) and ringed seals (Pusa hispida).

“…Mercury concentration in blood has been suggested to reflect recent diet in bottlenose dolphins (Correa et al 2013, Hong et al 2012, Woshner et al 2008 and the same can be assumed for ringed seals. Campbell et al (2005) analyzed THg and MeHg in an Arctic pelagic foodweb and observed varying proportions of MeHg ranging from 7.5 to 100% in zooplankton and 100% (whole organism) in Arctic cod (Boreogadus saida).…”

“…There was no correlation of Se and Hg concentrations in the blood of ringed seals. A positive correlation of Se and Hg was found in blood of one population of bottlenose dolphins but not in another (Correa et al 2013) and not in sperm whales (Nielsen et al 2000). In bottlenose dolphins the Hg concentration in blood has been proposed to be linked to recent diet, whereas Se is affected by additional processes, which maintain the function of biomolecules containing selenol (Correa et al 2013).…”

“…A positive correlation of Se and Hg was found in blood of one population of bottlenose dolphins but not in another (Correa et al 2013) and not in sperm whales (Nielsen et al 2000). In bottlenose dolphins the Hg concentration in blood has been proposed to be linked to recent diet, whereas Se is affected by additional processes, which maintain the function of biomolecules containing selenol (Correa et al 2013). The Se:Hg molar ratio in ringed seal blood does not reflect that of their prey as the main food items have much higher whole body Se:Hg molar ratios, Arctic/Polar cod (Boreagadus saida) (-200) (whole organism), Parathemisto libellula (-600) and other zooplankton (-900) (Campbell et al 2005).…”

“…The Se:Hg molar ratio in sperm whale (Physeter macrocephalus) whole blood ranged from 0.7 to 2.9 (Nielsen et al 2000). In different populations of bottlenose dolphins Se:Hg molar ratios ranged from of 3.7 to 18 (Stavros et al 2008) and from 1.7 to 15.5 (Correa et al 2013) were reported. In polar bear blood, the Se:Hg molar ratio reached up to 19 (Knott et al 2011).…”