Colleen E. Bryan

Avian mercury exposure and toxicological risk across western North America: a synthesis

Methylmercury contamination of the environment is an important issue globally, and birds are useful bioindicators for mercury monitoring programs. The available data on mercury contamination of birds in western North America were synthesized. Original data from multiple databases were obtained and a literature review was conducted to obtain additional mercury concentrations. In total, 29219 original bird mercury concentrations from 225 species were compiled, and an additional 1712 mean mercury concentrations, representing 19998 individuals and 176 species, from 200 publications were obtained. To make mercury data comparable across bird tissues, published equations of tissue mercury correlations were used to convert all mercury concentrations into blood-equivalent mercury concentrations. Blood-equivalent mercury concentrations differed among species, foraging guilds, habitat types, locations, and ecoregions. Piscivores and carnivores exhibited the greatest mercury concentrations, whereas herbivores and granivores exhibited the lowest mercury concentrations. Bird mercury concentrations were greatest in ocean and salt marsh habitats and lowest in terrestrial habitats. Bird mercury concentrations were above toxicity benchmarks in many areas throughout western North America, and multiple hotspots were identified. Additionally, published toxicity benchmarks established in multiple tissues were summarized and translated into a common blood-equivalent mercury concentration. Overall, 66% of birds sampled in western North American exceeded a blood-equivalent mercury concentration of 0.2 μg/g wet weight (ww; above background levels), which is the lowest-observed effect level, 28% exceeded 1.0 μg/g ww (moderate risk), 8% exceeded 3.0 μg/g ww (high risk), and 4% exceeded 4.0 μg/g ww (severe risk). Mercury monitoring programs should sample bird tissues, such as adult blood and eggs, that are most-easily translated into tissues with well-developed toxicity benchmarks and that are directly relevant to bird reproduction. Results indicate that mercury contamination of birds is prevalent in many areas throughout western North America, and large-scale ecological attributes are important factors influencing bird mercury concentrations.

Spatial and temporal trends of persistent organic pollutants and mercury in beluga whales (Delphinapterus leucas) from Alaska.

Remote locations, such as the Arctic, are often sinks for persistent contaminants which can ultimately bioaccumulate in local wildlife. Assessing temporal contaminant trends in the Arctic is important in understanding whether restrictions on legacy persistent organic pollutants (POPs) have led to concentration declines. Beluga whale (Delphinapterus leucas) tissue samples were collected from two subpopulations (Cook Inlet, Alaska and the eastern Chukchi Sea) between 1989 and 2006. Several POPs (polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethane and related compounds (DDTs), chlordanes, hexachlorocyclohexanes (HCHs), chlorobenzenes, mirex, polybrominated diphenyl ethers (PBDEs) and semi-quantitatively hexabromocyclododecanes (HBCDs)) were measured in 70 blubber samples, and total mercury (Hg) was measured in 67 liver samples from a similar set of individuals. Legacy POPs (PCBs, chlordanes, DDTs, and HCHs) were the predominant organic compound classes in both subpopulations, with median concentrations of 2360ng/g lipid for Σ80PCBs and 1890 ng/g lipid for Σ6DDTs. Backward stepwise multiple regressions showed that at least one of the four independent variables (subpopulation, sampling year, sex, and animal length) influenced the POP and Hg concentrations. ΣPCBs, ΣDDTs, Σchlordanes, Σchlorobenzenes, mirex, and Hg were significantly higher in belugas from the eastern Chukchi Sea than from the Cook Inlet (p≤0.0001). In contrast, Σ8PBDE and α-HBCD concentrations were significantly lower in belugas from the eastern Chukchi Sea than from the Cook Inlet (p<0.0001). Significant temporal increases in concentrations of Σ8PBDE and α-HBCD were observed for both subpopulations (p≤0.0003), and temporal declines were seen for ΣHCHs and Σchlorobenzenes in eastern Chukchi Sea belugas only (p≤0.0107). All other POP and Hg concentrations were stable, indicating either a lagging response of the Arctic to source reductions or the maintenance of concentrations by unregulated sources. Sex and length also significantly influenced some concentrations, and these findings are discussed.

Improved Calibration Strategy for Measurement of Trace Elements in Biological and Clinical Whole Blood Reference Materials via Collision-Cell Inductively Coupled Plasma Mass Spectrometry

A multi-element quantification strategy based on the method of standard additions incorporating internal standards and collision cell inductively coupled plasma mass spectrometry (ICP-MS) is presented. Approaches to experimental design are discussed in the context of streamlining analytical measurement protocols employing ratio-based standard additions quantification schemes for the certification of multiple elements in Certified Reference Materials, including reduction of the number of required analytical samples and measurement of analytes and internal standards at alternate quadrupole mass resolution settings. This strategy was implemented for the measurement of As, Se, Fe, Mn, Rb, Cu, and Zn levels in a candidate fish tissue NIST Standard Reference Material and measurement of Cd and Pb in two clinical, whole blood Certified Reference Materials. A simple approach to calculating analytical uncertainties for concentration data, as determined using standard additions calibrations, is presented which utilizes regression and prediction uncertainties and quotient propagation of error formulae.

Mercury risk to avian piscivores across western United States and Canada.

The widespread distribution of mercury (Hg) threatens wildlife health, particularly piscivorous birds. Western North America is a diverse region that provides critical habitat to many piscivorous bird species, and also has a well-documented history of mercury contamination from legacy mining and atmospheric deposition. The diversity of landscapes in the west limits the distribution of avian piscivore species, complicating broad comparisons across the region. Mercury risk to avian piscivores was evaluated across the western United States and Canada using a suite of avian piscivore species representing a variety of foraging strategies that together occur broadly across the region. Prey fish Hg concentrations were size-adjusted to the preferred size class of the diet for each avian piscivore (Bald Eagle=36cm, Osprey=30cm, Common and Yellow-billed Loon=15cm, Western and Clarks Grebe=6cm, and Belted Kingfisher=5cm) across each species breeding range. Using a combination of field and lab-based studies on Hg effect in a variety of species, wet weight blood estimates were grouped into five relative risk categories including: background (<0.5μg/g), low (0.5-1μg/g), moderate (1-2μg/g), high (2-3μg/g), and extra high (>3μg/g). These risk categories were used to estimate potential mercury risk to avian piscivores across the west at a 1degree-by-1degree grid cell resolution. Avian piscivores foraging on larger-sized fish generally were at a higher relative risk to Hg. Habitats with a relatively high risk included wetland complexes (e.g., prairie pothole in Saskatchewan), river deltas (e.g., San Francisco Bay, Puget Sound, Columbia River), and arid lands (Great Basin and central Arizona). These results indicate that more intensive avian piscivore sampling is needed across Western North America to generate a more robust assessment of exposure risk.

Influence of mercury and selenium chemistries on the progression of cardiomyopathy in pygmy sperm whales, Kogia breviceps.

More than half of pygmy sperm whales (Kogia breviceps) that strand exhibit signs of cardiomyopathy (CMP). Many factors may contribute to the development of idiopathic CMP in K. breviceps, including genetics, infectious agents, contaminants, biotoxins, and dietary intake (e.g. selenium, mercury, and pro-oxidants). This study assessed trace elements in K. breviceps at various stages of CMP progression using fresh frozen liver and heart samples collected from individuals that stranded along US Atlantic and Gulf coasts between 1993 and 2007. Standard addition calibration and collision cell inductively coupled plasma mass spectrometry (ICP-MS) were employed for total Se analysis and pyrolysis atomic absorption (AA) was utilized for total Hg analysis to examine if the Se/Hg detoxification pathway inhibits the bioavailability of Se. Double spike speciated isotope dilution gas chromatography ICP-MS was utilized to measure methyl Hg and inorganic Hg. Immunoblot detection and colorimetric assays were used to assess protein oxidation status. Data collected on trace elements, selenoproteins, and oxidative status were evaluated in the context of animal life history and other complementary histological information to gain insight into the biochemical pathways contributing to the development of CMP in K. breviceps. Cardiomyopathy was only observed in adult pygmy sperm whales, predominantly in male animals. Both Hg:Se molar ratios and overall protein oxidation were greater in males than females and increased with progression of CMP.

Application of ICP-MS to Examining the Utility of Skin as a Monitoring Tissue for Trace Elements in Bottlenose Dolphin, Tursiops Truncatus

Collision cell technology inductively coupled plasma mass spectrometry (CCT-ICP-MS) was applied to answer fundamental questions about the utility of bottlenose dolphin skin as a monitoring tissue for trace element concentrations. Bottlenose dolphin skin samples were obtained from two freshly dead animals during necropsies. The samples were collected from twelve standardized locations across each animal, representing a significant spatial surface area to test among site trace element concentration variability. Skin biopsy samples were analyzed for As, Cd, Cu, Mn, Mo, Pb, Rb, Se, Sr, V and Zn concentrations by CCT-ICP-MS, and Hg concentrations were separately measured by atomic fluorescence spectrometry (AFS). Wet mass concentrations ranged from > 100 μg/g (Zn) to < 0.0100 μg/g (V, Mo, Cd, and Pb). Relative standard deviations of less than 20% among sample sites were observed for Cu, As, Se, and Hg, demonstrating that deposition of these elements may be tightly regulated in skin tissue. Multifactor mixed-effect analysis of variance analyses (ANOVA) showed significant effects (p < 0.05) longitudinally (dorsal-ventral) for Cu, Mo, Ru, Se, V, and Zn indicating that standardized sample collection sites may be needed for comparative evaluation of these elements between animals, due to relatively heterogeneous distribution in skin.

Selenium protein identification and profiling by mass spectrometry: A tool to assess progression of cardiomyopathy in a whale model

Non-ischemic cardiomyopathy is a leading cause of congestive heart failure and sudden cardiac death in humans and in some cases the etiology of cardiomyopathy can include the downstream effects of an essential element deficiency. Of all mammal species, pygmy sperm whales (Kogia breviceps) present the greatest known prevalence of cardiomyopathy with more than half of examined individuals indicating the presence of cardiomyopathy from gross and histo-pathology. Several factors such as genetics, infectious agents, contaminants, biotoxins, and inappropriate dietary intake (vitamins, selenium, mercury, and pro-oxidants), may contribute to the development of idiopathic cardiomyopathy in K. breviceps. Due to the important role Se can play in antioxidant biochemistry and protein formation, Se protein presence and relative abundance were explored in cardiomyopathy related cases. Selenium proteins were separated and detected by multi-dimension liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS), Se protein identification was performed by liquid chromatography electrospray tandem mass spectrometry (LC-ESI-MS/MS), and Se protein profiles were examined in liver (n=30) and heart tissue (n=5) by SEC/UV/ICP-MS detection. Data collected on selenium proteins was evaluated in the context of individual animal trace element concentration, life history, and histological information. Selenium containing protein peak profiles varied in presence and intensity between animals with no pathological findings of cardiomyopathy and animals exhibiting evidence of cardiomyopathy. In particular, one class of proteins, metallothioneins, was found to be associated with Se and was in greater abundance in animals with cardiomyopathy than those with no pathological findings. Profiling Se species with SEC/ICP-MS proved to be a useful tool to identify Se protein pattern differences between heart disease stages in K. breviceps and an approach similar to this may be applied to other species to study Se protein associations with cardiomyopathy.